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arxiv_dataset-600804.3721 | F(R) gravity equation of state
hep-th astro-ph gr-qc math-ph math.MP quant-ph
The ${\bf f}(R)$ gravity field equations are derived as an equation of state
of local space-time thermodynamics. Jacobson's arguments are non-trivially
extended, by means of a more general definition of local entropy, for which
Wald's definition of dynamic black hole entropy is used, as well as the concept
of an effective Newton constant for graviton exchange, recently appeared in the
literature.
| arxiv topic:hep-th astro-ph gr-qc math-ph math.MP quant-ph |
arxiv_dataset-601804.3821 | Fourier expansions for the potentials of lattices of charge
physics.chem-ph
We apply the Poisson sum rule to obtain formal expressions for the Fourier
coefficients of the potential of a lattice of generalized charge. Each
generalized charge is assumed to contribute to the potential a term which
depends only on the vector displacement from the charge's location. The
coefficients are explicitly calculated for Coulomb and Yukawa-type individual
particle potentials. The potentials of finite and disordered lattices are also
briefly considered.
| arxiv topic:physics.chem-ph |
arxiv_dataset-602804.3921 | Overspinning a nearly extreme black hole and the Weak Cosmic Censorship
conjecture
gr-qc
We revisit here the recent proposal for overspinning a nearly extreme black
hole by means of a quantum tunneling process. We show that electrically neutral
massless fermions evade possible back reactions effects related to
superradiance, confirming the view that it would be indeed possible to form a
naked singularity due to quantum effects.
| arxiv topic:gr-qc |
arxiv_dataset-603804.4021 | Effects of interfacial curvature on Rayleigh-Taylor instability
physics.flu-dyn
In this work a non-trivial effect of the interfacial curvature on the
stability of accelerated interfaces, such as liquid rims, is uncovered. The new
stability analysis, based on operator and boundary perturbation theories,
reveals and quantifies influence of the interfacial curvature on the growth
rate and on the wavenumber selection of the Rayleigh-Taylor instability. The
systematic approach developed here also provides a rigorous generalization of
the widely used \textit{ad hoc} idea, due to Layzer [Astrophys. J.
\textbf{122}, 1-12 (1955)], of approximating the potential velocity field near
the interface.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-604804.4121 | Possibility of a new universality class: The anisotropic Heisenberg
model with dipolar interactions
cond-mat.stat-mech cond-mat.other
This paper has been withdrawn by the authors due to a possible inconsistency
in the program code.
| arxiv topic:cond-mat.stat-mech cond-mat.other |
arxiv_dataset-605804.4221 | Quantum Gravity and Recovery of Information in Black Hole Evaporation
gr-qc
The Generalized Uncertainty Principle (GUP), motivated by current
alternatives of quantum gravity, produces significant modifications to the
Hawking radiation and the final stage of black hole evaporation. We show that
incorporation of the GUP into the quantum tunneling process (based on the
null-geodesic method) causes correlations between the tunneling probability of
different modes in the black hole radiation spectrum. In this manner, the
quantum information becomes encrypted in the Hawking radiation, and information
can be recovered as non-thermal GUP correlations between tunneling
probabilities of different modes.
| arxiv topic:gr-qc |
arxiv_dataset-606804.4321 | Ideal and nonideal electromagnetic cloaks
physics.optics
We employ the analytical results for the spatial transformation of the
electromagnetic fields to obtain and analyze explicit expressions for the
structure of the electromagnetic fields in invisibility cloaks, beam splitters,
and field concentrators. We study the efficiency of nonideal electromagnetic
cloaks and discuss the effect of scattering losses on the cloak invisibility.
| arxiv topic:physics.optics |
arxiv_dataset-607804.4421 | Self-consistent simulations of Nuclear Cluster formation through
Globular Cluster orbital decay and merging
astro-ph
We present results of fully self-consistent N-body simulations of the motion
of four globular clusters moving in the inner region of their parent galaxy.
With regard to previous simplified simulations, we confirm merging and
formation of an almost steady nuclear cluster, in a slightly shorter time. The
projected surface density profile shows strong similarity to that of resolved
galactic nuclei. This similarity reflects also in the velocity dispersion
profile which exhibits a central colder component as observed in many nucleated
galaxies.
| arxiv topic:astro-ph |
arxiv_dataset-608804.4521 | Numerical solutions of integrodifferential systems by hybrid of general
block-pulse functions and the second Chebyshev polynomials
math.NA
By applying hybrid functions of general block-pulse functions and the second
Chebyshev polynomials,integrodifferential systems are converted into a system
of algebraic equations. The approximate solutions of integrodifferential
systems are derived. The numerical examples illustrate that the algorithms are
valid.
| arxiv topic:math.NA |
arxiv_dataset-609804.4621 | An Optimal Transport View On Schroedinger's Equation
math-ph math.AP math.MP
We show that the Schroedinger equation is a lift of Newton's law of motion on
the space of probability measures, where derivatives are taken w.r.t. the
Wasserstein Riemannian metric. Here the potential is the sum of the total
classical potential energy of the extended system and its Fisher information.
The precise relation is established via a well known ('Madelung') transform
which is shown to be a symplectic submersion of the standard symplectic
structure of complex valued functions into the canonical symplectic space over
the Wasserstein space. All computations are conducted in the framework of
Otto's formal Riemannian calculus for optimal transportation of probability
measures
| arxiv topic:math-ph math.AP math.MP |
arxiv_dataset-610804.4721 | Minimal Open Strings
hep-th
We study FZZT-branes and open string amplitudes in (p,q) minimal string
theory. We focus on the simplest boundary changing operators in two-matrix
models, and identify the corresponding operators in worldsheet theory through
the comparison of amplitudes. Along the way, we find a novel linear relation
among FZZT boundary states in minimal string theory. We also show that the
boundary ground ring is realized on physical open string operators in a very
simple manner, and discuss its use for perturbative computation of higher open
string amplitudes.
| arxiv topic:hep-th |
arxiv_dataset-611804.4821 | Relativistic Universe Scenario
gr-qc
The luminocity-distance -- redshift SN Ia data and the Cosmic Microwave
Background power spectrum are discussed in the context of the results and ideas
of the eminent Russian physicist-theorist N.A. Chernikov. His results include
the Boltzmann-Chernikov distribution in the kinetic theory of relativistic gas,
conformal invariant theory of scalar field, and the vacuum cosmological
creation of particles. We use these results for explanation of the origin of
matter content of the Universe in the modern relativistic physics.
| arxiv topic:gr-qc |
arxiv_dataset-612805.0023 | Two-Component Nonlinear Schrodinger Models with a Double-Well Potential
nlin.PS cond-mat.other
We introduce a model motivated by studies of Bose-Einstein condensates (BECs)
trapped in double-well potentials. We assume that a mixture of two hyperfine
states of the same atomic species is loaded in such a trap.The analysis is
focused on symmetry-breaking bifurcations in the system, starting at the linear
limit and gradually increasing the nonlinearity. Depending on values of the
chemical potentials of the two species, we find numerous states, as well as
symmetry-breaking bifurcations, in addition to those known in the
single-component setting. These branches, which include all relevant stationary
solutions of the problem, are predicted analytically by means of a two-mode
approximation, and confirmed numerically. For unstable branches, outcomes of
the instability development are explored in direct simulations.
| arxiv topic:nlin.PS cond-mat.other |
arxiv_dataset-613805.0123 | Study of the effects induced by lead on the emulsion films of the OPERA
experiment
physics.ins-det
The OPERA neutrino oscillation experiment is based on the use of the Emulsion
Cloud Chamber (ECC). In the OPERA ECC, nuclear emulsion films acting as very
high precision tracking detectors are interleaved with lead plates providing a
massive target for neutrino interactions. We report on studies related to the
effects occurring from the contact between emulsion and lead. A low
radioactivity lead is required in order to minimize the number of background
tracks in emulsions and to achieve the required performance in the
reconstruction of neutrino events. It was observed that adding other chemical
elements to the lead, in order to improve the mechanical properties, may
significantly increase the level of radioactivity on the emulsions. A detailed
study was made in order to choose a lead alloy with good mechanical properties
and an appropriate packing technique so as to have a low enough effective
radioactivity.
| arxiv topic:physics.ins-det |
arxiv_dataset-614805.0223 | Low energy defibrillation in human cardiac tissue: a simulation study
q-bio.TO
We aim to assess the effectiveness of feedback controlled resonant drift
pacing as a method for low energy defibrillation. Antitachycardia pacing is the
only low energy defibrillation approach to have gained clinical significance,
but it is still suboptimal. Low energy defibrillation would avoid adverse side
effects associated with high voltage shocks and allow the application of ICD
therapy where it is not tolerated today. We present results of computer
simulations of a bidomain model of cardiac tissue with human atrial ionic
kinetics. Re-entry was initiated and low energy shocks were applied with the
same period as the re-entry, using feedback to maintain resonance. We
demonstrate that such stimulation can move the core of re-entrant patterns, in
the direction depending on location of electrodes and a time delay in the
feedback. Termination of re-entry is achieved with shock strength one order of
magnitude weaker than in conventional single-shock defibrillation. We conclude
that resonant drift pacing can terminate re-entry at a fraction of the shock
strength currently used for defibrillation and can potentially work where
antitachycardia pacing fails, due to the feedback mechanisms. Success depends
on a number of details which these numerical simulations have uncovered.
\emph{Keywords} Re-entry; Bidomain model; Resonant drift; ICD; Defibrillation;
Antitachycardia pacing; Feedback.
| arxiv topic:q-bio.TO |
arxiv_dataset-615805.0323 | On submanifolds with tamed second fundamental form
math.DG
We show that a complete submanifold $M$ with tamed second fundamental form in
a complete Riemannian manifold $N$ with sectional curvature $K_{N}\leq \kappa
\leq 0$ are proper, (compact if $N$ is compact). In addition, if $N$ is
Hadamard then $M$ has finite topology. We also show that the fundamental tone
is an obstruction for a Riemannian manifold to be realized as submanifold with
tamed second fundamental form of a Hadamard manifold with sectional curvature
bounded below.
| arxiv topic:math.DG |
arxiv_dataset-616805.0423 | Tripartite entanglement dynamics for atom in a two-mode nonlinear cavity
quant-ph
In this communication we introduce a new model which represents the
interaction between an atom and two fields injected simultaneously within a
cavity including the nonlinear couplers. By using the canonical transformation
the model can be regarded as a generalization of several well-known models. We
calculate and discuss entanglement between the tripartite system of one atom
and the two cavity modes. For a short interaction time, similarities between
the behavior based on our solution compared with the other simulation based on
a numerical linear algebra solution of the original Hamiltonian with truncated
Fock bases for each mode, is shown. For a specific value of the Kerr-like
medium defined in this letter, we find that the entanglement, as measured by
concurrence, may terminate abruptly in a finite time.
| arxiv topic:quant-ph |
arxiv_dataset-617805.0523 | Initial-state randomness as a universal source of decoherence
quant-ph nlin.CD
We study time evolution of entanglement between two qubits, which are part of
a larger system, after starting from a random initial product state. We show
that, due to randomness in the initial product state, entanglement is present
only between directly coupled qubits and only for short times. Time dependence
of the entanglement appears essentially independent of the specific hamiltonian
used for time evolution and is well reproduced by a parameter-free two-body
random matrix model.
| arxiv topic:quant-ph nlin.CD |
arxiv_dataset-618805.0623 | Realization of a strongly interacting Bose-Fermi mixture from a
two-component Fermi gas
cond-mat.stat-mech
We show the emergence of a strongly interacting Bose-Fermi mixture from a
two-component Fermi mixture with population imbalance. By analyzing in situ
density profiles of $^6$Li atoms in the BCS-BEC crossover regime we identify a
critical interaction strength, beyond which all minority atoms pair up with
majority atoms, and form a Bose condensate. This is the regime where the system
can be effectively described as a boson-fermion mixture. We determine the
dimer-fermion and dimer-dimer scattering lengths and beyond-mean-field
contributions. Our study realizes a Gedanken experiment of bosons immersed in a
Fermi sea of one of their constituents, revealing the composite nature of the
bosons.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-619805.0723 | Free subalgebras of Lie algebras close to nilpotent
math.RA math.GR
We prove that for every automata algebra of exponential growth, the
associated Lie algebra contains a free subalgebra. For n\geq 1, let L_{n+2} be
a Lie algebra with generator set x_1,..., x_{n+2} and the following relations:
for k\leq n, any commutator of length $k$ which consists of fewer than k
different symbols from {x_1,...,x_{n+2}} is zero. As an application of this
result about automata algebras, we prove that for every n\geq 1, L_{n+2}
contains a free subalgebra. We also prove the similar result about groups
defined by commutator relations.
| arxiv topic:math.RA math.GR |
arxiv_dataset-620805.0823 | A Spectroscopic Survey for Omega Centauri Members at and beyond the
Cluster Tidal Radius
astro-ph
We have used the two-degree field (2dF) multi-fibre spectrograph of the
Anglo-Australian Telescope to search for candidate members of the unusual
globular cluster omega Centauri at and beyond the cluster tidal radius.
Velocities with an accuracy of ~10 kms-1 were obtained for 4105 stars selected
to lie in the vicinity of the lower giant branch in the cluster
colour-magnitude diagram and which cover an area on the sky of ~2.4x3.9 deg2
centered on the cluster. Within the velocity interval 190-270 kms-1, the
cluster member candidates have a steeply declining surface density distribution
consistent with the adopted tidal radius of 57`. For stars in the sample beyond
the tidal radius, an analysis of line-strengths from the spectra, as well as
radial velocities, identifies only six stars as possible candidates for
extra-tidal association with the cluster. If all six of these stars are indeed
related to the cluster, then a maximum of 0.7 +/- 0.2 per cent of the total
cluster mass is contained in the region between one and two tidal radii. Given
this limit, we conclude that there is no compelling evidence for any
significant extra-tidal population in omega Cen. The effects of tidal shocks on
the outer parts of the cluster are consistent with this limit. Theories for the
origin of omega Cen frequently suggest that the cluster is the former nucleus
of a tidally stripped dwarf galaxy. Our results require that the stripping
process must have been largely complete at early epochs, consistent with
dynamical models of the process. The stripped former dwarf galaxy stars are
therefore now widely distributed around the Galaxy.
| arxiv topic:astro-ph |
arxiv_dataset-621805.0923 | Pairing symmetry and properties of iron-based high temperature
superconductors
cond-mat.supr-con cond-mat.str-el
Pairing symmetry is important to indentify the pairing mechanism. The
analysis becomes particularly timely and important for the newly discovered
iron-based multi-orbital superconductors. From group theory point of view we
classified all pairing matrices (in the orbital space) that carry irreducible
representations of the system. The quasiparticle gap falls into three
categories: full, nodal and gapless. The nodal-gap states show conventional
Volovik effect even for on-site pairing. The gapless states are odd in orbital
space, have a negative superfluid density and are therefore unstable. In
connection to experiments we proposed possible pairing states and implications
for the pairing mechanism.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-622805.1023 | Width and flow of hypersurfaces by curvature functions
math.DG
We give a bound on the extinction time for a compact, strictly convex
hypersurface in R^{n+1} evolving by a geometric flow where the velocity is
given in terms of the curvature. This result generalizes a theorem of Colding
and Minicozzi for mean curvature flow solutions to a wider class of flows
studied by Ben Andrews. In the proof, we use the concept of the width of a
hypersurface, introduced by Colding and Minicozzi. We also extend the result to
2-convex hypersurfaces, using the 2-width.
| arxiv topic:math.DG |
arxiv_dataset-623805.1123 | Measurement and control of spatial qubits generated by passing photons
through double-slits
quant-ph
We present an experimental study of the non-classical correlations of a pair
of spatial qubits formed by passing two down-converted photons through a pair
of double slits. After confirming the entanglement generated in our setup by
quantum tomography using separate measurements of the slit images and the
interference patterns, we show that the complete Hilbert space of the spatial
qubits can be accessed by measurements performed in a single plane between the
image plane and the focal plane of a lens. Specifically, it is possible to
obtain both the which-path and the interference information needed for quantum
tomography in a single scan of the transversal distribution of photon
coincidences. Since this method can easily be extended to multi-dimensional
systems, it may be a valuable tool in the application of spatial qudits to
quantum information processes.
| arxiv topic:quant-ph |
arxiv_dataset-624805.1223 | Observation of the Little-Parks Oscillations in a System of Asymmetric
Superconducting Rings
cond-mat.supr-con cond-mat.stat-mech
Little-Parks oscillations are observed in a system of 110 series-connected
aluminum rings 2000 nm in diameter with the use of measuring currents from 10
nA to 1000 nA. The measurements show that the amplitude and character of the
oscillations are independent of the relation between the measuring current and
the amplitude of the persistent current. By using asymmetric rings, it is
demonstrated that the persistent current has clockwise or contra-clockwise
direction. This means that the total current in one of the semi-rings may be
directed against the electric field at measurement of the Little-Parks
oscillations. The measurements at zero and low measuring current have revealed
that the persistent current, like the conventional circulating current, causes
a potential difference on the semi-rings with different cross sections in spite
of the absence of the Faraday's voltage.
| arxiv topic:cond-mat.supr-con cond-mat.stat-mech |
arxiv_dataset-625805.1323 | A trace formula for varieties over a discretely valued field
math.AG
We study the motivic Serre invariant of a smoothly bounded algebraic or rigid
variety $X$ over a complete discretely valued field $K$ with perfect residue
field $k$. If $K$ has characteristic zero, we extend the definition to
arbitrary $K$-varieties using Bittner's presentation of the Grothendieck ring
and a process of N\'eron smoothening of pairs of varieties.
The motivic Serre invariant can be considered as a measure for the set of
unramified points on $X$. Under certain tameness conditions, it admits a
cohomological interpretation by means of a trace formula. In the curve case, we
use T. Saito's geometric criterion for cohomological tameness to obtain more
detailed results. We discuss some applications to Weil-Ch\^atelet groups, Chow
motives, and the structure of the Grothendieck ring.
| arxiv topic:math.AG |
arxiv_dataset-626805.1423 | Five Dimensional bigravity. New topological description of the Universe
physics.gen-ph
We extend the bimetric description of the Universe to a five-dimensional
framework. Starting from Souriau's work (1964) we use two Robertson-Walker
metrics with an extra term corresponding to the additional Kaluza fifth
dimension. This first order model is limited to zero electric charge and
electromagnetic energy densities. Assuming the massive particles, with positive
or negative mass and energies owing finite lifetimes, it restores the O(3)
symmetry and makes the generalized gauge process to restart. As a consequence
the speed of light tends to zero. We assume the Universe to be closed over all
its dimensions. Then, following an idea introduced in 1994 we describe the
Universe as the two folds cover of a projective space. The arrow of time, mass
and energy inversions arise as consequences of this geometrical hypothesis and
fits the bimetric model. We choose to eliminate the "initial singularity",
replaced by a boundary space, which is found to be euclidean.
| arxiv topic:physics.gen-ph |
arxiv_dataset-627805.1523 | On higher-power moments of $\Delta(x)$(III)
math.NT
Let $\Delta(x)$ be the error term of the Dirichlet divisor problem. An
asymptotic formula with the error term $O(T^{53/28+\epsilon})$ is established
for the integral $\int_1^T\Delta^4(x)dx.$
Similar results are also established for some other well-known error terms in
the analytic number theory .
| arxiv topic:math.NT |
arxiv_dataset-628805.1623 | Rotational quenching rate coefficients for H_2 in collisions with H_2
from 2 to 10,000 K
astro-ph
Rate coefficients for rotational transitions in H_2 induced by H_2 impact are
presented. Extensive quantum mechanical coupled-channel calculations based on a
recently published (H_2)_2 potential energy surface were performed. The
potential energy surface used here is presumed to be more reliable than
surfaces used in previous work. Rotational transition cross sections with
initial levels J <= 8 were computed for collision energies ranging between
0.0001 and 2.5 eV, and the corresponding rate coefficients were calculated for
the temperature range 2 < T <10,000 K. In general, agreement with earlier
calculations, which were limited to 100-6000 K, is good though discrepancies
are found at the lowest and highest temperatures. Low-density-limit cooling
functions due to para- and ortho-H_2 collisions are obtained from the
collisional rate coefficients. Implications of the new results for non-thermal
H_2 rotational distributions in molecular regions are also investigated.
| arxiv topic:astro-ph |
arxiv_dataset-629805.1723 | A Wireless Embedded Tongue Tactile Biofeedback System for Balance
Control
q-bio.NC
We describe the architecture of an original biofeedback system for balance
improvement for fall prevention and present results of a feasibility study. The
underlying principle of this biofeedback consists of providing supplementary
information related to foot sole pressure distribution through a wireless
embedded tongue-placed tactile output device. Twelve young healthy adults
voluntarily participated in this experiment. They were asked to stand as
immobile as possible with their eyes closed in two conditions of nobiofeedback
and biofeedback. Centre of foot pressure (CoP) displacements were recorded
using a force platform. Results showed reduced CoP displacements in the
biofeedback relative to the no-biofeedback condition. On the whole, the present
findings evidence the effectiveness of this system in improving postural
control on young healthy adults. Further investigations are needed to
strengthen the potential clinical value of this device.
| arxiv topic:q-bio.NC |
arxiv_dataset-630805.1823 | The radial alignment of dark matter subhalos: from simulations to
observations
astro-ph
We explore the radial alignment of subhalos in 2-dimensional projections of
cosmological simulations. While most other recent studies focussed on
quantifying the signal utilizing the full 3-dimensional spatial information any
comparison to observational data has to be done in projection along random
lines-of-sight. We have a suite of well resolved host dark matter halos at our
disposal ranging from 6 x 10^14 Msun/h down to 6 x 10^13Msun/h. For these host
systems we do observe that the major axis of the projected 2D mass distribution
of subhalos aligns with its (projected) distance vector to the host's centre.
The signal is actually stronger than the observed alignment. However, when
considering only the innermost 10-20% of the subhalo's particles for the 2D
shape measurement we recover the observed correlation. We further acknowledge
that this signal is independent of subhalo mass.
| arxiv topic:astro-ph |
arxiv_dataset-631805.1923 | Muon-spin rotation studies of SmFeAsO_0.85 and NdFeAsO_0.85
superconductors
cond-mat.supr-con
Measurements of the in-plane magnetic field penetration depth \lambda_{ab} in
Fe-based superconductors with the nominal composition SmFeAsO_0.85
(T_c\simeq52K) and NdFeAsO_0.85 (T_c\simeq51K) were carried out by means of
muon-spin-rotation. The absolute values of \lambda_{ab} at T=0 were found to be
189(5)nm and 195(5)nm for Sm and Nd substituted samples, respectively. The
analysis of the magnetic penetration depth data within the Uemura
classification scheme, which considers the correlation between the
superconducting transition temperature T_c and the effective Fermi temperature
T_F, reveal that both families of Fe-based superconductors (with and without
fluorine) falls to the same class of unconventional superconductors.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-632805.2023 | The Kinematics of a Globally Propagating Disturbance in the Solar Corona
astro-ph
The kinematics of a globally propagating disturbance (also known as an ``EIT
wave") is discussed using Extreme UltraViolet Imager (EUVI) data Solar
Terrestrial Relations Observatory (STEREO). We show for the first time that an
impulsively generated propagating disturbance has similar kinematics in all
four EUVI passbands (304, 171, 195, and 284 A). In the 304 A passband the
disturbance shows a velocity peak of 238+/-20 kms-1 within ~28 minutes of its
launch, varying in acceleration from 76 ms-2 to -102 ms-2. This passband
contains a strong contribution from a Si XI line (303.32 A) with a peak
formation temperature of ~1.6 MK. The 304 A emission may therefore be coronal
rather than chromospheric in origin. Comparable velocities and accelerations
are found in the coronal 195 A passband, while lower values are found in the
lower cadence 284 A passband. In the higher cadence 171 A passband the velocity
varies significantly, peaking at 475+/-47 kms-1 within ~20 minutes of launch,
with a variation in acceleration from 816 ms-2 to -413 ms-2. The high image
cadence of the 171 A passband (2.5 minutes compared to 10 minutes for the
similar temperature response 195 A passband) is found to have a major effect on
the measured velocity and acceleration of the pulse, which increase by factors
of ~2 and ~10, respectively. This implies that previously measured values
(e.g., using EIT) may have been underestimated. We also note that the
disturbance shows strong reflection from a coronal hole in both the 171 and 195
A passbands. The observations are consistent with an impulsively generated
fast-mode magnetoacoustic wave.
| arxiv topic:astro-ph |
arxiv_dataset-633805.2123 | Bypassing Cowling's theorem in axisymmetric fluid dynamos
physics.flu-dyn
We present a numerical study of the magnetic field generated by an
axisymmetrically forced flow in a spherical domain. At small enough Reynolds
number, Re, the flow is axisymmetric and generates an equatorial dipole above a
critical magnetic Reynolds number Rmc . The magnetic field thus breaks
axisymmetry, in agreement with Cowling's theorem. This structure of the
magnetic field is however replaced by a dominant axial dipole when Re is larger
and allows non axisymmetric fluctuations in the flow. We show here that even in
the absence of such fluctuations, an axial dipole can also be generated, at low
Re, through a secondary bifurcation, when Rm is increased above the dynamo
threshold. The system therefore always find a way to bypass the constraint
imposed by Cowling's theorem. We understand the dynamical behaviors that result
from the interaction of equatorial and axial dipolar modes using simple model
equations for their amplitudes derived from symmetry arguments.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-634805.2223 | Higgs Production via b bbar -> H in Hadron Colliders
hep-ph
I present NNNLO collinear and soft gluon corrections for Higgs production via
the process b bbar -> H. I show that the collinear corrections dominate and
contribute large enhancements to the cross section at both the Tevatron and the
LHC.
| arxiv topic:hep-ph |
arxiv_dataset-635805.2323 | Rotation profiles of solar-like stars with magnetic fields
astro-ph
The aim of this work is to investigate rotation profile of solar-like stars
with magnetic fields. A diffusion coefficient of magnetic angular momentum
transport is deduced. Rotating stellar models with different mass are computed
under the effect of the coefficient. Then rotation profiles are obtained from
the theoretical stellar models. The total angular momentum of solar model with
only hydrodynamic instabilities is about 13 times larger than that of the Sun
at the age of the Sun, and this model can not reproduce quasi-solid rotation in
the radiative region. However, not only can the solar model with magnetic
fields reproduce an almost uniform rotation in the radiative region, but its
total angular momentum is consistent with helioseismic result at the level of 3
$\sigma$ at the age of the Sun. The rotation of solar-like stars with magnetic
fields is almost uniform in the radiative region. But there is an obvious
transition region of angular velocity between the convective core and the
radiative region of models with 1.2 - 1.5 $M_{\odot}$, where angular velocity
has a sharp radial change, which is different from the rotation profile of the
Sun and massive stars with magnetic fields. Moreover the changes of the angular
velocity in the transition region increase with the increasing in the age and
mass.
| arxiv topic:astro-ph |
arxiv_dataset-636805.2423 | Green Codes: Energy-Efficient Short-Range Communication
cs.IT math.IT
A green code attempts to minimize the total energy per-bit required to
communicate across a noisy channel. The classical information-theoretic
approach neglects the energy expended in processing the data at the encoder and
the decoder and only minimizes the energy required for transmissions. Since
there is no cost associated with using more degrees of freedom, the
traditionally optimal strategy is to communicate at rate zero.
In this work, we use our recently proposed model for the power consumed by
iterative message passing. Using generalized sphere-packing bounds on the
decoding power, we find lower bounds on the total energy consumed in the
transmissions and the decoding, allowing for freedom in the choice of the rate.
We show that contrary to the classical intuition, the rate for green codes is
bounded away from zero for any given error probability. In fact, as the desired
bit-error probability goes to zero, the optimizing rate for our bounds
converges to 1.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-637805.2523 | Model selection and sensitivity analysis for sequence pattern models
math.ST stat.ME stat.TH
In this article we propose a maximal a posteriori (MAP) criterion for model
selection in the motif discovery problem and investigate conditions under which
the MAP asymptotically gives a correct prediction of model size. We also
investigate robustness of the MAP to prior specification and provide guidelines
for choosing prior hyper-parameters for motif models based on sensitivity
considerations.
| arxiv topic:math.ST stat.ME stat.TH |
arxiv_dataset-638805.2623 | Triplet Extended Supersymmetric Standard Model
hep-ph
We revisit an extension of the MSSM by adding a hypercharge-neutral,
SU(2)-triplet chiral superfield. Similar to the NMSSM, the triplet gives an
additional contribution to the quartic coupling in the Higgs potential, and the
mass of the lightest CP-even Higgs boson can be greater than tne mass of the
Z-bosn at tree-level. In addition to discussing the perturbativity,
fine-tuning, and decoupling issues of this model, we compute the dominant
1-loop corrections to the mass of the lightest CP-even Higgs boson from the
triplet sector. When the Higgs-Higgs-Triplet coupling in the superpotential is
comparable to the top Yukawa coupling, we find that the Higgs mass can be as
heavy as 140 GeV even without the traditional contributions from the top--s-top
sector, and at the same time consistent with the precision electroweak
constraints. At the expense of having Landau poles before the GUT scale, this
opens up a previously forbidden region in the MSSM parameter space where both
s-tops are light. In addition to having relatively small fine-tuning (about one
part in 30), this leads to a gluo-philic Higgs boson whose production via
gluon-gluon fusion at the LHC can be twice as large as the SM prediction.
| arxiv topic:hep-ph |
arxiv_dataset-639805.2723 | Efficient $6j$ symbol evaluations for atomic calculations
physics.atom-ph physics.chem-ph physics.comp-ph
We have developed an efficient tabulation scheme to evaluate $6j$ symbol for
atomic calculations. The scheme is appropriate for coupled-cluster based
calculations. In particular, for perturbed coupled-clusters calculations, which
has another perturbation in addition to the residual Coulomb interaction. The
scheme relies on the symmetry of the $6j$ symbol and the triangular conditions.
| arxiv topic:physics.atom-ph physics.chem-ph physics.comp-ph |
arxiv_dataset-640805.2823 | Note on the magnetic moment of the nucleon
hep-ph
The Goldberger-Treiman relation $M=2\pi/\sqrt{3}f^{\rm cl}_\pi$ where $M$ is
the constituent quark mass in the chiral limit (cl) and $f^{\rm cl}_\pi$ the
pion decay constant in the chiral limit predicts constituent quark masses of
$m_u=328.8\pm 1.1$ MeV and $m_d=332.3\pm 1.1$ MeV for the up and down quark,
respectively, when $f^{\rm cl}_\pi=89.8\pm 0.3$ MeV is adopted. Treating the
constituent quarks as bare Dirac particles the following zero order values
$\mu^{(0)}}_p=2.850\pm 0.009$ and $\mu^{(0)}}_n= -1.889\pm 0.006$ are obtained
for the proton and neutron magnetic moments, leading to deviations from the
experimental data of 2.0% and 1.3%, respectively. These unavoidable deviations
are discussed in terms of contributions to the magnetic moments proposed in
previous work.
| arxiv topic:hep-ph |
arxiv_dataset-641805.2923 | K$^+$-nucleon interaction
nucl-th
The Born approximation to the quark-gluon-exchange mechanism for K$^+$N
scattering is used as a starting point to generate a potential for this system.
The valence quark wave function of the nucleon is generalized from a single
Gaussian to a sum of Gaussians in order to have a more flexible representation
than previous work. We obtain a potential derived from a valence density given
by lattice calculations. By comparing with a recent amplitude analysis it is
found that the strength of the quark-gluon based potential needs to be
increased by a factor of order 2-4 relative to the normalization given by more
traditional values of the governing parameters. The method is used to estimate
the change in effective K$^+$N amplitudes which would result from changes in
the valence quark distributions or strength of the interaction which might
arise from nuclear medium effects in K$^+$ scattering from nuclei.
| arxiv topic:nucl-th |
arxiv_dataset-642805.3023 | Representation of nonequilibrium steady states in large mechanical
systems
cond-mat.stat-mech
Recently a novel concise representation of the probability distribution of
heat conducting nonequilibrium steady states was derived. The representation is
valid to the second order in the ``degree of nonequilibrium'', and has a very
suggestive form where the effective Hamiltonian is determined by the excess
entropy production. Here we extend the representation to a wide class of
nonequilibrium steady states realized in classical mechanical systems where
baths (reservoirs) are also defined in terms of deterministic mechanics. The
present extension covers such nonequilibrium steady states with a heat
conduction, with particle flow (maintained either by external field or by
particle reservoirs), and under an oscillating external field. We also simplify
the derivation and discuss the corresponding representation to the full order.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-643805.3123 | Nonlinear unbalanced Bessel beams in the collapse of Gaussian beams
arrested by nonlinear losses
physics.optics
Collapse of a Gaussian beam in self-focusing Kerr media arrested by nonlinear
losses may lead to the spontaneous formation of a quasi-stationary nonlinear
unbalanced Bessel beam with finite energy, which can propagate without
significant distortion over tens of diffraction lengths, and without peak
intensity attenuation while the beam power is drastically diminishing.
| arxiv topic:physics.optics |
arxiv_dataset-644805.3223 | Origin of Metallic States at Heterointerface between Band Insulators
LaAlO$_3$ and SrTiO$_3$
cond-mat.mtrl-sci
We have studied the electronic structure at the heterointerface between the
band insulators LaAlO$_3$ and SrTiO$_3$ using $in situ$ photoemission
spectroscopy. Our experimental results clearly reveal the formation of a
notched structure on the SrTiO$_3$ side due to band bending at the metallic
LaAlO$_3$/TiO$_2$-SrTiO$_3$ interface. The structure, however, is absent at the
insulating LaAlO$_3$/SrO-SrTiO$_3$ interface. The present results indicate that
the metallic states originate not from the charge transfer through the
interface on a short-range scale but from the accumulation of carriers on a
long-range scale.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-645805.3323 | Any counterexample to Makienko's conjecture is an indecomposable
continuum
math.DS math.GN
Makienko's conjecture, a proposed addition to Sullivan's dictionary, can be
stated as follows: The Julia set of a rational function R has buried points if
and only if no component of the Fatou set is completely invariant under the
second iterate of R. We prove Makienko's conjecture for rational functions with
Julia sets that are decomposable continua. This is a very broad collection of
Julia sets; it is not known if there exists a rational functions whose Julia
set is an indecomposable continuum.
| arxiv topic:math.DS math.GN |
arxiv_dataset-646805.3423 | Electroweak Bremsstrahlung in Dark Matter Annihilation
hep-ph astro-ph
A conservative upper bound on the total dark matter (DM) annihilation rate
can be obtained by constraining the appearance rate of the annihilation
products which are hardest to detect. The production of neutrinos, via the
process $\chi \chi \to \bar\nu \nu $, has thus been used to set a strong
general bound on the dark matter annihilation rate. However, Standard Model
radiative corrections to this process will inevitably produce photons which may
be easier to detect. We present an explicit calculation of the branching ratios
for the electroweak bremsstrahlung processes $\chi \chi \to \bar\nu \nu Z$ and
$\chi \chi \to \bar\nu e W$. These modes inevitably lead to electromagnetic
showers and further constraints on the DM annihilation cross-section. In
addition to annihilation, our calculations are also applicable to the case of
dark matter decay.
| arxiv topic:hep-ph astro-ph |
arxiv_dataset-647805.3523 | Reliability of Layered Neural Oscillator Networks
q-bio.NC cond-mat.dis-nn nlin.AO
We study the reliability of large networks of coupled neural oscillators in
response to fluctuating stimuli. Reliability means that a stimulus elicits
essentially identical responses upon repeated presentations. We view the
problem on two scales: neuronal reliability, which concerns the repeatability
of spike times of individual neurons embedded within a network, and
pooled-response reliability, which addresses the repeatability of the total
synaptic output from the network. We find that individual embedded neurons can
be reliable or unreliable depending on network conditions, whereas pooled
responses of sufficiently large networks are mostly reliable. We study also the
effects of noise, and find that some types affect reliability more seriously
than others.
| arxiv topic:q-bio.NC cond-mat.dis-nn nlin.AO |
arxiv_dataset-648805.3623 | High order radiative corrections for unpolarized electron proton elastic
scattering at low $Q^2$
hep-ph
We investigate the effect of high order radiative corrections in unpolarized
electron proton elastic scattering and compare with the calculations at lowest
order, which are usually applied to experimental data. We show that higher
order terms play a role, starting from values of the momentum transfer squared,
$Q^2$, larger than the electron mass. Particular attention is devoted to the
$\epsilon$ dependence of radiative corrections.
| arxiv topic:hep-ph |
arxiv_dataset-649805.3723 | Dispersive optomechanics: a membrane inside a cavity
quant-ph
We present the results of theoretical and experimental studies of
dispersively coupled (or "membrane in the middle") optomechanical systems. We
calculate the linear optical properties of a high finesse cavity containing a
thin dielectric membrane. We focus on the cavity's transmission, reflection,
and finesse as a function of the membrane's position along the cavity axis and
as a function of its optical loss. We compare these calculations with
measurements and find excellent agreement in cavities with empty-cavity
finesses in the range 10^4 to 10^5. The imaginary part of the membrane's index
of refraction is found to be approximately 10^(-4). We calculate the laser
cooling performance of this system, with a particular focus on the
less-intuitive regime in which photons "tunnel" through the membrane on a time
scale comparable to the membrane's period of oscillation. Lastly, we present
calculations of quantum non-demolition measurements of the membrane's phonon
number in the low signal-to-noise regime where the phonon lifetime is
comparable to the QND readout time.
| arxiv topic:quant-ph |
arxiv_dataset-650805.3823 | Fractional Calculus: Integral and Differential Equations of Fractional
Order
math-ph cond-mat.stat-mech math.CV math.HO math.MP
We introduce the linear operators of fractional integration and fractional
differentiation in the framework of the Riemann-Liouville fractional calculus.
Particular attention is devoted to the technique of Laplace transforms for
treating these operators in a way accessible to applied scientists, avoiding
unproductive generalities and excessive mathematical rigor. By applying this
technique we shall derive the analytical solutions of the most simple linear
integral and differential equations of fractional order. We show the
fundamental role of the Mittag-Leffler function, whose properties are reported
in an ad hoc Appendix. The topics discussed here will be: (a) essentials of
Riemann-Liouville fractional calculus with basic formulas of Laplace
transforms, (b) Abel type integral equations of first and second kind, (c)
relaxation and oscillation type differential equations of fractional order.
| arxiv topic:math-ph cond-mat.stat-mech math.CV math.HO math.MP |
arxiv_dataset-651805.3923 | Estimate of a Trigonometrical Sum Involving Naturals with Binary
Decompositions of a Special Kind
math.NT
Let $\mathbb{N}_0$ be a class of natural numbers whose binary decompositions
has even number of 1. We estimate of the sum $\sum\limits_{n\in
\mathbf{N}_0,n\le X}\exp(2\pi i \alpha n^2)$.
| arxiv topic:math.NT |
arxiv_dataset-652805.4023 | Robust Joint Source-Channel Coding for Delay-Limited Applications
cs.IT math.IT
In this paper, we consider the problem of robust joint source-channel coding
over an additive white Gaussian noise channel. We propose a new scheme which
achieves the optimal slope of the signal-to-distortion (SDR) curve (unlike the
previously known coding schemes). Also, we propose a family of robust codes
which together maintain a bounded gap with the optimum SDR curve (in terms of
dB). To show the importance of this result, we drive some theoretical bounds on
the asymptotic performance of delay-limited hybrid digital-analog (HDA) coding
schemes. We show that, unlike the delay-unlimited case, for any family of
delay-limited HDA codes, the asymptotic performance loss is unbounded (in terms
of dB).
| arxiv topic:cs.IT math.IT |
arxiv_dataset-653805.4123 | Understanding the Very High-Energy Emission from Microquasars
astro-ph
Microquasars are X-ray binaries with relativistic jets. These jets are
powerful energy carriers, thought to be fed by accretion, which produce
non-thermal emission at different energy bands. To date, several Galactic
sources showing extended radio emission, among them at least one confirmed
microquasar, Cygnus X-1, have been detected in the TeV range. All of them show
complex patterns of spectral and temporal behavior. In this work, we discuss
the physics behind the very high-energy emission in microquasars. In concrete,
we focus on the microquasar Cygnus X-1, and also in the other two TeV binaries
with detected extended outflows, LS 5039 and LS I +61 303, pointing out
relevant aspects of the complex phenomena occurring in them. We conclude that
the TeV emission is likely of leptonic origin, although hadrons cannot be
discarded. In addition, efficient electromagnetic cascades can hardly develop
since even relatively low magnetic fields suppress them. Also, the modeling of
the radiation from some of the detected sources points to them as either
extremely efficient accelerators, and/or having the TeV emitter at a distance
from the compact object of about 10e12 cm. Finally, we point out that the role
of a massive and hot stellar companion, due to its strong photon field and
wind, cannot be neglected when trying to understand the behavior of
microquasars at high and very high energies. The complexity of microquasars
precludes straightforward generalizations to a whole population, and are better
studied presently in a source by source base.
| arxiv topic:astro-ph |
arxiv_dataset-654805.4223 | Are Self-explaining and Coached Problem Solving More Effective When Done
by Pairs of Students Than Alone?
physics.ed-ph
Although cognitive science has discovered several methods for increasing the
learning of complex skills, such as physics problem solving, detailed
examination of verbal protocols suggests there is still room for improvement.
Basically, students do not always apply the meta-cognitive strategies that the
instruction invites. For instance, when prompted to self-explain, students may
still choose to not explain. We conjecture that most students know which
meta-cognitive strategies are good and bad. When they work in pairs, they are
more likely to choose the good strategies. We hypothesize that social
accountability improves meta-cognitive strategy choice, which thereby improves
learning. Our experiment compared individuals and pairs learning from
state-of-the-art instruction. The results suggest that the dyads solved more
problems and requested fewer hints during problem solving than individuals. We
also discovered a new form of self-explanation, wherein students generate
explanations to account for the differences between their solutions and the
instructor's.
| arxiv topic:physics.ed-ph |
arxiv_dataset-655805.4323 | Network Connection Games with Disconnected Equilibria
cs.GT
In this paper we extend a popular non-cooperative network creation game (NCG)
to allow for disconnected equilibrium networks. There are n players, each is a
vertex in a graph, and a strategy is a subset of players to build edges to. For
each edge a player must pay a cost \alpha, and the individual cost for a player
represents a trade-off between edge costs and shortest path lengths to all
other players. We extend the model to a penalized game (PCG), for which we
reduce the penalty counted towards the individual cost for a pair of
disconnected players to a finite value \beta. Our analysis concentrates on
existence, structure, and cost of disconnected Nash and strong equilibria.
Although the PCG is not a potential game, pure Nash equilibria always and pure
strong equilibria very often exist. We provide tight conditions under which
disconnected Nash (strong) equilibria can evolve. Components of these
equilibria must be Nash (strong) equilibria of a smaller NCG. However, in
contrast to the NCG, for almost all parameter values no tree is a stable
component. Finally, we present a detailed characterization of the price of
anarchy that reveals cases in which the price of anarchy is \Theta(n) and thus
several orders of magnitude larger than in the NCG. Perhaps surprisingly, the
strong price of anarchy increases to at most 4. This indicates that global
communication and coordination can be extremely valuable to overcome socially
inferior topologies in distributed selfish network design.
| arxiv topic:cs.GT |
arxiv_dataset-656805.4423 | Does Khovanov homology detect the unknot?
math.GT math.QA
We determine a wide class of knots, which includes unknotting number one
knots, within which Khovanov homology detects the unknot. A corollary is that
the Khovanov homology of many satellite knots, including the Whitehead double,
detects the unknot.
| arxiv topic:math.GT math.QA |
arxiv_dataset-657805.4523 | $\alpha$ particle preformation in heavy nuclei and penetration
probability
nucl-ex
The $\alpha$ particle preformation in the even-even nuclei from $^{108}$Te to
$^{294}$118 and the penetration probability have been studied. The isotopes
from Pb to U have been firstly investigated since the experimental data allow
us to extract the microscopic features for each element. The assault frequency
has been estimated using classical methods and the penetration probability from
tunneling through the Generalized Liquid Drop Model (GLDM) potential barrier.
The preformation factor has been extracted from experimental $\alpha$ decay
energies and half-lives. The shell closure effects play the key role in the
$\alpha$ preformation. The more the nucleon number is close to the magic
numbers, the more the formation of $\alpha$ cluster is difficult inside the
mother nucleus. The penetration probabilities reflect that 126 is a neutron
magic number. The penetration probability range is very large compared to that
of the preformation factor. The penetration probability determines mainly the
$\alpha$ decay half-life while the preformation factor allows us to obtain
information on the nuclear structure. The study has been extended to the newly
observed heaviest nuclei.
| arxiv topic:nucl-ex |
arxiv_dataset-658805.4623 | Symmetry-breaking Fermi surface deformations from central interactions
in two dimensions
cond-mat.str-el cond-mat.stat-mech
We present a mean field theory of the Pomeranchuk instability in two
dimensions, starting from a generic central interaction potential described in
terms of a few microscopic parameters. For a significant range of parameters,
the instability is found to be pre-empted by a first-order quantum phase
transition. We provide the ground state phase diagram in terms of our generic
parameters.
| arxiv topic:cond-mat.str-el cond-mat.stat-mech |
arxiv_dataset-659805.4723 | Dynamical symmetries of the Klein-Gordon equation
quant-ph nucl-th
The dynamical symmetries of the two-dimensional Klein-Gordon equations with
equal scalar and vector potentials (ESVP) are studied. The dynamical symmetries
are considered in the plane and the sphere respectively. The generators of the
SO(3) group corresponding to the Coulomb potential, and the SU(2) group
corresponding to the harmonic oscillator potential are derived. Moreover, the
generators in the sphere construct the Higgs algebra. With the help of the
Casimir operators, the energy levels of the Klein-Gordon systems are yielded
naturally.
| arxiv topic:quant-ph nucl-th |
arxiv_dataset-660805.4823 | Positivity, local smoothing, and Harnack inequalities for very fast
diffusion equations
math.AP
We investigate qualitative properties of local solutions $u(t,x)\ge 0$ to the
fast diffusion equation, $\partial_t u =\Delta (u^m)/m$ with $m<1$,
corresponding to general nonnegative initial data. Our main results are
quantitative positivity and boundedness estimates for locally defined solutions
in domains of the form $[0,T]\times\RR^d$. They combine into forms of new
Harnack inequalities that are typical of fast diffusion equations. Such results
are new for low $m$ in the so-called very fast diffusion range, precisely for
all $m\le m_c=(d-2)/d.$ The boundedness statements are true even for $m\le 0$,
while the positivity ones cannot be true in that range.
| arxiv topic:math.AP |
arxiv_dataset-661806.0087 | Postural destabilization induced by trunk extensor muscles fatigue is
suppressed by use of a plantar pressure-based electro-tactile biofeedback
q-bio.NC
Separate studies have reported that postural control during quiet standing
could be (1) impaired with muscle fatigue localized at the lower back, and (2)
improved through the use of plantar pressure-based electro-tactile biofeedback,
under normal neuromuscular state. The aim of this experiment was to investigate
whether this biofeedback could reduce postural destabilization induced by trunk
extensor muscles. Ten healthy adults were asked to stand as immobile as
possible in four experimental conditions: (1) no fatigue/no biofeedback, (2) no
fatigue/biofeedback, (3) fatigue/no biofeedback and (4) fatigue/biofeedback.
Muscular fatigue was achieved by performing trunk repetitive extensions until
maximal exhaustion. The underlying principle of the biofeedback consisted of
providing supplementary information related to foot sole pressure distribution
through electro-tactile stimulation of the tongue. Centre of foot pressure
(CoP) displacements were recorded using a force platform. Results showed (1)
increased CoP displacements along the antero-posterior axis in the fatigue than
no fatigue condition in the absence of biofeedback and (2) no significant
difference between the no fatigue and fatigue conditions in the presence of
biofeedback. This suggests that subjects were able to efficiently integrate an
artificial plantar pressure information delivered through electro-tactile
stimulation of the tongue that allowed them to suppress the destabilizing
effect induced by trunk extensor muscles fatigue.
| arxiv topic:q-bio.NC |
arxiv_dataset-662806.0187 | Nitrogen abundances in giant stars of the globular cluster NGC 6752
astro-ph
We present N abundances for 21 bright giants in the globular cluster NGC 6752
based on high-resolution UVES spectra of the 3360A NH lines. We confirm that
the Stromgren c1 index traces the N abundance and find that the star-to-star N
abundance variation is 1.95 dex, at the sample's luminosity. We find
statistically significant correlations, but small amplitude variations, between
the abundances of N and alpha-, Fe-peak, and s-process elements. Analyses using
model atmospheres with appropriate N, O, Na, and Al abundances would
strengthen, rather than mute, these correlations. If the small variations of
heavy elements are real, then the synthesis of the N anomalies must take place
in stars which also synthesize alpha-, Fe-peak, and s-process elements. These
correlations offer support for contributions from both AGB and massive stars to
the globular cluster abundance anomalies.
| arxiv topic:astro-ph |
arxiv_dataset-663806.0287 | Perturbative Approach on Financial Markets
q-fin.PR math.PR
We study the point of transition between complete and incomplete financial
models thanks to Dirichlet Forms methods. We apply recent techniques,
developped by Bouleau, to hedging procedures in order to perturbate parameters
and stochastic processes, in the case of a volatility parameter fixed but
uncertain for traders; we call this model Perturbed Black Scholes (PBS) Model.
We show that this model can reproduce at the same time a smile effect and a
bid-ask spread; we exhibit the volatility function associated to the
local-volatility model equivalent to PBS model when vanilla options are
concerned.
Lastly, we present a connection between Error Theory using Dirichlet Forms
and Utility Function Theory.
| arxiv topic:q-fin.PR math.PR |
arxiv_dataset-664806.0387 | Euler-Lagrange models with complex currents of three-phase electrical
machines and observability issues
math.OC physics.class-ph
A new Lagrangian formulation with complex currents is developed and yields a
direct and simple method for modeling three-phase permanent-magnet and
induction machines. The Lagrangian is the sum a mechanical one and of a
magnetic one. This magnetic Lagrangian is expressed in terms of rotor angle,
complex stator and rotor currents. A complexification procedure widely used in
quantum electrodynamic is applied here in order to derive the Euler-Lagrange
equations with complex stator and rotor currents. Such complexification process
avoids the usual separation into real and imaginary parts and simplifies
notably the calculations. Via simple modifications of such magnetic Lagrangians
we derive new dynamical models describing permanent-magnet machines with both
saturation and saliency, and induction machines with both magnetic saturation
and space harmonics. For each model we also provide its Hamiltonian thus its
magnetic energy. This energy is also expressed with complex currents and can be
directly used in Lyapunov and/or passivity based control. Further, we briefly
investigate the observability of this class of Euler-Lagrange models, in the
so-called sensorless case when the measured output is the stator current and
the load torque is constant but unknown. For all the dynamical models obtained
via such variational principles, we prove that their linear tangent systems are
unobservable around a one-dimensional family of steady-states attached to the
same constant stator voltage and current. This negative result explains why
sensorless control of three-phase electrical machines around zero stator
frequency remains yet a difficult control problem.
| arxiv topic:math.OC physics.class-ph |
arxiv_dataset-665806.0487 | Lower bounds for the normalized height and non-dense subsets of
varieties in an abelian variety
math.NT
This work is the third part of a series of papers. In the first two we
consider curves and varieties in a power of an elliptic curve. Here we deal
with subvarieties of an abelian variety in general.
Let V be an irreducible variety of dimension d embedded in an abelian variety
A, both defined over the algebraic numbers. We say that V is weak-transverse if
V is not contained in any proper algebraic subgroup of A, and transverse if it
is not contained in any translate of such a subgroup.
Assume a conjectural lower bound for the normalized height of V. For V
transverse, we prove that the algebraic points of bounded height of V which lie
in the union of all algebraic subgroups of A of codimension at least d+1
translated by the points close to a subgroup G of finite rank are non
Zariski-dense in V. If G has rank zero, it is sufficient to assume that V is
weak-transverse.
The notion of closeness is defined using a height function.
| arxiv topic:math.NT |
arxiv_dataset-666806.0587 | Collisional stability of a three-component degenerate Fermi gas
cond-mat.other
We report on the creation of a degenerate Fermi gas consisting of a balanced
mixture of atoms in three different hyperfine states of $^6$Li. This new system
consists of three distinguishable Fermions with different and tunable
interparticle scattering lengths $a_{12}$, $a_{13}$ and $a_{23}$. We are able
to prepare samples containing $5 \cdot 10^4$ atoms in each state at a
temperature of about $215 $nK, which corresponds to $T/T_F \approx 0.37$. We
investigated the collisional stability of the gas for magnetic fields between 0
and 600 G and found a prominent loss feature at 130 G. From lifetime
measurements we determined three-body loss coefficients, which vary over nearly
three orders of magnitude.
| arxiv topic:cond-mat.other |
arxiv_dataset-667806.0687 | A Temperley-Lieb analogue for the BMW algebra
math.RT math.QA
The Temperley-Lieb algebra may be thought of as a quotient of the Hecke
algebra of type A, acting on tensor space as the commutant of the usual action
of quantum sl(2) on the n-th tensor power of the 2-dimensional irreducible
module. We define and study a quotient of the Birman-Wenzl-Murakami algebra,
which plays an analogous role for the 3-dimensional representation of quantum
sl(2). In the course of the discussion we prove some general results about the
radical of a cellular algebra, which may be of independent interest.
| arxiv topic:math.RT math.QA |
arxiv_dataset-668806.0787 | Power reductivity over an arbitrary base
math.RT
Our starting point is Mumford's conjecture, on representations of Chevalley
groups over fields, as it is phrased in the preface of "Geometric Invariant
Theory". After extending the conjecture appropriately, we show that it holds
over an arbitrary commutative base ring. We thus obtain the first fundamental
theorem of invariant theory (often referred to as Hilbert's fourteenth problem)
over an arbitrary Noetherian ring. We also prove results on the Grosshans
graded deformation of an algebra in the same generality. We end with tentative
finiteness results for rational cohomology over the integers.
| arxiv topic:math.RT |
arxiv_dataset-669806.0887 | Partial K-way negativities and three tangle for three qubit states
quant-ph
We obtain, analytically, the global negativity, partial $K-$way negativities
(K=2, 3), Wooter's tangle and three tangle for the generic three qubit
canonical state. It is found that the product of global negativity and partial
three way negativity is equal to three tangle, while the partial two way
negativity is related to tangle of qubit pairs. We also calculate similar
quantities for the state canonical to a single parameter (0<q<1) pure state
which is a linear combination of a GHZ state and a W state. In this case for
q=0.62685, the state has zero three tangle and zero three-way negativity,
having only W-like entanglement. The difference between the product of global
and partial three way negativity and three tangle for a given state is a
quantitative measure of two qubit coherences transformed by unitary
transformations on canonical state into three qubit coherences. The global
negativity and partial K-way negativities, obtained by selective partial
transpositions on multi-qubit state operator, satisfy inequalities which for
three qubits are equivalent to CKW (Coffman-Kundu-Wootter) inequality.
| arxiv topic:quant-ph |
arxiv_dataset-670806.0987 | Decoherence, Entanglement and Irreversibility in Quantum Dynamical
Systems with Few Degrees of Freedom
quant-ph cond-mat.mes-hall nlin.CD
This review summarizes and amplifies on recent investigations of coupled
quantum dynamical systems in the short wavelength limit. We formulate and
attempt to answer three fundamental questions: (i) What drives a dynamical
quantum system to behave classically ? (ii) What determines the rate at which
two coupled quantum--mechanical systems become entangled ? (iii) How does
irreversibility occur in quantum systems with few degrees of freedom ? We embed
these three questions in the broader context of the quantum--classical
correspondence, which motivates the use of short--wavelength approximations to
quantum mechanics such as the trajectory-based semiclassical methods and random
matrix theory. Doing so, we propose a novel investigative procedure towards
decoherence and the emergence of classicality out of quantumness in dynamical
systems coupled to external degrees of freedom. We reproduce known results
derived using master equation or Lindblad approaches but also generate novel
ones. In particular we show how local exponential instability also affects the
temporal evolution of quantum chaotic dynamical systems. We extensively rely on
numerical experiments to illustrate our findings and briefly comment on
possible extensions to more complex problems involving environments with $n \gg
1$ interacting dynamical systems, going beyond the uncoupled harmonic
oscillator model of Caldeira and Leggett.
| arxiv topic:quant-ph cond-mat.mes-hall nlin.CD |
arxiv_dataset-671806.1087 | Surface Solitons in Three Dimensions
nlin.PS
We study localized modes on the surface of a three-dimensional dynamical
lattice. The stability of these structures on the surface is investigated and
compared to that in the bulk of the lattice. Typically, the surface makes the
stability region larger, an extreme example of that being the three-site
"horseshoe"-shaped structure, which is always unstable in the bulk, while at
the surface it is stable near the anti-continuum limit. We also examine effects
of the surface on lattice vortices. For the vortex placed parallel to the
surface this increased stability region feature is also observed, while the
vortex cannot exist in a state normal to the surface. More sophisticated
localized dynamical structures, such as five-site horseshoes and pyramids, are
also considered.
| arxiv topic:nlin.PS |
arxiv_dataset-672806.1187 | Is the ground state of Yang-Mills theory Coulombic?
hep-lat hep-ph hep-th
We study trial states modelling the heavy quark-antiquark ground state in
SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a
thin string of glue is found to be a poor description of the continuum ground
state; the infinitesimal thickness of the string leads to UV artifacts which
suppress the overlap with the ground state. Contrastingly, a state which
surrounds the quarks with non-abelian Coulomb fields is found to have a good
overlap with the ground state for all charge separations. In fact, the overlap
increases as the lattice regulator is removed. This opens up the possibility
that the Coulomb state is the true ground state in the continuum limit.
| arxiv topic:hep-lat hep-ph hep-th |
arxiv_dataset-673806.1287 | Quasi-cycles in a spatial predator-prey model
q-bio.PE cond-mat.stat-mech
We show that spatial models of simple predator-prey interactions predict that
predator and prey numbers oscillate in time and space. These oscillations are
not seen in the deterministic versions of the models, but are due to stochastic
fluctuations about the time-independent solutions of the deterministic
equations which are amplified due to the existence of a resonance. We calculate
the power spectra of the fluctuations analytically and show that they agree
well with results obtained from stochastic simulations. This work extends the
analysis of these quasi-cycles from that previously developed for well-mixed
systems to spatial systems, and shows that the ideas and methods used for
non-spatial models naturally generalize to the spatial case.
| arxiv topic:q-bio.PE cond-mat.stat-mech |
arxiv_dataset-674806.1387 | Prospects and pitfalls of gravitational lensing in large supernova
surveys
astro-ph
To investigate the effect of gravitational lensing of supernovae in large
ongoing surveys, we simulate the effect of gravitational lensing magnification
on individual supernovae using observational data input from two large
supernova surveys. To estimate the magnification due to matter in the
foreground, we simulate galaxy catalogs and compute the magnification along
individual lines of sight using the multiple lens plane algorithm. The dark
matter haloes of the galaxies are modelled as gravitational lenses using
singular isothermal sphere or Navarro-Frenk-White profiles. Scaling laws
between luminosity and mass, provided by Faber-Jackson and Tully-Fisher
relations, are used to estimate the masses of the haloes.
While our simulations show that the SDSSII supernova survey is marginally
affected by gravitational lensing, we find that the effect will be measurable
in the SNLS survey that probes higher redshifts. Our simulations show that the
probability to measure a significant (3 sigma) correlation between the Hubble
diagram residuals and the calculated lensing magnification is ~95% in the SNLS
data. Moreover, with this data it should be possible to constrain the
normalisation of the masses of the lensing galaxy haloes at the 1 sigma and 2
sigma confidence level with ~30% and ~60% accuracy, respectively.
| arxiv topic:astro-ph |
arxiv_dataset-675806.1487 | Simulations and cosmological inference: A statistical model for power
spectra means and covariances
astro-ph
We describe an approximate statistical model for the sample variance
distribution of the non-linear matter power spectrum that can be calibrated
from limited numbers of simulations. Our model retains the common assumption of
a multivariate Normal distribution for the power spectrum band powers, but
takes full account of the (parameter dependent) power spectrum covariance. The
model is calibrated using an extension of the framework in Habib et al. (2007)
to train Gaussian processes for the power spectrum mean and covariance given a
set of simulation runs over a hypercube in parameter space. We demonstrate the
performance of this machinery by estimating the parameters of a power-law model
for the power spectrum. Within this framework, our calibrated sample variance
distribution is robust to errors in the estimated covariance and shows rapid
convergence of the posterior parameter constraints with the number of training
simulations.
| arxiv topic:astro-ph |
arxiv_dataset-676806.1587 | Fixed points in models of continuous opinion dynamics under bounded
confidence
physics.soc-ph math.DS
We present two models of continuous opinion dynamics under bounded confidence
which are representable as nonnegative discrete dynamical systems, namely the
Hegselmann-Krause model (Hegselmann and Krause, Journal of Artificial Societies
and Social Simulation 5(3), 2002) and the Deffuant-Weisbuch model (Deffuant et
al, Advances in Complex Systems, 3, 2000). We fully characterize the set of
fixed points for both models. They are identical. Further on, we present
reformulations of both models on the more general level of densities of agents
in the opinion space as interactive Markov chains. We also characterize the
sets of fixed points as identical in both models.
| arxiv topic:physics.soc-ph math.DS |
arxiv_dataset-677806.1687 | Superconductivity induced by oxygen deficiency in Sr-doped LaOFeAs
cond-mat.supr-con cond-mat.mtrl-sci
We synthesized Sr-doped $La_{0.85}Sr_{0.15}OFeAs$ sample with single phase,
and systematically studied the effect of oxygen deficiency in the Sr-doped
LaOFeAs system. It is found that substitution of Sr for La indeed induces the
hole carrier evidenced by positive thermoelectric power (TEP), but no bulk
superconductivity is observed. The superconductivity can be realized by
annealing the as-grown sample in vacuum to produce the oxygen deficiency. With
increasing the oxygen deficiency, the superconducting transition temperature
($T_c$) increases and maximum $T_c$ reaches about 26 K the same as that in
La(O,F)FeAs. TEP dramatically changes from positive to negative in the
nonsuperconducting as-grown sample to the superconducting samples with oxygen
deficiency. While $R_H$ is always negative for all samples (even for Sr-doped
as grown sample). It suggests that the $La_{0.85}Sr_{0.15}O_{1-\delta}FeAs$ is
still electron-type superconductor.
| arxiv topic:cond-mat.supr-con cond-mat.mtrl-sci |
arxiv_dataset-678806.1787 | The Origin and Evolution of \civ Baldwin Effect in QSOs from the Sloan
Digital Sky Survey
astro-ph
Using a large sample of 26623 quasars with redshifts in the range $1.5 \le
z\le 5.1$ with \civ $\lambda$1549 \AA emission line in Fifth Data Release of
the Sloan Digital Sky Survey (SDSS), we investigate the cosmological evolution
of the Baldwin Effect, i.e. the relation between the equivalent width (EW) of
the \civ emission line and continuum luminosity. We confirm the earlier result
that there exists a strong correlation between the \civ EW and the continuum
luminosity, and we find that, up to $z\approx 5$, the slope of the Baldwin
Effect seems to have no effect of cosmological evolution. A sub-sample of 13960
quasars with broad \civ $\lambda$1549 \AA emission line from SDSS is used to
explore the origin of the Baldwin Effect. We find that \civ EW have a strong
correlation with the mass of supermassive black hole (SMBH), and a weak
correlation with the Eddington ratio, $\lb/\ledd$. This suggests that the SMBH
mass is probably the primary drive for the Baldwin Effect.
| arxiv topic:astro-ph |
arxiv_dataset-679806.1887 | A family of transversely nonsimple knots
math.GT math.SG
We apply knot Floer homology to exhibit an infinite family of transversely
nonsimple prime knots starting with $10_{132}$. We also discuss the
combinatorial relationship between grid diagrams, braids, and Legendrian and
transverse knots in standard contact $\mathbb{R}^3$.
| arxiv topic:math.GT math.SG |
arxiv_dataset-680806.1987 | Renormalizable minimal SO(10) GUT in 4D and 5D
hep-ph
This report is a review of the present status of GUT, especially
renormalizable minimal SO(10) GUT, and its future prospect.
It consists of two parts. In part I, I review how the minimal renormalizable
supersymmetric SO(10) GUT, an SO(10) framework with only one ${\bf 10}$ and one
$\bar{\bf 126}$ Higgs multiplets in the Yukawa sector, is attractive because of
its high predictivity. Indeed it not only gave a consistent predictions on
neutrino oscillation data but also did reasonable and interesting values for
Leptogenesis, LFV, muon g-2, neutrinoless double beta decay etc. However, this
model suffers from problems, apart from the small deviations from the observed
values, related to running of gauge couplings and proton decay. The gauge
coupling unification may be spoiled due to the presence of intermediate scales
much lighter than the grand unification (GUT) scale. In addition, the gauge
couplings blow up around the GUT scale because of the presence of Higgs
multiplets of large representations. In order to remedy these pathologies, in
part II, we extend GUT into 5D. We propose two approaches: one is to consider
the warped extra dimension, using the bulk Higgs profile to explain the
intermediate energy scales. Another is to use the orbifold GUT. Both approaches
are complementary to each other.
| arxiv topic:hep-ph |
arxiv_dataset-681806.2087 | Probing the low-x structure of nuclear matter with diffractive hadron
production in pA collisions
hep-ph nucl-ex nucl-th
We argue that hadron production in coherent diffraction of proton on a heavy
nucleus provides a very sensitive probe of the low-x QCD dynamics. This process
probes the BFKL dynamics in proton and the non-linear gluon evolution in
nucleus. We calculate the diffractive hadron production cross sections in the
RHIC and LHC kinematic regions. To study the nuclear effects we introduce the
diffractive nuclear modification factor. We show that unlike the nuclear
modification factor for inclusive hadron production that has a very interesting
dynamics at RHIC but is expected to be almost completely saturated at the LHC,
the nuclear modification factor for diffractive production exhibits a
non-trivial behavior both at RHIC and LHC.
| arxiv topic:hep-ph nucl-ex nucl-th |
arxiv_dataset-682806.2187 | Asymptotic analysis of a boundary-value problem with the nonlinear
boundary multiphase interactions in a perforated domain
math.AP
We consider a boundary-value problem for the second order elliptic
differential operator with rapidly oscillating coefficients in a domain
$\Omega_{\epsilon}$ that is $\epsilon-$periodically perforated by small holes.
The holes are divided into two $\epsilon-$periodical sets depending on the
boundary interaction at their surfaces. Therefore, two different nonlinear
Robin boundary conditions $\sigma_\epsilon (u_\epsilon) + \epsilon \kappa_{m}
(u_\epsilon) = \epsilon g^{(m)}_\epsilon, m=1, 2,$ are given on the
corresponding boundaries of the small holes. The asymptotic analysis of this
problem is made as $\epsilon\to0,$ namely the convergence theorem both for the
solution and for the energy integral is proved without using extension
operators, the asymptotic approximations both for the solution and for the
energy integral are constructed and the corresponding error estimates are
obtained.
| arxiv topic:math.AP |
arxiv_dataset-683806.2287 | Approximately Counting Embeddings into Random Graphs
cs.DS cs.DM
Let H be a graph, and let C_H(G) be the number of (subgraph isomorphic)
copies of H contained in a graph G. We investigate the fundamental problem of
estimating C_H(G). Previous results cover only a few specific instances of this
general problem, for example, the case when H has degree at most one
(monomer-dimer problem). In this paper, we present the first general subcase of
the subgraph isomorphism counting problem which is almost always efficiently
approximable. The results rely on a new graph decomposition technique.
Informally, the decomposition is a labeling of the vertices such that every
edge is between vertices with different labels and for every vertex all
neighbors with a higher label have identical labels. The labeling implicitly
generates a sequence of bipartite graphs which permits us to break the problem
of counting embeddings of large subgraphs into that of counting embeddings of
small subgraphs. Using this method, we present a simple randomized algorithm
for the counting problem. For all decomposable graphs H and all graphs G, the
algorithm is an unbiased estimator. Furthermore, for all graphs H having a
decomposition where each of the bipartite graphs generated is small and almost
all graphs G, the algorithm is a fully polynomial randomized approximation
scheme.
We show that the graph classes of H for which we obtain a fully polynomial
randomized approximation scheme for almost all G includes graphs of degree at
most two, bounded-degree forests, bounded-length grid graphs, subdivision of
bounded-degree graphs, and major subclasses of outerplanar graphs,
series-parallel graphs and planar graphs, whereas unbounded-length grid graphs
are excluded.
| arxiv topic:cs.DS cs.DM |
arxiv_dataset-684806.2387 | Radio observations of NGC 2808 and other globular clusters: constraints
on intermediate mass black holes
astro-ph
We present the results of a deep radio observation of the globular cluster
NGC 2808. We show that there are no sources detected within the core of the
cluster, placing constraints on both the pulsar population of the cluster and
the mass of a possible intermediate mass black hole in NGC 2808. We compare the
results for this cluster with other constraints on intermediate mass black
holes derived from accretion measures. With the exception of G1 in M~31 which
has previously shown radio emission, even with considerably more conservative
assumptions, only the clusters with the poorest of observational constraints
are consistent with falling on the $M_{BH}-\sigma$ relation. This result is
interpreted in terms of the fundamental differences between galaxies and
globular clusters.
| arxiv topic:astro-ph |
arxiv_dataset-685806.2487 | Electron - Dark Matter Scattering in an Evacuated Tube
hep-ex
The light dark matter model can explain both the primordial abundance of dark
matter and the anomalous 511 keV gamma-ray signal from the galactic center.
This model posits a light neutral scalar, \chi, with a mass in the range 1 MeV
< Mchi < 10 MeV, as well as a light neutral spin-1 boson, U, which mediates the
annihilation channel \chi\chi -> e+e-. Since the dark matter particle is light,
its number density is relatively large if it accounts for a local dark matter
density of 0.3 GeV/cm^3. We consider an experiment in which a low-energy,
high-current electron beam is passed through a long evacuated tube, and elastic
scattering of electrons off dark matter particles is observed. The kinematics
of this process allow a clean separation of the signal process from scattering
off residual gas in the tube, and also a direct measurement of Mchi.
| arxiv topic:hep-ex |
arxiv_dataset-686806.2587 | q-Deformation and Semidualisation in 3d Quantum Gravity
gr-qc hep-th math-ph math.MP
We explore in detail the role in euclidean 3d quantum gravity of quantum Born
reciprocity or `semidualisation'. The latter is an algebraic operation defined
using quantum group methods that interchanges position and momentum. Using this
we are able to clarify the structural relationships between the effective
non-commutative geometries that have been discussed in the context of 3d
gravity. We show that the spin model based on D(U(su_2)) for quantum gravity
without cosmological constant is the semidual of a quantum particle on a
three-sphere, while the bicrossproduct (DSR) model is the semidual of a quantum
particle on hyperbolic space. We show further how the different models are all
specific limits of q-deformed models with q=e^{-\hbar \sqrt{-\Lambda}/m_p},
where m_p is the Planck mass and \Lambda is the cosmological constant, and
argue that semidualisation interchanges m_p and l_c, where l_c is the
cosmological length scale l_c=1/\sqrt{|\Lambda|}. We investigate the physics of
semidualisation by studying representation theory. In both the spin model and
its semidual we show that irreducible representations have a physical picture
as solutions of a respectively non-commutative/curved wave equation. We
explain, moreover, that the q-deformed model, at a certain algebraic level, is
self-dual under semidualisation.
| arxiv topic:gr-qc hep-th math-ph math.MP |
arxiv_dataset-687806.2687 | Forward Production of Protons and Pions in Heavy-ion Collisions
nucl-th
The problem of forward production of hadrons in heavy-ion collision at RHIC
is revisited with modification of the theoretical treatment on the one hand and
with the use of new data on the other. The basic formalism for hadronization
remains the same as before, namely, recombination, but the details of momentum
degradation and quark regeneration are improved. Recent data on the p/pi and
pbar/p ratios are used to constrain the value of the degradation parameter. The
p_T spectrum of the average charged particles is well reproduced. A prediction
on the p_T dependence of the pbar/p ratio at eta=3.2 is made.
| arxiv topic:nucl-th |
arxiv_dataset-688806.2787 | Sorting a Permutation by block moves
math.CO
We prove a lower and an upper bound on the number of block moves necessary to
sort a permutation. We put our results in contrast with existing results on
sorting by block transpositions, and raise some open questions.
| arxiv topic:math.CO |
arxiv_dataset-689806.2887 | Simulating Cosmic Reionization
astro-ph
The Cosmic Dark Ages and the Epoch of Reionization constitute a crucial
missing link in our understanding of the evolution of the intergalactic medium
and the formation and evolution of galaxies. Due to the complex nature of this
global process it is best studied through large-scale numerical simulations.
This presents considerable computational challenges. The dominant contributors
of ionizing radiation were dwarf galaxies. These tiny galaxies must be resolved
in very large cosmological volumes in order to derive their clustering
properties and the corresponding observational signatures correctly, which
makes this one of the most challenging problems of numerical cosmology. We have
recently performed the largest and most detailed simulations of the formation
of early cosmological large-scale structures and their radiative feedback
leading to cosmic reionization. This was achieved by running extremely large
(up to 29 billion-particle) N-body simulations of the formation of the Cosmic
Web, with enough particles and sufficient force resolution to resolve all the
galactic halos with total masses larger than 10^8 Solar masses in computational
volumes of up to (163 Mpc)^3. These results were then post-processed by
propagating the ionizing radiation from all sources by using fast and accurate
ray-tracing radiative transfer method. Both of our codes are parallelized using
a combination of MPI and OpenMP and to this date have been run efficiently on
up to 2048 cores (N-body) and up to 10000 cores (radiative transfer) on the
newly-deployed Sun Constellation Linux Cluster at the Texas Advanced Computing
Center. In this paper we describe our codes, parallelization strategies,
scaling and some preliminary scientific results. (abridged)
| arxiv topic:astro-ph |
arxiv_dataset-690806.2987 | Energy improvement for energy minimizing functions in the complement of
generalized Reifenberg-flat sets
math.AP
Let P be an hyperplane in R^N, and denote by dH the Hausdorff distance. We
show that for all positive radius r < 1 there is an epsilon > 0, such that if K
is a Reifenberg-flat set in B(0; 1), a ball in R^N, that contains the origin,
with d_H(K; P) <epsilon, and if u is an energy minimizing function in B(0; 1)\K
with restricted values on @B(0; 1)\K, then the normalized energy of u in B(0;
r)\K is bounded by the normalized energy of u in B(0; 1)\K. We also prove the
same result in R^3 when K is a epsilon-minimal set, that is a generalization of
Reifenberg-flat sets with minimal cones of type Y and T. Moreover, the result
is still true for a further generalization of sets called (eps; eps_0)-minimal.
This article is a preliminary study for a forthcoming paper where a regularity
result for the singular set of the Mumford-Shah functional close to minimal
cones in R^3 is proved by the same author.
| arxiv topic:math.AP |
arxiv_dataset-691806.3087 | The seesaw mechanism at TeV scale in the 3-3-1 model with right-handed
neutrinos
hep-ph
We implement the seesaw mechanism in the 3-3-1 model with right-handed
neutrinos. This is accomplished by the introduction of a scalar sextet into the
model and the spontaneous violation of the lepton number. We identify the
Majoron as a singlet under $SU_L(2)\otimes U_Y(1)$ symmetry, which makes it
safe under the current bounds imposed by electroweak data. The main result of
this work is that the seesaw mechanism works already at TeV scale with the
outcome that the right-handed neutrino masses lie in the electroweak scale, in
the range from MeV to tens of GeV. This window provides a great opportunity to
test their appearance at current detectors, though when we contrast our results
with some previous analysis concerning detection sensitivity at LHC, we
conclude that further work is needed in order to validate this search.
| arxiv topic:hep-ph |
arxiv_dataset-692806.3187 | On Transmission Line Resonances in High T$_C$ dc SQUIDs
cond-mat.supr-con
In this paper, we study transmission line resonances in high $T_C$ dc SQUIDs.
These resonances are exhibited in the characteristics of SQUIDs which are
fabricated on substrates with high dielectric constant, such as strontium
titanate. The power balance equation is analytically derived both for symmetric
and asymmetric SQUIDs. Using this, we investigate SQUID current - voltage
$I(V)$, voltage - flux $V(\Phi)$ and voltage modulation $\Delta V$
characteristics.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-693806.3287 | Multi-layered Spectral Formation in SNe Ia Around Maximum Light
astro-ph
We use the radiative transfer code PHOENIX to study the line formation of the
wavelength region 5000-7000 Angstroms. This is the region where the SNe Ia
defining Si II feature occurs. This region is important since the ratio of the
two nearby silicon lines has been shown to correlate with the absolute blue
magnitude. We use a grid of LTE synthetic spectral models to investigate the
formation of line features in the spectra of SNe Ia. By isolating the main
contributors to the spectral formation we show that the ions that drive the
spectral ratio are Fe III, Fe II, Si II, and S II. While the first two strongly
dominate the flux transfer, the latter two form in the same physical region
inside of the supernova. We also show that the naive blackbody that one would
derive from a fit to the observed spectrum is far different than the true
underlying continuum.
| arxiv topic:astro-ph |
arxiv_dataset-694806.3387 | Dissipative dynamics of a biased qubit coupled to a harmonic oscillator:
Analytical results beyond the rotating wave approximation
quant-ph cond-mat.mes-hall cond-mat.supr-con
We study the dissipative dynamics of a biased two-level system (TLS) coupled
to a harmonic oscillator (HO), the latter interacting with an Ohmic
environment. Using Van-Vleck perturbation theory and going to second order in
the coupling between TLS and HO, we show how the Hamiltonian of the TLS-HO
system can be diagonalized analytically. Our model represents an improvement to
the usually used Jaynes-Cummings Hamiltonian as an initial rotating wave
approximation is avoided. By assuming a weak coupling to the thermal bath,
analytical expressions for the time evolution of the populations of the TLS are
found: the population is characterized by a multiplicity of damped oscillations
together with a complex relaxation dynamics towards thermal equilibrium. The
long time evolution is characterized by a single relaxation rate, which is
largest at resonance and whose expression can be given in closed analytic form.
| arxiv topic:quant-ph cond-mat.mes-hall cond-mat.supr-con |
arxiv_dataset-695806.3487 | The twisted Floer homology of torus bundles
math.GT
Given a torus bundle $Y$ over the circle and a cohomology class $[\omega]\in
H^2(Y;\mathbb{Z})$ which evaluates nontrivially on the fiber, we compute the
Heegaard Floer homology of $Y$ with twisted coefficients in the universal
Novikov ring.
| arxiv topic:math.GT |
arxiv_dataset-696806.3587 | A Maximum Principle for Elliptic Pseudo-differential Operators on
Closed, Riemannian Manifolds
math.AP math-ph math.MP
In this note we establish the positivity of Green's functions for a class of
elliptic differential operators on closed, Riemannian manifolds.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-697806.3687 | Quantum Group of Orientation preserving Riemannian Isometries
math.QA math.OA
We formulate a quantum group analogue of the group of orinetation-preserving
Riemannian isometries of a compact Riemannian spin manifold, more generally, of
a (possibly $R$-twisted in the sense of a paper of one of the authors, and of
compact type) spectral triple. The main advantage of this formulation, which is
directly in terms of the Dirac operator, is that it does not need the existence
of any `good ' Laplacian as in our previous works on quantum isometry groups.
Several interesting examples, including those coming from Rieffel-type
deformation as well as the equivariant spectral triples on $SU_\mu(2)$ and
$S^2_{\mu 0}$ are dicussed.
| arxiv topic:math.QA math.OA |
arxiv_dataset-698806.3787 | Computational Approaches to Measuring the Similarity of Short Contexts :
A Review of Applications and Methods
cs.CL
Measuring the similarity of short written contexts is a fundamental problem
in Natural Language Processing. This article provides a unifying framework by
which short context problems can be categorized both by their intended
application and proposed solution. The goal is to show that various problems
and methodologies that appear quite different on the surface are in fact very
closely related. The axes by which these categorizations are made include the
format of the contexts (headed versus headless), the way in which the contexts
are to be measured (first-order versus second-order similarity), and the
information used to represent the features in the contexts (micro versus macro
views). The unifying thread that binds together many short context applications
and methods is the fact that similarity decisions must be made between contexts
that share few (if any) words in common.
| arxiv topic:cs.CL |
arxiv_dataset-699806.3887 | Conceptualization of seeded region growing by pixels aggregation. Part
2: how to localize a final partition invariant about the seeded region
initialisation order
cs.CV
In the previous paper, we have conceptualized the localization and the
organization of seeded region growing by pixels aggregation (SRGPA) but we do
not give the issue when there is a collision between two distinct regions
during the growing process. In this paper, we propose two implementations to
manage two classical growing processes: one without a boundary region region to
divide the other regions and another with. Unfortunately, as noticed by Mehnert
and Jakway (1997), this partition depends on the seeded region initialisation
order (SRIO). We propose a growing process, invariant about SRIO such as the
boundary region is the set of ambiguous pixels.
| arxiv topic:cs.CV |
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