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arxiv_dataset-1000812.3874 | Vacuum Stability with Tachyonic Boundary Higgs Masses in No-Scale
Supersymmetry or Gaugino Mediation
hep-ph
No-scale supersymmetry or gaugino mediation augmented with large negative
Higgs soft masses at the input scale provides a simple solution to the
supersymmetric flavor problem while giving rise to a neutralino LSP. However,
to obtain a neutralino LSP it is often necessary to have tachyonic input Higgs
soft masses that can give rise to charge-and-color-breaking (CCB) minima and
unbounded-from-below (UFB) directions in the low energy theory. We investigate
the vacuum structure in these theories to determine when such problematic
features are present. When the standard electroweak vacuum is only metastable,
we compute its lifetime under vacuum tunneling. We find that vacuum
metastability leads to severe restrictions on the parameter space for larger
$\tan\beta \sim 30$, while for smaller $\tan\beta\sim 10$, only minor
restrictions are found. Along the way, we derive an exact bounce solution for
tunneling through an inverted parabolic potential.
| arxiv topic:hep-ph |
arxiv_dataset-1001812.3974 | Braids, Shuffles and Symmetrizers
math.QA
Multiplicative analogues of the shuffle elements of the braid group rings are
introduced; in local representations they give rise to certain graded
associative algebras (b-shuffle algebras). For the Hecke and BMW algebras, the
(anti)-symmetrizers have simple expressions in terms of the multiplicative
shuffles. The (anti)-symmetrizers can be expressed in terms of the highest
multiplicative 1-shuffles (for the Hecke and BMW algebras) and in terms of the
highest additive 1-shuffles (for the Hecke algebras). The spectra and
multiplicities of eigenvalues of the operators of the multiplication by the
multiplicative and additive 1-shuffles are examined.
| arxiv topic:math.QA |
arxiv_dataset-1002812.4074 | Effect of Landau-Zener tunneling by the varying sweeping rate of
external field
quant-ph
We study the effect of Landau-Zener (LZ) tunneling caused by the varying
sweeping rate of external field, formulating and approximately solving the
problem with many levels of the LZ tunneling rate. Comparing with the steadily
vary about sweeping field, the LZ tunneling rate will be essentially changed
because of the unsteady variation of the sweeping field in time. Thus could
help us to make the particles with in lower states transit periodically to
upper states within the finite time.
| arxiv topic:quant-ph |
arxiv_dataset-1003812.4174 | Fragmented many-body ground states for scalar bosons in a single trap
cond-mat.other
We investigate whether the many-body ground states of bosons in a generalized
two-mode model with localized inhomogeneous single-particle orbitals and
anisotropic long-range interactions (e.g. dipole-dipole interactions), are
coherent or fragmented. It is demonstrated that fragmentation can take place in
a single trap for positive values of the interaction couplings, implying that
the system is potentially stable. Furthermore, the degree of fragmentation is
shown to be insensitive to small perturbations on the single-particle level.
| arxiv topic:cond-mat.other |
arxiv_dataset-1004812.4274 | Extracting the QGP viscosity from RHIC data -- a status report from
viscous hydrodynamics
nucl-th
We report recent progress on causal viscous hydrodynamics for relativistic
heavy ion collisions. For fixed specific shear viscosity eta/s, uncertainties
in the elliptic flow arising from initial conditions, equation of state, bulk
viscosity and numerical viscosity, and the treatment of the highly viscous
hadronic stage and freeze-out procedure are analysed. A comparison of current
viscous hydrodynamic results with experimental data yields a robust upper limit
eta/s < 5/(4pi).
| arxiv topic:nucl-th |
arxiv_dataset-1005812.4374 | Transition to amplitude death in scale-free networks
nlin.AO nlin.PS
Transition to amplitude death in scale-free networks of nonlinear oscillators
is investigated. As the coupling strength increases, the network will undergo
three stages in approaching to the state of complete amplitude death. The first
stage is featured by a \emph{"stair-like"} distribution of the node amplitude,
and the transition is accomplished by a \emph{hierarchical death} of the
amplitude stairs. The second and third stages are characterized by,
respectively, a continuing elimination of the synchronous clusters and a fast
death of the non-synchronized nodes.
| arxiv topic:nlin.AO nlin.PS |
arxiv_dataset-1006812.4474 | Feshbach molecule production in fermionic atomic gases
cond-mat.other cond-mat.supr-con
This paper examines the problem of molecule production in an atomic fermionic
gas close to an s-wave Feshbach resonance by means of a magnetic field sweep
through the resonance. The density of molecules at the end of the process is
derived for narrow resonance and slow sweep.
| arxiv topic:cond-mat.other cond-mat.supr-con |
arxiv_dataset-1007812.4574 | Dynamics of a Spherical Accretion Shock with Neutrino Heating and
Alpha-Particle Recombination
astro-ph
We investigate the effects of neutrino heating and alpha-particle
recombination on the hydrodynamics of core-collapse supernovae. Our focus is on
the non-linear dynamics of the shock wave that forms in the collapse, and the
assembly of positive energy material below it. To this end, we perform
time-dependent hydrodynamic simulations with FLASH2.5 in spherical and axial
symmetry. These generalize our previous calculations by allowing for bulk
neutrino heating and for nuclear statistical equilibrium between n, p and
alpha. The heating rate is freely tunable, as is the starting radius of the
shock relative to the recombination radius of alpha-particles. An explosion in
spherical symmetry involves the excitation of an overstable mode, which may be
viewed as the L=0 version of the `Standing Accretion Shock Instability'. In 2D
simulations, non-spherical deformations of the shock are driven by plumes of
material with positive Bernoulli parameter, which are concentrated well outside
the zone of strong neutrino heating. The non-spherical modes of the shock reach
a large amplitude only when the heating rate is also high enough to excite
convection below the shock. The critical heating rate that causes an explosion
depends sensitively on the initial position of the shock relative to the
recombination radius. Weaker heating is required to drive an explosion in 2D
than in 1D, but the difference also depends on the size of the shock. Forcing
the infalling heavy nuclei to break up into n and p below the shock only causes
a slight increase in the critical heating rate, except when the shock starts
out at a large radius. This shows that heating by neutrinos (or some other
mechanism) must play a significant role in pushing the shock far enough out
that recombination heating takes over.
| arxiv topic:astro-ph |
arxiv_dataset-1008812.4674 | Modelling of 1/f noise by sequences of stochastic pulses of different
duration
physics.data-an cond-mat.stat-mech nlin.AO
We present and analyze the simple analytically solvable model of 1/f noise,
which can be relevant for the understanding of the origin, main properties and
parameter dependencies of the flicker noise. In the model, the currents or
signals represented as sequences of the random pulses, which recurrence time
intervals between transit times of pulses are uncorrelated with the shape of
the pulse, are analyzed. It is shown that for the pulses of fixed area with
random duration, distributed uniformly in a wide interval, 1/f behavior of the
power spectrum of the signal or current in wide range of frequency may be
obtained.
| arxiv topic:physics.data-an cond-mat.stat-mech nlin.AO |
arxiv_dataset-1009812.4774 | Fourier's Law: insight from a simple derivation
cond-mat.stat-mech cond-mat.mes-hall
The onset of Fourier's law in a one-dimensional quantum system is addressed
via a simple model of weakly coupled quantum systems in contact with thermal
baths at their edges. Using analytical arguments we show that the crossover
from the ballistic (invalid Fourier's law) to diffusive (valid Fourier's law)
regimes is characterized by a thermal length-scale, which is directly related
to the profile of the local temperature. In the same vein, dephasing is shown
to give rise to a classical Fourier's law, similarly to the onset of Ohm's law
in mesoscopic conductors.
| arxiv topic:cond-mat.stat-mech cond-mat.mes-hall |
arxiv_dataset-1010812.4874 | Reaction of Accretion Disks to Abrupt Mass Loss During Binary Black Hole
Merger
astro-ph
The association of an electromagnetic signal with the merger of a pair of
supermassive black holes would have many important implications. For example,
it would provide new information about gas and magnetic field interactions in
dynamical spacetimes as well as a combination of redshift and luminosity
distance that would enable precise cosmological tests. A proposal first made by
Bode & Phinney (2007) is that because radiation of gravitational waves during
the final inspiral and merger of the holes is abrupt and decreases the mass of
the central object by a few percent, there will be waves in the disk that can
steepen into shocks and thus increase the disk luminosity in a characteristic
way. We evaluate this process analytically and numerically. We find that shocks
only occur when the fractional mass loss exceeds the half-thickness (h/r) of
the disk, hence significant energy release only occurs for geometrically thin
disks which are thus at low Eddington ratios. This strongly limits the
effective energy release, and in fact our simulations show that the natural
variations in disk luminosity are likely to obscure this effect entirely.
However, we demonstrate that the reduction of luminosity caused by the retreat
of the inner edge of the disk following mass loss is potentially detectable.
This decrease occurs even if the disk is geometrically thick, and lasts for a
duration on the order of the viscous time of the modified disk.
Observationally, the best prospect for detection would be a sensitive future
X-ray instrument with a field of view of on the order of a square degree, or
possibly a wide-field radio array such as the Square Kilometer Array, if the
disk changes produce or interrupt radio emission from a jet.
| arxiv topic:astro-ph |
arxiv_dataset-1011812.4974 | Using a computer algebra system to simplify expressions for
Titchmarsh-Weyl m-functions associated with the Hydrogen Atom on the half
line
math.SP cs.SC math.CO
In this paper we give simplified formulas for certain polynomials which arise
in some new Titchmarsh-Weyl m-functions for the radial part of the separated
Hydrogen atom on the half line and two independent programs for generating them
using the symbolic manipulator Mathematica.
| arxiv topic:math.SP cs.SC math.CO |
arxiv_dataset-1012812.5074 | Simplifying and Extending the AdS_5xS^5 Pure Spinor Formalism
hep-th
Although the AdS_5xS^5 worldsheet action is not quadratic, some features of
the pure spinor formalism are simpler in an AdS_5xS^5 background than in a flat
background. The BRST operator acts geometrically, the left and right-moving
pure spinor ghosts can be treated as complex conjugates, the zero mode measure
factor is trivial, and the b ghost does not require non-minimal fields.
Furthermore, a topological version of the AdS_5xS^5 action with the same
worldsheet variables and BRST operator can be constructed by gauge-fixing a G/G
principal chiral model where G=PSU(2,2|4). This topological model is argued to
describe the zero radius limit that is dual to free N=4 super-Yang-Mills and
can also be interpreted as an "unbroken phase" of superstring theory.
| arxiv topic:hep-th |
arxiv_dataset-1013901.0058 | The Classical Nature of Thermal Conduction in Nanofluids
cond-mat.soft
Several new mechanisms have been hypothesized in the recent years to
characterize the thermal conduction behavior in nanofluids. In this paper, we
show that a large set of nanofluid thermal conductivity data is enveloped by
the well-known Hashin and Shtrikman (HS) mean-field bounds for inhomogeneous
systems. The thermal conductivity in nanofluids, therefore, is largely
dependent on whether the nanoparticles stays dispersed in the base fluid, form
linear chain-like configurations, or assume an intermediate configuration. The
experimental data, which is strikingly analogous to those in most solid
composites and liquid mixtures, provides a strong evidence for the classical
nature of thermal conduction in nanofluids.
| arxiv topic:cond-mat.soft |
arxiv_dataset-1014901.0158 | Exact results for the criticality of quench dynamics in quantum Ising
models
cond-mat.stat-mech quant-ph
Based on the obtained exact results we systematically study the quench
dynamics of a one-dimensional spin-1/2 transverse field Ising model with zero-
and finite-temperature initial states. We focus on the magnetization of the
system after a sudden change of the external field and a coherent
time-evolution process. With a zero-temperature initial state, the quench
magnetic susceptibility as a function of the initial field strength exhibits
strongly similar scaling behaviors to those of the static magnetic
susceptibility, and the quench magnetic susceptibility as a function of the
final field strength shows a discontinuity at the quantum critical point. This
discontinuity remains robust and always occurs at the quantum critical point
even for the case of finite-temperature initial systems, which indicates a
great advantage of employing quench dynamics to study quantum phase
transitions.
| arxiv topic:cond-mat.stat-mech quant-ph |
arxiv_dataset-1015901.0258 | Comment on "Interplanetary coronal mass ejections that are undetected by
solar coronagraphs" by T. A. Howard and G. M. Simnett
physics.space-ph astro-ph.SR
Howard and Simnett (HS) employed a new technique for associating LASCO CMEs
to SMEI ICMEs. In order to extrapolate the SMEI data back to the LASCO field of
view they used nonlinear trajectories, dependent on a speed and direction, what
is more realistic than the linear extrapolation with only one parameter (a
speed). However, there are two errors and one mistake in their procedure: (1)
HS used two free parameters of the direction, whereas only one can be freely
selected, because the second is provided by SMEI data. As a result, the
directions determined by HS are incorrect. (2) HS overlooked that, since the
trajectory depends on more than one parameter, there is a broad set of
trajectories, for various speeds and directions, matching the event, and thus a
broad range of the onset times. HS select only one trajectory for each SMEI
event. Therefore the associations made by them are incomplete, and they should
be reexamined. As long as it is not done any conclusion about CMEs undetected
by solar coronagraphs are premature. (3) HS made some mistake in determination
of the SMEI speeds. The speeds given in their Table 1 are about twice as high
as those demanded to obtain the onset times given in the table. It explains why
the SMEI speed distribution is excessively shifted toward high speeds ; hence,
there is no reason to search for a physical explanation.
| arxiv topic:physics.space-ph astro-ph.SR |
arxiv_dataset-1016901.0358 | Weighted Naive Bayes Model for Semi-Structured Document Categorization
cs.IR
The aim of this paper is the supervised classification of semi-structured
data. A formal model based on bayesian classification is developed while
addressing the integration of the document structure into classification tasks.
We define what we call the structural context of occurrence for unstructured
data, and we derive a recursive formulation in which parameters are used to
weight the contribution of structural element relatively to the others. A
simplified version of this formal model is implemented to carry out textual
documents classification experiments. First results show, for a adhoc weighting
strategy, that the structural context of word occurrences has a significant
impact on classification results comparing to the performance of a simple
multinomial naive Bayes classifier. The proposed implementation competes on the
Reuters-21578 data with the SVM classifier associated or not with the splitting
of structural components. These results encourage exploring the learning of
acceptable weighting strategies for this model, in particular boosting
strategies.
| arxiv topic:cs.IR |
arxiv_dataset-1017901.0458 | Gravitational waves in the Hyperspace?
astro-ph.CO
In the framework of the debate on high-frequency gravitational waves (GWs),
after a review of GWs in standard General Relativity, which is due for
completness, the possibility of merging such a traditional analysis with the
Hyperspace formalism that has been recently introduced in some papers in the
literature, with the goal of a better understanding of manifolds dimensionality
also in a cosmological framework, is discussed. Using the concept of refractive
index in the Hyperspace, spherical solutions are given and the propagation of
GWs in a region of the Hyperspace with an unitary refractive index is also
discussed. Propagation phenomena associated to the higher dimensionality are
proposed, possibly including non-linear effects. Further and accurate studies
in this direction are needed.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1018901.0558 | Luminous buried AGNs as a function of galaxy infrared luminosity
revealed through Spitzer low-resolution infrared spectroscopy
astro-ph.GA
We present the results of Spitzer IRS infrared 5-35 micron low-resolution
spectroscopic energy diagnostics of ultraluminous infrared galaxies (ULIRGs) at
z > 0.15, classified optically as non-Seyferts. Based on the equivalent widths
of polycyclic aromatic hydrocarbon emission and the optical depths of silicate
dust absorption features, we searched for signatures of intrinsically luminous,
but optically elusive, buried AGNs in these optically non-Seyfert ULIRGs. We
then combined the results with those of non-Seyfert ULIRGs at z < 0.15 and
non-Seyfert galaxies with infrared luminosities L(IR) < 10^12Lsun. We found
that the energetic importance of buried AGNs clearly increases with galaxy
infrared luminosity, becoming suddenly discernible in ULIRGs with L(IR) >
10{12}Lsun. For ULIRGs with buried AGN signatures, a significant fraction of
infrared luminosities can be accounted for by detected buried AGN and
modestly-obscured (Av < 20 mag) starburst activity. The implied masses of
spheroidal stellar components in galaxies for which buried AGNs become
important roughly correspond to the value separating red massive and blue,
less-massive galaxies in the local universe. Our results may support the
widely-proposed AGN-feedback scenario as the origin of galaxy downsizing
phenomena, where galaxies with currently larger stellar masses previously had
higher AGN energetic contributions and star-formation-originating infrared
luminosities, and have finished their major star-formation more quickly, due to
stronger AGN feedback.
| arxiv topic:astro-ph.GA |
arxiv_dataset-1019901.0658 | Higher Apery-like numbers arising from special values of the spectral
zeta function for the non-commutative harmonic oscillator
math.NT
A generalization of the Apery-like numbers, which is used to describe the
special values $\zeta_Q(2)$ and $\zeta_Q(3)$ of the spectral zeta function for
the non-commutative harmonic oscillator, are introduced and studied. In fact,
we give a recurrence relation for them, which shows a ladder structure among
them. Further, we consider the `rational part' of the higher Apery-like
numbers. We discuss several kinds of congruence relations among them, which are
regarded as an analogue of the ones among Apery numbers.
| arxiv topic:math.NT |
arxiv_dataset-1020901.0758 | Real Space Visualization of Thermomagnetic Irreversibility within
Supercooling and Superheating Spinodals in $Mn_{1.85}Co_{0.15}Sb$ using
Scanning Hall Probe Microscopy
cond-mat.str-el
Phase coexistence across disorder-broadened and magnetic-field-induced first
order antiferromagnetic to ferrimagnetic transition in polycrystalline
$Mn_{1.85}Co_{0.15}Sb$ has been studied mesoscopically by Scanning Hall Probe
Microscope at 120K and up to 5 Tesla magnetic fields. We have observed
hysteresis with varying magnetic field and the evolution of coexisting
antiferromagnetic and ferrimagnetic state on mesoscopic length scale. These
studies show that the magnetic state of the system at low field depends on the
path followed to reach 120 K. The low field magnetic states are mesoscopically
different for virgin and second field increasing cycle when 120 K is reached by
warming from 5K, but are the same within measurement accuracy when the
measuring temperature of 120K is reached from 300K by cooling.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-1021901.0858 | Weighted Well-Covered Graphs without Cycles of Length 4, 5, 6 and 7
cs.DM cs.CC
A graph is well-covered if every maximal independent set has the same
cardinality. The recognition problem of well-covered graphs is known to be
co-NP-complete. Let w be a weight function defined on the vertices of G. Then G
is w-well-covered if all maximal independent sets of G are of the same weight.
The set of weight functions w for which a graph is w-well-covered is a vector
space. We prove that finding the vector space of weight functions under which
an input graph is w-well-covered can be done in polynomial time, if the input
graph does not contain cycles of length 4, 5, 6 and 7.
| arxiv topic:cs.DM cs.CC |
arxiv_dataset-1022901.0958 | Causality and Primordial Tensor Modes
astro-ph.CO gr-qc hep-ph hep-th
We introduce the real space correlation function of $B$-mode polarization of
the cosmic microwave background (CMB) as a probe of superhorizon tensor
perturbations created by inflation. By causality, any non-inflationary
mechanism for gravitational wave production after reheating, like global phase
transitions or cosmic strings, must have vanishing correlations for angular
separations greater than the angle subtended by the particle horizon at
recombination, i.e. $\theta \gtrsim 2^\circ$. Since ordinary $B$-modes are
defined non-locally in terms of the Stokes parameters $Q$ and $U$ and therefore
don't have to respect causality, special care is taken to define `causal
$\tilde B$-modes' for the analysis. We compute the real space $\tilde B$-mode
correlation function for inflation and discuss its detectability on
superhorizon scales where it provides an unambiguous test of inflationary
gravitational waves. The correct identification of inflationary tensor modes is
crucial since it relates directly to the energy scale of inflation. Wrongly
associating tensor modes from causal seeds with inflation would imply an
incorrect inference of the energy scale of inflation. We find that the
superhorizon $\tilde B$-mode signal is above cosmic variance for the angular
range $2^\circ < \theta < 4^\circ$ and is therefore in principle detectable. In
practice, the signal will be challenging to measure since it requires
accurately resolving the recombination peak of the $B$-mode power spectrum.
However, a future CMB satellite (CMBPol), with noise level $\Delta_P \simeq
1\mu$K-arcmin and sufficient resolution to efficiently correct for
lensing-induced $B$-modes, should be able to detect the signal at more than
3$\sigma$ if the tensor-to-scalar ratio isn't smaller than $r \simeq 0.01$.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
arxiv_dataset-1023901.1058 | Relativistic Entropy and Related Boltzmann Kinetics
physics.class-ph cond-mat.stat-mech hep-ph hep-th physics.plasm-ph
It is well known that the particular form of the two-particle correlation
function, in the collisional integral of the classical Boltzmman equation, fix
univocally the entropy of the system, which turn out to be the
Boltzmann-Gibbs-Shannon entropy.
In the ordinary relativistic Boltzmann equation, some standard
generalizations, with respect its classical version, imposed by the special
relativity, are customarily performed. The only ingredient of the equation,
which tacitly remains in its original classical form, is the two-particle
correlation function, and this fact imposes that also the relativistic kinetics
is governed by the Boltzmann-Gibbs-Shannon entropy. Indeed the ordinary
relativistic Boltzmann equation admits as stationary stable distribution, the
exponential Juttner distribution.
Here, we show that the special relativity laws and the maximum entropy
principle, suggest a relativistic generalization also of the two-particle
correlation function and then of the entropy. The so obtained, fully
relativistic Boltzmann equation, obeys the H-theorem and predicts a stationary
stable distribution, presenting power-law tails in the high energy region. The
ensued relativistic kinetic theory preserves the main features of the classical
kinetics, which recovers in the $c \to \infty$ limit.
| arxiv topic:physics.class-ph cond-mat.stat-mech hep-ph hep-th physics.plasm-ph |
arxiv_dataset-1024901.1158 | Automated Detection of EUV Polar Coronal Holes During Solar Cycle 23
astro-ph.SR
A new method for automated detection of polar coronal holes is presented.
This method, called perimeter tracing, uses a series of 171, 195, and 304 \AA\
full disk images from the Extreme ultraviolet Imaging Telescope (EIT) on SOHO
over solar cycle 23 to measure the perimeter of polar coronal holes as they
appear on the limbs. Perimeter tracing minimizes line-of-sight obscurations
caused by the emitting plasma of the various wavelengths by taking measurements
at the solar limb. Perimeter tracing also allows for the polar rotation period
to emerge organically from the data as 33 days. We have called this the Harvey
rotation rate and count Harvey rotations starting 4 January 1900. From the
measured perimeter, we are then able to fit a curve to the data and derive an
area within the line of best fit. We observe the area of the northern polar
hole area in 1996, at the beginning of solar cycle 23, to be about 4.2% of the
total solar surface area and about 3.6% in 2007. The area of the southern polar
hole is observed to be about 4.0% in 1996 and about 3.4% in 2007. Thus, both
the north and south polar hole areas are no more than 15% smaller now than they
were at the beginning of cycle 23. This compares to the polar magnetic field
measured to be about 40% less now than it was a cycle ago.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1025901.1258 | Quantum gravity, minimum length and Keplerian orbits
gr-qc hep-th
We conjecture that the modified commutation relations suggested in the
context of quantum gravity (QG) persist also in the classical limit, if the
momentum of the classical object is not too large, and calculate the
corresponding perihelion precession rate for Keplerian orbits.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-1026901.1358 | Anisotropic ground states of the quantum Hall system with currents
cond-mat.mes-hall
Anisotropic states at half-filled third and higher Landau levels are
investigated in the system with a finite electric current. We study the
response of the striped Hall state and the anisotropic charge density wave
(ACDW) state against the injected current using the effective action. Current
distributions and a current dependence of the total energy are determined for
both states. With no injected current, the energy of the ACDW state is lower
than that of the striped Hall state. We find that the energy of the ACDW state
increases faster than that of the striped Hall state as the injected current
increases. Hence, the striped Hall state becomes the lower energy state when
the current exceeds the critical value. The critical value is estimated at
about 0.04 - 0.05 nA which is much smaller than the current used in the
experiments. Our calculations are performed using a block diagonalization
technique on a von Neumann lattice. We review this technique in this thesis.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-1027901.1458 | An inverse problem in number theory and geometric group theory
math.NT math.MG
This paper describes a new link between combinatorial number theory and
geometry. The main result states that A is a finite set of relatively prime
positive integers if and only if A = (K-K) \cap N, where K is a compact set of
real numbers such that for every real number x there exists y in K with x
\equiv y mod 1. In one direction, given a finite set A of relatively prime
positive integers, the proof constructs an appropriate compact set K such that
A = (K-K) \cap N. In the other direction, a strong form of a fundamental
theorem in geometric group theory is applied to prove that (K-K)\cap N is a
finite set of relatively prime positive integers if K satisfies the appropriate
geometrical conditions. Some related results and open problems are also
discussed.
| arxiv topic:math.NT math.MG |
arxiv_dataset-1028901.1558 | The influence of spin-dependent phases of tunneling electrons on the
conductance of a point ferromagnet/isolator/d-wave superconductor contact
cond-mat.supr-con
The influence of phase shifts of electron waves passing through and reflected
by the potential barrier on the Andreev reflection in a
ferromagnet/isolator/d-wave superconductor (FIS) contact is studied. It is
found that in a superconductor the surface spin-dependent Andreev bound states
inside the superconducting gap are formed as a result of the interference of
electron-like and hole-like quasiparticles due to repeated Andreev reflections.
The peak in the conductance of the FIS contact at the zero potential for the
(110)-oriented superconductor disappears rapidly as the polarization of a
ferromagnet increases, whereas for the (100)-oriented superconductor it
appears. The physical reason for this behavior of conductance is discussed.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-1029901.1658 | Discs of Satellites: the new dwarf spheroidals
astro-ph.GA
The spatial distributions of the most recently discovered ultra faint dwarf
satellites around the Milky Way and the Andromeda galaxy are compared to the
previously reported discs-of-satellites (DoS) of their host galaxies. In our
investigation we pay special attention to the selection bias introduced due to
the limited sky coverage of SDSS. We find that the new Milky Way satellite
galaxies follow closely the DoS defined by the more luminous dwarfs, thereby
further emphasizing the statistical significance of this feature in the
Galactic halo. We also notice a deficit of satellite galaxies with
Galactocentric distances larger than 100 kpc that are away from the
disc-of-satellites of the Milky Way. In the case of Andromeda, we obtain
similar results, naturally complementing our previous finding and strengthening
the notion that the discs-of-satellites are optical manifestations of a
phase-space correlation of satellite galaxies.
| arxiv topic:astro-ph.GA |
arxiv_dataset-1030901.1758 | A Geometric Derivation of the Dyon Wall-Crossing Group
hep-th
Recently, using supergravity analysis, a hyperbolic reflection group was
found to underlie the structure of wall-crossing, or the discontinuous moduli
dependence of the supersymmetric index due to the presence of walls of marginal
stability, of the BPS dyons in the N=4, d=4 compactification. In this paper we
work in the regime where four-dimensional gravity decouples and we show how the
presence of such a group structure can be easily understood as a consequence of
the supersymmetry of a system of (p,q) five-brane network, or equivalently the
holomorphicity of the Riemann surface wrapped by the appropriate M5 branes in
the Euclidean M-theory frame.
| arxiv topic:hep-th |
arxiv_dataset-1031901.1858 | Generalized Nonanalytic Expansions, PT-Symmetry and Large-Order Formulas
for Odd Anharmonic Oscillators
math-ph hep-th math.MP quant-ph
The concept of a generalized nonanalytic expansion which involves nonanalytic
combinations of exponentials, logarithms and powers of a coupling is introduced
and its use illustrated in various areas of physics. Dispersion relations for
the resonance energies of odd anharmonic oscillators are discussed, and
higher-order formulas are presented for cubic and quartic potentials.
| arxiv topic:math-ph hep-th math.MP quant-ph |
arxiv_dataset-1032901.1958 | Numerical analysis of a penalization method for the three-dimensional
motion of a rigid body in an incompressible viscous fluid
math.AP math.NA physics.class-ph
We present and analyze a penalization method wich extends the the method of
[1] to the case of a rigid body moving freely in an incompressible fluid. The
fluid-solid system is viewed as a single variable density flow with an
interface captured by a level set method. The solid velocity is computed by
averaging at avery time the flow velocity in the solid phase. This velocity is
used to penalize the flow velocity at the fluid-solid interface and to move the
interface. Numerical illustrations are provided to illustrate our convergence
result. A discussion of our result in the light of existing existence results
is also given. [1] Ph. Angot, C.-H. Bruneau and P. Fabrie, A penalization
method to take into account obstacles in incompressible viscous flows, Numer.
Math. 81: 497--520 (1999)
| arxiv topic:math.AP math.NA physics.class-ph |
arxiv_dataset-1033901.2058 | "Old" Locked Inflation
hep-th hep-ph
In this paper, we revisit the idea of locked inflation, which does not
require a potential satisfying the normal slow-roll condition, but suffers from
the problems associated with "saddle inflation". We propose a scenario based on
locked inflation, however, with an alternative evolution mechanism of the
"waterfall field" $\phi$. Instead of rolling down along the potential, the
$\phi$ field will tunnel to end the inflation stage like in old inflation, by
which the saddle inflation could be avoided. Further, we study a cascade of old
locked inflation, which can be motivated by the string landscape. Our model is
based on the consideration of making locked inflation feasible so as to give a
working model without slow roll; It also can be seen as an effort to embed the
old inflation in string landscape.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-1034901.2158 | A Note on a Brill-Noether Locus over a Non-hyperelliptic curve of genus
4
math.AG
We prove that a certain Brill-Noether locus over a non-hyperelliptic curve
$C$ of genus 4, is isomorphic to the \textit{Donagi-Izadi cubic threefold} in
the case when the pencils of the two trigonal line bundles of $C$ coincide.
| arxiv topic:math.AG |
arxiv_dataset-1035901.2258 | Hawking Radiation due to Photon and Gravitino Tunneling
hep-th gr-qc
Applying the Hamilton--Jacobi method we investigate the tunneling of photon
across the event horizon of a static spherically symmetric black hole. The
necessity of the gauge condition on the photon field, to derive the
semiclassical Hawking temperature, is explicitly shown. Also, the tunneling of
photon and gravitino beyond this semiclassical approximation are presented
separately. Quantum corrections of the action for both cases are found to be
proportional to the semiclassical contribution. Modifications to the Hawking
temperature and Bekenstein-Hawking area law are thereby obtained. Using this
corrected temperature and Hawking's periodicity argument, the modified metric
for the Schwarzschild black hole is given. This corrected version of the
metric, upto $\hbar$ order is equivalent to the metric obtained by including
one loop back reaction effect. Finally, the coefficient of the leading order
correction of entropy is shown to be related to the trace anomaly.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-1036901.2358 | Relative Unitary Implementability of Perturbed Quantum Field Dynamics on
de-Sitter Space
gr-qc
In this article, we study the quantum dynamics of a Klein-Gordon field on
de-Sitter space. We prove time evolution is not unitarily implementable. We
also consider a Klein-Gordon field perturbed by a local potential V. In this
case we prove that the deviation from the V=0 dynamics is unitarily
implementable.
| arxiv topic:gr-qc |
arxiv_dataset-1037901.2458 | Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy
Disks and Compact Spheroids
astro-ph.GA astro-ph.CO
We present a simple theoretical framework for massive galaxies at high
redshift, where the main assembly and star formation occurred, and report on
the first cosmological simulations that reveal clumpy disks consistent with our
analysis. The evolution is governed by the interplay between smooth and clumpy
cold streams, disk instability, and bulge formation. Intense, relatively smooth
streams maintain an unstable dense gas-rich disk. Instability with high
turbulence and giant clumps, each a few percent of the disk mass, is
self-regulated by gravitational interactions within the disk. The clumps
migrate into a bulge in ~10 dynamical times, or ~0.5Gyr. The cosmological
streams replenish the draining disk and prolong the clumpy phase to several
Gigayears in a steady state, with comparable masses in disk, bulge, and dark
matter within the disk radius. The clumps form stars in dense subclumps
following the overall accretion rate, ~100 Msun/yr, and each clump converts
into stars in ~0.5 Gyr. While the clumps coalesce dissipatively to a compact
bulge, the star-forming disk is extended because the incoming streams keep the
outer disk dense and susceptible to instability and because of angular momentum
transport. Passive spheroid-dominated galaxies form when the streams are more
clumpy: the external clumps merge into a massive bulge and stir up disk
turbulence that stabilize the disk and suppress in situ clump and star
formation. We predict a bimodality in galaxy type by z~3, involving giant-clump
star-forming disks and spheroid-dominated galaxies of suppressed star
formation. After z~1, the disks tend to be stabilized by the dominant stellar
disks and bulges. Most of the high-z massive disks are likely to end up as
today's early-type galaxies.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-1038901.2558 | Light scattering from an isotropic layer between uniaxial crystals
cond-mat.mtrl-sci cond-mat.other physics.geo-ph
We develop a model for the reflection and transmission of plane waves by an
isotropic layer sandwiched between two uniaxial crystals of arbitrary
orientation. In the laboratory frame, reflection and transmission coefficients
corresponding to the principal polarization directions in each crystal are
given explicitly in terms of the c-axis and propagation directions. The
solution is found by first deriving explicit expressions for reflection and
transmission amplitude coefficients for waves propagating from an arbitrarily
oriented uniaxial anisotropic material into an isotropic material. By combining
these results with Lekner's (1991) earlier treatment of waves propagating from
isotropic media to anisotropic media and employing a matrix method we determine
a solution to the general form of the multiple reflection case. The example
system of a wetted interface between two ice crystals is used to contextualize
the results.
| arxiv topic:cond-mat.mtrl-sci cond-mat.other physics.geo-ph |
arxiv_dataset-1039901.2658 | Rational points on certain del Pezzo surfaces of degree one
math.NT
Let $f(z)=z^5+az^3+bz^2+cz+d \in \Z[z]$ and let us consider a del Pezzo
surface of degree one given by the equation $\cal{E}_{f}: x^2-y^3-f(z)=0$. In
this note we prove that if the set of rational points on the curve $E_{a,
b}:Y^2=X^3+135(2a-15)X-1350(5a+2b-26)$ is infinite, then the set of rational
points on the surface $\cal{E}_{f}$ is dense in the Zariski topology.
| arxiv topic:math.NT |
arxiv_dataset-1040901.2758 | Field angle dependence of the zero-energy density of states in
unconventional superconductors: analysis of the borocarbide superconductor
YNi2B2C
cond-mat.supr-con
We investigate the field-angle-dependent zero-energy density of states for
YNi2B2C with using realistic Fermi surfaces obtained by band calculations. Both
the 17th and 18th bands are taken into account. For calculating the oscillating
density of states, we adopt the Kramer-Pesch approximation, which is found to
improve accuracy in the oscillation amplitude. We show that superconducting gap
structure determined by analyzing STM experiments is consistent with thermal
transport and heat capacity measurements.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-1041901.2858 | QPOs from Random X-ray Bursts around Rotating Black Holes
astro-ph.HE
We continue our earlier studies of quasi-periodic oscillations (QPOs) in the
power spectra of accreting, rapidly-rotating black holes that originate from
the geometric "light echoes" of X-ray flares occurring within the black hole
ergosphere. Our present work extends our previous treatment to
three-dimensional photon emission and orbits to allow for arbitrary latitudes
in the positions of the distant observers and the X-ray sources in place of the
mainly equatorial positions and photon orbits of the earlier consideration.
Following the trajectories of a large number of photons we calculate the
response functions of a given geometry and use them to produce model light
curves which we subsequently analyze to compute their power spectra and
autocorrelation functions. In the case of an optically-thin environment,
relevant to advection-dominated accretion flows, we consistently find QPOs at
frequencies of order of ~kHz for stellar-mass black hole candidates while order
of ~mHz for typical active galactic nuclei (~10^7 Msun) for a wide range of
viewing angles (30 to 80deg) from X-ray sources predominantly concentrated
toward the equator within the ergosphere. As in our previous treatment, here
too, the QPO signal is produced by the frame-dragging of the photons by the
rapidly-rotating black hole, which results in photon "bunches" separated by
constant time-lags, the result of multiple photon orbits around the hole. Our
model predicts for various source/observer configurations the robust presence
of a new class of QPOs, which is inevitably generic to curved spacetime
structure in rotating black hole systems.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1042901.2958 | Gravitational-wave confusion background from cosmological compact
binaries: Implications for future terrestrial detectors
gr-qc astro-ph.CO astro-ph.HE
Increasing the sensitivity of a gravitational-wave (GW) detector improves our
ability to measure the characteristics of detected sources. It also increases
the number of weak signals that contribute to the data. Because GW detectors
have nearly all-sky sensitivity, they can be subject to a confusion limit: Many
sources which cannot be distinguished may be measured simultaneously, defining
a stochastic noise floor to the sensitivity. For GW detectors operating at
present and for their planned upgrades, the projected event rate is
sufficiently low that we are far from the confusion-limited regime. However,
some detectors currently under discussion may have large enough reach to binary
inspiral that they enter the confusion-limited regime. In this paper, we
examine the binary inspiral confusion limit for terrestrial detectors. We
consider a broad range of inspiral rates in the literature, several planned
advanced gravitational-wave detectors, and the highly advanced "Einstein
Telescope" design. Though most advanced detectors will not be impacted by this
limit, the Einstein Telescope with a very low frequency "seismic wall" may be
subject to confusion noise. At a minimum, careful data analysis will be require
to separate signals which will appear confused. This result should be borne in
mind when designing highly advanced future instruments.
| arxiv topic:gr-qc astro-ph.CO astro-ph.HE |
arxiv_dataset-1043901.3058 | Conventional nuclear effects on generalized parton distributions of
trinucleons
nucl-th hep-ph
The measurement of nuclear Generalized Parton Distributions (GPDs) will
represent a valuable tool to understand the structure of bound nucleons in the
nuclear medium, as well as the role of non-nucleonic degrees of freedom in the
phenomenology of hard scattering off nuclei. By using a realistic microscopic
approach for the evaluation of GPDs of 3He, it will be shown that conventional
nuclear effects, such as isospin and binding ones, or the uncertainty related
to the use of a given nucleon-nucleon potential, are rather bigger than in the
forward case. These findings suggest that, if great attention is not paid to
infer the properties of nuclear GPDs from those of nuclear parton
distributions, conventional nuclear effects can be easily mistaken for exotic
ones. It is stressed therefore that 3He, for which the best realistic
calculations are possible, represents a unique target to discriminate between
conventional and exotic effects. The complementary information which could be
obtained by using a 3H target is also addressed.
| arxiv topic:nucl-th hep-ph |
arxiv_dataset-1044901.3158 | Renormalizability of a quark-gluon model with soft BRST breaking in the
infrared region
hep-th
We prove the renormalizability of a quark-gluon model with a soft breaking of
the BRST symmetry, which accounts for the modification of the large distance
behavior of the quark and gluon correlation functions. The proof is valid to
all orders of perturbation theory, by making use of softly broken Ward
identities.
| arxiv topic:hep-th |
arxiv_dataset-1045901.3258 | Measuring the neutron star equation of state with gravitational wave
observations
gr-qc astro-ph.HE
We report the results of a first study that uses numerical simulations to
estimate the accuracy with which one can use gravitational wave observations of
double neutron star inspiral to measure parameters of the neutron-star equation
of state. The simulations use the evolution and initial-data codes of Shibata
and Uryu to compute the last several orbits and the merger of neutron stars,
with matter described by a parametrized equation of state. Previous work
suggested the use of an effective cutoff frequency to place constraints on the
equation of state. We find, however, that greater accuracy is obtained by
measuring departures from the point-particle limit of the gravitational
waveform produced during the late inspiral.
As the stars approach their final plunge and merger, the gravitational wave
phase accumulates more rapidly for smaller values of the neutron star
compactness (the ratio of the mass of the neutron star to its radius). We
estimate that realistic equations of state will lead to gravitational waveforms
that are distinguishable from point particle inspirals at an effective distance
(the distance to an optimally oriented and located system that would produce an
equivalent waveform amplitude) of 100 Mpc or less. As Lattimer and Prakash
observed, neutron-star radius is closely tied to the pressure at density not
far above nuclear. Our results suggest that broadband gravitational wave
observations at frequencies between 500 and 1000 Hz will constrain this
pressure, and we estimate the accuracy with which it can be measured. Related
first estimates of radius measurability show that the radius can be determined
to an accuracy of ~1 km at 100 Mpc.
| arxiv topic:gr-qc astro-ph.HE |
arxiv_dataset-1046901.3358 | Dark Matter Production at LHC from Black Hole Remnants
hep-ph astro-ph.CO gr-qc hep-ex hep-th
We study dark matter production at CERN LHC from black hole remnants (BHR).
We find that the typical mass of these BHR at LHC is ~ 5-10 TeV which is
heavier than other dark matter candidates such as: axion, axino, neutralino
etc. We propose the detection of this dark matter via single jet production in
the process pp -> jet +BHR(dark matter) at CERN LHC. We find that for zero
impact parameter partonic collisions, the monojet cross section is not
negligible in comparison to the standard model background and is much higher
than the other dark matter scenarios studied so far. We also find that
d\sigma/dp_T of jet production in this process increases as p_T increases,
whereas in all other dark matter scenarios the d\sigma/dp_T decreases at CERN
LHC. This may provide an useful signature for dark matter detection at LHC.
However, we find that when the impact parameter dependent effect of
inelasticity is included, the monojet cross section from the above process
becomes much smaller than the standard model background and may not be
detectable at LHC.
| arxiv topic:hep-ph astro-ph.CO gr-qc hep-ex hep-th |
arxiv_dataset-1047901.3458 | The long wavelength limit of hard thermal loop effective actions
hep-th
We derive a closed form expression for the long wavelength limit of the
effective action for hard thermal loops in an external gravitational field. It
is a function of the metric, independent of time derivatives. It is compared
and contrasted with the static limit, and with the corresponding limits in an
external Yang-Mills field.
| arxiv topic:hep-th |
arxiv_dataset-1048901.3558 | Bethe ansatz of the open spin-s XXZ chain with nondiagonal boundary
terms
hep-th
We consider the open spin-s XXZ quantum spin chain with nondiagonal boundary
terms. By exploiting certain functional relations at roots of unity, we propose
the Bethe ansatz solution for the transfer matrix eigenvalues for cases where
atmost two of the boundary parameters are set to be arbitrary and the bulk
anisotropy parameter has values \eta = i \pi/3, i \pi/5,... We present
numerical evidence to demonstrate completeness of the Bethe ansatz solutions
derived for s = 1/2 and s = 1.
| arxiv topic:hep-th |
arxiv_dataset-1049901.3658 | Global Solutions for Incompressible Viscoelastic Fluids
math.AP
We prove the existence of both local and global smooth solutions to the
Cauchy problem in the whole space and the periodic problem in the n-dimensional
torus for the incompressible viscoelastic system of Oldroyd-B type in the case
of near equilibrium initial data. The results hold in both two and three
dimensional spaces. The results and methods presented in this paper are also
valid for a wide range of elastic complex fluids, such as magnetohydrodynamics,
liquid crystals and mixture problems.
| arxiv topic:math.AP |
arxiv_dataset-1050901.3758 | Carbon Nanotubes in Biology and Medicine: in vitro and in vivo
Detection, Imaging and Drug Delivery
cond-mat.mtrl-sci
Carbon nanotubes exhibit many unique intrinsic physical and chemical
properties and have been intensively explored for biological and biomedical
applications. In this review, we summarize the main results of our and other
groups in this field and clarify that surface functionalization is critical to
the behaviors of carbon nanotubes in biological systems. Ultra-sensitive
detection of biological species with carbon nanotubes can be realized after
surface passivation to inhibit the non-specific binding of bio-molecules on the
hydrophobic nanotube surface. Electrical nanosensors based on nanotubes provide
a label-free approach to biological detections. Surface enhanced Raman
spectroscopy of CNT opens up a method of protein microarray with down to 1 fM
detection sensitivity. In vitro and in vivo toxicity studies reveal that well
water soluble and serum stable nanotubes are biocompatible, non-toxic and
potentially useful for biomedical applications. In vivo biodistributions vary
with the functionalization and possibly also sizes of nanotubes, with a
tendency of accumulation in the reticuloendothelial systems, including the
liver and spleen, after intravenous administration. If well functionalized,
nanotubes may be excreted mainly through the biliary pathway in feces. Carbon
nanotube-based drug delivery has shown promises in various in vitro and in vivo
experiments including delivery pf small interfering RNA, paclitaxel and
doxorubicin. Moreover, SWNTs with various interesting intrinsic optical
properties have been used as novel photoluminance, Raman and photoacoustic
contrast agents for imaging of cells and animals. Further multidisciplinary
explorations in this field are promising and may bring new opportunities to the
realm of biomedicine.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-1051901.3858 | Disk-Magnetosphere Interaction and Outflows: Conical Winds and Axial
Jets
astro-ph.SR
We investigate outflows from the disk-magnetosphere boundary of rotating
magnetized stars in cases where the magnetic field of a star is bunched into an
X-type configuration using axisymmetric and full 3D MHD simulations. Such
configuration appears if viscosity in the disk is larger than diffusivity, or
if the accretion rate in the disk is enhanced. Conical outflows flow from the
inner edge of the disk to a narrow shell with an opening angle 30-45 degrees.
Outflows carry 0.1-0.3 of the disk mass and part of the disk's angular momentum
outward. Conical outflows appear around stars of different periods, however in
case of stars in the "propeller" regime, an additional - much faster component
appears: an axial jet, where matter is accelerated up to very high velocities
at small distances from the star by magnetic pressure force above the surface
of the star. Exploratory 3D simulations show that conical outflows are
symmetric about rotational axis of the disk even if magnetic dipole is
significantly misaligned. Conical outflows and axial jets may appear in
different types of young stars including Class I young stars, classical T Tauri
stars, and EXors.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1052901.3958 | Gedanken Worlds without Higgs: QCD-Induced Electroweak Symmetry Breaking
hep-ph
To illuminate how electroweak symmetry breaking shapes the physical world, we
investigate toy models in which no Higgs fields or other constructs are
introduced to induce spontaneous symmetry breaking. Two models incorporate the
standard SU(3)_c x SU(2)_L x U(1)_Y gauge symmetry and fermion content similar
to that of the standard model. The first class--like the standard electroweak
theory--contains no bare mass terms, so the spontaneous breaking of chiral
symmetry within quantum chromodynamics is the only source of electroweak
symmetry breaking. The second class adds bare fermion masses sufficiently small
that QCD remains the dominant source of electroweak symmetry breaking and the
model can serve as a well-behaved low-energy effective field theory to energies
somewhat above the hadronic scale. A third class of models is based on the
left-right--symmetric SU(3)_c x SU(2)_L x SU(2)_R x U(1)_{B-L} gauge group. In
a fourth class of models, built on SU(4)_{PS} x SU(2)_L x SU(2)_R gauge
symmetry, lepton number is treated as a fourth color. Many interesting
characteristics of the models stem from the fact that the effective strength of
the weak interactions is much closer to that of the residual strong
interactions than in the real world. The Higgs-free models not only provide
informative contrasts to the real world, but also lead us to consider
intriguing issues in the application of field theory to the real world.
| arxiv topic:hep-ph |
arxiv_dataset-1053901.4059 | No cross-interactions among different tensor fields with the mixed
symmetry (3,1) intermediated by a vector field
hep-th
Under the hypotheses of analyticity in the coupling constant, locality,
Lorentz covariance, and Poincare invariance of the deformations, combined with
the preservation of the number of derivatives on each field, the consistent
interactions between a collection of free massless tensor gauge fields with the
mixed symmetry of a two-column Young diagram of the type (3,1) and one Abelian
vector field, respectively a $p$-form gauge field, are addressed. The main
result is that a single mixed symmetry tensor field from the collection gets
coupled to the vector field/$p$-form. Our final result resembles to the well
known fact from General Relativity according to which there is one graviton in
a given world.
| arxiv topic:hep-th |
arxiv_dataset-1054901.4159 | Electronic Cooling in Graphene
cond-mat.mes-hall
Energy transfer to acoustic phonons is the dominant low-temperature cooling
channel of electrons in a crystal.For cold neutral graphene we find that the
weak cooling power of its acoustical modes relative to the heat capacity of the
system leads to a power law decay of the electronic temperature when far from
equilibrium. For heavily doped graphene a high electronic temperature is shown
to initially decrease linearly with time at a rate proportional to n^(3/2) with
n being the electronic density. We discuss the relative importance of optical
and acoustic phonons to cooling.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-1055901.4259 | X-ray Magnetic Circular Dichroism of Valence Fluctuating State in Eu at
High Magnetic Fields
cond-mat.str-el cond-mat.mtrl-sci
X-ray magnetic circular dichroism (XMCD) at the Eu L-edge (2p->5d) in two
compounds exhibiting valence fluctuation, namely EuNi2(Si0.18Ge0.82)2 and
EuNi2P2, has been investigated at pulsed high magnetic fields of up to 40 T. A
distinct XMCD peak corresponding to the trivalent state (Eu3+; f6), whose
ground state is nonmagnetic (J=0), was observed in addition to the main XMCD
peak corresponding to the magnetic (J=7/2) divalent state (Eu2+; f7). This
result indicates that the 5d electrons belonging to both valence states are
magnetically polarized. It was also found that the ratio P5d(3+)/P5d(2+)
between the polarization of 5d electrons (P5d) in the Eu3+ state and that of
Eu2+ is ~ 0.1 in EuNi2(Si0.18Ge0.82)2 and ~ 0.3 in EuNi2P2 at magnetic fields
where their macroscopic magnetization values are the same. The possible origin
of the XMCD of the Eu3+ state and an explanation of the dependence of
P5d(3+)/P5d(2+) on the material are discussed in terms of hybridization between
the conduction electrons and the f electrons.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-1056901.4359 | Global regularity of solutions to systems of reaction-diffusion with
Sub-Quadratic Growth in any dimension
math.AP math-ph math.MP
This paper is devoted to the study of the regularity of solutions to some
systems of reaction--diffusion equations, with reaction terms having a
subquadratic growth. We show the global boundedness and regularity of
solutions, without smallness assumptions, in any dimension $N$.
The proof is based on blow-up techniques. The natural entropy of the system
plays a crucial role in the analysis. It allows us to use of De Giorgi type
methods introduced for elliptic regularity with rough coefficients. In spite
these systems are entropy supercritical, it is possible to control the
hypothetical blow-ups, in the critical scaling, via a very weak norm. Analogies
with the Navier-Stokes equation are briefly discussed in the introduction.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-1057901.4459 | Multiplicity of positive solutions for nonlinear field equations in
$\R^{N}$
math.AP
In this paper we study the multiplicity of positive solutions for nonlinear
elliptic equations on $\R^N$. The number of solutions is greater or equal than
the number of disjoint intervals on which the nonlinear term is negative.
Applications are given to multiplicity of standing waves for the nonlinear
Schr\"odinger and Klein-Gordon equations.
| arxiv topic:math.AP |
arxiv_dataset-1058901.4559 | Optical polarisation of the Crab pulsar: precision measurements and
comparison to the radio emission
astro-ph.SR
The linear polarisation of the Crab pulsar and its close environment was
derived from observations with the high-speed photo-polarimeter OPTIMA at the
2.56-m Nordic Optical Telescope in the optical spectral range (400 - 750 nm).
Time resolution as short as 11 microseconds, which corresponds to a phase
interval of 1/3000 of the pulsar rotation, and high statistics allow the
derivation of polarisation details never achieved before. The degree of optical
polarisation and the position angle correlate in surprising details with the
light curves at optical wavelengths and at radio frequencies of 610 and 1400
MHz. Our observations show that there exists a subtle connection between
presumed non-coherent (optical) and coherent (radio) emissions. This finding
supports previously detected correlations between the optical intensity of the
Crab and the occurrence of giant radio pulses. Interpretation of our
observations require more elaborate theoretical models than those currently
available in the literature.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1059901.4659 | An "algebraic" reconstruction of piecewise-smooth functions from
integral measurements
math.CA
This paper presents some results on a well-known problem in Algebraic Signal
Sampling and in other areas of applied mathematics: reconstruction of
piecewise-smooth functions from their integral measurements (like moments,
Fourier coefficients, Radon transform, etc.). Our results concern
reconstruction (from the moments) of signals in two specific classes: linear
combinations of shifts of a given function, and "piecewise $D$-finite
functions" which satisfy on each continuity interval a linear differential
equation with polynomial coefficients.
| arxiv topic:math.CA |
arxiv_dataset-1060901.4759 | Non-BCS behavior of optical properties across the cuprate phase diagram
cond-mat.supr-con cond-mat.str-el
The finite-frequency optical properties of the underdoped cuprates, in both
the normal and superconducting state, display features which go beyond a Fermi
liquid and a BCS description. We provide an understanding of these properties
within a simplified analytical model, which has been evolved out of the Hubbard
model and ideas based on a resonating valence bond spin liquid. We find that:
1) in underdoped samples, the missing area integrals reveal a second energy
scale due to the pseudogap, not present at optimum or overdoping; 2) the real
part of the optical self-energy shows a large sharp peak, that emerges with the
opening of the pseudogap which exists within the superconducting state and
persists in the normal state; and 3) the amount of optical spectral weight
which is transferred to the condensate is greatly reduced by the presence of
the pseudogap as compared to the Fermi liquid case. These non-BCS features of
the superconducting state are in good qualitative agreement with a body of
experimental work on different cuprate systems and provide strong evidence from
optical conductivity that they are all a manifestation of the pseudogap energy
scale.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-1061901.4859 | An absolute Johnson noise thermometer
physics.ins-det physics.gen-ph
We developed an absolute Johnson noise thermometer (JNT), an instrument to
measure the thermodynamic temperature of a sensing resistor, with traceability
to voltage, resistance and frequency quantities. The temperature is measured in
energy units, and can be converted to SI units (kelvin) with the accepted value
of the Boltzmann constant kb; or, conversely, it can be employed to perform
measurements at the triple point of water, and obtain a determination of kb.
The thermometer is composed of a correlation spectrum analyzer an a calibrated
noise source, both constructed around commercial mixed-signal boards. The
calibrator generates a pseudorandom noise, by digital synthesis and amplitude
scaling with inductive voltage dividers; the signal spectrum is a frequency
comb covering the measurement bandwidth. JNT measurements at room temperature
are compatible with those of a standard platinum resistance thermometer within
the combined uncertainty of 60 ppm. A path towards future improvements of JNT
accuracy is also sketched.
| arxiv topic:physics.ins-det physics.gen-ph |
arxiv_dataset-1062901.4959 | Persistent entanglement due to helicity conservation in excitable media
math-ph math.MP
This work addresses the topic of knotted stable structures in excitable
media. These structures appear in a wide variety of situations, such as cardiac
fibrillation, chemical reactions, etc. Entangled curves have been found in
numerical computations of the equations that describe excitable media. They
present an unusual stability. An explanation for this behaviour has been an
open question. In the present work we introduce for the first time the meaning
of the helicity in an excitable media as a new tool to study the stability of
these systems. The helicity is related to the total entanglement of the system.
We have studied how the helicity is conserved or lost through the walls of the
medium and shown that these behaviours are dominated by the boundary
conditions, so the distortion of these conditions could lead to the
disappearance of the structures.
| arxiv topic:math-ph math.MP |
arxiv_dataset-1063902.0084 | On a problem of Frobenius in three numbers
cs.DM
For three positive integers ai, aj, ak pairwise coprime, we present an
algorithm that find the least multiple of ai that is a positive linear
combination of aj, ak. The average running time of this algorithm is O(1).
Using this algorithm and the chinese remainder theorem leads to a direct
computation of the Frobenius number f(a1, a2, a3).
| arxiv topic:cs.DM |
arxiv_dataset-1064902.0184 | Transverse Spin Physics at COMPASS
hep-ex
The study of transverse spin effects is part of the scientific program of
COMPASS, a fixed target experiment at the CERN SPS. COMPASS investigates the
transversity PDFs in semi-inclusive DIS, using a longitudinally polarized muon
beam of 160 GeV/c impinging on a transversely polarized target. From 2002 to
2004, data have been collected using a $^6$LiD target transversely polarized.
Transversity has been measured using different quark polarimeters: the
azimuthal distribution of single hadrons, the azimuthal dependence of the plane
containing hadron pairs, and the measurement of the transverse polarization of
baryons ($\Lambda$ hyperons). All the asymmetries have been found to be small,
and compatible with zero, a result which has been interpreted as a cancellation
between the u and d-quark contributions. In 2007 COMPASS has taken data using a
NH$_3$ polarized proton target which will give complementary information on
transverse spin effects.
| arxiv topic:hep-ex |
arxiv_dataset-1065902.0284 | Critical properties of superconducting Ba1-xKxFe2As2
cond-mat.supr-con cond-mat.str-el
Magnetisation and magnetoresistance measurements have been carried out on
superconducting Ba1-xKxFe2As2 samples with x=0.40 and 0.50. From low field
magnetization data carried out at different temperatures below TC, HC1 has been
extracted. The plot of HC1 versus temperature shows an anomalous increase at
low temperatures. From high field magnetization hysterisis measurements carried
out in fields up to 16 T at 4.2 K and 20 K, the critical current density has
been evaluated using the Bean critical state model. The JC determined from the
high field data is >104A/cm2 at 4.2 K and 5 T. The superconducting transitions
were also measured resistively in increasing applied magnetic fields up to 12
Tesla. From the variation of the TC onset with applied field, dHC2/dT at TC was
obtained to be -7.708 T/K and -5.57 T/K in the samples with x=0.40 and 0.50.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-1066902.0384 | Evidence for a Non-Uniform Initial Mass Function in the Local Universe
astro-ph.GA astro-ph.CO astro-ph.SR
Many results in modern astrophysics rest on the notion that the Initial Mass
Function (IMF) is universal. Our observations of HI selected galaxies in the
light of H-alpha and the far-ultraviolet (FUV) challenge this notion. The flux
ratio H-alpha/FUV from these two star formation tracers shows strong
correlations with the surface-brightness in H-alpha and the R band: Low Surface
Brightness (LSB) galaxies have lower ratios compared to High Surface Brightness
galaxies and to expectations from equilibrium star formation models using
commonly favored IMF parameters. Weaker but significant correlations of
H-alpha/FUV with luminosity, rotational velocity and dynamical mass are found
as well as a systematic trend with morphology. The correlated variations of
H-alpha/FUV with other global parameters are thus part of the larger family of
galaxy scaling relations. The H-alpha/FUV correlations can not be due to dust
correction errors, while systematic variations in the star formation history
can not explain the trends with both H-alpha and R surface brightness. LSB
galaxies are unlikely to have a higher escape fraction of ionizing photons
considering their high gas fraction, and color-magnitude diagrams. The most
plausible explanation for the correlations are systematic variations of the
upper mass limit and/or slope of the IMF at the upper end. We outline a
scenario of pressure driving the correlations by setting the efficiency of the
formation of the dense star clusters where the highest mass stars form. Our
results imply that the star formation rate measured in a galaxy is highly
sensitive to the tracer used in the measurement. A non-universal IMF also calls
into question the interpretation of metal abundance patterns in dwarf galaxies
and star formation histories derived from color magnitude diagrams. Abridged.
| arxiv topic:astro-ph.GA astro-ph.CO astro-ph.SR |
arxiv_dataset-1067902.0484 | Spin relaxation in sub-monolayer and monolayer InAs structures grown in
GaAs matrix
cond-mat.mes-hall
Electron spin dynamics in InAs/GaAs heterostructures consisting of a single
layer of InAs (1/3$\sim$1 monolayer) embeded in (001) and (311)A GaAs matrix
was studied by means of time-resolved Kerr rotation spectroscopy. The spin
relaxation time of the sub-monolayer InAs samples is significantly enhanced,
compared with that of the monolayer InAs sample. We attributed the slowing of
the spin relaxation to dimensionally constrained
D\textquoteright{}yakonov-Perel\textquoteright{} mechanism in the motional
narrowing regime. The electron spin relaxation time and the effective g-factor
in sub-monolayer samples were found to be strongly dependent on the
photon-generated carrier density. The contribution from both
D\textquoteright{}yakonov-Perel\textquoteright{} mechanism and Bir-Aronov-Pikus
mechanism were discussed to interpret the temperature dependence of spin
decoherence at various carrier densities.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-1068902.0584 | Variance limite d'une marche al\'eatoire r\'eversible en milieu
al\'eatoire sur Z (Limit of the Variance of a Reversible Random Walk in
Random Medium on Z)
math.PR
The Central Limit Theorem for the random walk on a stationary random network
of conductances has been studied by several authors. In one dimension, when
conductances and resistances are integrable, and following a method of
martingale introduced by S. Kozlov (1985), we can prove the Quenched Central
Limit Theorem. In that case the variance of the limit law is not null. When
resistances are not integrable, the Annealed Central Limit Theorem with null
variance was established by Y. Derriennic and M. Lin (personal communication).
The quenched version of this last theorem is proved here, by using a very
simple method. The similar problem for the continuous diffusion is then
considered. Finally our method allows us to prove an inequality for the
quadratic mean of a diffusion (X_t)_t at all time t.
| arxiv topic:math.PR |
arxiv_dataset-1069902.0684 | Projective reflection groups
math.CO math.RT
We introduce the class of projective reflection groups which includes all
complex reflection groups. We show that several aspects involving the
combinatorics and the representation theory of all non exceptional irreducible
complex reflection groups find a natural description in this wider setting.
| arxiv topic:math.CO math.RT |
arxiv_dataset-1070902.0784 | Campbell diagrams of weakly anisotropic flexible rotors
math-ph astro-ph.EP math.MP nlin.PS physics.class-ph physics.flu-dyn physics.geo-ph physics.plasm-ph
We consider an axi-symmetric rotor perturbed by dissipative, conservative,
and non-conservative positional forces originated at the contact with the
anisotropic stator. The Campbell diagram of the unperturbed system is a
mesh-like structure in the frequency-speed plane with double eigenfrequencies
at the nodes. The diagram is convenient for the analysis of the traveling waves
in the rotating elastic continuum. Computing sensitivities of the doublets we
find that at every particular node the untwisting of the mesh into the branches
of complex eigenvalues in the first approximation is generically determined by
only four 2x2 sub-blocks of the perturbing matrix. Selection of the unstable
modes that cause self-excited vibrations in the subcritical speed range, is
governed by the exceptional points at the corners of the singular eigenvalue
surfaces--`double coffee filter' and `viaduct'--which are associated with the
crossings of the unperturbed Campbell diagram with the definite Krein
signature. The singularities connect the problems of wave propagation in the
rotating continua with that of electromagnetic and acoustic wave propagation in
non-rotating anisotropic chiral media. As mechanical examples a model of a
rotating shaft with two degrees of freedom and a continuous model of a rotating
circular string passing through the eyelet are studied in detail.
| arxiv topic:math-ph astro-ph.EP math.MP nlin.PS physics.class-ph physics.flu-dyn physics.geo-ph physics.plasm-ph |
arxiv_dataset-1071902.0884 | Translated Poisson approximation to equilibrium distributions of Markov
population processes
math.PR
The paper is concerned with the equilibrium distributions of continuous-time
density dependent Markov processes on the integers. These distributions are
known typically to be approximately normal, and the approximation error, as
measured in Kolmogorov distance, is of the smallest order that is compatible
with their having integer support. Here, an approximation in the much stronger
total variation norm is established, without any loss in the asymptotic order
of accuracy; the approximating distribution is a translated Poisson
distribution having the same variance and (almost) the same mean. Our arguments
are based on the Stein-Chen method and Dynkin's formula.
| arxiv topic:math.PR |
arxiv_dataset-1072902.0984 | Multiband superfluidity and superfluid to band-insulator transition of
strongly interacting fermions in an optical lattice
cond-mat.other
We study the multiband superfluid and the superfluid (SF) to band insulator
(BI) transition of strongly interacting fermionic atoms in an optical lattice
at a filling of two fermions per well. We present physical arguments to show
that a consistent mean field description of this problem is obtained by
retaining only intraband pairing between the fermions. Using this approach we
obtain a reasonable account of the experimentally observed critical lattice
depth for the SF-BI transition and the modulated components of the condensate
density, and make predictions for the lattice depth dependence of the
quasiparticle gap which can be tested in future experiments. We also highlight
some interesting features unique to cold atom superfluids within this intraband
pairing approximation; for instance, the pair field is forced to be uniform in
space and the Hartree field vanishes identically. These arise as a result of
the fact that while the pairing interaction is cut off at the scale of the
Debye frequency in conventional superconductors, or at the lattice scale in
tight binding model Hamiltonians, such a cutoff is absent for cold Fermi gases.
| arxiv topic:cond-mat.other |
arxiv_dataset-1073902.1084 | Scale-dependent bias from primordial non-Gaussianity in general
relativity
astro-ph.CO
In this note we examine the derivation of scale-dependent bias due to
primordial non-Gaussianity of the local type in the context of general
relativity. We justify the use of the Poisson equation in general relativistic
perturbation theory and thus the derivation of scale-dependent bias as a test
of primordial non-Gaussianity, using the spherical collapse model. The
corollary is that the form of scale-dependent bias does not receive general
relativistic corrections on scales larger than the Hubble radius. This leads to
a formally divergent correlation function for biased tracers of the mass
distribution which we discuss.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1074902.1184 | Golden Sections of Interatomic Distances as Exact Ionic Radii and
Additivity of Atomic and Ionic Radii in Chemical Bonds
physics.gen-ph
The Golden ratio which appears in the geometry of a variety of creations in
Nature is found to arise right in the Bohr radius of the hydrogen atom due to
the opposite charges of the electron and proton. The bond length of the
hydrogen molecule is the diagonal of a square on the Bohr radius and hence also
has two Golden sections, which form the cationic and anionic radii of hydrogen.
It is shown here that these radii account for the bond lengths of many hydrides
when added to the atomic and Golden ratio based ionic radii of many other
atoms.
| arxiv topic:physics.gen-ph |
arxiv_dataset-1075902.1284 | Multi-Label Prediction via Compressed Sensing
cs.LG
We consider multi-label prediction problems with large output spaces under
the assumption of output sparsity -- that the target (label) vectors have small
support. We develop a general theory for a variant of the popular error
correcting output code scheme, using ideas from compressed sensing for
exploiting this sparsity. The method can be regarded as a simple reduction from
multi-label regression problems to binary regression problems. We show that the
number of subproblems need only be logarithmic in the total number of possible
labels, making this approach radically more efficient than others. We also
state and prove robustness guarantees for this method in the form of regret
transform bounds (in general), and also provide a more detailed analysis for
the linear prediction setting.
| arxiv topic:cs.LG |
arxiv_dataset-1076902.1384 | Photoproduction of scalar and pseudoscalar mesons on a lepton within the
local Nambu-Jona-Lasinio model
hep-ph
Using the description of the subprocess $\gamma\gamma^*\to S(P)$ in terms of
local Nambu-Jona-Lasinio model we calculate the cross sections of
photoproduction of scalar and pseudoscalar mesons in high energy photon-lepton
collisions processes. The dependence on the transversal momentum and the total
cross sections in Weizsaecker-Williams approximation are presented.
| arxiv topic:hep-ph |
arxiv_dataset-1077902.1484 | Oscillatory Notch pathway activity in a delay model of neuronal
differentiation
q-bio.CB
Lateral inhibition resulting from a double-negative feedback loop underlies
the assignment of different fates to cells in many developmental processes.
Previous studies have shown that the presence of time delays in models of
lateral inhibition can result in significant oscillatory transients before
patterned steady states are reached. We study the impact of local feedback
loops in a model of lateral inhibition based on the Notch signalling pathway,
elucidating the roles of intracellular and intercellular delays in controlling
the overall system behaviour. The model exhibits both in-phase and out-of-phase
oscillatory modes, and oscillation death. Interactions between oscillatory
modes can generate complex behaviours such as intermittent oscillations. Our
results provide a framework for exploring the recent observation of transient
Notch pathway oscillations during fate assignment in vertebrate neurogenesis.
| arxiv topic:q-bio.CB |
arxiv_dataset-1078902.1584 | Maximally localized Wannier function within linear combination of
pseudo-atomic orbital method: Implementation and applications to
transition-metal-benzene complex
cond-mat.mtrl-sci cond-mat.other
Construction of maximally localized Wannier functions (MLWFs) has been
implemented within the linear combination of pseudo-atomic orbital (LCPAO)
method. Detailed analysis using MLWFs is applied to three closely related
materials, single benzene (Bz) molecule, organometallic Vanadium-Bz infinite
chain, and V$_2$Bz$_{3}$ sandwich cluster. Two important results come out from
the present analysis: 1) for the infinite chain, the validity of the basic
assumption in the mechanism of Kanamori and Terakura for the ferromagnetic (FM)
state stability is confirmed; 2) for V$_2$Bz$_3$, an important role played by
the difference in the orbital energy between the edge Bzs and the middle Bz is
newly revealed: the on-site energy of p$\delta$ states of edge Bzs is higher
than that of middle Bz, which further reduces the FM stability of V$_2$Bz$_3$.
| arxiv topic:cond-mat.mtrl-sci cond-mat.other |
arxiv_dataset-1079902.1684 | Entanglement of Identical Particles and the Detection Process
quant-ph
We introduce detector-level entanglement, a unified entanglement concept for
identical particles that takes into account the possible deletion of
many-particle which-way information through the detection process. The concept
implies a measure for the effective indistinguishability of the particles,
which is controlled by the measurement setup and which quantifies the extent to
which the (anti-)symmetrization of the wave-function impacts on physical
observables. Initially indistinguishable particles can gain or loose
entanglement on their transition to distinguishability, and their quantum
statistical behavior depends on their initial entanglement. Our results show
that entanglement cannot be attributed to a state of identical particles alone,
but that the detection process has to be incorporated in the analysis.
| arxiv topic:quant-ph |
arxiv_dataset-1080902.1784 | Fixed points of holomorphic transformations of operator balls
math.MG math.OA
A new technique for proving fixed point theorems for families of holomorphic
transformations of operator balls is developed. One of these theorems is used
to show that a bounded representation in a real or complex Hilbert space is
orthogonalizable or unitarizable (that is similar to an orthogonal or unitary
representation), respectively, provided the representation has an invariant
indefinite quadratic form with finitely many negative squares.
| arxiv topic:math.MG math.OA |
arxiv_dataset-1081902.1884 | A Proof of Concept for Optimizing Task Parallelism by Locality Queues
cs.PF cs.DC
Task parallelism as employed by the OpenMP task construct, although ideal for
tackling irregular problems or typical producer/consumer schemes, bears some
potential for performance bottlenecks if locality of data access is important,
which is typically the case for memory-bound code on ccNUMA systems. We present
a programming technique which ameliorates adverse effects of dynamic task
distribution by sorting tasks into locality queues, each of which is preferably
processed by threads that belong to the same locality domain. Dynamic
scheduling is fully preserved inside each domain, and is preferred over
possible load imbalance even if non-local access is required. The effectiveness
of the approach is demonstrated using a blocked six-point stencil solver as a
toy model.
| arxiv topic:cs.PF cs.DC |
arxiv_dataset-1082902.1984 | Blazars in hard X-rays
astro-ph.CO astro-ph.HE
Although blazars are thought to emit most of their luminosity in the
gamma-ray band, there are subclasses of them very prominent in hard X-rays.
These are the best candidates to be studied by Simbol-X. They are at the
extremes of the blazar sequence, having very small or very high jet powers. The
former are the class of TeV emitting BL Lacs, whose synchrotron emission often
peaks at tens of keV or more. The latter are the blazars with the most powerful
jets and have high black hole masses accreting at high (i.e. close to
Eddington) rates. These sources are predicted to have their high energy peak
even below the MeV band, and therefore are very promising candidates to be
studied with Simbol-X.
| arxiv topic:astro-ph.CO astro-ph.HE |
arxiv_dataset-1083902.2084 | The Strange Prospects for Astrophysics
astro-ph.HE nucl-th
The implications of the formation of strange quark matter in neutron stars
and in core-collapse supernovae is discussed with special emphasis on the
possibility of having a strong first order QCD phase transition at high baryon
densities. If strange quark matter is formed in core-collapse supernovae
shortly after the bounce, it causes the launch of a second outgoing shock which
is energetic enough to lead to a explosion. A signal for the formation of
strange quark matter can be read off from the neutrino spectrum, as a second
peak in antineutrinos is released when the second shock runs over the
neutrinosphere.
| arxiv topic:astro-ph.HE nucl-th |
arxiv_dataset-1084902.2184 | Conventions spreading in open-ended systems
physics.soc-ph
We introduce a simple open-ended model that describes the emergence of a
shared vocabulary. The ordering transition toward consensus is generated only
by an agreement mechanism. This interaction defines a finite and small number
of states, despite each individual having the ability to invent an unlimited
number of new words. The existence of a phase transition is studied by
analyzing the convergence times, the cognitive efforts of the agents and the
scaling behavior in memory and time
| arxiv topic:physics.soc-ph |
arxiv_dataset-1085902.2284 | Surface plasmon resonances of an arbitrarily shaped nanoparticle: High
frequency asymptotics via pseudo-differential operators
math-ph math.MP
We study the surface plasmon modes of an arbitrarily shaped nanoparticle in
the electrostatic limit. We first deduce an eigenvalue equation for these
modes, expressed in terms of the Dirichlet-Neumann operators. We then use the
properties of these pseudo-differential operators for deriving the limit of the
high-order modes.
| arxiv topic:math-ph math.MP |
arxiv_dataset-1086902.2384 | Transport Properties of a Non-relativistic Delta-Shell Gas with Long
Scattering Lengths
quant-ph astro-ph.SR cond-mat.stat-mech nucl-th physics.atom-ph
The coefficients of diffusion, thermal conductivity, and shear viscosity are
calculated for a system of non-relativistic particles interacting via a
delta-shell potential V(r)=-v \delta(r-R) when the average distance between
particles is smaller than R. The roles of resonances and long scattering
lengths including the unitary limit are examined. Results for ratios of
diffusion to viscosity and viscosity to entropy density are presented for
varying scattering lengths.
| arxiv topic:quant-ph astro-ph.SR cond-mat.stat-mech nucl-th physics.atom-ph |
arxiv_dataset-1087902.2484 | The number of eigenstates: counting function and heat kernel
math-ph hep-th math.MP
The main aim of this paper is twofold: (1) revealing a relation between the
counting function N(lambda) (the number of the eigenstates with eigenvalue
smaller than a given number) and the heat kernel K(t), which is still an open
problem in mathematics, and (2) introducing an approach for the calculation of
N(lambda), for there is no effective method for calculating N(lambda) beyond
leading order. We suggest a new expression of N(lambda) which is more suitable
for practical calculations. A renormalization procedure is constructed for
removing the divergences which appear when obtaining N(lambda) from a
nonuniformly convergent expansion of K(t). We calculate N(lambda) for
D-dimensional boxes, three-dimensional balls, and two-dimensional
multiply-connected irregular regions. By the Gauss-Bonnet theorem, we
generalize the simply-connected heat kernel to the multiply-connected case;
this result proves Kac's conjecture on the two-dimensional multiply-connected
heat kernel. The approaches for calculating eigenvalue spectra and state
densities from N(lambda) are introduced.
| arxiv topic:math-ph hep-th math.MP |
arxiv_dataset-1088902.2584 | Electronic Refrigeration at the Quantum Limit
cond-mat.mes-hall cond-mat.supr-con
We demonstrate quantum limited electronic refrigeration of a metallic island
in a low temperature micro-circuit. We show that matching the impedance of the
circuit enables refrigeration at a distance, of about 50 um in our case,
through superconducting leads with a cooling power determined by the quantum of
thermal conductance. In a reference sample with a mismatched circuit this
effect is absent. Our results are consistent with the concept of
electromagnetic heat transport. We observe and analyze the crossover between
electromagnetic and quasiparticle heat flux in a superconductor.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-1089902.2684 | Le lemme fondamental pond\'er\'e I : constructions g\'eom\'etriques
math.AG math.RT
This work is the geometric part of our proof of the weighted fundamental
lemma, which is an extension of Ng\^o Bao Ch\^au's proof of the
Langlands-Shelstad fundamental lemma.
Ng\^o's approach is based on a study of the elliptic part of the Hichin
fibration. The total space of this fibration is the algebraic stack of Hitchin
bundles and its base space is the affine space of "characteristic polynomials".
Over the elliptic set, the Hitchin fibration is proper and the number of points
of its fibers over a finite field can be expressed in terms of orbital
integrals.
In this paper, we study the Hitchin fibration over an open set bigger than
the elliptic set, namely the "generically regular semi-simple set". The fibers
are in general neither of finite type nor separeted. By analogy with Arthur's
truncation, we introduce the substack of $\xi$-stable Hitchin bundles. We show
that it is a Deligne-Mumford stack, smooth over the base field and proper over
the base space of "characteristic polynomials". Moreover, the number of points
of the $\xi$-stable fibers over a finite field can be expressed as a sum of
weighted orbital integrals, which appear in the Arthur-Selberg trace formula.
| arxiv topic:math.AG math.RT |
arxiv_dataset-1090902.2784 | Physical conditions in the ISM of intensely star-forming galaxies at
redshift~2
astro-ph.CO
We analyze the physical conditions in the interstellar gas of 11 actively
star-forming galaxies at z~2, based on integral-field spectroscopy from the
ESO-VLT and HST/NICMOS imaging. We concentrate on the high H-alpha surface
brightnesses, large line widths, line ratios and the clumpy nature of these
galaxies. We show that photoionization calculations and emission line
diagnostics imply gas pressures and densities that are similar to the most
intense nearby star-forming regions at z=0 but over much larger scales (10-20
kpc). A relationship between surface brightness and velocity dispersion can be
explained through simple energy injection arguments and a scaling set by nearby
galaxies with no free parameters. The high velocity dispersions are a natural
consequence of intense star formation thus regions of high velocity dispersion
are not evidence for mass concentrations such as bulges or rings. External
mechanisms like cosmological gas accretion generally do not have enough energy
to sustain the high velocity dispersions. In some cases, the high pressures and
low gas metallicites may make it difficult to robustly distinguish between AGN
ionization cones and star formation, as we show for BzK-15504 at z=2.38. We
construct a picture where the early stages of galaxy evolution are driven by
self-gravity which powers strong turbulence until the velocity dispersion is
high. Then massive, dense, gas-rich clumps collapse, triggering star formation
with high efficiencies and intensities as observed. At this stage, the intense
star formation is likely self-regulated by the mechanical energy output of
massive stars.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1091902.2884 | On the description of Leibniz superalgebras of nilindex n+m
math.RA math.AG
In this work we investigate the complex Leibniz superalgebras with
characteristic sequence $(n_1,...,n_k|m)$ and nilindex n+m, where
$n=n_1+...+n_k,$ n and m (m is not equal to zero) are dimensions of even and
odd parts, respectively. Such superalgebras with condition n_1 > n-2 were
classified in \cite{FilSup}--\cite{C-G-O-Kh}. Here we prove that in the case
$n_1 < n-1$ the Leibniz superalgebras have nilindex less than $n+m.$ Thus, we
get the classification of Leibniz superalgebras with characteristic sequence
$(n_1, ...,n_k|m)$ and nilindex n+m.
| arxiv topic:math.RA math.AG |
arxiv_dataset-1092902.2984 | Causal and Anticausal Operators Associated with Input and State to
Output Descriptions of Switched Linear Dynamic Systems with Point Lags
math.DS
The causality properties of linear time-varing systems under constant time
lags are investigated based on the definition and use of the definitions of
appropriate Hankel and Toeplitz causal and anticausal operators.
| arxiv topic:math.DS |
arxiv_dataset-1093902.3084 | An extension of the Duistermaat-Singer Theorem to the semi-classical
Weyl algebra
math-ph math.AP math.MP
Motivated by many recent works (by L. Charles, V. Guillemin, T. Paul, J.
Sj\"ostrand, A. Uribe, S. Vu Ngoc, S. Zelditch and others) on the
semi-classical Birkhoff normal forms, we investigate the structure of the group
of automorphisms of the graded semi-classical Weyl algebra which is used to get
the normal forms. The answer is quite similar to the Theorem of Duistermaat and
Singer for the usual algebra of pseudo-differential operators where all
automorphisms are given by conjugation by an elliptic Fourier Integral Operator
(a FIO). Here what replaces general non-linear symplectic diffeomeorhisms is
just linear complex symplectic maps, because everything is localized at a
single point.
| arxiv topic:math-ph math.AP math.MP |
arxiv_dataset-1094902.3184 | Algebraic aspects of quantum indiscernibility
quant-ph
Quasi-set theory was proposed as a mathematical context to investigate
collections of indistinguishable objects. After presenting an outline of this
theory, we define an algebra that has most of the standard properties of an
orthocomplete orthomodular lattice, which is the lattice of the closed
subspaces of a Hilbert space. We call the mathematical structure so obtained
$\mathfrak{I}$-lattice. After discussing, in a preliminary form, some aspects
of such a structure, we indicate the next problem of axiomatizing the
corresponding logic, that is, a logic which has $\mathfrak{I}$-lattices as its
algebraic models. We suggest that the intuitions that the `logic of quantum
mechanics' would be not classical logic (with its Boolean algebra), is
consonant with the idea of considering indistinguishability right from the
start, that is, as a primitive concept. In other words, indiscernibility seems
to lead `directly' to $\mathfrak{I}$-lattices. In the first sections, we
present the main motivations and a `classical' situation which mirrors that one
we focus on the last part of the paper. This paper is our first study of the
algebraic structure of indiscernibility within quasi-set theory.
| arxiv topic:quant-ph |
arxiv_dataset-1095902.3284 | Constraining the EOS of neutron-rich nuclear matter and properties of
neutron stars with heavy-ion reactions
nucl-th astro-ph.SR nucl-ex
Heavy-ion reactions especially those induced by radioactive beams provide
useful information about the density dependence of the nuclear symmetry energy,
thus the Equation of State of neutron-rich nuclear matter, relevant for many
astrophysical studies. The latest developments in constraining the symmetry
energy at both sub- and supra-saturation densities from analyses of the isopsin
diffusion and the $\pi^-/\pi^+$ ratio in heavy-ion collisions using the IBUU04
transport model are discussed. Astrophysical ramifications of the partially
constrained symmetry energy on properties of neutron star crusts, gravitational
waves emitted by deformed pulsars and the w-mode oscillations of neutron stars
are presented briefly.
| arxiv topic:nucl-th astro-ph.SR nucl-ex |
arxiv_dataset-1096902.3384 | Remarks on Bootstrap Percolation in Metric Networks
cond-mat.stat-mech physics.bio-ph q-bio.NC
We examine bootstrap percolation in d-dimensional, directed metric graphs in
the context of recent measurements of firing dynamics in 2D neuronal cultures.
There are two regimes, depending on the graph size N. Large metric graphs are
ignited by the occurrence of critical nuclei, which initially occupy an
infinitesimal fraction, f_* -> 0, of the graph and then explode throughout a
finite fraction. Smaller metric graphs are effectively random in the sense that
their ignition requires the initial ignition of a finite, unlocalized fraction
of the graph, f_* >0. The crossover between the two regimes is at a size N_*
which scales exponentially with the connectivity range \lambda like_* \sim
\exp\lambda^d. The neuronal cultures are finite metric graphs of size N \simeq
10^5-10^6, which, for the parameters of the experiment, is effectively random
since N<< N_*. This explains the seeming contradiction in the observed finite
f_* in these cultures. Finally, we discuss the dynamics of the firing front.
| arxiv topic:cond-mat.stat-mech physics.bio-ph q-bio.NC |
arxiv_dataset-1097902.3484 | SEGUE-2 and APOGEE: Revealing the History of the Milky Way
astro-ph.GA astro-ph.SR
The history of the Milky Way is encoded in the spatial distributions,
kinematics, and chemical enrichment patterns of its resolved stellar
populations. SEGUE-2 and APOGEE, two of the four surveys that comprise SDSS-III
(the Sloan Digital Sky Survey III), will map these distributions and enrichment
patterns at optical and infrared wavelengths, respectively. Using the existing
SDSS spectrographs, SEGUE-2 will obtain spectra of 140,000 stars in selected
high-latitude fields to a magnitude limit r ~ 19.5, more than doubling the
sample of distant halo stars observed in the SDSS-II survey SEGUE (the Sloan
Extension for Galactic Understanding and Exploration). With spectral resolution
R ~ 2000 and typical S/N per pixel of 20-25, SEGUE and SEGUE-2 measure radial
velocities with typical precision of 5-10 km/s and metallicities ([Fe/H]) with
a typical external error of 0.25 dex. APOGEE (the Apache Point Observatory
Galactic Evolution Experiment) will use a new, 300-fiber H-band spectrograph
(1.5-1.7 micron) to obtain high-resolution (R ~ 24,000), high signal-to-noise
ratio (S/N ~ 100 per pixel) spectra of 100,000 red giant stars to a magnitude
limit H ~ 12.5. Infrared spectroscopy penetrates the dust that obscures the
inner Galaxy from our view, allowing APOGEE to carry out the first large,
homogeneous spectroscopic survey of all Galactic stellar populations. APOGEE
spectra will allow radial velocity measurements with < 0.5 km/s precision and
abundance determinations (with ~ 0.1 dex precision) of 15 chemical elements for
each program star, which can be used to reconstruct the history of star
formation that produced these elements. (abridged)
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-1098902.3584 | Quantum and classical dynamics of Langmuir wave packets
physics.plasm-ph
The quantum Zakharov system in three-spatial dimensions and an associated
Lagrangian description, as well as its basic conservation laws are derived. In
the adiabatic and semiclassical case, the quantum Zakharov system reduces to a
quantum modified vector nonlinear Schr\"odinger (NLS) equation for the envelope
electric field. The Lagrangian structure for the resulting vector NLS equation
is used to investigate the time-dependence of the Gaussian shaped localized
solutions, via the Rayleigh-Ritz variational method. The formal classical limit
is considered in detail. The quantum corrections are shown to prevent the
collapse of localized Langmuir envelope fields, in both two and three-spatial
dimensions. Moreover, the quantum terms can produce an oscillatory behavior of
the width of the approximate Gaussian solutions. The variational method is
shown to preserve the essential conservation laws of the quantum modified
vector NLS equation.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-1099902.3684 | Residual attractive force between superparamagnetic nanoparticles
cond-mat.other
A superparamagnetic nanoparticle (SPN) is a nanometre-sized piece of a
material that would, in bulk, be a permanent magnet. In the SPN the individual
atomic spins are aligned via Pauli effects into a single giant moment that has
easy orientations set by shape or magnetocrystalline anisotropy. Above a
size-dependent blocking temperature $T_{b}(V,\tau_{obs})$, thermal fluctuations
destroy the average moment by flipping the giant spin between easy orientations
at a rate that is rapid on the scale of the observation time $\tau_{obs}$.
We show that, depite the vanising of the average moment, two SPNs experience
a net attractive force of magnetic origin, analogous to the van der Waals force
between molecules that lack a permanent electric dipole. This could be relevant
for ferrofluids, for the clumping of SPNs used for drug delivery, and for
ultra-dense magnetic recording media.
| arxiv topic:cond-mat.other |
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