Search is not available for this dataset
id
stringlengths 36
36
| adv_source_id
stringlengths 36
36
| source_id
stringlengths 36
36
| model
stringclasses 1
value | decoding
float64 | repetition_penalty
float64 | attack
stringclasses 1
value | domain
stringclasses 8
values | title
stringlengths 1
488
| prompt
float64 | generation
stringlengths 9
25.4k
⌀ |
|---|---|---|---|---|---|---|---|---|---|---|
2162d503-35a3-48cc-ab6e-1ee8c36ecaff | 2162d503-35a3-48cc-ab6e-1ee8c36ecaff | 2162d503-35a3-48cc-ab6e-1ee8c36ecaff | human | null | null | none | abstracts | An invariance principle for semimartingale reflecting Brownian motions
in domains with piecewise smooth boundaries | null | Semimartingale reflecting Brownian motions (SRBMs) living in the closures of
domains with piecewise smooth boundaries are of interest in applied probability
because of their role as heavy traffic approximations for some stochastic
networks. In this paper, assuming certain conditions on the domains and
directions of reflection, a perturbation result, or invariance principle, for
SRBMs is proved. This provides sufficient conditions for a process that
satisfies the definition of an SRBM, except for small random perturbations in
the defining conditions, to be close in distribution to an SRBM. A crucial
ingredient in the proof of this result is an oscillation inequality for
solutions of a perturbed Skorokhod problem. We use the invariance principle to
show weak existence of SRBMs under mild conditions. We also use the invariance
principle, in conjunction with known uniqueness results for SRBMs, to give some
sufficient conditions for validating approximations involving (i) SRBMs in
convex polyhedrons with a constant reflection vector field on each face of the
polyhedron, and (ii) SRBMs in bounded domains with piecewise smooth boundaries
and possibly nonconstant reflection vector fields on the boundary surfaces.
|
aae54d4a-b8e5-41f9-82d2-d37613f5ba11 | aae54d4a-b8e5-41f9-82d2-d37613f5ba11 | aae54d4a-b8e5-41f9-82d2-d37613f5ba11 | human | null | null | none | abstracts | Photoconductance of organic single-molecule contacts | null | We study the dc conductance of organic single-molecule contacts in the
presence of external electromagnetic radiation (photoconductance). In agreement
with previous predictions, we find that the radiation can lead to large
enhancements of the conductance of such contacts by bringing off-resonant
levels into resonance through photoassisted processes. In our analysis we make
use of the simplifying fact that, under certain assumptions, the
photoconductance can be expressed in terms of the transmission function in the
absence of the radiation. The conductance enhancement is demonstrated for
oligophenylene molecules between gold electrodes, whose electronic structure is
calculated based on density-functional theory. It is shown that the exponential
decay of the conductance with the length of the molecule can be replaced by a
length-independent value in the presence of radiation.
|
ef886ca6-f902-4cc2-ace4-d1fae263e360 | ef886ca6-f902-4cc2-ace4-d1fae263e360 | ef886ca6-f902-4cc2-ace4-d1fae263e360 | human | null | null | none | abstracts | The Sigma-D Relation for Planetary Nebulae: Preliminary Analysis | null | An analysis of the relation between radio surface brightness and diameter,
so-called Sigma-D relation, for planetary nebulae (PNe) is presented: i) the
theoretical Sigma-D relation for the evolution of bremsstrahlung surface
brightness is derived; ii) contrary to the results obtained earlier for the
Galactic supernova remnant (SNR) samples, our results show that the updated
sample of Galactic PNe does not severely suffer from volume selection effect -
Malmquist bias (same as for the extragalactic SNR samples) and; iii) we
conclude that the empirical Sigma-D relation for PNe derived in this paper is
not useful for valid determination of distances for all observed PNe with
unknown distances.
|
93424dfd-73e9-4cb1-81a2-b8436e4a928a | 93424dfd-73e9-4cb1-81a2-b8436e4a928a | 93424dfd-73e9-4cb1-81a2-b8436e4a928a | human | null | null | none | abstracts | Stopping effects in U+U collisions with a beam energy of 520 MeV/nucleon | null | A Relativistic Transport Model (ART1.0) is applied to simulate the stopping
effects in tip-tip and body-body U+U collisions, at a beam kinetic energy of
520 MeV/nucleon. Our simulation results have demonstrated that both central
collisions of the two extreme orientations can achieve full stopping, and also
form a bulk of hot, dense nuclear matter with a sufficiently large volume and
long duration, due to the largely deformed uranium nuclei. The nucleon sideward
flow in the tip-tip collisions is nearly 3 times larger than that in body-body
ones at normalized impact parameter $b/b_{max}<0.5$, and that the body-body
central collisions have a largest negative nucleon elliptic flow $v_{2}=-12%$
in contrast to zero in tip-tip ones. Thus the extreme circumstance and the
novel experimental observables in tip-tip and body-body collisions can provide
a good condition and sensitive probe to study the nuclear EoS, respectively.
The Cooling Storage Ring (CSR) External Target Facility (ETF) to be built at
Lanzhou, China, delivering the uranium beam up to 520 MeV/nucleon is expected
to make significant contribution to explore the nuclear equation of state
(EoS).
|
8e265546-3eda-48da-869f-02e7a720191c | 8e265546-3eda-48da-869f-02e7a720191c | 8e265546-3eda-48da-869f-02e7a720191c | human | null | null | none | abstracts | QED for fields obeying a square root operator equation | null | Instead of using local field equations - like the Dirac equation for spin-1/2
and the Klein-Gordon equation for spin-0 particles - one could try to use
non-local field equations in order to describe scattering processes. The latter
equations can be obtained by means of the relativistic energy together with the
correspondence principle, resulting in equations with a square root operator.
By coupling them to an electromagnetic field and expanding the square root (and
taking into account terms of quadratic order in the electromagnetic coupling
constant e), it is possible to calculate scattering matrix elements within the
framework of quantum electrodynamics, e.g. like those for Compton scattering or
for the scattering of two identical particles. This will be done here for the
scalar case. These results are then compared with the corresponding ones based
on the Klein-Gordon equation. A proposal of how to transfer these reflections
to the spin-1/2 case is also presented.
|
81f014d1-209a-4544-ba1e-50b7d277ccef | 81f014d1-209a-4544-ba1e-50b7d277ccef | 81f014d1-209a-4544-ba1e-50b7d277ccef | human | null | null | none | abstracts | Feedback from first radiation sources: H- photodissociation | null | During the epoch of reionization, the formation of radiation sources is
accompanied by the growth of a H- photodissociating flux. We estimate the
impact of this flux on the formation of molecular hydrogen and cooling in the
first galaxies, assuming different types of radiation sources (e.g. Pop II and
Pop III stars, miniquasars). We find that H- photodissociation reduces the
formation of H2 molecules by a factor of ~1+1000k_s*x/(f_esc*delta), where x is
the mean ionized fraction in the IGM, f_esc is the fraction of ionizing photons
that escape from their progenitor halos, delta is the local gas overdensity and
k_s is an order unity constant which depends on the type of radiation source.
By the time a significant fraction of the universe becomes ionized, H-
photodissociation may significantly reduce the H2 abundance and, with it, the
primordial star formation rate, delaying the progress of reionization.
|
c789f3d5-7fb6-45eb-bcf7-0b8bdc4bd1d0 | c789f3d5-7fb6-45eb-bcf7-0b8bdc4bd1d0 | c789f3d5-7fb6-45eb-bcf7-0b8bdc4bd1d0 | human | null | null | none | abstracts | The 3D +-J Ising model at the ferromagnetic transition line | null | We study the critical behavior of the three-dimensional $\pm J$ Ising model
[with a random-exchange probability $P(J_{xy}) = p \delta(J_{xy} - J) + (1-p)
\delta(J_{xy} + J)$] at the transition line between the paramagnetic and
ferromagnetic phase, which extends from $p=1$ to a multicritical (Nishimori)
point at $p=p_N\approx 0.767$. By a finite-size scaling analysis of Monte Carlo
simulations at various values of $p$ in the region $p_N<p<1$, we provide strong
numerical evidence that the critical behavior along the ferromagnetic
transition line belongs to the same universality class as the three-dimensional
randomly-dilute Ising model. We obtain the results $\nu=0.682(3)$ and
$\eta=0.036(2)$ for the critical exponents, which are consistent with the
estimates $\nu=0.683(2)$ and $\eta=0.036(1)$ at the transition of
randomly-dilute Ising models.
|
8964d6ec-35b7-4e4f-98ac-b6d7ec8535fb | 8964d6ec-35b7-4e4f-98ac-b6d7ec8535fb | 8964d6ec-35b7-4e4f-98ac-b6d7ec8535fb | human | null | null | none | abstracts | Star Formation in the Bok Globule CB54 | null | We present mid-infrared (10.4 \micron, 11.7 \micron, and 18.3 \micron)
imaging intended to locate and characterize the suspected protostellar
components within the Bok globule CB54. We detect and confirm the protostellar
status for the near-infrared source CB54YC1-II. The mid-infrared luminosity for
CB54YC1-II was found to be $L_{midir} \approx 8 L_\sun$, and we estimate a
central source mass of $M_* \approx 0.8 M_\sun$ (for a mass accretion rate of
${\dot M}=10^{-6} M_\sun yr^{-1}$). CB54 harbors another near-infrared source
(CB54YC1-I), which was not detected by our observations. The non-detection is
consistent with CB54YC1-I being a highly extinguished embedded young A or B
star or a background G or F giant. An alternative explanation for CB54YC1-I is
that the source is an embedded protostar viewed at an extremely high
inclination angle, and the near-infrared detections are not of the central
protostar, but of light scattered by the accretion disk into our line of sight.
In addition, we have discovered three new mid-infrared sources, which are
spatially coincident with the previously known dense core in CB54. The source
temperatures ($\sim100$K) and association of the mid-infrared sources with the
dense core suggests that these mid-infrared objects may be embedded class 0
protostars.
|
c6d52719-3681-4d3f-94ec-ed92400bdd99 | c6d52719-3681-4d3f-94ec-ed92400bdd99 | c6d52719-3681-4d3f-94ec-ed92400bdd99 | human | null | null | none | abstracts | Quantitative Resolution to some "Absolute Discrepancies" in Cancer
Theories: a View from Phage lambda Genetic Switch | null | Is it possible to understand cancer? Or more specifically, is it possible to
understand cancer from genetic side? There already many answers in literature.
The most optimistic one has claimed that it is mission-possible. Duesberg and
his colleagues reviewed the impressive amount of research results on cancer
accumulated over 100 years. It confirms the a general opinion that considering
all available experimental results and clinical observations there is no cancer
theory without major difficulties, including the prevailing gene-based cancer
theories. They have then listed 9 "absolute discrepancies" for such cancer
theory. In this letter the quantitative evidence against one of their major
reasons for dismissing mutation cancer theory, by both in vivo experiment and a
first principle computation, is explicitly pointed out.
|
541b8099-0112-419a-903e-fddbd2ba0651 | 541b8099-0112-419a-903e-fddbd2ba0651 | 541b8099-0112-419a-903e-fddbd2ba0651 | human | null | null | none | abstracts | Reduced phase space and toric variety coordinatizations of Delzant
spaces | null | In this note we describe the natural coordinatizations of a Delzant space
defined as a reduced phase space (symplectic geometry view-point) and give
explicit formulas for the coordinate transformations. For each fixed point of
the torus action on the Delzant polytope, we have a maximal coordinatization of
an open cell in the Delzant space which contains the fixed point. This cell is
equal to the domain of definition of one of the natural coordinatizations of
the Delzant space as a toric variety (complex algebraic geometry view-point),
and we give an explicit formula for the toric variety coordinates in terms of
the reduced phase space coordinates. We use considerations in the maximal
coordinate neighborhoods to give simple proofs of some of the basic facts about
the Delzant space, as a reduced phase space, and as a toric variety. These can
be viewed as a first application of the coordinatizations, and serve to make
the presentation more self-contained.
|
d3656e8d-97e2-4323-a696-4e1e2d514842 | d3656e8d-97e2-4323-a696-4e1e2d514842 | d3656e8d-97e2-4323-a696-4e1e2d514842 | human | null | null | none | abstracts | Measurement of B(D_S^+ --> ell^+ nu) and the Decay Constant f_D_{S^+} | null | We examine e+e- --> Ds- Ds*+ and Ds*- Ds+ interactions at 4170 MeV using the
CLEO-c detector in order to measure the decay constant fDs+. We use the Ds+ -->
l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+
--> pi+ nu. Analyzing both modes independently, we determine B(Ds+ --> mu+ nu)
= (0.594 +- 0.066 +- 0.031)%, and B(Ds+ --> tau+ nu) = (8.0 +- 1.3 +- 0.4)%. We
also analyze them simultaneously to find an effective value of B{eff}(Ds+ -->
mu+ nu) = (0.638 +- 0.059 +- 0.033)% and extract fDs = (274 +- 13 +- 7) MeV.
Combining with our previous determination of B(D+ -> mu+ nu), we also find the
ratio fDs/fD+ = 1.23 +- 0.11 +- 0.04. We compare to current theoretical
estimates. Finally, we find B(Ds+ --> e+ nu) < 1.3 x10^{-4} at 90% confidence
level.
|
bf2a6d59-32c5-42a0-851d-541a0dc7784c | bf2a6d59-32c5-42a0-851d-541a0dc7784c | bf2a6d59-32c5-42a0-851d-541a0dc7784c | human | null | null | none | abstracts | Broadening the Higgs Boson with Right-Handed Neutrinos and a Higher
Dimension Operator at the Electroweak Scale | null | The existence of certain TeV suppressed higher-dimension operators may open
up new decay channels for the Higgs boson to decay into lighter right-handed
neutrinos. These channels may dominate over all other channels if the Higgs
boson is light. For a Higgs boson mass larger than $2 m_W$ the new decays are
subdominant yet still of interest. The right-handed neutrinos have macroscopic
decay lengths and decay mostly into final states containing leptons and quarks.
A distinguishing collider signature of this scenario is a pair of displaced
vertices violating lepton number. A general operator analysis is performed
using the minimal flavor violation hypothesis to illustrate that these novel
decay processes can occur while remaining consistent with experimental
constraints on lepton number violating processes. In this context the question
of whether these new decay modes dominate is found to depend crucially on the
approximate flavor symmetries of the right-handed neutrinos.
|
63655021-9c63-450e-bac6-d148b50082d4 | 63655021-9c63-450e-bac6-d148b50082d4 | 63655021-9c63-450e-bac6-d148b50082d4 | human | null | null | none | abstracts | Multiple Unfoldings of Orbifold Singularities: Engineering Geometric
Analogies to Unification | null | Katz and Vafa showed how charged matter can arise geometrically by the
deformation of ADE-type orbifold singularities in type IIa, M-theory, and
F-theory compactifications. In this paper we use those same basic ingredients,
used there to geometrically engineer specific matter representations, here to
deform the compactification manifold itself in a way which naturally
compliments many features of unified model building. We realize this idea
explicitly by deforming a manifold engineered to give rise to an $SU_5$ grand
unified model into a one giving rise to the Standard Model. In this framework,
the relative local positions of the singularities giving rise to Standard Model
fields are specified in terms of the values of a small number of complex
structure moduli which deform the original manifold, greatly reducing the
arbitrariness of their relative positions.
|
fc039b38-9eb6-488a-bfd4-f51590c5572d | fc039b38-9eb6-488a-bfd4-f51590c5572d | fc039b38-9eb6-488a-bfd4-f51590c5572d | human | null | null | none | abstracts | Geometrically Engineering the Standard Model: Locally Unfolding Three
Families out of E8 | null | This paper extends and builds upon the results of an earlier paper, in which
we described how to use the tools of geometrical engineering to deform
geometrically-engineered grand unified models into ones with lower symmetry.
This top-down unfolding has the advantage that the relative positions of
singularities giving rise to the many `low energy' matter fields are related by
only a few parameters which deform the geometry of the unified model. And
because the relative positions of singularities are necessary to compute the
superpotential, for example, this is a framework in which the arbitrariness of
geometrically engineered models can be greatly reduced.
In our earlier paper, this picture was made concrete for the case of
deforming the representations of an SU(5) model into their Standard Model
content. In this paper we continue that discussion to show how a geometrically
engineered 16 of SO(10) can be unfolded into the Standard Model, and how the
three families of the Standard Model uniquely emerge from the unfolding of a
single, isolated E8 singularity.
|
e3fdba42-2b0d-4215-861d-d48229b2e0c8 | e3fdba42-2b0d-4215-861d-d48229b2e0c8 | e3fdba42-2b0d-4215-861d-d48229b2e0c8 | human | null | null | none | abstracts | Giant Planet Migration in Viscous Power-Law Discs | null | Many extra-solar planets discovered over the past decade are gas giants in
tight orbits around their host stars. Due to the difficulties of forming these
`hot Jupiters' in situ, they are generally assumed to have migrated to their
present orbits through interactions with their nascent discs. In this paper, we
present a systematic study of giant planet migration in power law discs. We
find that the planetary migration rate is proportional to the disc surface
density. This is inconsistent with the assumption that the migration rate is
simply the viscous drift speed of the disc. However, this result can be
obtained by balancing the angular momentum of the planet with the viscous
torque in the disc. We have verified that this result is not affected by
adjusting the resolution of the grid, the smoothing length used, or the time at
which the planet is released to migrate.
|
660d61a5-b544-4771-8038-098007040d52 | 660d61a5-b544-4771-8038-098007040d52 | 660d61a5-b544-4771-8038-098007040d52 | human | null | null | none | abstracts | Worldsheet Instantons and Torsion Curves, Part B: Mirror Symmetry | null | We apply mirror symmetry to the problem of counting holomorphic rational
curves in a Calabi-Yau threefold X with Z_3 x Z_3 Wilson lines. As we found in
Part A [hep-th/0703182], the integral homology group H_2(X,Z)=Z^3 + Z_3 + Z_3
contains torsion curves. Using the B-model on the mirror of X as well as its
covering spaces, we compute the instanton numbers. We observe that X is
self-mirror even at the quantum level. Using the self-mirror property, we
derive the complete prepotential on X, going beyond the results of Part A. In
particular, this yields the first example where the instanton number depends on
the torsion part of its homology class. Another consequence is that the
threefold X provides a non-toric example for the conjectured exchange of
torsion subgroups in mirror manifolds.
|
22e2239c-8c9c-40b9-af79-c8ad62d31601 | 22e2239c-8c9c-40b9-af79-c8ad62d31601 | 22e2239c-8c9c-40b9-af79-c8ad62d31601 | human | null | null | none | abstracts | Electromigrated nanoscale gaps for surface-enhanced Raman spectroscopy | null | Single-molecule detection with chemical specificity is a powerful and much
desired tool for biology, chemistry, physics, and sensing technologies.
Surface-enhanced spectroscopies enable single molecule studies, yet reliable
substrates of adequate sensitivity are in short supply. We present a simple,
scaleable substrate for surface-enhanced Raman spectroscopy (SERS)
incorporating nanometer-scale electromigrated gaps between extended electrodes.
Molecules in the nanogap active regions exhibit hallmarks of very high Raman
sensitivity, including blinking and spectral diffusion. Electrodynamic
simulations show plasmonic focusing, giving electromagnetic enhancements
approaching those needed for single-molecule SERS.
|
51acacb4-512e-4d76-aedd-5025af29e394 | 51acacb4-512e-4d76-aedd-5025af29e394 | 51acacb4-512e-4d76-aedd-5025af29e394 | human | null | null | none | abstracts | Dramatic Variability of X-ray Absorption Lines in the Black Hole
Candidate Cygnus X-1 | null | We report results from a 30 ks observation of Cygnus X-1 with the High Energy
Transmission Grating Spectrometer (HETGS) on board the {\em Chandra X-ray
Observatory}. Numerous absorption lines were detected in the HETGS spectrum.
The lines are associated with highly ionized Ne, Na, Mg, Al, Si, S, and Fe,
some of which have been seen in earlier HETGS observations. Surprisingly,
however, we discovered dramatic variability of the lines over the duration of
the present observation. For instance, the flux of the Ne X line at 12.14 \AA\
was about $5 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$ in the early part of
the observation but became subsequently undetectable, with a 99% upper limit of
$0.06 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$ on the flux of the line. This
implies that the line weakened by nearly two orders of magnitude on a timescale
of hours. The overall X-ray flux of the source did also vary during the
observation but only by 20--30%. For Cyg X-1, the absorption lines are
generally attributed to the absorption of X-rays by ionized stellar wind in the
binary system. Therefore, they may provide valuable diagnostics on the physical
condition of the wind. We discuss the implications of the results.
|
7f9389fc-5240-4ddf-b657-8f62bc1ddd70 | 7f9389fc-5240-4ddf-b657-8f62bc1ddd70 | 7f9389fc-5240-4ddf-b657-8f62bc1ddd70 | human | null | null | none | abstracts | An Extrasolar Planet Census with a Space-based Microlensing Survey | null | A space-based gravitational microlensing exoplanet survey will provide a
statistical census of exoplanets with masses down to 0.1 Earth-masses and
orbital separations ranging from 0.5AU to infinity. This includes analogs to
all the Solar System's planets except for Mercury, as well as most types of
planets predicted by planet formation theories. Such a survey will provide
results on the frequency of planets around all types of stars except those with
short lifetimes. Close-in planets with separations < 0.5 AU are invisible to a
space-based microlensing survey, but these can be found by Kepler. Other
methods, including ground-based microlensing, cannot approach the comprehensive
statistics on the mass and semi-major axis distribution of extrasolar planets
that a space-based microlensing survey will provide. The terrestrial planet
sensitivity of a ground-based microlensing survey is limited to the vicinity of
the Einstein radius at 2-3 AU, and space-based imaging is needed to identify
and determine the mass of the planetary host stars for the vast majority of
planets discovered by microlensing. Thus, a space-based microlensing survey is
likely to be the only way to gain a comprehensive understanding of the nature
of planetary systems, which is needed to understand planet formation and
habitability. The proposed Microlensing Planet Finder (MPF) mission is an
example of a space-based microlensing survey that can accomplish these
objectives with proven technology and a cost that fits comfortably under the
NASA Discovery Program cost cap.
|
ad167abf-46b8-4f74-bc94-8be4f97b9f36 | ad167abf-46b8-4f74-bc94-8be4f97b9f36 | ad167abf-46b8-4f74-bc94-8be4f97b9f36 | human | null | null | none | abstracts | USco1606-1935: An Unusually Wide Low-Mass Triple System? | null | We present photometric, astrometric, and spectroscopic observations of
USco160611.9-193532 AB, a candidate ultrawide (~1600 AU), low-mass (M_tot~0.4
M_sun) multiple system in the nearby OB association Upper Scorpius. We conclude
that both components are young, comoving members of the association; we also
present high-resolution observations which show that the primary is itself a
close binary system. If the Aab and B components are gravitationally bound, the
system would fall into the small class of young multiple systems which have
unusually wide separations as compared to field systems of similar mass.
However, we demonstrate that physical association can not be assumed purely on
probabilistic grounds for any individual candidate system in this separation
range. Analysis of the association's two-point correlation function shows that
there is a significant probability (25%) that at least one pair of low-mass
association members will be separated in projection by <15", so analysis of the
wide binary population in Upper Sco will require a systematic search for all
wide systems; the detection of another such pair would represent an excess at
the 98% confidence level.
|
256b1459-456a-44e2-b6dc-ff36f5d1fb1a | 256b1459-456a-44e2-b6dc-ff36f5d1fb1a | 256b1459-456a-44e2-b6dc-ff36f5d1fb1a | human | null | null | none | abstracts | Rotation Measures of Extragalactic Sources Behind the Southern Galactic
Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky
Way | null | We present new Faraday rotation measures (RMs) for 148 extragalactic radio
sources behind the southern Galactic plane (253o < l < 356o, |b| < 1.5o), and
use these data in combination with published data to probe the large-scale
structure of the Milky Way's magnetic field. We show that the magnitudes of
these RMs oscillate with longitude in a manner that correlates with the
locations of the Galactic spiral arms. The observed pattern in RMs requries the
presence of at least one large-scale magnetic reversal in the fourth Galactic
quadrant, located between the Sagittarius- Carina and Scutum-Crux spiral arms.
To quantitatively compare our measurements to other recent studies, we consider
all available extragalactic and pulsar RMs in the region we have surveyed, and
jointly fit these data to simple models in which the large-scale field follows
the spiral arms. In the best-fitting model, the magnetic field in the fourth
Galactic quadrant is directed clockwise in the Sagittarius-Carina spiral arm
(as viewed from the North Galactic pole), but is oriented counter- clockwise in
the Scutum-Crux arm. This contrasts with recent analyses of pulsar RMs alone,
in which the fourth-quadrant field was presumed to be directed
counter-clockwise in the Sagittarius- Carina arm. Also in contrast to recent
pulsar RM studies, our joint modeling of pulsar and extragalactic RMs
demonstrates that large numbers of large-scale magnetic field reversals are not
required to account for observations.
|
cccae260-c1a7-4878-9998-076579b2048c | cccae260-c1a7-4878-9998-076579b2048c | cccae260-c1a7-4878-9998-076579b2048c | human | null | null | none | abstracts | On iterated image size for point-symmetric relations | null | Let $\Gamma =(V,E)$ be a point-symmetric reflexive relation and let $v\in V$
such that
$|\Gamma (v)|$ is finite (and hence $|\Gamma (x)|$ is finite for all $x$, by
the transitive action of the group of automorphisms). Let $j\in \N$ be an
integer such that $\Gamma ^j(v)\cap \Gamma ^{-}(v)=\{v\}$. Our main result
states that
$$ |\Gamma ^{j} (v)|\ge | \Gamma ^{j-1} (v)| + |\Gamma (v)|-1.$$
As an application we have $ |\Gamma ^{j} (v)| \ge 1+(|\Gamma (v)|-1)j.$ The
last result confirms a recent conjecture of Seymour in the case of
vertex-symmetric graphs. Also it gives a short proof for the validity of the
Caccetta-H\"aggkvist conjecture for vertex-symmetric graphs and generalizes an
additive result of Shepherdson.
|
cb7fd534-8a53-4113-af55-5a19e6b5c839 | cb7fd534-8a53-4113-af55-5a19e6b5c839 | cb7fd534-8a53-4113-af55-5a19e6b5c839 | human | null | null | none | abstracts | Entanglement increase from local interactions with
not-completely-positive maps | null | Simple examples are constructed that show the entanglement of two qubits
being both increased and decreased by interactions on just one of them. One of
the two qubits interacts with a third qubit, a control, that is never entangled
or correlated with either of the two entangled qubits and is never entangled,
but becomes correlated, with the system of those two qubits. The two entangled
qubits do not interact, but their state can change from maximally entangled to
separable or from separable to maximally entangled. Similar changes for the two
qubits are made with a swap operation between one of the qubits and a control;
then there are compensating changes of entanglement that involve the control.
When the entanglement increases, the map that describes the change of the state
of the two entangled qubits is not completely positive. Combination of two
independent interactions that individually give exponential decay of the
entanglement can cause the entanglement to not decay exponentially but,
instead, go to zero at a finite time.
|
2e8d67d2-f6c2-4a99-b07d-4088b720544c | 2e8d67d2-f6c2-4a99-b07d-4088b720544c | 2e8d67d2-f6c2-4a99-b07d-4088b720544c | human | null | null | none | abstracts | Extended solar emission - an analysis of the EGRET data | null | The Sun was recently predicted to be an extended source of gamma-ray
emission, produced by inverse-Compton scattering of cosmic-ray electrons with
the solar radiation. The emission was predicted to contribute to the diffuse
extragalactic background even at large angular distances from the Sun. While
this emission is expected to be readily detectable in future by GLAST, the
situation for available EGRET data is more challenging. We present a detailed
study of the EGRET database, using a time dependent analysis, accounting for
the effect of the emission from 3C 279, the moon, and other sources, which
interfere with the solar signal. The technique has been tested on the moon
signal, with results consistent with previous work. We find clear evidence for
emission from the Sun and its vicinity. The observations are compared with our
model for the extended emission.
|
8e94e898-bade-412d-8cd4-e6d41cd2b8b0 | 8e94e898-bade-412d-8cd4-e6d41cd2b8b0 | 8e94e898-bade-412d-8cd4-e6d41cd2b8b0 | human | null | null | none | abstracts | Mass and Temperature of the TWA 7 Debris Disk | null | We present photometric detections of dust emission at 850 and 450 micron
around the pre-main sequence M1 dwarf TWA 7 using the SCUBA camera on the James
Clerk Maxwell Telescope. These data confirm the presence of a cold dust disk
around TWA 7, a member of the TW Hydrae Association. Based on the 850 micron
flux, we estimate the mass of the disk to be 18 lunar masses (0.2 Earth masses)
assuming a mass opacity of 1.7 cm^2/g with a temperature of 45 K. This makes
the TWA 7 disk (d=55 pc) an order of magnitude more massive than the disk
reported around AU Microscopii (GL 803), the closest (9.9 pc) debris disk
detected around an M dwarf. This is consistent with TWA 7 being slightly
younger than AU Mic. We find that the mid-IR and submillimeter data require the
disk to be comprised of dust at a range of temperatures. A model in which the
dust is at a single radius from the star, with a range of temperatures
according to grain size, is as effective at fitting the emission spectrum as a
model in which the dust is of uniform size, but has a range of temperatures
according to distance. We discuss this disk in the context of known disks in
the TW Hydrae Association and around low-mass stars; a comparison of masses of
disks in the TWA reveals no trend in mass or evolutionary state (gas-rich vs.
debris) as a function of spectral type.
|
77690e24-aa8c-4438-8ba3-ba3614785c6b | 77690e24-aa8c-4438-8ba3-ba3614785c6b | 77690e24-aa8c-4438-8ba3-ba3614785c6b | human | null | null | none | abstracts | Annealed importance sampling of dileucine peptide | null | Annealed importance sampling is a means to assign equilibrium weights to a
nonequilibrium sample that was generated by a simulated annealing protocol. The
weights may then be used to calculate equilibrium averages, and also serve as
an ``adiabatic signature'' of the chosen cooling schedule. In this paper we
demonstrate the method on the 50-atom dileucine peptide, showing that
equilibrium distributions are attained for manageable cooling schedules. For
this system, as naively implemented here, the method is modestly more efficient
than constant temperature simulation. However, the method is worth considering
whenever any simulated heating or cooling is performed (as is often done at the
beginning of a simulation project, or during an NMR structure calculation), as
it is simple to implement and requires minimal additional CPU expense.
Furthermore, the naive implementation presented here can be improved.
|
c00565d8-89f5-4f29-81e3-6ee7089c2a1f | c00565d8-89f5-4f29-81e3-6ee7089c2a1f | c00565d8-89f5-4f29-81e3-6ee7089c2a1f | human | null | null | none | abstracts | A General Nonlinear Fokker-Planck Equation and its Associated Entropy | null | A recently introduced nonlinear Fokker-Planck equation, derived directly from
a master equation, comes out as a very general tool to describe
phenomenologically systems presenting complex behavior, like anomalous
diffusion, in the presence of external forces. Such an equation is
characterized by a nonlinear diffusion term that may present, in general, two
distinct powers of the probability distribution. Herein, we calculate the
stationary-state distributions of this equation in some special cases, and
introduce associated classes of generalized entropies in order to satisfy the
H-theorem. Within this approach, the parameters associated with the transition
rates of the original master-equation are related to such generalized
entropies, and are shown to obey some restrictions. Some particular cases are
discussed.
|
b6161eff-ae90-49b8-ac79-7cf52a1d1c43 | b6161eff-ae90-49b8-ac79-7cf52a1d1c43 | b6161eff-ae90-49b8-ac79-7cf52a1d1c43 | human | null | null | none | abstracts | Modeling Accretion Disk X-ray Continuum of Black Hole Candidates | null | We critically examine issues associated with determining the fundamental
properties of the black hole and the surrounding accretion disk in an X-ray
binary based on modeling the disk X-ray continuum of the source. We base our
work mainly on two XMM-Newton observations of GX 339-4, because they provided
high-quality data at low energies (below 1 keV) which are critical for reliably
modeling the spectrum of the accretion disk. A key issue examined is the
determination of the so-called "color correction factor", which is often
empirically introduced to account for the deviation of the local disk spectrum
from a blackbody (due to electron scattering). This factor cannot be
pre-determined theoretically because it may vary with, e.g., mass accretion
rate, among a number of important factors. We follow up on an earlier
suggestion to estimate the color correction observationally by modeling the
disk spectrum with saturated Compton scattering. We show that the spectra can
be fitted well and the approach yields reasonable values for the color
correction factor. For comparison, we have also attempted to fit the spectra
with other models. We show that even the high-soft-state continuum (which is
dominated by the disk emission) cannot be satisfactorily fitted by
state-of-the-art disk models. We discuss the implication of the results.
|
0157689b-1e8a-45f8-babd-9a10c01c3955 | 0157689b-1e8a-45f8-babd-9a10c01c3955 | 0157689b-1e8a-45f8-babd-9a10c01c3955 | human | null | null | none | abstracts | Inapproximability of Maximum Weighted Edge Biclique and Its Applications | null | Given a bipartite graph $G = (V_1,V_2,E)$ where edges take on {\it both}
positive and negative weights from set $\mathcal{S}$, the {\it maximum weighted
edge biclique} problem, or $\mathcal{S}$-MWEB for short, asks to find a
bipartite subgraph whose sum of edge weights is maximized. This problem has
various applications in bioinformatics, machine learning and databases and its
(in)approximability remains open. In this paper, we show that for a wide range
of choices of $\mathcal{S}$, specifically when $| \frac{\min\mathcal{S}} {\max
\mathcal{S}} | \in \Omega(\eta^{\delta-1/2}) \cap O(\eta^{1/2-\delta})$ (where
$\eta = \max\{|V_1|, |V_2|\}$, and $\delta \in (0,1/2]$), no polynomial time
algorithm can approximate $\mathcal{S}$-MWEB within a factor of $n^{\epsilon}$
for some $\epsilon > 0$ unless $\mathsf{RP = NP}$. This hardness result gives
justification of the heuristic approaches adopted for various applied problems
in the aforementioned areas, and indicates that good approximation algorithms
are unlikely to exist. Specifically, we give two applications by showing that:
1) finding statistically significant biclusters in the SAMBA model, proposed in
\cite{Tan02} for the analysis of microarray data, is
$n^{\epsilon}$-inapproximable; and 2) no polynomial time algorithm exists for
the Minimum Description Length with Holes problem \cite{Bu05} unless
$\mathsf{RP=NP}$.
|
aa3e7902-d479-44dc-8d42-b212f63fd318 | aa3e7902-d479-44dc-8d42-b212f63fd318 | aa3e7902-d479-44dc-8d42-b212f63fd318 | human | null | null | none | abstracts | Density dependence of the symmetry energy and the nuclear equation of
state: A Dynamical and Statistical model perspective | null | The density dependence of the symmetry energy in the equation of state of
isospin asymmetric nuclear matter is of significant importance for studying the
structure of systems as diverse as the neutron-rich nuclei and the neutron
stars. A number of reactions using the dynamical and the statistical models of
multifragmentation, and the experimental isoscaling observable, is studied to
extract information on the density dependence of the symmetry energy. It is
observed that the dynamical and the statistical model calculations give
consistent results assuming the sequential decay effect in dynamical model to
be small. A comparison with several other independent studies is also made to
obtain important constraint on the form of the density dependence of the
symmetry energy. The comparison rules out an extremely " stiff " and " soft "
form of the density dependence of the symmetry energy with important
implications for astrophysical and nuclear physics studies.
|
3508b2cf-bfd8-4b70-a0ad-ce6da88beec5 | 3508b2cf-bfd8-4b70-a0ad-ce6da88beec5 | 3508b2cf-bfd8-4b70-a0ad-ce6da88beec5 | human | null | null | none | abstracts | Competitive nucleation and the Ostwald rule in a generalized Potts model
with multiple metastable phases | null | We introduce a simple nearest-neighbor spin model with multiple metastable
phases, the number and decay pathways of which are explicitly controlled by the
parameters of the system. With this model we can construct, for example, a
system which evolves through an arbitrarily long succession of metastable
phases. We also construct systems in which different phases may nucleate
competitively from a single initial phase. For such a system, we present a
general method to extract from numerical simulations the individual nucleation
rates of the nucleating phases. The results show that the Ostwald rule, which
predicts which phase will nucleate, must be modified probabilistically when the
new phases are almost equally stable. Finally, we show that the nucleation rate
of a phase depends, among other things, on the number of other phases
accessible from it.
|
a8a72224-d23e-4ed3-96cc-9cdb417b9301 | a8a72224-d23e-4ed3-96cc-9cdb417b9301 | a8a72224-d23e-4ed3-96cc-9cdb417b9301 | human | null | null | none | abstracts | Application of Ewald summations to long-range dispersion forces | null | We present results illustrating the effects of using explicit summation terms
for the $r^{-6}$ dispersion term on the interfacial properties of a
Lennard-Jones fluid and SPC/E water. For the Lennard-Jones fluid, we find that
the use of long-range summations, even with a short ``crossover radius,''
yields results that are consistent with simulations using large cutoff radii.
Simulations of SPC/E water demonstrate that the long-range dispersion forces
are of secondary importance to the Coulombic forces. In both cases, we find
that the ratio of box size $L_{\parallel}$ to crossover radius $r_{\rm
c}^{\mathbf k}$ plays an important role in determining the magnitude of the
long-range dispersion correction, although its effect is secondary when
Coulombic interactions are also present.
|
19f5462e-0d1e-44a9-b465-08e72546c2b5 | 19f5462e-0d1e-44a9-b465-08e72546c2b5 | 19f5462e-0d1e-44a9-b465-08e72546c2b5 | human | null | null | none | abstracts | Possible non-thermal nature of the soft-excess emission in the cluster
of galaxies Sersic 159-03 | null | We present an analysis of new Suzaku data and archival data from XMM-Newton
of the cluster of galaxies Sersic 159-03, which has a strong soft X-ray excess
emission component. The Suzaku observation confirms the presence of the soft
excess emission, but it does not confirm the presence of redshifted OVII lines
in the cluster. Radial profiles and 2D maps derived from XMM-Newton
observations show that the soft excess emission has a strong peak at the
position of the central cD galaxy and the maps do not show any significant
azimuthal variations. Although the soft excess emission can be fitted equally
well with both thermal and non-thermal models, its spatial distribution is
neither consistent with the models of intercluster warm-hot filaments, nor with
models of clumpy warm intracluster gas associated with infalling groups. Using
the data obtained by the XMM-Newton Reflection Grating Spectrometers we do not
confirm the presence of the warm gas in the cluster centre with the expected
properties assuming the soft excess is of thermal origin. The observed
properties of the soft excess emission are consistent with the non-thermal
interpretation. While the high density of relativistic electrons associated
with the peak of the soft emission in the cluster centre might have been
provided by an active galactic nucleus in the central cD galaxy, the underlying
population might have been accelerated in diffuse shocks.
|
9e6b6c98-0429-4e2c-8a84-98f19c889893 | 9e6b6c98-0429-4e2c-8a84-98f19c889893 | 9e6b6c98-0429-4e2c-8a84-98f19c889893 | human | null | null | none | abstracts | Geometric phase of an atom inside an adiabatic radio frequency potential | null | We investigate the geometric phase of an atom inside an adiabatic radio
frequency (rf) potential created from a static magnetic field (B-field) and a
time dependent rf field. The spatial motion of the atomic center of mass is
shown to give rise to a geometric phase, or Berry's phase, to the adiabatically
evolving atomic hyperfine spin along the local B-field. This phase is found to
depend on both the static B-field along the semi-classical trajectory of the
atomic center of mass and an ``effective magnetic field'' of the total B-field,
including the oscillating rf field. Specific calculations are provided for
several recent atom interferometry experiments and proposals utilizing
adiabatic rf potentials.
|
463cf7d9-45c9-4a32-819c-676dbfa2ef91 | 463cf7d9-45c9-4a32-819c-676dbfa2ef91 | 463cf7d9-45c9-4a32-819c-676dbfa2ef91 | human | null | null | none | abstracts | The Transition from the First Stars to the Second Stars in the Early
Universe | null | We observe a sharp transition from a singular, high-mass mode of star
formation, to a low-mass dominated mode, in numerical simulations, at a
metallicity of 10^-3 Zsolar. We incorporate a new method for including the
radiative cooling from metals into adaptive mesh-refinement hydrodynamic
simulations. Our results illustrate how metals, produced by the first stars,
led to a transition from the high-mass star formation mode of Pop III stars, to
the low-mass mode that dominates today. We ran hydrodynamic simulations with
cosmological initial conditions in the standard LambdaCDM model, with
metallicities, from zero to 10^-2 Zsolar, beginnning at redshift, z = 99. The
simulations were run until a dense core forms at the center of a 5 x 10^5
Msolar dark matter halo, at z ~ 18. Analysis of the central 1 Msolar core
reveals that the two simulations with the lowest metallicities, Z = 0 and 10^-4
Zsolar, contain one clump with 99% of the mass, while the two with
metallicities, Z = 10^-3 and 10^-2 Zsolar, each contain two clumps that share
most of the mass. The Z = 10^-3 Zsolar simulation also produced two low-mass
proto-stellar objects with masses between 10^-2 and 10^-1 Msolar. Gas with Z >=
10^-3 Zsolar is able to cool to the temperature of the CMB, which sets a lower
limit to the minimum fragmentation mass. This suggests that the second
generation stars produced a spectrum of lower mass stars, but were still more
massive on average than stars formed in the local universe.
|
25ffe99a-f770-4b8c-9e00-db18f61d6141 | 25ffe99a-f770-4b8c-9e00-db18f61d6141 | 25ffe99a-f770-4b8c-9e00-db18f61d6141 | human | null | null | none | abstracts | Super Star Cluster Velocity Dispersions and Virial Masses in the M82
Nuclear Starburst | null | We use high-resolution near-infrared spectroscopy from Keck Observatory to
measure the stellar velocity dispersions of 19 super star clusters (SSCs) in
the nuclear starburst of M82. The clusters have ages on the order of 10 Myr,
which is many times longer than the crossing times implied by their velocity
dispersions and radii. We therefore apply the Virial Theorem to derive the
kinematic mass for 15 of the SSCs. The SSCs have masses of 2 x 10^5 to 4 x 10^6
solar masses, with a total population mass of 1.4 x 10^7 solar masses.
Comparison of the loci of the young M82 SSCs and old Milky Way globular
clusters in a plot of radius versus velocity dispersion suggests that the SSCs
are a population of potential globular clusters. We present the mass function
for the SSCs, and find a power law fit with an index of gamma = -1.91 +/- 0.06.
This result is nearly identical to the mass function of young SSCs in the
Antennae galaxies.
|
d92350a4-a95e-4013-8141-b34194b6974d | d92350a4-a95e-4013-8141-b34194b6974d | d92350a4-a95e-4013-8141-b34194b6974d | human | null | null | none | abstracts | Implementation of holonomic quantum computation through engineering and
manipulating environment | null | We consider an atom-field coupled system, in which two pairs of four-level
atoms are respectively driven by laser fields and trapped in two distant
cavities that are connected by an optical fiber. First, we show that an
effective squeezing reservoir can be engineered under appropriate conditions.
Then, we show that a two-qubit geometric CPHASE gate between the atoms in the
two cavities can be implemented through adiabatically manipulating the
engineered reservoir along a closed loop. This scheme that combines engineering
environment with decoherence-free space and geometric phase quantum computation
together has the remarkable feature: a CPHASE gate with arbitrary phase shift
is implemented by simply changing the strength and relative phase of the
driving fields.
|
ddf750f9-7925-42e0-bc84-f38d6e825b0b | ddf750f9-7925-42e0-bc84-f38d6e825b0b | ddf750f9-7925-42e0-bc84-f38d6e825b0b | human | null | null | none | abstracts | Kinematic Decoupling of Globular Clusters with Extended
Horizontal-Branch | null | About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended
color distribution of stars in the horizontal-branch (HB) phase. This
phenomenon is now best understood as due to the presence of helium enhanced
second generation subpopulations, which has raised a possibility that these
peculiar GCs might have a unique origin. Here we show that these GCs with
extended HB are clearly distinct from other normal GCs in kinematics and mass.
The GCs with extended HB are more massive than normal GCs, and are dominated by
random motion with no correlation between kinematics and metallicity.
Surprisingly, however, when they are excluded, most normal GCs in the inner
halo show clear signs of dissipational collapse that apparently led to the
formation of the disk. Normal GCs in the outer halo share their kinematic
properties with the extended HB GCs, which is consistent with the accretion
origin. Our result further suggests heterogeneous origins of GCs, and we
anticipate this to be a starting point for more detailed investigations of
Milky Way formation, including early mergers, collapse, and later accretion.
|
1c0ecd7b-ee63-4a95-8efc-1517c1e808a9 | 1c0ecd7b-ee63-4a95-8efc-1517c1e808a9 | 1c0ecd7b-ee63-4a95-8efc-1517c1e808a9 | human | null | null | none | abstracts | Scalar potential model progress | null | Because observations of galaxies and clusters have been found inconsistent
with General Relativity (GR), the focus of effort in developing a Scalar
Potential Model (SPM) has been on the examination of galaxies and clusters. The
SPM has been found to be consistent with cluster cellular structure, the flow
of IGM from spiral galaxies to elliptical galaxies, intergalactic redshift
without an expanding universe, discrete redshift, rotation curve (RC) data
without dark matter, asymmetric RCs, galaxy central mass, galaxy central
velocity dispersion, and the Pioneer Anomaly. In addition, the SPM suggests a
model of past expansion, past contraction, and current expansion of the
universe. GR corresponds to the SPM in the limit in which the effect of the
Sources and Sinks approximate a flat scalar potential field such as between
clusters and on the solar system scale, which is small relative to the distance
to a Source.
|
ec393f52-3fe7-4a8a-96b5-dbf6fc57604e | ec393f52-3fe7-4a8a-96b5-dbf6fc57604e | ec393f52-3fe7-4a8a-96b5-dbf6fc57604e | human | null | null | none | abstracts | Teleparallel Version of the Stationary Axisymmetric Solutions and their
Energy Contents | null | This work contains the teleparallel version of the stationary axisymmetric
solutions. We obtain the tetrad and the torsion fields representing these
solutions. The tensor, vector and axial-vector parts of the torsion tensor are
evaluated. It is found that the axial-vector has component only along $\rho$
and $z$ directions. The three possibilities of the axial vector depending on
the metric function $B$ are discussed. The vector related with spin has also
been evaluated and the corresponding extra Hamiltonian is furnished. Further,
we use the teleparallel version of M$\ddot{o}$ller prescription to find the
energy-momentum distribution of the solutions. It is interesting to note that
(for $\lambda=1$) energy and momentum densities in teleparallel theory are
equal to the corresponding quantities in GR plus an additional quantity in
each, which may become equal under certain conditions. Finally, we discuss the
two special cases of the stationary axisymmetric solutions.
|
c1600623-ac01-4770-9044-b4820cefbb74 | c1600623-ac01-4770-9044-b4820cefbb74 | c1600623-ac01-4770-9044-b4820cefbb74 | human | null | null | none | abstracts | Weighted percolation on directed networks | null | We present an analysis of the percolation transition for general node removal
strategies valid for locally tree-like directed networks. On the basis of
heuristic arguments we predict that, if the probability of removing node $i$ is
$p_i$, the network disintegrates if $p_i$ is such that the largest eigenvalue
of the matrix with entries $A_{ij}(1-p_i)$ is less than 1, where $A$ is the
adjacency matrix of the network. The knowledge or applicability of a Markov
network model is not required by our theory, thus making it applicable to
situations not covered by previous works. We test our predicted percolation
criterion against numerical results for different networks and node removal
strategies.
|
68e5ad0d-c00f-4804-ade9-a2677ec6a9ed | 68e5ad0d-c00f-4804-ade9-a2677ec6a9ed | 68e5ad0d-c00f-4804-ade9-a2677ec6a9ed | human | null | null | none | abstracts | Refuting the Pseudo Attack on the REESSE1+ Cryptosystem | null | We illustrate through example 1 and 2 that the condition at theorem 1 in [8]
dissatisfies necessity, and the converse proposition of fact 1.1 in [8] does
not hold, namely the condition Z/M - L/Ak < 1/(2 Ak^2) is not sufficient for
f(i) + f(j) = f(k). Illuminate through an analysis and ex.3 that there is a
logic error during deduction of fact 1.2, which causes each of fact 1.2, 1.3, 4
to be invalid. Demonstrate through ex.4 and 5 that each or the combination of
qu+1 > qu * D at fact 4 and table 1 at fact 2.2 is not sufficient for f(i) +
f(j) = f(k), property 1, 2, 3, 4, 5 each are invalid, and alg.1 based on fact 4
and alg.2 based on table 1 are disordered and wrong logically. Further,
manifest through a repeated experiment and ex.5 that the data at table 2 is
falsified, and the example in [8] is woven elaborately. We explain why Cx = Ax
* W^f(x) (% M) is changed to Cx = (Ax * W^f(x))^d (% M) in REESSE1+ v2.1. To
the signature fraud, we point out that [8] misunderstands the existence of T^-1
and Q^-1 % (M-1), and forging of Q can be easily avoided through moving H.
Therefore, the conclusion of [8] that REESSE1+ is not secure at all (which
connotes that [8] can extract a related private key from any public key in
REESSE1+) is fully incorrect, and as long as the parameter Omega is fitly
selected, REESSE1+ with Cx = Ax * W^f(x) (% M) is secure.
|
c93a4fe4-5c88-4344-b89f-9bc10caeafb9 | c93a4fe4-5c88-4344-b89f-9bc10caeafb9 | c93a4fe4-5c88-4344-b89f-9bc10caeafb9 | human | null | null | none | abstracts | Phase structure of a surface model on dynamically triangulated spheres
with elastic skeletons | null | We find three distinct phases; a tubular phase, a planar phase, and the
spherical phase, in a triangulated fluid surface model. It is also found that
these phases are separated by discontinuous transitions. The fluid surface
model is investigated within the framework of the conventional curvature model
by using the canonical Monte Carlo simulations with dynamical triangulations.
The mechanical strength of the surface is given only by skeletons, and no
two-dimensional bending energy is assumed in the Hamiltonian. The skeletons are
composed of elastic linear-chains and rigid junctions and form a
compartmentalized structure on the surface, and for this reason the vertices of
triangles can diffuse freely only inside the compartments. As a consequence, an
inhomogeneous structure is introduced in the model; the surface strength inside
the compartments is different from the surface strength on the compartments.
However, the rotational symmetry is not influenced by the elastic skeletons;
there is no specific direction on the surface. In addition to the three phases
mentioned above, a collapsed phase is expected to exist in the low bending
rigidity regime that was not studied here. The inhomogeneous structure and the
fluidity of vertices are considered to be the origin of such variety of phases.
|
888dbdb1-3163-4b1b-b2af-f47721dd2a56 | 888dbdb1-3163-4b1b-b2af-f47721dd2a56 | 888dbdb1-3163-4b1b-b2af-f47721dd2a56 | human | null | null | none | abstracts | Vortex Dynamics at the Initial Stage of Resistive Transition in
Superconductors with Fractal Cluster Structure | null | The effect of fractal normal-phase clusters on vortex dynamics in a
percolative superconductor is considered. The superconductor contains
percolative superconducting cluster carrying a transport current and clusters
of a normal phase, acting as pinning centers. A prototype of such a structure
is YBCO film, containing clusters of columnar defects, as well as the BSCCO/Ag
sheathed tape, which is of practical interest for wire fabrication. Transition
of the superconductor into a resistive state corresponds to the percolation
transition from a pinned vortex state to a resistive state when the vortices
are free to move. The dependencies of the free vortex density on the fractal
dimension of the cluster boundary as well as the resistance on the transport
current are obtained. It is revealed that a mixed state of the vortex glass
type is realized in the superconducting system involved. The current-voltage
characteristics of superconductors containing fractal clusters are obtained and
their features are studied.
|
26886937-cef0-48d0-9970-b1c1eab6b806 | 26886937-cef0-48d0-9970-b1c1eab6b806 | 26886937-cef0-48d0-9970-b1c1eab6b806 | human | null | null | none | abstracts | Fusion process studied with preequilibrium giant dipole resonance in
time dependent Hartree-Fock theory | null | The equilibration of macroscopic degrees of freedom during the fusion of
heavy nuclei, like the charge and the shape, are studied in the Time-Dependent
Hartree-Fock theory. The pre-equilibrium Giant Dipole Resonance (GDR) is used
to probe the fusion path. It is shown that such isovector collective state is
excited in N/Z asymmetric fusion and to a less extent in mass asymmetric
systems. The characteristics of this GDR are governed by the structure of the
fused system in its preequilibrium phase, like its deformation, rotation and
vibration. In particular, we show that a lowering of the pre-equilibrium GDR
energy is expected as compared to the statistical one. Revisiting experimental
data, we extract an evidence of this lowering for the first time. We also
quantify the fusion-evaporation enhancement due to gamma-ray emission from the
pre-equilibrium GDR. This cooling mechanism along the fusion path may be
suitable to synthesize in the future super heavy elements using radioactive
beams with strong N/Z asymmetries in the entrance channel.
|
0229252d-f0cd-4f07-aab3-9054acfb6e15 | 0229252d-f0cd-4f07-aab3-9054acfb6e15 | 0229252d-f0cd-4f07-aab3-9054acfb6e15 | human | null | null | none | abstracts | A unified analysis of the reactor neutrino program towards the
measurement of the theta_13 mixing angle | null | We present in this article a detailed quantitative discussion of the
measurement of the leptonic mixing angle theta_13 through currently scheduled
reactor neutrino oscillation experiments. We thus focus on Double Chooz (Phase
I & II), Daya Bay (Phase I & II) and RENO experiments. We perform a unified
analysis, including systematics, backgrounds and accurate experimental setup in
each case. Each identified systematic error and background impact has been
assessed on experimental setups following published data when available and
extrapolating from Double Chooz acquired knowledge otherwise. After reviewing
the experiments, we present a new analysis of their sensitivities to sin^2(2
theta_13) and study the impact of the different systematics based on the pulls
approach. Through this generic statistical analysis we discuss the advantages
and drawbacks of each experimental setup.
|
0e13c7a5-b69b-427d-90dc-3d9d23e6787e | 0e13c7a5-b69b-427d-90dc-3d9d23e6787e | 0e13c7a5-b69b-427d-90dc-3d9d23e6787e | human | null | null | none | abstracts | Optimal Routing for Decode-and-Forward based Cooperation in Wireless
Networks | null | We investigate cooperative wireless relay networks in which the nodes can
help each other in data transmission. We study different coding strategies in
the single-source single-destination network with many relay nodes. Given the
myriad of ways in which nodes can cooperate, there is a natural routing
problem, i.e., determining an ordered set of nodes to relay the data from the
source to the destination. We find that for a given route, the
decode-and-forward strategy, which is an information theoretic cooperative
coding strategy, achieves rates significantly higher than that achievable by
the usual multi-hop coding strategy, which is a point-to-point non-cooperative
coding strategy. We construct an algorithm to find an optimal route (in terms
of rate maximizing) for the decode-and-forward strategy. Since the algorithm
runs in factorial time in the worst case, we propose a heuristic algorithm that
runs in polynomial time. The heuristic algorithm outputs an optimal route when
the nodes transmit independent codewords. We implement these coding strategies
using practical low density parity check codes to compare the performance of
the strategies on different routes.
|
0b03c368-af9d-4db9-8fbe-db1dedbb4df4 | 0b03c368-af9d-4db9-8fbe-db1dedbb4df4 | 0b03c368-af9d-4db9-8fbe-db1dedbb4df4 | human | null | null | none | abstracts | E_6 and the bipartite entanglement of three qutrits | null | Recent investigations have established an analogy between the entropy of
four-dimensional supersymmetric black holes in string theory and entanglement
in quantum information theory. Examples include: (1) N=2 STU black holes and
the tripartite entanglement of three qubits (2-state systems), where the common
symmetry is [SL(2)]^3 and (2) N=8 black holes and the tripartite entanglement
of seven qubits where the common symmetry is E_7 which contains [SL(2)]^7. Here
we present another example: N=8 black holes (or black strings) in five
dimensions and the bipartite entanglement of three qutrits (3-state systems),
where the common symmetry is E_6 which contains [SL(3)]^3. Both the black hole
(or black string) entropy and the entanglement measure are provided by the
Cartan cubic E_6 invariant. Similar analogies exist for ``magic'' N=2
supergravity black holes in both four and five dimensions.
|
c282539b-03c5-47d4-936f-d64eb388b4b2 | c282539b-03c5-47d4-936f-d64eb388b4b2 | c282539b-03c5-47d4-936f-d64eb388b4b2 | human | null | null | none | abstracts | Stable oscillations of a predator-prey probabilistic cellular automaton:
a mean-field approach | null | We analyze a probabilistic cellular automaton describing the dynamics of
coexistence of a predator-prey system. The individuals of each species are
localized over the sites of a lattice and the local stochastic updating rules
are inspired on the processes of the Lotka-Volterra model. Two levels of
mean-field approximations are set up. The simple approximation is equivalent to
an extended patch model, a simple metapopulation model with patches colonized
by prey, patches colonized by predators and empty patches. This approximation
is capable of describing the limited available space for species occupancy. The
pair approximation is moreover able to describe two types of coexistence of
prey and predators: one where population densities are constant in time and
another displaying self-sustained time-oscillations of the population
densities. The oscillations are associated with limit cycles and arise through
a Hopf bifurcation. They are stable against changes in the initial conditions
and, in this sense, they differ from the Lotka-Volterra cycles which depend on
initial conditions. In this respect, the present model is biologically more
realistic than the Lotka-Volterra model.
|
97851709-b6a7-4897-a7d4-4459c9c947d7 | 97851709-b6a7-4897-a7d4-4459c9c947d7 | 97851709-b6a7-4897-a7d4-4459c9c947d7 | human | null | null | none | abstracts | SDSS J233325.92+152222.1 and the evolution of intermediate polars | null | Intermediate polars (IPs) are cataclysmic variables which contain magnetic
white dwarfs with a rotational period shorter than the binary orbital period.
Evolutionary theory predicts that IPs with long orbital periods evolve through
the 2-3 hour period gap, but it is very uncertain what the properties of the
resulting objects are. Whilst a relatively large number of long-period IPs are
known, very few of these have short orbital periods. We present phase-resolved
spectroscopy and photometry of SDSS J233325.92+152222.1 and classify it as the
IP with the shortest known orbital period (83.12 +/- 0.09 min), which contains
a white dwarf with a relatively long spin period (41.66 +/- 0.13 min). We
estimate the white dwarf's magnetic moment to be mu(WD) \approx 2 x 10^33 G
cm^3, which is not only similar to three of the other four confirmed
short-period IPs but also to those of many of the long-period IPs. We suggest
that long-period IPs conserve their magnetic moment as they evolve towards
shorter orbital periods. Therefore the dominant population of long-period IPs,
which have white dwarf spin periods roughly ten times shorter than their
orbital periods, will likely end up as short-period IPs like SDSS J2333, with
spin periods a large fraction of their orbital periods.
|
6e9f606b-d996-4c23-9aa3-b09d9a2569d2 | 6e9f606b-d996-4c23-9aa3-b09d9a2569d2 | 6e9f606b-d996-4c23-9aa3-b09d9a2569d2 | human | null | null | none | abstracts | Complexity Considerations, cSAT Lower Bound | null | This article discusses completeness of Boolean Algebra as First Order Theory
in Goedel's meaning. If Theory is complete then any possible transformation is
equivalent to some transformation using axioms, predicates etc. defined for
this theory. If formula is to be proved (or disproved) then it has to be
reduced to axioms. If every transformation is deducible then also optimal
transformation is deducible. If every transformation is exponential then
optimal one is too, what allows to define lower bound for discussed problem to
be exponential (outside P). Then we show algorithm for NDTM solving the same
problem in O(n^c) (so problem is in NP), what proves that P \neq NP.
Article proves also that result of relativisation of P=NP question and oracle
shown by Baker-Gill-Solovay distinguish between deterministic and
non-deterministic calculation models. If there exists oracle A for which
P^A=NP^A then A consists of infinite number of algorithms, DTMs, axioms and
predicates, or like NDTM infinite number of simultaneous states.
|
0447a2d2-756c-41e7-a6c7-f7ac67351378 | 0447a2d2-756c-41e7-a6c7-f7ac67351378 | 0447a2d2-756c-41e7-a6c7-f7ac67351378 | human | null | null | none | abstracts | Using decomposed household food acquisitions as inputs of a Kinetic
Dietary Exposure Model | null | Foods naturally contain a number of contaminants that may have different and
long term toxic effects. This paper introduces a novel approach for the
assessment of such chronic food risk that integrates the pharmacokinetic
properties of a given contaminant. The estimation of such a Kinetic Dietary
Exposure Model (KDEM) should be based on long term consumption data which, for
the moment, can only be provided by Household Budget Surveys such as the
SECODIP panel in France. A semi parametric model is proposed to decompose a
series of household quantities into individual quantities which are then used
as inputs of the KDEM. As an illustration, the risk assessment related to the
presence of methyl mercury in seafood is revisited using this novel approach.
|
a93f01d3-8ca1-4eaa-abfc-3e240e2d3cb8 | a93f01d3-8ca1-4eaa-abfc-3e240e2d3cb8 | a93f01d3-8ca1-4eaa-abfc-3e240e2d3cb8 | human | null | null | none | abstracts | Fractionally charged excitations on frustrated lattices | null | Systems of strongly correlated fermions on certain geometrically frustrated
lattices at particular filling factors support excitations with fractional
charges $\pm e/2$. We calculate quantum mechanical ground states, low--lying
excitations and spectral functions of finite lattices by means of numerical
diagonalization. The ground state of the most thoroughfully studied case, the
criss-crossed checkerboard lattice, is degenerate and shows long--range order.
Static fractional charges are confined by a weak linear force, most probably
leading to bound states of large spatial extent. Consequently, the
quasi-particle weight is reduced, which reflects the internal dynamics of the
fractionally charged excitations. By using an additional parameter, we
fine--tune the system to a special point at which fractional charges are
manifestly deconfined--the so--called Rokhsar--Kivelson point. For a deeper
understanding of the low--energy physics of these models and for numerical
advantages, several conserved quantum numbers are identified.
|
1fd214d2-e35a-4bd8-83f3-425f30944e50 | 1fd214d2-e35a-4bd8-83f3-425f30944e50 | 1fd214d2-e35a-4bd8-83f3-425f30944e50 | human | null | null | none | abstracts | Many-to-One Throughput Capacity of IEEE 802.11 Multi-hop Wireless
Networks | null | This paper investigates the many-to-one throughput capacity (and by symmetry,
one-to-many throughput capacity) of IEEE 802.11 multi-hop networks. It has
generally been assumed in prior studies that the many-to-one throughput
capacity is upper-bounded by the link capacity L. Throughput capacity L is not
achievable under 802.11. This paper introduces the notion of "canonical
networks", which is a class of regularly-structured networks whose capacities
can be analyzed more easily than unstructured networks. We show that the
throughput capacity of canonical networks under 802.11 has an analytical upper
bound of 3L/4 when the source nodes are two or more hops away from the sink;
and simulated throughputs of 0.690L (0.740L) when the source nodes are many
hops away. We conjecture that 3L/4 is also the upper bound for general
networks. When all links have equal length, 2L/3 can be shown to be the upper
bound for general networks. Our simulations show that 802.11 networks with
random topologies operated with AODV routing can only achieve throughputs far
below the upper bounds. Fortunately, by properly selecting routes near the
gateway (or by properly positioning the relay nodes leading to the gateway) to
fashion after the structure of canonical networks, the throughput can be
improved significantly by more than 150%. Indeed, in a dense network, it is
worthwhile to deactivate some of the relay nodes near the sink judiciously.
|
066f3c90-e9b7-442d-acac-8aaae1cdbb83 | 066f3c90-e9b7-442d-acac-8aaae1cdbb83 | 066f3c90-e9b7-442d-acac-8aaae1cdbb83 | human | null | null | none | abstracts | Scanning Tunneling Spectroscopy in the Superconducting State and Vortex
Cores of the beta-pyrochlore KOs2O6 | null | We performed the first scanning tunneling spectroscopy measurements on the
pyrochlore superconductor KOs2O6 (Tc = 9.6 K) in both zero magnetic field and
the vortex state at several temperatures above 1.95 K. This material presents
atomically flat surfaces, yielding spatially homogeneous spectra which reveal
fully-gapped superconductivity with a gap anisotropy of 30%. Measurements
performed at fields of 2 and 6 T display a hexagonal Abrikosov flux line
lattice. From the shape of the vortex cores, we extract a coherence length of
31-40 {\AA}, in agreement with the value derived from the upper critical field
Hc2. We observe a reduction in size of the vortex cores (and hence the
coherence length) with increasing field which is consistent with the
unexpectedly high and unsaturated upper critical field reported.
|
8c43b50d-5a16-4f17-88ea-0056e54bc14a | 8c43b50d-5a16-4f17-88ea-0056e54bc14a | 8c43b50d-5a16-4f17-88ea-0056e54bc14a | human | null | null | none | abstracts | Non-resonant and Resonant X-ray Scattering Studies on Multiferroic
TbMn2O5 | null | Comprehensive x-ray scattering studies, including resonant scattering at Mn
L-edge, Tb L- and M-edges, were performed on single crystals of TbMn2O5. X-ray
intensities were observed at a forbidden Bragg position in the ferroelectric
phases, in addition to the lattice and the magnetic modulation peaks.
Temperature dependences of their intensities and the relation between the
modulation wave vectors provide direct evidences of exchange striction induced
ferroelectricity. Resonant x-ray scattering results demonstrate the presence of
multiple magnetic orders by exhibiting their different temperature dependences.
The commensurate-to-incommensurate phase transition around 24 K is attributed
to discommensuration through phase slipping of the magnetic orders in spin
frustrated geometries. We proposed that the low temperature incommensurate
phase consists of the commensurate magnetic domains separated by anti-phase
domain walls which reduce spontaneous polarizations abruptly at the transition.
|
1dd6bc1e-fd15-479c-a865-774953e6c660 | 1dd6bc1e-fd15-479c-a865-774953e6c660 | 1dd6bc1e-fd15-479c-a865-774953e6c660 | human | null | null | none | abstracts | Self-diffusion and Interdiffusion in Al80Ni20 Melts: Simulation and
Experiment | null | A combination of experimental techniques and molecular dynamics (MD) computer
simulation is used to investigate the diffusion dynamics in Al80Ni20 melts.
Experimentally, the self-diffusion coefficient of Ni is measured by the
long-capillary (LC) method and by quasielastic neutron scattering. The LC
method yields also the interdiffusion coefficient. Whereas the experiments were
done in the normal liquid state, the simulations provided the determination of
both self-diffusion and interdiffusion constants in the undercooled regime as
well. The simulation results show good agreement with the experimental data. In
the temperature range 3000 K >= T >= 715 K, the interdiffusion coefficient is
larger than the self-diffusion constants. Furthermore the simulation shows that
this difference becomes larger in the undercooled regime. This result can be
refered to a relatively strong temperature dependence of the thermodynamic
factor \Phi, which describes the thermodynamic driving force for
interdiffusion. The simulations also indicate that the Darken equation is a
good approximation, even in the undercooled regime. This implies that dynamic
cross correlations play a minor role for the temperature range under
consideration.
|
d233b5c7-6fb9-4397-95f8-43c55dae5272 | d233b5c7-6fb9-4397-95f8-43c55dae5272 | d233b5c7-6fb9-4397-95f8-43c55dae5272 | human | null | null | none | abstracts | The Formation of Globular Cluster Systems in Massive Elliptical
Galaxies: Globular Cluster Multimodality from Radial Variation of Stellar
Populations | null | The most massive elliptical galaxies show a prominent multi-modality in their
globular cluster system color distributions. Understanding the mechanisms which
lead to multiple globular cluster sub-populations is essential for a complete
picture of massive galaxy formation. By assuming that globular cluster
formation traces the total star formation and taking into account the radial
variations in the composite stellar populations predicted by the Pipino &
Matteucci (2004) multi-zone photo-chemical evolution code, we compute the
distribution of globular cluster properties as a function of galactocentric
radius. We compare our results to the spectroscopic measurements of globular
clusters in nearby early-type galaxies by Puzia et al. (2006) and show that the
observed multi-modality in globular cluster systems of massive ellipticals can
be, at least partly, ascribed to the radial variation in the mix of stellar
populations. Our model predicts the presence of a super-metal-rich population
of globular clusters in the most massive elliptical galaxies, which is in very
good agreement with the spectroscopic observations. Furthermore, we investigate
the impact of other non-linear mechanisms that shape the metallicity
distribution of globular cluster systems, in particular the role of
merger-induced globular cluster formation and a non-linear color-metallicity
transformation, and discuss their influence in the context of our model
(abridged)
|
21ef549d-e9b7-471c-80e2-660a8540eb19 | 21ef549d-e9b7-471c-80e2-660a8540eb19 | 21ef549d-e9b7-471c-80e2-660a8540eb19 | human | null | null | none | abstracts | Binaries, microquasars and GLAST | null | Radio and X-ray observations of the relativistic jets of microquasars show
evidence for the acceleration of particles to very high energies. Signatures of
non-thermal processes occurring closer in to the compact object can also be
found. In addition, three binaries are now established emitters of high (> 100
MeV) and/or very high (> 100GeV) energy gamma-rays. High-energy emission can
originate from a microquasar jet (accretion-powered) or from a shocked pulsar
wind (rotation-powered). I discuss the impact GLAST will have in the very near
future on studies of such binaries. GLAST is expected to shed new light on the
link between accretion and ejection in microquasars and to enable to probe
pulsar winds on small scales in rotation-powered binaries.
|
6d905097-e72d-4c31-809d-b582d5a3fca0 | 6d905097-e72d-4c31-809d-b582d5a3fca0 | 6d905097-e72d-4c31-809d-b582d5a3fca0 | human | null | null | none | abstracts | Linearisation of finite abelian subgroups of the Cremona group of the
plane | null | This article gives the proof of results announced in [J. Blanc, Finite
Abelian subgroups of the Cremona group of the plane, C.R. Acad. Sci. Paris,
S\'er. I 344 (2007), 21-26.] and some description of automorphisms of rational
surfaces.
Given a finite Abelian subgroup of the Cremona group of the plane, we provide
a way to decide whether it is birationally conjugate to a group of
automorphisms of a minimal surface.
In particular, we prove that a finite cyclic group of birational
transformations of the plane is linearisable if and only if none of its
non-trivial elements fix a curve of positive genus. For finite Abelian groups,
there exists only one surprising exception, a group isomorphic to Z/2ZxZ/4Z,
whose non-trivial elements do not fix a curve of positive genus but which is
not conjugate to a group of automorphisms of a minimal rational surface.
We also give some descriptions of automorphisms (not necessarily of finite
order) of del Pezzo surfaces and conic bundles.
|
5320eeb5-f651-47aa-9c47-bb9e51867717 | 5320eeb5-f651-47aa-9c47-bb9e51867717 | 5320eeb5-f651-47aa-9c47-bb9e51867717 | human | null | null | none | abstracts | Oriented growth of pentacene films on vacuum-deposited
polytetrafluoroethylene layers aligned by rubbing technique | null | We investigated structure and morphology of PTFE layers deposited by vacuum
process in dependence on deposition parameters: deposition rate, deposition
temperature, electron activation energy and activation current. Pentacene (PnC)
layers deposited on top of those PTFE films are used as a tool to demonstrate
the orienting ability of the PTFE layers. The molecular structure of the PTFE
films was investigated by use of infrared spectroscopy. By means of
ellipsometry, values of refractive index between 1.33 and 1.36 have been
obtained for PTFE films in dependence on deposition conditions. Using the cold
friction technique orienting PTFE layers with unidirectional grooves are
obtained. On top of these PTFE films oriented PnC layers were grown. The
obtained order depends both on the PTFE layer thickness and on PnC growth
temperature.
|
3365b311-1c7e-437d-82c0-23934ce06129 | 3365b311-1c7e-437d-82c0-23934ce06129 | 3365b311-1c7e-437d-82c0-23934ce06129 | human | null | null | none | abstracts | On the Achievable Rate Regions for Interference Channels with Degraded
Message Sets | null | The interference channel with degraded message sets (IC-DMS) refers to a
communication model in which two senders attempt to communicate with their
respective receivers simultaneously through a common medium, and one of the
senders has complete and a priori (non-causal) knowledge about the message
being transmitted by the other. A coding scheme that collectively has
advantages of cooperative coding, collaborative coding, and dirty paper coding,
is developed for such a channel. With resorting to this coding scheme,
achievable rate regions of the IC-DMS in both discrete memoryless and Gaussian
cases are derived, which, in general, include several previously known rate
regions. Numerical examples for the Gaussian case demonstrate that in the
high-interference-gain regime, the derived achievable rate regions offer
considerable improvements over these existing results.
|
c2acca16-411a-4b1c-816f-7fd1f3408227 | c2acca16-411a-4b1c-816f-7fd1f3408227 | c2acca16-411a-4b1c-816f-7fd1f3408227 | human | null | null | none | abstracts | Hilbert functions of points on Schubert varieties in Orthogonal
Grassmannians | null | A solution is given to the following problem: how to compute the
multiplicity, or more generally the Hilbert function, at a point on a Schubert
variety in an orthogonal Grassmannian. Standard monomial theory is applied to
translate the problem from geometry to combinatorics. The solution of the
resulting combinatorial problem forms the bulk of the paper. This approach has
been followed earlier to solve the same problem for the Grassmannian and the
symplectic Grassmannian.
As an application, we present an interpretation of the multiplicity as the
number of non-intersecting lattice paths of a certain kind.
Taking the Schubert variety to be of a special kind and the point to be the
"identity coset," our problem specializes to a problem about Pfaffian ideals
treatments of which by different methods exist in the literature. Also
available in the literature is a geometric solution when the point is a
"generic singularity."
|
bf43db0b-1261-498f-8487-a7f861171306 | bf43db0b-1261-498f-8487-a7f861171306 | bf43db0b-1261-498f-8487-a7f861171306 | human | null | null | none | abstracts | Crossover behavior in fluids with Coulomb interactions | null | According to extensive experimental findings, the Ginzburg temperature
$t_{G}$ for ionic fluids differs substantially from that of nonionic fluids
[Schr\"oer W., Weig\"{a}rtner H. 2004 {\it Pure Appl. Chem.} {\bf 76} 19]. A
theoretical investigation of this outcome is proposed here by a mean field
analysis of the interplay of short and long range interactions on the value of
$t_{G}$. We consider a quite general continuous charge-asymmetric model made of
charged hard spheres with additional short-range interactions (without
electrostatic interactions the model belongs to the same universality class as
the 3D Ising model). The effective Landau-Ginzburg Hamiltonian of the full
system near its gas-liquid critical point is derived from which the Ginzburg
temperature is calculated as a function of the ionicity. The results obtained
in this way for $t_{G}$ are in good qualitative and sufficient quantitative
agreement with available experimental data.
|
1665dc55-92af-4831-878d-4c752ecb1383 | 1665dc55-92af-4831-878d-4c752ecb1383 | 1665dc55-92af-4831-878d-4c752ecb1383 | human | null | null | none | abstracts | The old open clusters Berkeley 32 and King 11 | null | We have obtained CCD BVI imaging of the old open clusters Berkeley 32 and
King 11. Using the synthetic colour-magnitude diagram method with three
different sets of stellar evolution models of various metallicities, with and
without overshooting, we have determined their age, distance, reddening, and
indicative metallicity, as well as distance from the Galactic centre and height
from the Galactic plane. The best parameters derived for Berkeley 32 are:
subsolar metallicity (Z=0.008 represents the best choice, Z=0.006 or 0.01 are
more marginally acceptable), age = 5.0-5.5 Gyr (models with overshooting;
without overshooting the age is 4.2-4.4 Gyr with poorer agreement),
(m-M)_0=12.4-12.6, E(B-V)=0.12-0.18 (with the lower value being more probable
because it corresponds to the best metallicity), Rgc ~ 10.7-11 kpc, and |Z| ~
231-254 pc. The best parameters for King 11 are: Z=0.01, age=3.5-4.75 Gyr,
(m-M)_0=11.67-11.75, E(B-V)=1.03-1.06, Rgc ~ 9.2-10 kpc, and |Z| ~ 253-387 pc.
|
1af57ad6-3bbd-46a4-9848-c8d831855108 | 1af57ad6-3bbd-46a4-9848-c8d831855108 | 1af57ad6-3bbd-46a4-9848-c8d831855108 | human | null | null | none | abstracts | The Genetic Programming Collaboration Network and its Communities | null | Useful information about scientific collaboration structures and patterns can
be inferred from computer databases of published papers. The genetic
programming bibliography is the most complete reference of papers on GP\@. In
addition to locating publications, it contains coauthor and coeditor
relationships from which a more complete picture of the field emerges. We treat
these relationships as undirected small world graphs whose study reveals the
community structure of the GP collaborative social network. Automatic analysis
discovers new communities and highlights new facets of them. The investigation
reveals many similarities between GP and coauthorship networks in other
scientific fields but also some subtle differences such as a smaller central
network component and a high clustering.
|
95cc48a0-d7b8-4fe8-a641-bc1385ca46e0 | 95cc48a0-d7b8-4fe8-a641-bc1385ca46e0 | 95cc48a0-d7b8-4fe8-a641-bc1385ca46e0 | human | null | null | none | abstracts | Spontaneous Lorentz Violation: Non-Abelian Gauge Fields as
Pseudo-Goldstone Vector Bosons | null | We argue that non-Abelian gauge fields can be treated as the pseudo-Goldstone
vector bosons caused by spontaneous Lorentz invariance violation (SLIV). To
this end, the SLIV which evolves in a general Yang-Mills type theory with the
nonlinear vector field constraint $Tr(% \boldsymbol{A}_{\mu
}\boldsymbol{A}^{\mu})=\pm M^{2}$ ($M$ is a proposed SLIV scale) imposed is
considered in detail. With an internal symmetry group $G$ having $D$ generators
not only the pure Lorentz symmetry SO(1,3), but the larger accidental symmetry
$SO(D,3D)$ of the SLIV constraint in itself appears to be spontaneously broken
as well. As a result, while the pure Lorentz violation still generates only one
genuine Goldstone vector boson, the accompanying pseudo-Goldstone vector bosons
related to the $SO(D,3D)$ breaking also come into play in the final arrangement
of the entire Goldstone vector field multiplet. Remarkably, they remain
strictly massless, being protected by gauge invariance of the Yang-Mills theory
involved. We show that, although this theory contains a plethora of Lorentz and
$CPT$ violating couplings, they do not lead to physical SLIV effects which turn
out to be strictly cancelled in all the lowest order processes considered.
However, the physical Lorentz violation could appear if the internal gauge
invariance were slightly broken at very small distances influenced by gravity.
For the SLIV scale comparable with the Planck one the Lorentz violation could
become directly observable at low energies.
|
aa5faca1-1bfa-46bc-ba4e-bb50ff06af70 | aa5faca1-1bfa-46bc-ba4e-bb50ff06af70 | aa5faca1-1bfa-46bc-ba4e-bb50ff06af70 | human | null | null | none | abstracts | In-medium effects on particle production in heavy ion collisions | null | The effect of possible in-medium modifications of nucleon-nucleon ($NN$)
cross sections on particle production is investigated in heavy ion collisions
($HIC$) at intermediate energies. In particular, using a fully covariant
relativistic transport approach, we see that the density dependence of the {\it
inelastic} cross sections appreciably affects the pion and kaon yields and
their rapidity distributions. However, the $(\pi^{-}/\pi^{+})$- and
$(K^{0}/K^{+})$-ratios depend only moderately on the in-medium behavior of the
inelastic cross sections. This is particularly true for kaon yield ratios,
since kaons are more uniformly produced in high density regions. Kaon
potentials are also suitably evaluated in two schemes, a chiral perturbative
approach and an effective meson-quark coupling method, with consistent results
showing a similar repulsive contribution for $K^{+}$ and $K^{0}$. As a
consequence we expect rather reduced effects on the yield ratios. We conclude
that particle ratios appear to be robust observables for probing the nuclear
equation of state ($EoS$) at high baryon density and, particularly, its
isovector sector.
|
9769aef3-6c6e-44da-bac4-9f5f5ea4a4ee | 9769aef3-6c6e-44da-bac4-9f5f5ea4a4ee | 9769aef3-6c6e-44da-bac4-9f5f5ea4a4ee | human | null | null | none | abstracts | Effective conservation of energy and momentum algorithm using switching
potentials suitable for molecular dynamics simulation of thermodynamical
systems | null | During a crossover via a switching mechanism from one 2-body potential to
another as might be applied in modeling (chemical) reactions in the vicinity of
bond formation, energy violations would occur due to finite step size which
determines the trajectory of the particles relative to the potential
interactions of the unbonded state by numerical (e.g. Verlet) integration. This
problem is overcome by an algorithm which preserves the coordinates of the
system for each move, but corrects for energy discrepancies by ensuring both
energy and momentum conservation in the dynamics. The algorithm is tested for a
hysteresis loop reaction model with an without the implementation of the
algorithm. The tests involve checking the rate of energy flow out of the MD
simulation box; in the equilibrium state, no net rate of flows within
experimental error should be observed. The temperature and pressure of the box
should also be invariant within the range of fluctuation of these quantities.
It is demonstrated that the algorithm satisfies these criteria.
|
04a3ab2a-e5c7-4cd5-bf3c-c6a684b516a0 | 04a3ab2a-e5c7-4cd5-bf3c-c6a684b516a0 | 04a3ab2a-e5c7-4cd5-bf3c-c6a684b516a0 | human | null | null | none | abstracts | Signal for space-time noncommutativity: the Z -> gamma gamma decay in
the renormalizable gauge sector of the theta-expanded NCSM | null | We propose the Z -> gamma gamma decay, a process strictly forbidden in the
standard model, as a signal suitable for the search of noncommutativity of
coordinates at very short distances. We compute the Z -> gamma gamma partial
widthin the framework of the recently proposed renormalizable gauge sector of
the noncommutative standard model. The one-loop renormalizability is obtained
for the model containing the usual six representations of matter fields of the
first generation. Even more, the noncommutative part is finite or free of
divergences, showing that perhaps new interaction symmetry exists in the
noncommutative gauge sector of the model. Discovery of such symmetry would be
of tremendous importance in further search for the violation of the Lorentz
invariance at very high energies. Experimental possibilities of Z -> gamma
gamma decay are analyzed and a firm bound to the scale of the noncommutativity
parameter is set around 1 TeV.
|
e44aed55-9a28-46b5-b510-8782f65c2ae4 | e44aed55-9a28-46b5-b510-8782f65c2ae4 | e44aed55-9a28-46b5-b510-8782f65c2ae4 | human | null | null | none | abstracts | New Organic thermally stable materials for optoelectronics devices - A
linear spectroscopy study | null | Thermally stable polymers have attracted a lot of interest due to their
potential use as the active component in electronic, optical and optoelectronic
applications, such as light-emitting diodes, light emitting electrochemical
cells, photodiodes, photovoltaic cells, field effect transistors, optocouplers
and optically pumped lasers in solution and solid state.We report results of
investigations into the use of thermal treatment of poly(p-phenylene vinylene)
(PPV) films grown on a variety of substrates (quartz and glass). Film
thickness, morphology and structural properties were investigated by a range of
techniques in particular: atomic force microscope - AFM, DEKTAK method,
Ellipsometry and UV-VIS spectroscopy.
|
0d28cf03-b3fb-4422-8a17-5336b33558c8 | 0d28cf03-b3fb-4422-8a17-5336b33558c8 | 0d28cf03-b3fb-4422-8a17-5336b33558c8 | human | null | null | none | abstracts | On the potential of transit surveys in star clusters: Impact of
correlated noise and radial velocity follow-up | null | We present an extension of the formalism recently proposed by Pepper & Gaudi
to evaluate the yield of transit surveys in homogeneous stellar systems,
incorporating the impact of correlated noise on transit time-scales on the
detectability of transits, and simultaneously incorporating the magnitude
limits imposed by the need for radial velocity follow-up of transit candidates.
New expressions are derived for the different contributions to the noise budget
on transit time-scales and the least-squares detection statistic for box-shaped
transits, and their behaviour as a function of stellar mass is re-examined.
Correlated noise that is constant with apparent stellar magnitude implies a
steep decrease in detection probability at the high mass end which, when
considered jointly with the radial velocity requirements, can severely limit
the potential of otherwise promising surveys in star clusters. However, we find
that small-aperture, wide field surveys may detect hot Neptunes whose radial
velocity signal can be measured with present-day instrumentation in very nearby
(<100 pc) clusters.
|
00378b3f-b639-4abe-8639-f00f41a89dd3 | 00378b3f-b639-4abe-8639-f00f41a89dd3 | 00378b3f-b639-4abe-8639-f00f41a89dd3 | human | null | null | none | abstracts | Neutron-Capture Elements in the Double-Enhanced Star HE 1305-0007: a New
s- and r-Process Paradigm | null | The star HE 1305-0007 is a metal-poor double-enhanced star with metallicity
[Fe/H] $=-2.0$, which is just at the upper limit of the metallicity for the
observed double-enhanced stars. Using a parametric model, we find that almost
all s-elements were made in a single neutron exposure. This star should be a
member of a post-common-envelope binary. After the s-process material has
experienced only one neutron exposure in the nucleosynthesis region and is
dredged-up to its envelope, the AGB evolution is terminated by the onset of
common-envelope evolution. Based on the high radial-velocity of HE 1305-0007,
we speculate that the star could be a runaway star from a binary system, in
which the AIC event has occurred and produced the r-process elements.
|
1e1e54a9-2250-4ba4-acea-cf0162353e4d | 1e1e54a9-2250-4ba4-acea-cf0162353e4d | 1e1e54a9-2250-4ba4-acea-cf0162353e4d | human | null | null | none | abstracts | 3D photospheric velocity field of a Supergranular cell | null | We investigate the plasma flow properties inside a Supergranular (SG) cell,
in particular its interaction with small scale magnetic field structures. The
SG cell has been identified using the magnetic network (CaII wing brightness)
as proxy, applying the Two-Level Structure Tracking (TST) to high spatial,
spectral and temporal resolution observations obtained by IBIS. The full 3D
velocity vector field for the SG has been reconstructed at two different
photospheric heights. In order to strengthen our findings, we also computed the
mean radial flow of the SG by means of cork tracing. We also studied the
behaviour of the horizontal and Line of Sight plasma flow cospatial with
cluster of bright CaII structures of magnetic origin to better understand the
interaction between photospheric convection and small scale magnetic features.
The SG cell we investigated seems to be organized with an almost radial flow
from its centre to the border. The large scale divergence structure is probably
created by a compact region of constant up-flow close to the cell centre. On
the edge of the SG, isolated regions of strong convergent flow are nearby or
cospatial with extended clusters of bright CaII wing features forming the knots
of the magnetic network.
|
1ced5f1a-3cb2-4187-af0f-b44899715ac3 | 1ced5f1a-3cb2-4187-af0f-b44899715ac3 | 1ced5f1a-3cb2-4187-af0f-b44899715ac3 | human | null | null | none | abstracts | Substructures in WINGS clusters | null | We search for and characterize substructures in the projected distribution of
galaxies observed in the wide field CCD images of the 77 nearby clusters of the
WIde-field Nearby Galaxy-cluster Survey (WINGS). This sample is complete in
X-ray flux in the redshift range 0.04<z<0.07. We search for substructures in
WINGS clusters with DEDICA, an adaptive-kernel procedure. We test the procedure
on Monte-Carlo simulations of the observed frames and determine the reliability
for the detected structures. DEDICA identifies at least one reliable structure
in the field of 55 clusters. 40 of these clusters have a total of 69
substructures at the same redshift of the cluster (redshift estimates of
substructures are from color-magnitude diagrams). The fraction of clusters with
subclusters (73%) is higher than in most studies. The presence of subclusters
affects the relative luminosities of the brightest cluster galaxies (BCGs).
Down to L ~ 10^11.2 L_Sun, our observed differential distribution of subcluster
luminosities is consistent with the theoretical prediction of the differential
mass function of substructures in cosmological simulations.
|
6ec4ac2f-88fa-453f-ada0-d2924f490e12 | 6ec4ac2f-88fa-453f-ada0-d2924f490e12 | 6ec4ac2f-88fa-453f-ada0-d2924f490e12 | human | null | null | none | abstracts | Ising-like dynamics and frozen states in systems of ultrafine magnetic
particles | null | We use Monte-Carlo simulations to study aging phenomena and the occurence of
spinglass phases in systems of single-domain ferromagnetic nanoparticles under
the combined influence of dipolar interaction and anisotropy energy, for
different combinations of positional and orientational disorder. We find that
the magnetic moments oriente themselves preferably parallel to their anisotropy
axes and changes of the total magnetization are solely achieved by 180 degree
flips of the magnetic moments, as in Ising systems. Since the dipolar
interaction favorizes the formation of antiparallel chain-like structures,
antiparallel chain-like patterns are frozen in at low temperatures, leading to
aging phenomena characteristic for spin-glasses. Contrary to the intuition,
these aging effects are more pronounced in ordered than in disordered
structures.
|
9cdaf251-3e54-4230-b4f7-fcfec2c01eee | 9cdaf251-3e54-4230-b4f7-fcfec2c01eee | 9cdaf251-3e54-4230-b4f7-fcfec2c01eee | human | null | null | none | abstracts | Continuous interfaces with disorder: Even strong pinning is too weak in
2 dimensions | null | We consider statistical mechanics models of continuous height effective
interfaces in the presence of a delta-pinning at height zero. There is a
detailed mathematical understanding of the depinning transition in 2 dimensions
without disorder. Then the variance of the interface height w.r.t. the Gibbs
measure stays bounded uniformly in the volume for any positive pinning force
and diverges like the logarithm of the pinning force when it tends to zero.
How does the presence of a quenched disorder term in the Hamiltonian modify
this transition? We show that an arbitarily weak random field term is enough to
beat an arbitrarily strong delta-pinning in 2 dimensions and will cause
delocalization. The proof is based on a rigorous lower bound for the overlap
between local magnetizations and random fields in finite volume. In 2
dimensions it implies growth faster than the volume which is a contradiction to
localization. We also derive a simple complementary inequality which shows that
in higher dimensions the fraction of pinned sites converges to one when the
pinning force tends to infinity.
|
f4b56fb9-271f-4508-ae9a-0b39651b7418 | f4b56fb9-271f-4508-ae9a-0b39651b7418 | f4b56fb9-271f-4508-ae9a-0b39651b7418 | human | null | null | none | abstracts | On the KK-theory of strongly self-absorbing C*-algebras | null | Let $\Dh$ and $A$ be unital and separable $C^{*}$-algebras; let $\Dh$ be
strongly self-absorbing. It is known that any two unital $^*$-homomorphisms
from $\Dh$ to $A \otimes \Dh$ are approximately unitarily equivalent. We show
that, if $\Dh$ is also $K_{1}$-injective, they are even asymptotically
unitarily equivalent. This in particular implies that any unital endomorphism
of $\Dh$ is asymptotically inner. Moreover, the space of automorphisms of $\Dh$
is compactly-contractible (in the point-norm topology) in the sense that for
any compact Hausdorff space $X$, the set of homotopy classes $[X,\Aut(\Dh)]$
reduces to a point. The respective statement holds for the space of unital
endomorphisms of $\Dh$. As an application, we give a description of the
Kasparov group $KK(\Dh, A\ot \Dh)$ in terms of $^*$-homomorphisms and
asymptotic unitary equivalence. Along the way, we show that the Kasparov group
$KK(\Dh, A\ot \Dh)$ is isomorphic to $K_0(A\ot \Dh)$.
|
d6c48aca-f9f4-4111-8ec4-9c50f2621384 | d6c48aca-f9f4-4111-8ec4-9c50f2621384 | d6c48aca-f9f4-4111-8ec4-9c50f2621384 | human | null | null | none | abstracts | Dust Formation and Survival in Supernova Ejecta | null | The presence of dust at high redshift requires efficient condensation of
grains in SN ejecta, in accordance with current theoretical models. Yet,
observations of the few well studied SNe and SN remnants imply condensation
efficiencies which are about two orders of magnitude smaller. Motivated by this
tension, we have (i) revisited the model of Todini & Ferrara (2001) for dust
formation in the ejecta of core collapse SNe and (ii) followed, for the first
time, the evolution of newly condensed grains from the time of formation to
their survival - through the passage of the reverse shock - in the SN remnant.
We find that 0.1 - 0.6 M_sun of dust form in the ejecta of 12 - 40 M_sun
stellar progenitors. Depending on the density of the surrounding ISM, between
2-20% of the initial dust mass survives the passage of the reverse shock, on
time-scales of about 4-8 x 10^4 yr from the stellar explosion. Sputtering by
the hot gas induces a shift of the dust size distribution towards smaller
grains. The resulting dust extinction curve shows a good agreement with that
derived by observations of a reddened QSO at z =6.2. Stochastic heating of
small grains leads to a wide distribution of dust temperatures. This supports
the idea that large amounts (~ 0.1 M_sun) of cold dust (T ~ 40K) can be present
in SN remnants, without being in conflict with the observed IR emission.
|
3b202abd-fa9f-4f97-b7bb-062d273111d1 | 3b202abd-fa9f-4f97-b7bb-062d273111d1 | 3b202abd-fa9f-4f97-b7bb-062d273111d1 | human | null | null | none | abstracts | Preferential interaction coefficient for nucleic acids and other
cylindrical poly-ions | null | The thermodynamics of nucleic acid processes is heavily affected by the
electric double-layer of micro-ions around the polyions. We focus here on the
Coulombic contribution to the salt-polyelectrolyte preferential interaction
(Donnan) coefficient and we report extremely accurate analytical expressions
valid in the range of low salt concentration (when polyion radius is smaller
than the Debye length). The analysis is performed at Poisson-Boltzmann level,
in cylindrical geometry, with emphasis on highly charged poly-ions (beyond
``counter-ion condensation''). The results hold for any electrolyte of the form
$z_-$:$z_+$. We also obtain a remarkably accurate expression for the electric
potential in the vicinity of the poly-ion.
|
638ebd4d-6e94-45fa-a6b3-645f880f8c15 | 638ebd4d-6e94-45fa-a6b3-645f880f8c15 | 638ebd4d-6e94-45fa-a6b3-645f880f8c15 | human | null | null | none | abstracts | Analysis of the real estate market in Las Vegas: Bubble, seasonal
patterns, and prediction of the CSW indexes | null | We analyze 27 house price indexes of Las Vegas from Jun. 1983 to Mar. 2005,
corresponding to 27 different zip codes. These analyses confirm the existence
of a real-estate bubble, defined as a price acceleration faster than
exponential, which is found however to be confined to a rather limited time
interval in the recent past from approximately 2003 to mid-2004 and has
progressively transformed into a more normal growth rate comparable to
pre-bubble levels in 2005. There has been no bubble till 2002 except for a
medium-sized surge in 1990. In addition, we have identified a strong yearly
periodicity which provides a good potential for fine-tuned prediction from
month to month. A monthly monitoring using a model that we have developed could
confirm, by testing the intra-year structure, if indeed the market has returned
to ``normal'' or if more turbulence is expected ahead. We predict the evolution
of the indexes one year ahead, which is validated with new data up to Sep.
2006. The present analysis demonstrates the existence of very significant
variations at the local scale, in the sense that the bubble in Las Vegas seems
to have preceded the more global USA bubble and has ended approximately two
years earlier (mid 2004 for Las Vegas compared with mid-2006 for the whole of
the USA).
|
c05422b8-3106-4437-9c76-cb277c63e364 | c05422b8-3106-4437-9c76-cb277c63e364 | c05422b8-3106-4437-9c76-cb277c63e364 | human | null | null | none | abstracts | Quantum criticality and disorder in the antiferromagnetic critical point
of NiS$_{2}$ pyrite | null | A quantum critical point (QCP) between the antiferromagnetic and the
paramagnetic phases was realized by applying a hydrostatic pressure of ~ 7 GPa
on single crystals of NiS_{2} pyrite with a low residual resistivity, rho_{0},
of 0.5 mu-Omega-cm. We found that the critical behavior of the resistivity,
rho, in this clean system contrasts sharply with those observed in its
disordered analogue, NiS_{2-x}Se_{x} solid-solution, demonstrating the
unexpectedly drastic effect of disorder on the quantum criticality. Over a
whole paramagnetic region investigated up to P = 9 GPa, a crossover
temperature, defined as the onset of T^{2} dependence of rho, an indication of
Fermi liquid, was suppressed to a substantially low temperature T sim 2 K and,
instead, a non Fermi liquid behavior of rho, T^{3/2}-dependence, robustly
showed up.
|
e222b5ea-2f3f-486a-a95c-4e10915aff68 | e222b5ea-2f3f-486a-a95c-4e10915aff68 | e222b5ea-2f3f-486a-a95c-4e10915aff68 | human | null | null | none | abstracts | Local-field effects in radiatively broadened magneto-dielectric media:
negative refraction and absorption reduction | null | We give a microscopic derivation of the Clausius-Mossotti relations for a
homogeneous and isotropic magneto-dielectric medium consisting of radiatively
broadened atomic oscillators. To this end the diagram series of electromagnetic
propagators is calculated exactly for an infinite bi-cubic lattice of
dielectric and magnetic dipoles for a lattice constant small compared to the
resonance wavelength $\lambda$. Modifications of transition frequencies and
linewidth of the elementary oscillators are taken into account in a
selfconsistent way by a proper incorporation of the singular self-interaction
terms. We show that in radiatively broadened media sufficiently close to the
free-space resonance the real part of the index of refraction approaches the
value -2 in the limit of $\rho \lambda^3 \gg 1$, where $\rho$ is the number
density of scatterers. Since at the same time the imaginary part vanishes as
$1/\rho$ local field effects can have important consequences for realizing
low-loss negative index materials.
|
e3ba627c-b10e-4cae-a2e1-125d34d79f9f | e3ba627c-b10e-4cae-a2e1-125d34d79f9f | e3ba627c-b10e-4cae-a2e1-125d34d79f9f | human | null | null | none | abstracts | About curvature, conformal metrics and warped products | null | We consider the curvature of a family of warped products of two
pseduo-Riemannian manifolds $(B,g_B)$ and $(F,g_F)$ furnished with metrics of
the form $c^{2}g_B \oplus w^2 g_F$ and, in particular, of the type $w^{2
\mu}g_B \oplus w^2 g_F$, where $c, w \colon B \to (0,\infty)$ are smooth
functions and $\mu$ is a real parameter. We obtain suitable expressions for the
Ricci tensor and scalar curvature of such products that allow us to establish
results about the existence of Einstein or constant scalar curvature structures
in these categories. If $(B,g_B)$ is Riemannian, the latter question involves
nonlinear elliptic partial differential equations with concave-convex
nonlinearities and singular partial differential equations of the
Lichnerowicz-York type among others.
|
b796e0ba-3b6c-4b96-abeb-0cc4ba929f9b | b796e0ba-3b6c-4b96-abeb-0cc4ba929f9b | b796e0ba-3b6c-4b96-abeb-0cc4ba929f9b | human | null | null | none | abstracts | Investigation of Colour Reconnection in WW Events with the DELPHI
detector at LEP-2 | null | In the reaction e+e- -> WW -> (q_1 qbar_2)(q_3 qbar_4) the usual
hadronization models treat the colour singlets q_1 qbar_2 and q_3 qbar_4 coming
from two W bosons independently. However, since the final state partons may
coexist in space and time, cross-talk between the two evolving hadronic systems
may be possible during fragmentation through soft gluon exchange. This effect
is known as Colour Reconnection. In this article the results of the
investigation of Colour Reconnection effects in fully hadronic decays of W
pairs in DELPHI at LEP are presented. Two complementary analyses were
performed, studying the particle flow between jets and W mass estimators, with
negligible correlation between them, and the results were combined and compared
to models. In the framework of the SK-I model, the value for its kappa
parameter most compatible with the data was found to be: kappa_{SK-I} =
2.2^{+2.5}_{-1.3} corresponding to the probability of reconnection P_{reco} to
be in the range 0.31 < P_{reco} < 0.68 at 68% confidence level with its best
value at 0.52.
|
db6ea24e-81e8-4200-82f1-f7358365c649 | db6ea24e-81e8-4200-82f1-f7358365c649 | db6ea24e-81e8-4200-82f1-f7358365c649 | human | null | null | none | abstracts | Evolutionary Neural Gas (ENG): A Model of Self Organizing Network from
Input Categorization | null | Despite their claimed biological plausibility, most self organizing networks
have strict topological constraints and consequently they cannot take into
account a wide range of external stimuli. Furthermore their evolution is
conditioned by deterministic laws which often are not correlated with the
structural parameters and the global status of the network, as it should happen
in a real biological system. In nature the environmental inputs are noise
affected and fuzzy. Which thing sets the problem to investigate the possibility
of emergent behaviour in a not strictly constrained net and subjected to
different inputs. It is here presented a new model of Evolutionary Neural Gas
(ENG) with any topological constraints, trained by probabilistic laws depending
on the local distortion errors and the network dimension. The network is
considered as a population of nodes that coexist in an ecosystem sharing local
and global resources. Those particular features allow the network to quickly
adapt to the environment, according to its dimensions. The ENG model analysis
shows that the net evolves as a scale-free graph, and justifies in a deeply
physical sense- the term gas here used.
|
2ef14f64-3667-445f-b447-93706de32a7e | 2ef14f64-3667-445f-b447-93706de32a7e | 2ef14f64-3667-445f-b447-93706de32a7e | human | null | null | none | abstracts | D-\bar D mixing and rare D decays in the Littlest Higgs model with
non-unitarity matrix | null | We study the $D-\bar D$ mixing and rare D decays in the Littlest Higgs model.
As the new weak singlet quark with the electric charge of 2/3 is introduced to
cancel the quadratic divergence induced by the top-quark, the standard unitary
$3\times 3$ Cabibbo-Kobayashi-Maskawa matrix is extended to a non-unitary
$4\times 3$ matrix in the quark charged currents and Z-mediated flavor changing
neutral currents are generated at tree level. In this model, we show that the
$D-\bar D$ mixing parameter can be as large as the current experimental value
and the decay branching ratio (BR) of $D\to X_u \ga$ is small but its direct CP
asymmetry could be $O(10%)$. In addition, we find that the BRs of $D\to X_u
\ell^{+} \ell^{-}$, $D\to X_u\nu \bar \nu$ and $D\to \mu^{+} \mu^{-}$ could be
enhanced to be $O(10^{-9})$, $O(10^{-8})$ and $O(10^{-9})$, respectively.
|
bca25963-8fc1-403f-a61b-2dd1ba3c40d5 | bca25963-8fc1-403f-a61b-2dd1ba3c40d5 | bca25963-8fc1-403f-a61b-2dd1ba3c40d5 | human | null | null | none | abstracts | Reconciling the X(3872) with the near-threshold enhancement in the
D^0\bar{D}^{*0} final state | null | We investigate the enhancement in the D^0\bar{D}^0\pi^0 final state with the
mass M=3875.2\pm 0.7^{+0.3}_{-1.6}\pm 0.8 MeV found recently by the Belle
Collaboration in the B\to K D^0\bar{D}^0\pi^0 decay and test the possibility
that this is yet another manifestation of the well-established resonance
X(3872). We perform a combined Flatte analysis of the data for the
D^0\bar{D}^0\pi^0 mode, and for the \pi^+\pi^- J/\psi mode of the X(3872). Only
if the X(3872) is a virtual state in the D^0\bar{D}^{*0} channel, the data on
the new enhancement comply with those on the X(3872). In our fits, the mass
distribution in the D^0\bar{D}^{*0} mode exhibits a peak at 2-3 MeV above the
D^0\bar{D}^{*0} threshold, with a distinctive non-Breit-Wigner shape.
|
a8389e9d-7626-4dac-8de5-6bf4d8e4c315 | a8389e9d-7626-4dac-8de5-6bf4d8e4c315 | a8389e9d-7626-4dac-8de5-6bf4d8e4c315 | human | null | null | none | abstracts | Plasmon Amplification through Stimulated Emission at Terahertz
Frequencies in Graphene | null | We show that plasmons in two-dimensional graphene can have net gain at
terahertz frequencies. The coupling of the plasmons to interband electron-hole
transitions in population inverted graphene layers can lead to plasmon
amplification through the process of stimulated emission. We calculate plasmon
gain for different electron-hole densities and temperatures and show that the
gain values can exceed $10^{4}$ cm$^{-1}$ in the 1-10 terahertz frequency
range, for electron-hole densities in the $10^{9}$-$10^{11}$ cm$^{-2}$ range,
even when plasmon energy loss due to intraband scattering is considered.
Plasmons are found to exhibit net gain for intraband scattering times shorter
than 100 fs. Such high gain values could allow extremely compact terahertz
amplifiers and oscillators that have dimensions in the 1-10 $\mu$m range.
|
9fb590d4-194a-467c-a549-6d0e23e6d78f | 9fb590d4-194a-467c-a549-6d0e23e6d78f | 9fb590d4-194a-467c-a549-6d0e23e6d78f | human | null | null | none | abstracts | Solving The High Energy Evolution Equation Including Running Coupling
Corrections | null | We study the solution of the nonlinear BK evolution equation with the
recently calculated running coupling corrections [hep-ph/0609105,
hep-ph/0609090]. Performing a numerical solution we confirm the earlier result
of [hep-ph/0408216] that the high energy evolution with the running coupling
leads to a universal scaling behavior for the dipole scattering amplitude. The
running coupling corrections calculated recently significantly change the shape
of the scaling function as compared to the fixed coupling case leading to a
considerable increase in the anomalous dimension and to a slow-down of the
evolution with rapidity. The difference between the two recent calculations is
due to an extra contribution to the evolution kernel, referred to as the
subtraction term, which arises when running coupling corrections are included.
These subtraction terms were neglected in both recent calculations. We evaluate
numerically the subtraction terms for both calculations, and demonstrate that
when the subtraction terms are added back to the evolution kernels obtained in
the two works the resulting dipole amplitudes agree with each other! We then
use the complete running coupling kernel including the subtraction term to find
the numerical solution of the resulting full non-linear evolution equation with
the running coupling corrections. Again the scaling regime is recovered at very
large rapidity.
|
6ece21be-f0b6-4cbe-8c6b-6654cf0c9170 | 6ece21be-f0b6-4cbe-8c6b-6654cf0c9170 | 6ece21be-f0b6-4cbe-8c6b-6654cf0c9170 | human | null | null | none | abstracts | Millimeter imaging of HD 163296: probing the disk structure and
kinematics | null | We present new multi-wavelength millimeter interferometric observations of
the Herbig Ae star HD 163296 obtained with the IRAM/PBI, SMA and VLA arrays
both in continuum and in the 12CO, 13CO and C18O emission lines. Gas and dust
properties have been obtained comparing the observations with self-consistent
disk models for the dust and CO emission. The circumstellar disk is resolved
both in the continuum and in CO. We find strong evidence that the circumstellar
material is in Keplerian rotation around a central star of 2.6 Msun. The disk
inclination with respect to the line of sight is 46+-4 deg with a position
angle of 128+-4 deg. The slope of the dust opacity measured between 0.87 and 7
mm (beta=1) confirms the presence of mm/cm-size grains in the disk midplane.
The dust continuum emission is asymmetric and confined inside a radius of 200
AU while the CO emission extends up to 540 AU. The comparison between dust and
CO temperature indicates that CO is present only in the disk interior. Finally,
we obtain an increasing depletion of CO isotopomers from 12CO to 13CO and C18O.
We argue that these results support the idea that the disk of HD 163296 is
strongly evolved. In particular, we suggest that there is a strong depletion of
dust relative to gas outside 200 AU; this may be due to the inward migration of
large bodies that form in the outer disk or to clearing of a large gap in the
dust distribution by a low mass companion.
|
43d6dd09-f1a1-483d-a428-c3122cbe2e3e | 43d6dd09-f1a1-483d-a428-c3122cbe2e3e | 43d6dd09-f1a1-483d-a428-c3122cbe2e3e | human | null | null | none | abstracts | Spectropolarimetric observations of the Ca II 8498 A and 8542 A lines in
the quiet Sun | null | The Ca II infrared triplet is one of the few magnetically sensitive
chromospheric lines available for ground-based observations. We present
spectropolarimetric observations of the 8498 A and 8542 A lines in a quiet Sun
region near a decaying active region and compare the results with a simulation
of the lines in a high plasma-beta regime. Cluster analysis of Stokes V profile
pairs shows that the two lines, despite arguably being formed fairly close,
often do not have similar shapes. In the network, the local magnetic topology
is more important in determining the shapes of the Stokes V profiles than the
phase of the wave, contrary to what our simulations show. We also find that
Stokes V asymmetries are very common in the network, and the histograms of the
observed amplitude and area asymmetries differ significantly from the
simulation. Both the network and internetwork show oscillatory behavior in the
Ca II lines. It is stronger in the network, where shocking waves, similar to
those in the high-beta simulation, are seen and large self-reversals in the
intensity profiles are common.
|
6b5f8b29-c370-49b7-a7b5-1ee612828c46 | 6b5f8b29-c370-49b7-a7b5-1ee612828c46 | 6b5f8b29-c370-49b7-a7b5-1ee612828c46 | human | null | null | none | abstracts | Number of moduli of irreducible families of plane curves with nodes and
cusps | null | Consider the family S of irreducible plane curves of degree n with d nodes
and k cusps as singularities. Let W be an irreducible component of S. We
consider the natural rational map from W to the moduli space of curves of genus
g=(n-1)(n-2)/2-d-k. We define the "number of moduli of W" as the dimension of
the image of W with respect to this map. If W has the expected dimension equal
to 3n+g-1-k, then the number of moduli of W is at most equal to the min(3g-3,
3g-3+\rho-k), dove \rho is the Brill-Neother number of the linear series of
degree n and dimension 2 on a smooth curve of genus g. We say that W has the
expected number of moduli if the equality holds. In this paper we construct
examples of families of irreducible plane curves with nodes and cusps as
singularities having expected number of moduli and with non-positive
Brill-Noether number.
|
39a10090-9f6a-466d-9784-b862249b5a6b | 39a10090-9f6a-466d-9784-b862249b5a6b | 39a10090-9f6a-466d-9784-b862249b5a6b | human | null | null | none | abstracts | Search for Heavy Neutral MSSM Higgs Bosons with CMS: Reach and
Higgs-Mass Precision | null | The search for MSSM Higgs bosons will be an important goal at the LHC. We
analyze the search reach of the CMS experiment for the heavy neutral MSSM Higgs
bosons with an integrated luminosity of 30 or 60 fb^-1. This is done by
combining the latest results for the CMS experimental sensitivities based on
full simulation studies with state-of-the-art theoretical predictions of MSSM
Higgs-boson properties. The results are interpreted in MSSM benchmark scenarios
in terms of the parameters tan_beta and the Higgs-boson mass scale, M_A. We
study the dependence of the 5 sigma discovery contours in the M_A-tan_beta
plane on variations of the other supersymmetric parameters. The largest effects
arise from a change in the higgsino mass parameter mu, which enters both via
higher-order radiative corrections and via the kinematics of Higgs decays into
supersymmetric particles. While the variation of $\mu$ can shift the
prospective discovery reach (and correspondingly the ``LHC wedge'' region) by
about Delta tan_beta = 10, we find that the discovery reach is rather stable
with respect to the impact of other supersymmetric parameters. Within the
discovery region we analyze the accuracy with which the masses of the heavy
neutral Higgs bosons can be determined. We find that an accuracy of 1-4% should
be achievable, which could make it possible in favourable regions of the MSSM
parameter space to experimentally resolve the signals of the two heavy MSSM
Higgs bosons at the LHC.
|
079de142-0ef6-4a59-8434-dc4520c37c2f | 079de142-0ef6-4a59-8434-dc4520c37c2f | 079de142-0ef6-4a59-8434-dc4520c37c2f | human | null | null | none | abstracts | White dwarf masses derived from planetary nebulae modelling | null | We compare the mass distribution of central stars of planetary nebulae (CSPN)
with those of their progeny, white dwarfs (WD). We use a dynamical method to
measure masses with an uncertainty of 0.02 M$_\odot$. The CSPN mass
distribution is sharply peaked at $0.61 \rm M_\odot$. The WD distribution peaks
at lower masses ($0.58 \rm M_\odot$) and shows a much broader range of masses.
Some of the difference can be explained if the early post-AGB evolution is
faster than predicted by the Bl\"ocker tracks. Between 30 and 50 per cent of WD
may avoid the PN phase because of too low mass. However, the discrepancy cannot
be fully resolved and WD mass distributions may have been broadened by
observational or model uncertainties.
|
e7fcc770-078b-4cdb-b1e7-842ae6e3abe2 | e7fcc770-078b-4cdb-b1e7-842ae6e3abe2 | e7fcc770-078b-4cdb-b1e7-842ae6e3abe2 | human | null | null | none | abstracts | Uniqueness theorems for Cauchy integrals | null | If $\mu$ is a finite complex measure in the complex plane $\C$ we denote by
$C^\mu$ its Cauchy integral defined in the sense of principal value. The
measure $\mu$ is called reflectionless if it is continuous (has no atoms) and
$C^\mu=0$ at $\mu$-almost every point. We show that if $\mu$ is reflectionless
and its Cauchy maximal function $C^\mu_*$ is summable with respect to $|\mu|$
then $\mu$ is trivial. An example of a reflectionless measure whose maximal
function belongs to the "weak" $L^1$ is also constructed, proving that the
above result is sharp in its scale. We also give a partial geometric
description of the set of reflectionless measures on the line and discuss
connections of our results with the notion of sets of finite perimeter in the
sense of De Giorgi.
|
edeea3b2-f80e-4d6f-bc8c-8ad1dc91258f | edeea3b2-f80e-4d6f-bc8c-8ad1dc91258f | edeea3b2-f80e-4d6f-bc8c-8ad1dc91258f | human | null | null | none | abstracts | Temporal Evolution of Step-Edge Fluctuations Under Electromigration
Conditions | null | The temporal evolution of step-edge fluctuations under electromigration
conditions is analysed using a continuum Langevin model. If the
electromigration driving force acts in the step up/down direction, and
step-edge diffusion is the dominant mass-transport mechanism, we find that
significant deviations from the usual $t^{1/4}$ scaling of the terrace-width
correlation function occurs for a critical time $\tau$ which is dependent upon
the three energy scales in the problem: $k_{B}T$, the step stiffness, $\gamma$,
and the bias associated with adatom hopping under the influence of an
electromigration force, $\pm \Delta U$. For ($t < \tau$), the correlation
function evolves as a superposition of $t^{1/4}$ and $t^{3/4}$ power laws. For
$t \ge \tau$ a closed form expression can be derived. This behavior is
confirmed by a Monte-Carlo simulation using a discrete model of the step
dynamics. It is proposed that the magnitude of the electromigration force
acting upon an atom at a step-edge can by estimated by a careful analysis of
the statistical properties of step-edge fluctuations on the appropriate
time-scale.
|
56e037b4-e231-4da3-8357-fc777c11dd0c | 56e037b4-e231-4da3-8357-fc777c11dd0c | 56e037b4-e231-4da3-8357-fc777c11dd0c | human | null | null | none | abstracts | Probing dark energy with steerable wavelets through correlation of WMAP
and NVSS local morphological measures | null | Using local morphological measures on the sphere defined through a steerable
wavelet analysis, we examine the three-year WMAP and the NVSS data for
correlation induced by the integrated Sachs-Wolfe (ISW) effect. The steerable
wavelet constructed from the second derivative of a Gaussian allows one to
define three local morphological measures, namely the signed-intensity,
orientation and elongation of local features. Detections of correlation between
the WMAP and NVSS data are made with each of these morphological measures. The
most significant detection is obtained in the correlation of the
signed-intensity of local features at a significance of 99.9%. By inspecting
signed-intensity sky maps, it is possible for the first time to see the
correlation between the WMAP and NVSS data by eye. Foreground contamination and
instrumental systematics in the WMAP data are ruled out as the source of all
significant detections of correlation. Our results provide new insight on the
ISW effect by probing the morphological nature of the correlation induced
between the cosmic microwave background and large scale structure of the
Universe. Given the current constraints on the flatness of the Universe, our
detection of the ISW effect again provides direct and independent evidence for
dark energy. Moreover, this new morphological analysis may be used in future to
help us to better understand the nature of dark energy.
|
d34bafa0-9101-4159-8a86-d6c9556e825c | d34bafa0-9101-4159-8a86-d6c9556e825c | d34bafa0-9101-4159-8a86-d6c9556e825c | human | null | null | none | abstracts | Black hole puncture initial data with realistic gravitational wave
content | null | We present improved post-Newtonian-inspired initial data for non-spinning
black-hole binaries, suitable for numerical evolution with punctures. We
revisit the work of Tichy et al. [W. Tichy, B. Bruegmann, M. Campanelli, and P.
Diener, Phys. Rev. D 67, 064008 (2003)], explicitly calculating the remaining
integral terms. These terms improve accuracy in the far zone and, for the first
time, include realistic gravitational waves in the initial data. We investigate
the behavior of these data both at the center of mass and in the far zone,
demonstrating agreement of the transverse-traceless parts of the new metric
with quadrupole-approximation waveforms. These data can be used for numerical
evolutions, enabling a direct connection between the merger waveforms and the
post-Newtonian inspiral waveforms.
|
c3b02568-e914-4002-ba1a-ac1743b773b3 | c3b02568-e914-4002-ba1a-ac1743b773b3 | c3b02568-e914-4002-ba1a-ac1743b773b3 | human | null | null | none | abstracts | The $e^+ e^-\to K^+ K^- \pi^+\pi^-$, $K^+ K^- \pi^0\pi^0$ and $K^+ K^-
K^+ K^-$ Cross Sections Measured with Initial-State Radiation | null | We study the processes $e^+ e^-\to K^+ K^- \pi^+\pi^-\gamma$,
$K^+K^-\pi^0\pi^0\gamma$ and $K^+ K^- K^+ K^-\gamma$, where the photon is
radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed
events, respectively, are selected from 232 \invfb of \babar data. The
invariant mass of the hadronic final state defines the effective \epem
center-of-mass energy, so that the $K^+ K^- \pi^+\pi^-\gamma$ data can be
compared with direct measurements of the $e^+ e^-\to K^+K^- \pipi$ reaction; no
direct measurements exist for the $e^+ e^-\to K^+ K^- \pi^0\pi^0$ or $\epem\to
K^+ K^- K^+ K^-$ reactions. Studying the structure of these events, we find
contributions from a number of intermediate states, and we extract their cross
sections where possible. In particular, we isolate the contribution from $e^+
e^-\to\phi(1020) f_{0}(980)$ and study its structure near threshold. In the
charmonium region, we observe the $J/\psi$ in all three final states and
several intermediate states, as well as the $\psi(2S)$ in some modes, and
measure the corresponding branching fractions. We see no signal for the Y(4260)
and obtain an upper limit of
$\BR_{Y(4260)\to\phi\pi^+\pi^-}\cdot\Gamma^{Y}_{ee}<0.4 \ev$ at 90% C.L.
|