pinecone/core-2020-05-10-deduplication huggingface dataset:
Particle acceleration with anomalous pitch angle scattering in 2D magnetohydrodynamic reconnection simulations

A.B. would like to thank the University of St Andrews for financial support from the 7th Century Scholarship and the Scottish Government for support from the Saltire Scholarship. E.P.K.’s work is partially supported by a STFC consolidated grant ST/L000741/1. J.T. and T.N. gratefully acknowledge the support of the UK STFC (consolidated grant SN/N000609/1).The conversion of magnetic energy into other forms (such as plasma heating, bulk plasma flows, and non-thermal particles) during solar flares is one of the outstanding open problems in solar physics. It is generally accepted that magnetic reconnection plays a crucialrole in these conversion processes. In order to achieve the rapid energy release required in solar flares, an anomalous resistivity, which is orders of magnitude higher than the Spitzer resistivity, is often used in magnetohydrodynamic (MHD) simulations of reconnection in the corona. The origin of Spitzer resistivity is based on Coulomb scattering, which becomes negligible at the high energies achieved by accelerated particles. As a result, simulations of particle acceleration in reconnection events are often performed in the absence of any interaction between accelerated particles and any background plasma. This need not be the case for scattering associated with anomalous resistivity caused by turbulence within solar flares, as the higher resistivity implies an elevated scattering rate. We present results of test particle calculations, with and without pitch angle scattering, subject to fields derived from MHD simulations of two-dimensional (2D) X-point reconnection. Scattering rates proportional to the ratio of the anomalous resistivity to the local Spitzer resistivity, as well as at fixed values, are considered. Pitch angle scattering, which is independent of the anomalous resistivity, causes higher maximum energies in comparison to those obtained without scattering. Scattering rates which are dependent on the local anomalous resistivity tend to produce fewer highly energised particles due to weaker scattering in the separatrices, even though scattering in the current sheet may be stronger when compared to resistivity-independent scattering. Strong scattering also causes an increase in the number of particles exiting the computational box in the reconnection outflow region, as opposed to along the separatrices as is the case in the absence of scattering.Publisher PDFPeer reviewe
Low-temperature photocarrier dynamics in monolayer MoS₂

The band structure of MoS2 strongly depends on the number of layers, and a transition from indirect to direct-gap semiconductor has been observed recently for a single layer of MoS2. Single-layer MoS2 therefore becomes an efficient emitter of photoluminescence even at room temperature. Here, we report on scanning Raman and on temperature-dependent, as well as time-resolved photoluminescence measurements on single-layer MoS2 flakes prepared by exfoliation. We observe the emergence of two distinct photoluminescence peaks at low temperatures. The photocarrier recombination at low temperatures occurs on the few-picosecond timescale, but with increasing temperatures, a biexponential photoluminescence decay with a longer-lived component is observed.
Finite volume POD-Galerkin stabilised reduced order methods for the
  parametrised incompressible Navier-Stokes equations

In this work a stabilised and reduced Galerkin projection of the
incompressible unsteady Navier-Stokes equations for moderate Reynolds number is
presented. The full-order model, on which the Galerkin projection is applied,
is based on a finite volumes approximation. The reduced basis spaces are
constructed with a POD approach. Two different pressure stabilisation
strategies are proposed and compared: the former one is based on the supremizer
enrichment of the velocity space, and the latter one is based on a pressure
Poisson equation approach.Comment: 16 pages, 10 figures, 3 table
Measurement of the total and differential inclusive B+ hadron cross sections in pp collisions at sqrt(s) = 13 TeV

The differential cross sections for inclusive production of B+ hadrons are measured as a function of the B+ transverse momentum pT[B] and rapidity y[B] in pp collisions at a centre-of-mass energy of 13 TeV, using data collected by the CMS experiment that correspond to an integrated luminosity of 49.4 inverse picobarns. The measurement uses the exclusive decay channel B+ to J/psi K+, with J/psi mesons that decay to a pair of muons. The results show a reasonable agreement with theoretical calculations within the uncertainties
The last forests on Antarctica : reconstructing flora and temperature from the Neogene Sirius Group, Transantarctic Mountains

R.L.R.O. thanks the Natural Environmental Research Council (NERC) for supporting her PhD studentship (NE/K500847/1) and BGS for CASE support. R.I. was supported by a NERC Independent Fellowship (NE/K008536/1). F.L..G was supported by a Royal Society Dorothy Hodgkin Fellowship.Fossil-bearing deposits in the Transantarctic Mountains, Antarctica indicate that, despite the cold nature of the continent’s climate, a tundra ecosystem grew during periods of ice sheet retreat in the mid to late Neogene (17–2.5 Ma), 480 km from the South Pole. To date, palaeotemperature reconstruction has been based only on biological ranges, thereby calling for a geochemical approach to understanding continental climate and environment. There is contradictory evidence in the fossil record as to whether this flora was mixed angiosperm-conifer vegetation, or whether by this point conifers had disappeared from the continent. In order to address these questions, we have analysed, for the first time in sediments of this age, plant and bacterial biomarkers in terrestrial sediments from the Transantarctic Mountains to reconstruct past temperature and vegetation during a period of East Antarctic Ice Sheet retreat. From tetraether lipids (MBT’/CBT palaeothermometer), we conclude that the mean continental summer temperature was ca. 5 °C, in agreement with previous reconstructions. This was warm enough to have allowed woody vegetation to survive and reproduce even during the austral winter. Biomarkers from vascular plants indicate a low diversity and spatially variable flora consisting of higher plants, moss and algal mats growing in microenvironments in a glacial outwash system. Abietane-type compounds were abundant in some samples, indicating that conifers, most likely Podocarpaceae, grew on the Antarctic continent well into the Neogene. This is supported by the palynological record, but not the macrofossil record for the continent, and has implications for the evolution of vegetation on Antarctica.Publisher PDFPeer reviewe
A lattice field theoretical model for high-T_(c) superconductivity

We present a 2+1-dimensional lattice model for the copper oxide superconductors and their parent compounds, in which both the charge and spin degrees of freedom are treated dynamically. The spin-charge coupling parameter is associated to the doping fraction in the cuprates. The model is able to account for the various phases of the cuprates and their properties, not only at low and intermediate doping but also for (highly) over-doped compounds. We acquire a qualitative understanding of highTc superconductivity as a Bose-Einstein condensation of boun d charge pairs
Pulsating low-mass white dwarfs in the frame of new evolutionary sequences. I: adiabatic properties

Context. Many low-mass white dwarfs with masses M∗/M⊙ ≲ 0.45, including the so-called extremely low-mass white dwarfs (M∗/M⊙ ≲ 0.20 − 0.25), have recently been discovered in the field of our Galaxy through dedicated photometric surveys. The subsequent discovery of pulsations in some of them has opened the unprecedented opportunity of probing the internal structure of these ancient stars.
Aims. We present a detailed adiabatic pulsational study of these stars based on full evolutionary sequences derived from binary star evolution computations. The main aim of this study is to provide a detailed theoretical basis of reference for interpreting present and future observations of variable low-mass white dwarfs.
Methods. Our pulsational analysis is based on a new set of He-core white-dwarf models with masses ranging from 0.1554 to 0.4352 M⊙ derived by computing the non-conservative evolution of a binary system consisting of an initially 1 M⊙ ZAMS star and a 1.4 M⊙ neutron star. We computed adiabatic radial (ℓ = 0) and non-radial (ℓ = 1,2) p and g modes to assess the dependence of the pulsational properties of these objects on stellar parameters such as the stellar mass and the effective temperature, as well as the effects of element diffusion.
Results. We found that for white dwarf models with masses below ~ 0.18 M⊙, g modes mainly probe the core regions and p modes the envelope, therefore pulsations offer the opportunity of constraining both the core and envelope chemical structure of these stars via asteroseismology. For models with M∗ ≳ 0.18 M⊙, on the other hand, g modes are very sensitive to the He/H compositional gradient and therefore can be used as a diagnostic tool for constraining the H envelope thickness. Because both types of objects have not only very distinct evolutionary histories (according to whether the progenitor stars have experienced CNO-flashes or not), but also have strongly different pulsation properties, we propose to define white dwarfs with masses below ~ 0.18 M⊙ as ELM (extremely low-mass) white dwarfs, and white dwarfs with M∗ ≳ 0.18 M⊙ as LM (low-mass) white dwarfs.Fil: Corsico, Alejandro Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Althaus, Leandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin
Probabilistic response and rare events in Mathieu׳s equation under correlated parametric excitation

We derive an analytical approximation to the probability distribution function (pdf) for the response of Mathieu׳s equation under parametric excitation by a random process with a spectrum peaked at the main resonant frequency, motivated by the problem of large amplitude ship roll resonance in random seas. The inclusion of random stochastic excitation renders the otherwise straightforward response to a system undergoing intermittent resonances: randomly occurring large amplitude bursts. Intermittent resonance occurs precisely when the random parametric excitation pushes the system into the instability region, causing an extreme magnitude response. As a result, the statistics are characterized by heavy-tails. We apply a recently developed mathematical technique, the probabilistic decomposition-synthesis method, to derive an analytical approximation to the non-Gaussian pdf of the response. We illustrate the validity of this analytical approximation through comparisons with Monte-Carlo simulations that demonstrate our result accurately captures the strong non-Gaussianinty of the response. Keywords: Mathieu׳s equationColored stochastic excitationHeavy-tailsIntermittent instabilitiesRare eventsStochastic roll resonanceUnited States. Office of Naval Research (Grant ONR N00014- 14-1-0520)Massachusetts Institute of Technology. Naval Engineering Education Center (Grant 3002883706
Data in support of crystal structures of highly-ordered long-period stacking-ordered phases with 18R, 14H and 10H-type stacking sequences in the Mg-Zn-Y system

The crystal structures of highly-ordered Mg-Zn-Y long-period stacking-ordered (LPSO) phases with the 18. R, 14. H and 10. H-type stacking sequences have been investigated by atomic-resolution scanning transmission electron microscopy (STEM) and transmission electron microscopy (Kishida et al., 2015) [1]. This data article provides supporting materials for the crystal structure analysis based on the crystallographic theory of the order-disorder (OD) structure and the crystallographic information obtained through the structural optimization for various simple polytypes of the highly-ordered Mg-Zn-Y LPSO phases with the 18. R, 14. H and 10. H-type stacking sequences by first-principles density functional theory (DFT) calculations
Bystander-Activated Memory CD8 T Cells Control Early Pathogen Load in an Innate-like, NKG2D-Dependent Manner.

During an infection the antigen-nonspecific memory CD8 T cell compartment is not simply an inert pool of cells, but becomes activated and cytotoxic. It is unknown how these cells contribute to the clearance of an infection. We measured the strength of T cell receptor (TCR) signals that bystander-activated, cytotoxic CD8 T cells (BA-CTLs) receive in vivo and found evidence of limited TCR signaling. Given this marginal contribution of the TCR, we asked how BA-CTLs identify infected target cells. We show that target cells express NKG2D ligands following bacterial infection and demonstrate that BA-CTLs directly eliminate these target cells in an innate-like, NKG2D-dependent manner. Selective inhibition of BA-CTL-mediated killing led to a significant defect in pathogen clearance. Together, these data suggest an innate role for memory CD8 T cells in the early immune response before the onset of a de novo generated, antigen-specific CD8 T cell response
Kerr-Schild Structure and Harmonic 2-forms on (A)dS-Kerr-NUT Metrics

We demonstrate that the general (A)dS-Kerr-NUT solutions in D dimensions with
([D/2], [(D+1)/2]) signature admit [D/2] linearly-independent,
mutually-orthogonal and affinely-parameterised null geodesic congruences. This
enables us to write the metrics in a multi-Kerr-Schild form, where the mass and
all of the NUT parameters enter the metrics linearly. In the case of D=2n, we
also obtain n harmonic 2-forms, which can be viewed as charged (A)dS-Kerr-NUT
solution at the linear level of small-charge expansion, for the
higher-dimensional Einstein-Maxwell theories. In the BPS limit, these 2-forms
reduce to n-1 linearly-independent ones, whilst the resulting Calabi-Yau metric
acquires a Kahler 2-form, leaving the total number the same.Comment: Latex, 11 pages, references adde
Toric duality, Seiberg duality and Picard-Lefschetz transformations.

Toric Duality arises as an ambiguity in computing the quiver gauge theory living on a D3-brane which probes a toric singularity. It is reviewed how, in simple cases Toric Duality is Seiberg Duality. The set of all Seiberg Dualities on a single node in the quiver forms a group which is contained in a larger group given by a set of Picard-Lefschetz transformations. This leads to elements in the group (sometimes called fractional Seiberg Duals) which are not Seiberg Duality on a single node, thus providing a new set of gauge theories which flow to the same universality class in the Infra Red
There exist multilinear Bohnenblust-Hille constants (Cn)n=1(infinity) with limn ->infinity(Cn+1-Cn)=0

The n-linear Bohnenblust-Hille inequality asserts that there is a constant C-n is an element of [1, infinity) such that the l(2n/n+1)-norm of (U(e(i1), ..., e(in)))(i1, ...,in=1)(N) is bounded above by C-n times the supremum norm of U, for any n-linear form U :C-N x ... x C-N -> C and N is an element of N (the same holds for real scalars). We prove what we call Fundamental Lemma, which brings new information on the optimal constants, (K-n)(n=1)(infinity) for both real and complex scalars. For instance, Kn+1 - K-n < 0.87/n(0.473) for infinitely many n's. For complex scalars we give a formula (of surprisingly low growth), in which pi, e and the famous Euler-Mascheroni constant gamma appear: K-n < 1 (4/root pi (1 - e(gamma/2-1/2)) Sigma(n-1)(j=1) j(log2(e-gamma/2+1/2)-1)), for all(n) >= 2. We study the interplay between the Kahane-Salem-Zygmund and the Bohnenblust-Hille (polynomial and multilinear) inequalities and provide estimates for Bohnenblust-Hille-type inequality constants for any exponent q is an element of [2n/n+1, infinity). (C) 2012 Elsevier Inc. All rights reserved
The (K-,p) reaction on nuclei with in-flight kaons

We perform a theoretical study of the spectrum of protons with kinetic
energies of around 600 MeV, emitted following the interaction of 1 GeV/c kaons
with nuclei. A recent experimental analysis of this (K-,p) reaction on 12C,
based on the dominant quasielastic process, has suggested a deeply attractive
kaon nucleus potential. Our Monte Carlo simulation considers, in addition, the
one-and two-nucleon K- absorption processes producing hyperons that decay into
\pi N pairs. We find that this kaon in-flight reaction is not well suited to
determine the kaon optical potential due, essentially, to the limited
sensitivity of the cross section to its strength, but also to unavoidable
uncertainties from the coincidence requirement applied in the experiment. A
shallow kaon nucleus optical potential obtained in chiral models is perfectly
compatible with the observed spectrum.Comment: To appear in the proceedings of the 10th International Conference on
  Hypernuclear and Strange Particle Physics, Tokai, Ibaraki (Japan), 14-18
  September, 200
Herschel-ATLAS: Dust temperature and redshift distribution of SPIRE and
  PACS detected sources using submillimetre colours

We present colour-colour diagrams of detected sources in the Herschel-ATLAS
Science Demonstration Field from 100 to 500 microns using both PACS and SPIRE.
We fit isothermal modified black bodies to the spectral energy distribution
(SED) to extract the dust temperature of sources with counterparts in Galaxy
And Mass Assembly (GAMA) or SDSS surveys with either a spectroscopic or a
photometric redshift. For a subsample of 330 sources detected in at least three
FIR bands with a significance greater than 3 $\sigma$, we find an average dust
temperature of $(28 \pm 8)$K. For sources with no known redshift, we populate
the colour-colour diagram with a large number of SEDs generated with a broad
range of dust temperatures and emissivity parameters, and compare to colours of
observed sources to establish the redshift distribution of this sample. For
another subsample of 1686 sources with fluxes above 35 mJy at 350 microns and
detected at 250 and 500 microns with a significance greater than 3$\sigma$, we
find an average redshift of $2.2 \pm 0.6$.Comment: 5 pages; accepted for publication in A&A Special Issue on Herschel
  First Science Results (July 2010). H-ATLAS information available at
  http://www.h-atlas.or
The van Hove distribution function for Brownian hard spheres: dynamical
  test particle theory and computer simulations for bulk dynamics

We describe a test particle approach based on dynamical density functional
theory (DDFT) for studying the correlated time evolution of the particles that
constitute a fluid. Our theory provides a means of calculating the van Hove
distribution function by treating its self and distinct parts as the two
components of a binary fluid mixture, with the `self' component having only one
particle, the `distinct' component consisting of all the other particles, and
using DDFT to calculate the time evolution of the density profiles for the two
components. We apply this approach to a bulk fluid of Brownian hard spheres and
compare to results for the van Hove function and the intermediate scattering
function from Brownian dynamics computer simulations. We find good agreement at
low and intermediate densities using the very simple Ramakrishnan-Yussouff
[Phys. Rev. B 19, 2775 (1979)] approximation for the excess free energy
functional. Since the DDFT is based on the equilibrium Helmholtz free energy
functional, we can probe a free energy landscape that underlies the dynamics.
Within the mean-field approximation we find that as the particle density
increases, this landscape develops a minimum, while an exact treatment of a
model confined situation shows that for an ergodic fluid this landscape should
be monotonic. We discuss possible implications for slow, glassy and arrested
dynamics at high densities.Comment: Submitted to Journal of Chemical Physic
Counting loopy graphs with given degrees

Let d=(d_1,d_2,..., d_n) be a vector of non-negative integers. We study the
number of symmetric 0-1 matrices whose row sum vector equals d. While previous
work has focussed on the case of zero diagonal, we allow diagonal entries to
equal 1. When forming the row sum, each diagonal entry is multiplied by a
factor of D, where D is 1 or 2. The case D=1 corresponds to enumeration by the
usual row sum of matrices. The case D=2 corresponds to enumeration by degree
sequence of undirected graphs with loops but no repeated edges, due to the
convention that a loop contributes 2 to the degree of its incident vertex. We
obtain asymptotically precise formulae for the number of matrices in the sparse
range (where, roughly, the maximum row sum is o(n^{1/2})), and in the dense
range (where, roughly, the average row sum is proportional to n and the row
sums do not vary greatly).Comment: Fixed an obvious typo in Thm 1.
The Case for the Dual Halo of the Milky Way

Carollo et al. have recently resolved the stellar population of the Milky Way
halo into at least two distinct components, an inner halo and an outer halo.
This result has been criticized by Schoenrich et al., who claim that the
retrograde signature associated with the outer halo is due to the adoption of
faulty distances. We refute this claim, and demonstrate that the Schoenrich et
al. photometric distances are themselves flawed because they adopted an
incorrect main-sequence absolute magnitude relationship from the work of
Ivezi\'c et al. When compared to the recommended relation from Ivezi\'c et al.,
which is tied to a Milky Way globular cluster distance scale and accounts for
age and metallicity effects, the relation adopted by Schoenrich et al. yields
up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use
of the correct relationship yields agreement between the distances assigned by
Carollo et al. and Ivezi\'{c} et al. for low-metallicity dwarfs to within
6-10%. Schoenrich et al. also point out that intermediate-gravity stars (3.5 <=
log g <= 4.0) with colors redder than the TO region are likely misclassified,
with which we concur. We implement a new procedure to reassign luminosity
classifications for the TO stars that require it. New derivations of the
rotational behavior demonstrate that the retrograde signature and high velocity
dispersion of the outer-halo population remains. We summarize additional lines
of evidence for a dual halo, including a test of the retrograde signature based
on proper motions alone, and conclude that the preponderance of evidence
strongly rejects the single-halo interpretation.Comment: 46 pages, 2 tables, 15 figures, Accepted for publication in the
  Astrophysical Journa
Few electron double quantum dot in an isotopically purified $^{28}$Si
  quantum well

We present a few electron double quantum dot (QD) device defined in an
isotopically purified $^{28}$Si quantum well (QW). An electron mobility of $5.5
\cdot 10^4 cm^2(Vs)^{-1}$ is observed in the QW which is the highest mobility
ever reported for a 2D electron system in $^{28}$Si. The residual concentration
of $^{29}$Si nuclei in the $^{28}$Si QW is lower than $10^{3} ppm$, at the
verge where the hyperfine interaction is theoretically no longer expected to
dominantly limit the $T_{2}$ spin dephasing time. We also demonstrate a
complete suppression of hysteretic gate behavior and charge noise using a
negatively biased global top gate.Comment: 4 pages, 3 figure