pinecone/core-2020-05-10-deduplication huggingface dataset:
Investigation of electrocaloric effect in PMN-PT relaxor thin films

Permittivity measurements of a 0.93PMN-0.07PT thin film show a broad maximum near 35 ºC, and an anomaly at the depolarizing temperature Td = 18 ºC on heating only, suggesting a dipolar glass-relaxor phase transition. No structural phase transition at 18 ºC is apparent from ferroelectric hysteresis loops taken on field cooling and field heating. These loops show the thermal hysteresis expected for ferroelectric relaxors, which has not hitherto been experimentally verified in PMN-PT thin films. Our data suggest the intriguing possibility of a giant electrocaloric effect (DT = 9 K, DE = 720 kV cm-1) at and near room temperature
Self-Renewing Human Bone Marrow Mesenspheres Promote Hematopoietic Stem Cell Expansion.

Strategies for expanding hematopoietic stem cells (HSCs) include coculture with cells that recapitulate their natural microenvironment, such as bone marrow stromal stem/progenitor cells (BMSCs). Plastic-adherent BMSCs may be insufficient to preserve primitive HSCs. Here, we describe a method of isolating and culturing human BMSCs as nonadherent mesenchymal spheres. Human mesenspheres were derived from CD45- CD31- CD71- CD146+ CD105+ nestin+ cells but could also be simply grown from fetal and adult BM CD45--enriched cells. Human mesenspheres robustly differentiated into mesenchymal lineages. In culture conditions where they displayed a relatively undifferentiated phenotype, with decreased adherence to plastic and increased self-renewal, they promoted enhanced expansion of cord blood CD34+ cells through secreted soluble factors. Expanded HSCs were serially transplantable in immunodeficient mice and significantly increased long-term human hematopoietic engraftment. These results pave the way for culture techniques that preserve the self-renewal of human BMSCs and their ability to support functional HSCs
Massively parallel solvers for elliptic partial differential equations in numerical weather and climate prediction:scalability of elliptic solvers in NWP

The demand for substantial increases in the spatial resolution of global weather and climate prediction models makes it necessary to use numerically efficient and highly scalable algorithms to solve the equations of large-scale atmospheric fluid dynamics. For stability and efficiency reasons, several of the operational forecasting centres, in particular the Met Office and the European Centre for Medium-Range Weather Forecasts (ECMWF) in the UK, use semi-implicit semi-Lagrangian time-stepping in the dynamical core of the model. The additional burden with this approach is that a three-dimensional elliptic partial differential equation (PDE) for the pressure correction has to be solved at every model time step and this often constitutes a significant proportion of the time spent in the dynamical core. In global models, this PDE must be solved in a thin spherical shell. To run within tight operational time-scales, the solver has to be parallelized and there seems to be a (perceived) misconception that elliptic solvers do not scale to large processor counts and hence implicit time-stepping cannot be used in very high-resolution global models. After reviewing several methods for solving the elliptic PDE for the pressure correction and their application in atmospheric models, we demonstrate the performance and very good scalability of Krylov subspace solvers and multigrid algorithms for a representative model equation with more than 1010 unknowns on 65 536 cores on the High-End Computing Terascale Resource (HECToR), the UK's national supercomputer. For this, we tested and optimized solvers from two existing numerical libraries (the Distributed and Unified Numerics Environment (DUNE) and Parallel High Performance Preconditioners (hypre)) and implemented both a conjugate gradient solver and a geometric multigrid algorithm based on a tensor-product approach, which exploits the strong vertical anisotropy of the discretized equation. We study both weak and strong scalability and compare the absolute solution times for all methods; in contrast to one-level methods, the multigrid solver is robust with respect to parameter variations
Dynamical phase coexistence: A simple solution to the "savanna problem"

We introduce the concept of 'dynamical phase coexistence' to provide a simple
solution for a long-standing problem in theoretical ecology, the so-called
"savanna problem". The challenge is to understand why in savanna ecosystems
trees and grasses coexist in a robust way with large spatio-temporal
variability. We propose a simple model, a variant of the Contact Process (CP),
which includes two key extra features: varying external
(environmental/rainfall) conditions and tree age. The system fluctuates locally
between a woodland and a grassland phase, corresponding to the active and
absorbing phases of the underlying pure contact process. This leads to a highly
variable stable phase characterized by patches of the woodland and grassland
phases coexisting dynamically. We show that the mean time to tree extinction
under this model increases as a power-law of system size and can be of the
order of 10,000,000 years in even moderately sized savannas. Finally, we
demonstrate that while local interactions among trees may influence tree
spatial distribution and the order of the transition between woodland and
grassland phases, they do not affect dynamical coexistence. We expect dynamical
coexistence to be relevant in other contexts in physics, biology or the social
sciences.Comment: 8 pages, 7 figures. Accepted for publication in Journal of
  Theoretical Biolog
Random walk with barycentric self-interaction

We study the asymptotic behaviour of a $d$-dimensional self-interacting
random walk $X_n$ ($n = 1,2,...$) which is repelled or attracted by the centre
of mass $G_n = n^{-1} \sum_{i=1}^n X_i$ of its previous trajectory. The walk's
trajectory $(X_1,...,X_n)$ models a random polymer chain in either poor or good
solvent. In addition to some natural regularity conditions, we assume that the
walk has one-step mean drift directed either towards or away from its current
centre of mass $G_n$ and of magnitude $\| X_n - G_n \|^{-\beta}$ for $\beta
\geq 0$. When $\beta <1$ and the radial drift is outwards, we show that $X_n$
is transient with a limiting (random) direction and satisfies a super-diffusive
law of large numbers: $n^{-1/(1+\beta)} X_n$ converges almost surely to some
random vector. When $\beta \in (0,1)$ there is sub-ballistic rate of escape.
For $\beta \geq 0$ we give almost-sure bounds on the norms $\|X_n\|$, which in
the context of the polymer model reveal extended and collapsed phases. Analysis
of the random walk, and in particular of $X_n - G_n$, leads to the study of
real-valued time-inhomogeneous non-Markov processes $Z_n$ on $[0,\infty)$ with
mean drifts at $x$ given approximately by $\rho x^{-\beta} - (x/n)$, where
$\beta \geq 0$ and $\rho \in \R$. The study of such processes is a
time-dependent variation on a classical problem of Lamperti; moreover, they
arise naturally in the context of the distance of simple random walk on $\Z^d$
from its centre of mass, for which we also give an apparently new result. We
give a recurrence classification and asymptotic theory for processes $Z_n$ just
described, which enables us to deduce the complete recurrence classification
(for any $\beta \geq 0$) of $X_n - G_n$ for our self-interacting walk.Comment: 36 pages, 2 colour figures; v2: minor revision, some correction
Numerical study on Anderson transitions in three-dimensional disordered
  systems in random magnetic fields

The Anderson transitions in a random magnetic field in three dimensions are
investigated numerically. The critical behavior near the transition point is
analyzed in detail by means of the transfer matrix method with high accuracy
for systems both with and without an additional random scalar potential. We
find the critical exponent $\nu$ for the localization length to be $1.45 \pm
0.09$ with a strong random scalar potential. Without it, the exponent is
smaller but increases with the system sizes and extrapolates to the above value
within the error bars. These results support the conventional classification of
universality classes due to symmetry. Fractal dimensionality of the wave
function at the critical point is also estimated by the equation-of-motion
method.Comment: 9 pages, 3 figures, to appear in Annalen der Physi
Toward the Rectilinear Crossing Number of $K_n$: New Drawings, Upper
  Bounds, and Asymptotics

Scheinerman and Wilf (1994) assert that `an important open problem in the
study of graph embeddings is to determine the rectilinear crossing number of
the complete graph K_n.' A rectilinear drawing of K_n is an arrangement of n
vertices in the plane, every pair of which is connected by an edge that is a
line segment. We assume that no three vertices are collinear, and that no three
edges intersect in a point unless that point is an endpoint of all three. The
rectilinear crossing number of K_n is the fewest number of edge crossings
attainable over all rectilinear drawings of K_n.
  For each n we construct a rectilinear drawing of K_n that has the fewest
number of edge crossings and the best asymptotics known to date. Moreover, we
give some alternative infinite families of drawings of K_n with good
asymptotics. Finally, we mention some old and new open problems.Comment: 13 Page
QCD Glueball Regge Trajectories and the Pomeron

We report a glueball Regge trajectory emerging from diagonalizing a confining
Coulomb gauge Hamiltonian for constituent gluons. Using a BCS vacuum ansatz and
gap equation, the dressed gluons acquire a mass, of order 800 $MeV$, providing
the quasiparticle degrees of freedom for a TDA glueball formulation. The TDA
eigenstates for two constituent gluons have orbital, $L$, excitations with a
characteristic energy of 400 $MeV$ revealing a clear Regge trajectory for
$\vec{J} = \vec{L} + \vec{S}$, where $S$ is the total (sum) gluon spin.
Significantly, the $S = 2$ glueball spectrum coincides with the Pomeron given
by $\alpha_P(t)=1.08+0.25 t $. Finally, we also ascertain that lattice data
supports our result, yielding an average intercept of 1.1 in good agreement
with the Pomeron.Comment: 10 pages, 4 ps figure
Theoretical uncertainties on quasielastic charged-current
  neutrino-nucleus cross sections

We estimate the theoretical uncertainties of the model developed in Phys.
Rev. C70 055503 for inclusive quasielastic charged-current neutrino-nucleus
reactions at intermediate energies. Besides we quantify the deviations of the
predictions of this many body framework from those obtained within a simple
Fermi gas model. An special attention has been paid to the ratio
\sigma(\mu)/\sigma(e) of interest for experiments on atmospheric neutrinos. We
show that uncertainties affecting this ratio are likely smaller than 5%Comment: 10 pages, 6 figures. Few errors corrected. Accepted in Physics
  Letters
Baby de Sitter Black Holes and dS$_3$/CFT$_2$

Unlike three-dimensional Einstein gravity, three-dimensional massive gravity
admits asymptotically de Sitter space (dS) black hole solutions. These black
holes present interesting features and provide us with toy models to study the
dS/CFT correspondence. A remarkable property of these black holes is that they
are always in thermal equilibrium with the cosmological horizon of the space
that hosts them. This invites us to study the thermodynamics of these solutions
within the context of dS/CFT. We study the asymptotic symmetry group of the
theory and find that it indeed coincides with the local two-dimensional
conformal algebra. The charge algebra associated to the asymptotic Killing
vectors consists of two copies of the Virasoro algebra with non-vanishing
central extension. We compute the mass and angular momentum of the dS black
holes and verify that a naive application of Cardy's formula exactly reproduces
the entropy of both the black hole and the cosmological horizon. By adapting
the holographic renormalization techniques to the case of dS space, we define
the boundary stress tensor of the dual Euclidean conformal field theory.Comment: 13 page
Bounding the greybody factors for scalar excitations of the Kerr-Newman
  spacetime

Finding exact solutions for black-hole greybody factors is generically
impractical; typically one resorts either to making semi-analytic or numerical
estimates, or alternatively to deriving rigorous analytic bounds. Indeed,
rigorous bounds have already been established for the greybody factors of
Schwarzschild and Riessner-Nordstrom black holes, and more generally for those
of arbitrary static spherically symmetric asymptotically flat black holes.
Adding rotation to the problem greatly increases the level of difficulty, both
for purely technical reasons (the Kerr or Kerr-Newman black holes are generally
much more difficult to work with than the Schwarzschild or Reissner-Nordstrom
black holes), but also at a conceptual level (due to the generic presence of
super-radiant modes). In the current article we analyze bounds on the greybody
factors for scalar excitations of the Kerr-Newman geometry in some detail,
first for zero-angular-momentum modes, then for the non-super-radiant modes,
and finally for the super-radiant modes.Comment: 22 page
Super-R\'enyi Entropy & Wilson Loops for N=4 SYM and their Gravity Duals

We compute the supersymmetric R\'enyi entropies across a spherical
entanglement surface in N=4 SU(N) SYM theory using localization on the
four-dimensional ellipsoid. We extract the leading result at large N and
\lambda, and match its universal part to a gravity calculation involving a
hyperbolically sliced supersymmetric black hole solution of N=4+ SU(2) X U(1)
gauged supergravity in five dimensions. We repeat the analysis in the presence
of a Wilson loop insertion and find again a perfect match with the dual string
theory. Understanding the Wilson loop operator requires knowledge of the full
ten-dimensional IIB supergravity solution which we elaborate upon.Comment: 30+1 pages, 1 table; minor corrections, references added; matches
  published version (JHEP
QED as the tensionless limit of the spinning string with contact
  interaction

We outline how QED with spinor matter can be described by the tensionless
limit of spinning strings with contact interactions. The strings represent
electric lines of force with charges at their ends. The contact interaction is
constructed from a delta-function on the world-sheet which, although off-shell,
decouples from the world-sheet metric. Integrating out the string degrees of
freedom with fixed boundary generates the super-Wilson loop that couples spinor
matter to electromagnetism in the world-line formalism. World-sheet and
world-line, but not spacetime, supersymmetry underpin the model.Comment: 11 pages, no figure
Stop Lepton Associated Production at Hadron Colliders

At hadron colliders, the search for R-parity violating supersymmetry can probe scalar masses beyond what is covered by pair production processes. We evaluate the next-to-leading order SUSY-QCD corrections to the associated stop or sbottom production with a lepton through R-parity violating interactions. We show that higher order corrections render the theoretical predictions more stable with respect to variations of the renormalization and factorization scales and that the total cross section is enhanced by a factor up to 70% at the Tevatron and 50% at the LHC. We investigate in detail how the heavy supersymmetric states decouple from the next-to-leading order process, which gives rise to a theory with an additional scalar leptoquark. In this scenario the inclusion of higher order QCD corrections increases the Tevatron reach on leptoquark masses by up to 40 GeV and the LHC reach by up to 200 GeV
Bridging Two Ways of Describing Final-State Interactions in A(e,e'p)
  Reactions

We outline a relativistic and unfactorized framework to treat the final-state
interactions in quasi-elastic A(e,e'p) reactions for four-momentum transfers
Q$^{2} \gtrsim 0.3$ (GeV/c)$^{2}$. The model, which relies on the eikonal
approximation, can be used in combination with optical potentials, as well as
with the Glauber multiple-scattering method. We argue that such a model can
bridge the gap between a typical ``low'' and ``high-energy'' description of
final-state interactions, in a reasonably smooth fashion. This argument is made
on the basis of calculated structure functions, polarization observables and
nuclear transparencies for the target nuclei $^{12}$C and $^{16}$O.Comment: revised versio
Microscopic shell-model description of the exotic nucleus ^{16}C

The structure of the neutron-rich carbon nucleus ^{16}C is described by
introducing a new microscopic shell model of no-core type. The model space is
composed of the 0s, 0p, 1s0d, and 1p0f shells. The effective interaction is
microscopically derived from the CD-Bonn potential and the Coulomb force
through a unitary transformation theory. Calculated low-lying energy levels of
^{16}C agree well with the experiment. The B(E2;2_{1}^{+} \to 0_{1}^{+}) value
is calculated with the bare charges. The anomalously hindered B(E2) value for
^{16}C, measured recently, is well reproduced.Comment: 14 pages, 4 figures, considerable results and discussion are added,
  but the main conclusion is unchanged, accepted for publication in Phys. Lett.
Quantum from principles

Quantum theory was discovered in an adventurous way, under the urge to solve
puzzles-like the spectrum of the blackbody radiation-that haunted the physics
community at the beginning of the 20th century. It soon became clear, though,
that quantum theory was not just a theory of specific physical systems, but
rather a new language of universal applicability. Can this language be
reconstructed from first principles? Can we arrive at it from logical
reasoning, instead of ad hoc guesswork? A positive answer was provided in Refs.
[1, 2], where we put forward six principles that identify quantum theory
uniquely in a broad class of theories. We first defined a class of "theories of
information", constructed as extensions of probability theory in which events
can be connected into networks. In this framework, we formulated the six
principles as rules governing the control and the accessibility of information.
Directly from these rules, we reconstructed a number of quantum information
features, and eventually, the whole Hilbert space framework. In short, our
principles characterize quantum theory as the theory of information that allows
for maximal control of randomness.Comment: 50 pages, no figures, published version. Summarizes the framework and
  the results of arXiv:0908.1583 and arXiv:1011.645
High Spatial Resolution X-Ray Spectroscopy of the IC443 Pulsar Wind
  Nebula and Environs

Deep Chandra ACIS observations of the region around the putative pulsar, CXOU
J061705.3+222127, in the supernova remnant IC443 reveal an
~5$^{\prime\prime}$-radius ring-like structure surrounding the pulsar and a
jet-like feature oriented roughly north-south across the ring and through the
pulsar's location at 06$^{\rm h}$17$^{\rm m}$5.200$^{\rm s}$
+22$^{\circ}$21$^{\prime}$27.52$^{\prime\prime}$ (J2000.0 coordinates). The
observations further confirm that (1) the spectrum and flux of the central
object are consistent with a rotation-powered pulsar, (2) the non-thermal
spectrum and morphology of the surrounding nebula are consistent with a pulsar
wind and, (3) the spectrum at greater distances is consistent with thermal
emission from the supernova remnant. The cometary shape of the nebula,
suggesting motion towards the southwest, appears to be subsonic: There is no
evidence either spectrally or morphologically for a bow shock or contact
discontinuity; the nearly circular ring is not distorted by motion through the
ambient medium; and the shape near the apex of the nebula is narrow. Comparing
this observation with previous observations of the same target, we set a 99%
confidence upper limit to the proper motion of CXOU J061705.3+222127 to be less
than 44 mas/yr (310 km/s for a distance of 1.5 kpc), with the best-fit (but not
statistically significant) projected direction toward the west.Comment: Accepted for publication in the Astrophysical Journa
Higgs effects in top anti-top production near threshold in e+ e-
  annihilation

The completion of the third-order QCD corrections to the inclusive top-pair
production cross section near threshold demonstrates that the strong dynamics
is under control at the few percent level. In this paper we consider the
effects of the Higgs boson on the cross section and, for the first time,
combine the third-order QCD result with the third-order P-wave, the leading QED
and the leading non-resonant contributions. We study the size of the different
effects and investigate the sensitivity of the cross section to variations of
the top-quark Yukawa coupling due to possible new physics effects.Comment: LaTeX, 17 page
Does the dynamics of sine-Gordon solitons predict active regions of DNA

In this work we analyze the possibility that the soliton dynamics in a simple nonlinear model allows functionally relevant predictions of the behaviour of DNA. This suggestion was first put forward by Salerno [M. Salerno, Phys. Rev. A 44 (1991) 5292] by showing results indicating that sine–Gordon kinks were set in motion at certain regions of a DNA sequence that include promoters. We revisit that system and show that the observed behaviour has nothing to do with promoters; on the contrary, it originates from the bases at the boundary, which are not part of the genome studied. We explain this phenomenology in terms of an effective potential for the kink center. This is further extended to disprove recent claims that the dynamics of kinks [E. Lennholm, M. H¨ornquist, Physica D 177 (2003) 233] or breathers [J.D. Bashford, J. Biol. Phys. 32 (2006) 27] has functional significance.We conclude that no such information can be extracted from this simple nonlinear model or its associated effective potentialThis work was supported by the Ministerio de Educación y Ciencia of Spain through grants BFM2003-07749- C05-01, FIS2004-01001, NAN2004-09087-C03-03, FIS2005- 973, by Comunidad de Madrid grant SIMUMAT-CM and by the Junta de Andaluc´ıa under projects 00481 and FQM-0207. S.C. is supported by a fellowship from the Consejería de Educación de la Comunidad de Madrid and the Fondo Social Europeo.Publicad