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arxiv_dataset-24001101.4587 | Quantum key distribution based on orthogonal states allows secure
quantum bit commitment
quant-ph
For more than a decade, it was believed that unconditionally secure quantum
bit commitment (QBC) is impossible. But basing on a previously proposed quantum
key distribution scheme using orthogonal states, here we build a QBC protocol
in which the density matrices of the quantum states encoding the commitment do
not satisfy a crucial condition on which the no-go proofs of QBC are based.
Thus the no-go proofs could be evaded. Our protocol is fault-tolerant and very
feasible with currently available technology. It reopens the venue for other
"post-cold-war" multi-party cryptographic protocols, e.g., quantum bit string
commitment and quantum strong coin tossing with an arbitrarily small bias. This
result also has a strong influence on the Clifton-Bub-Halvorson theorem which
suggests that quantum theory could be characterized in terms of
information-theoretic constraints.
| arxiv topic:quant-ph |
arxiv_dataset-24011101.4687 | On a Simple Representation of the Kinnersley-Chitre Metric
gr-qc astro-ph.SR hep-th
A concise form of the Kinnersley-Chitre five-parameter metric for a spinning
mass is obtained by exploiting a remarkable similarity between the metric's
factor structure and the analogous structure of the Tomimatsu-Sato solutions
with even distortion parameter delta. The corresponding general subfamily of
asymptotically flat spacetimes containing four arbitrary real parameters is
considered, and all configurations describing two extreme Kerr sources
separated by a strut are identified and briefly discussed.
| arxiv topic:gr-qc astro-ph.SR hep-th |
arxiv_dataset-24021101.4787 | Fuzzy h-ideals of a $\Gamma-$hemiring and its operator hemirings
math.GM
Various correspondence between fuzzy h-ideals of a $\Gamma$-hemiring and
fuzzy h-ideals of its operator hemirings are established and some of their
characterizations are given using lattice structure and cartesian product.
| arxiv topic:math.GM |
arxiv_dataset-24031101.4887 | A multivariate Gnedenko law of large numbers
math.PR math.FA
We show that the convex hull of a large i.i.d. sample from an absolutely
continuous log-concave distribution approximates a predetermined convex body in
the logarithmic Hausdorff distance and in the Banach-Mazur distance. For
log-concave distributions that decay super-exponentially, we also have
approximation in the Hausdorff distance. These results are multivariate
versions of the Gnedenko law of large numbers, which guarantees concentration
of the maximum and minimum in the one-dimensional case. We provide quantitative
bounds in terms of the number of points and the dimension of the ambient space.
| arxiv topic:math.PR math.FA |
arxiv_dataset-24041101.4987 | The light MSSM neutral Higgs boson production associated with an
electron and a jet at the LHeC
hep-ph hep-ex
We study the light CP-even neutral Higgs boson production in association with
an electron and a jet at the possible CERN large hadron-electron collider
within the minimal supersymmetric standard model. We investigate the possible
supersymmetric effects on this process and compare our standard model numerical
results with those in previous work. We present the leading-order and QCD
next-to-leading-order corrected total cross sections and the distributions of
the transverse momenta of the final electron, the light neutral Higgs boson,
and jet in the minimal supersymmetric standard model. Our results show that the
scale dependence of the leading-order cross section is obviously reduced by the
QCD next-to-leading-order corrections. The K factor of the QCD correction to
the total cross section at the large hadron-electron collider varies from 0.893
to 1.048 when the factorization/renormalization scale $\mu$ goes up from $0.2
m_Z$ to $3.8 m_Z$ in our chosen parameter space.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-24051101.5087 | Continuous monitoring of membrane protein micro-domain association
during cell signaling
physics.bio-ph cond-mat.soft q-bio.QM
Central to understanding membrane bound cell signaling is to quantify how the
membrane ultra-structure consisting of transient spatial domains modulates
signaling and how the signaling influences this ultra-structure. Yet, measuring
the association of membrane proteins with domains in living, intact cells poses
considerable challenges. Here, we describe a non-destructive method to quantify
protein-lipid domain and protein cytoskeleton interactions in single, intact
cells enabling continuous monitoring of the protein domains interaction over
time during signaling.
| arxiv topic:physics.bio-ph cond-mat.soft q-bio.QM |
arxiv_dataset-24061101.5187 | The GALEX-SDSS NUV & FUV Flux Density and Local Star-Formation Rate
astro-ph.CO
We calculate the local UV flux density in the GALEX MIS FUV and NUV bands
using redshifts provided by SDSS DR7. Luminosity functions are calculated for
the overlapping MIS and SDSS sample, allowing flux densities to be measured and
the local star formation rate (SFR) to be calculated using volumes much larger
than previous FUV based estimates. We calculate flux densities for a dust
corrected low redshift (0.013 < z < 0.1) sample of f[FUV] = 22.24 \pm 3.13
\times 10^25 h ergs s^-1 Hz^-1 Mpc^-3, f[NUV] = 38.54 \pm 5.30 \times 10^25 h
ergs s^-1 Hz^-1 Mpc^-3. The star formation rate density found is
0.0312\pm0.0045 h M\odot yr^-1 Mpc^-3. This is larger than published rates
recently found using the UV implied SFR, though the major discrepancy is the
correction made for dust attenuation and once this is dealt with consistently
the results agree well. These values are also consistent with recent Halpha
derived SFRs. Once cosmic variance is taken into account most of the recent
SFRs at low redshift (z < 0.3) found in the literature can be brought into
agreement, however the lowest redshift values (z < 0.045) do appear to be
significantly lower.
| arxiv topic:astro-ph.CO |
arxiv_dataset-24071101.5287 | Computation approach for CMB bispectrum from primordial magnetic fields
astro-ph.CO gr-qc hep-ph
We present a detailed calculation of our previous short paper [M. Shiraishi,
D. Nitta, S. Yokoyama, K. Ichiki, and K. Takahashi, Phys. Rev. D 82, 121302
(2010).] in which we have investigated a constraint on the magnetic field
strength through comic microwave background temperature bispectrum of vector
modes induced from primordial magnetic fields. By taking into account full
angular dependence of the bispectrum with spin spherical harmonics and Wigner
symbols, we explicitly show that the cosmic microwave background bispectrum
induced from the statistical-isotropic primordial vector fluctuations can be
also described as an angle-averaged form in the rotationally invariant way. We
also study the cases with different spectral indices of the power spectrum of
the primordial magnetic fields.
| arxiv topic:astro-ph.CO gr-qc hep-ph |
arxiv_dataset-24081101.5387 | Observations of ultraluminous X-ray sources
astro-ph.HE
Ultraluminous X-ray sources (ULXs), first observed ~30 years ago, have been
argued as extreme stellar mass black hole binaries or a new class intermediate
mass black hole. In order to settle this debate, scientists have utilised a
wide range of telescopes, exploiting large sections of the electro-magnetic
spectrum. Here we review some of the insight gained from these observational
studies, collating an overview of our current position in ULX research.
| arxiv topic:astro-ph.HE |
arxiv_dataset-24091101.5487 | Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing
astro-ph.CO astro-ph.GA hep-ph
One of the open questions of modern cosmology is the nature and properties of
the Dark Matter halo and its substructures. In this work we study the
gravitational effect of dark matter substructures on pulsar timing
observations. Since millisecond pulsars are stable and accurate emitters, they
have been proposed as plausible astrophysical tools to probe the gravitational
effects of dark matter structures. We study this effect on pulsar timing
through Shapiro time delay (or Integrated Sachs-Wolfe (ISW) effect) and Doppler
effects statistically, showing that the latter dominates the signal. For this
task, we relate the power spectrum of pulsar frequency change to the matter
power spectrum on small scales, which we compute using the stable clustering
hypothesis. We compare this power spectrum with the reach of current and future
observations of pulsar timing designed for gravitational wave (GW) detection.
Our results show that while current observations are unable to detect these
signals, the sensitivity of the upcoming Square Kilometer Array (SKA) is only a
factor of few weaker than our optimistic predictions.
| arxiv topic:astro-ph.CO astro-ph.GA hep-ph |
arxiv_dataset-24101101.5587 | Completely Integrable Contact Hamiltonian Systems and Toric Contact
Structures on $S^2\times S^3$
math.SG math-ph math.DG math.MP
I begin by giving a general discussion of completely integrable Hamiltonian
systems in the setting of contact geometry. We then pass to the particular case
of toric contact structures on the manifold $S^2\times S^3$. In particular we
give a complete solution to the contact equivalence problem for a class of
toric contact structures, $Y^{p,q}$, discovered by physicists by showing that
$Y^{p,q}$ and $Y^{p',q'}$ are inequivalent as contact structures if and only if
$p\neq p'$.
| arxiv topic:math.SG math-ph math.DG math.MP |
arxiv_dataset-24111101.5687 | A correspondence-less approach to matching of deformable shapes
cs.CV cs.CG
Finding a match between partially available deformable shapes is a
challenging problem with numerous applications. The problem is usually
approached by computing local descriptors on a pair of shapes and then
establishing a point-wise correspondence between the two. In this paper, we
introduce an alternative correspondence-less approach to matching fragments to
an entire shape undergoing a non-rigid deformation. We use diffusion geometric
descriptors and optimize over the integration domains on which the integral
descriptors of the two parts match. The problem is regularized using the
Mumford-Shah functional. We show an efficient discretization based on the
Ambrosio-Tortorelli approximation generalized to triangular meshes. Experiments
demonstrating the success of the proposed method are presented.
| arxiv topic:cs.CV cs.CG |
arxiv_dataset-24121101.5787 | Measurement of $\phi_s$ at D{\O} Experiment
hep-ex
Recent measurements of the D\O\ experiment related to the search for new
phenomena beyond the Standard Model are reviewed. The new measurement of the
like-sign dimuon charge asymmetry reveals a 3.2$\sigma$ deviation from the SM
prediction, while the updated study of the $B_s \to J/\psi \phi$ decay
demonstrates a better agreement with the SM. All experimental results on the
$CP$ violation in mixing are currently consistent with each other. The D\O\
collaboration has much more statistics to analyze, and all these results can be
significantly improved in the future.
| arxiv topic:hep-ex |
arxiv_dataset-24131101.5887 | Quotients of Representation Rings
math.QA
We give a proof, using so-called fusion rings and q-deformations of Brauer
algebras that the representation ring of an orthogonal or symplectic group can
be obtained as a quotient of a ring Gr(O(\infinity)). This is obtained here as
a limiting case for analogous quotient maps for fusion categories, with the
level going to \infinity. This in turn allows a detailed description of the
quotient map in terms of a reflection group. As an application, one obtains a
general description of the branching rules for the restriction of
representations of Gl(N) to O(N) and Sp(N) as well as detailed information
about the structure of the q-Brauer algebras in the nonsemisimple case for
certain specializations.
| arxiv topic:math.QA |
arxiv_dataset-24141101.5987 | Branes, Quantization and Fuzzy Spheres
hep-th math-ph math.MP math.QA
We propose generalized quantization axioms for Nambu-Poisson manifolds, which
allow for a geometric interpretation of n-Lie algebras and their enveloping
algebras. We illustrate these axioms by describing extensions of
Berezin-Toeplitz quantization to produce various examples of quantum spaces of
relevance to the dynamics of M-branes, such as fuzzy spheres in diverse
dimensions. We briefly describe preliminary steps towards making the notion of
quantized 2-plectic manifolds rigorous by extending the groupoid approach to
quantization of symplectic manifolds.
| arxiv topic:hep-th math-ph math.MP math.QA |
arxiv_dataset-24151102.0006 | Vector-Valued Modular Forms from the Mumford Form, Schottky-Igusa Form,
Product of Thetanullwerte and the Amazing Klein Formula
math.AG hep-th
Vector-valued Siegel modular forms are the natural generalization of the
classical elliptic modular forms as seen by studying the cohomology of the
universal abelian variety. We show that for g>=4, a new class of vector-valued
modular forms, defined on the Teichmuller space, naturally appears from the
Mumford forms, a question directly related to the Schottky problem. In this
framework we show that the discriminant of the quadric associated to the
complex curves of genus 4 is proportional to the square root of the products of
Thetanullwerte \chi_{68}, which is a proof of the recently rediscovered Klein
`amazing formula'. Furthermore, it turns out that the coefficients of such a
quadric are derivatives of the Schottky-Igusa form evaluated at the Jacobian
locus, implying new theta relations involving the latter, \chi_{68} and the
theta series corresponding to the even unimodular lattices E_8\oplus E_8 and
D_{16}^+. We also find, for g=4, a functional relation between the singular
component of the theta divisor and the Riemann period matrix.
| arxiv topic:math.AG hep-th |
arxiv_dataset-24161102.0106 | The Architecture of MEG Simulation and Analysis Software
physics.ins-det hep-ex
MEG (Mu to Electron Gamma) is an experiment dedicated to search for the
$\mu^+ \rightarrow e^+\gamma$ decay that is strongly suppressed in the Standard
Model but predicted in several Super Symmetric extensions of it at an
accessible rate. MEG is a small-size experiment ($\approx 50-60$ physicists at
any time) with a life span of about 10 years. The limited human resource
available, in particular in the core offline group, emphasized the importance
of reusing software and exploiting existing expertise. Great care has been
devoted to provide a simple system that hides implementation details to the
average programmer. That allowed many members of the collaboration to
contribute to the development of the software of the experiment with limited
programming skill. The offline software is based on two frameworks: {\bf REM}
in FORTRAN 77 used for the event generation and detector simulation package
{\bf GEM}, based on GEANT 3, and {\bf ROME} in C++ used in the readout
simulation {\bf Bartender} and in the reconstruction and analysis program {\bf
Analyzer}. Event display in the simulation is based on GEANT 3 graphic
libraries and in the reconstruction on ROOT graphic libraries. Data are stored
in different formats in various stage of the processing. The frameworks include
utilities for input/output, database handling and format conversion transparent
to the user.
| arxiv topic:physics.ins-det hep-ex |
arxiv_dataset-24171102.0206 | First observation of Bs -> J/psi f0(980) decays
hep-ex hep-ph
Using data collected with the LHCb detector in proton-proton collisions at a
centre-of-mass energy of 7 TeV, the hadronic decay Bs -> J/psi f0(980) is
observed. This CP eigenstate mode could be used to measure mixing-induced CP
violation in the B_s system. Using a fit to the pi+ pi- mass spectrum with
interfering resonances gives R_{f0/phi} = [Gamma(Bs -> J/psi f0, f0 -> pi+
pi-)]/[Gamma(Bs -> J/psi phi, phi -> K+K-)] =
0.252^{+0.046+0.027}_{-0.032-0.033}, where the uncertainties are statistical
and systematic, respectively.
| arxiv topic:hep-ex hep-ph |
arxiv_dataset-24181102.0306 | On Nonlinear Higher Spin Curvature
hep-th gr-qc math-ph math.MP
We present the first nonlinear term of the higher spin curvature which is
covariant with respect to deformed gauge transformations that are linear in the
field. We consider in detail the case of spin 3 after presenting spin 2 as an
example, and then construct the general spin s quadratic term of the
deWit-Freedman curvature.
| arxiv topic:hep-th gr-qc math-ph math.MP |
arxiv_dataset-24191102.0406 | Threshold Saturation on Channels with Memory via Spatial Coupling
cs.IT math.IT
We consider spatially coupled code ensembles. A particular instance are
convolutional LDPC ensembles. It was recently shown that, for transmission over
the memoryless binary erasure channel, this coupling increases the belief
propagation threshold of the ensemble to the maximum a-posteriori threshold of
the underlying component ensemble. This paved the way for a new class of
capacity achieving low-density parity check codes. It was also shown
empirically that the same threshold saturation occurs when we consider
transmission over general binary input memoryless channels.
In this work, we report on empirical evidence which suggests that the same
phenomenon also occurs when transmission takes place over a class of channels
with memory. This is confirmed both by simulations as well as by computing EXIT
curves.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-24201102.0506 | Latest Results from the DODO Survey: Imaging Planets around White Dwarfs
astro-ph.EP
The aim of the Degenerate Objects around Degenerate Objects (DODO) survey is
to search for very low mass brown dwarfs and extrasolar planets in wide orbits
around white dwarfs via direct imaging. The direct detection of such companions
would allow the spectroscopic investigation of objects with temperatures lower
(< 500 K) than the coolest brown dwarfs currently observed. The discovery of
planets around white dwarfs would prove that such objects can survive the final
stages of stellar evolution and place constraints on the frequency of planetary
systems around their progenitors (with masses between 1.5 - 8 M*, i.e., early B
to mid-F). An increasing number of planetary mass companions have been directly
imaged in wide orbits around young main sequence stars. For example, the
planets around HR 8799 and 1RXS J160929.1 - 210524 are in wide orbits of 24 -
68 AU and 330 AU, respectively. The DODO survey has the ability to directly
image planets in post-main sequence analogues of these systems. These
proceedings present the latest results of our multi-epoch J band common proper
motion survey of nearby white dwarfs.
| arxiv topic:astro-ph.EP |
arxiv_dataset-24211102.0606 | On a question of Sean Keel
math.AG
We answer a question of Sean Keel in the affirmative in the case of ruled
surfaces
| arxiv topic:math.AG |
arxiv_dataset-24221102.0706 | Strategic Issues For A Successful E-Commerce
cs.CY
E-commerce is an emerging technology. Impact of this new technology is
getting clearer with time and results are tangible to the user community. In
this paper we have tried to focus some of its issues like paradigms,
infrastructure integration, and security, which is considered to be the most
important issue in E-Commerce. At first we have elaborated the paradigms of
E-Commerce (Business-to-Business and Business-to-Consumer). Then comes the
necessity of infrastructure integration with the legacy system. Security
concerns comes next. Rest of the part contains conclusion and references.
| arxiv topic:cs.CY |
arxiv_dataset-24231102.0806 | Rare $B$ Decays Potential at Super$B$
hep-ex
We present a short overview of the most important rare $B$ decay analyses
which will be performed using $75~{\rm ab}^{-1}$ dataset which is expected to
be provided by Super$B$ Factory within five years from its starting date.
| arxiv topic:hep-ex |
arxiv_dataset-24241102.0906 | Solar cycle variations of large frequency separations of acoustic modes:
Implications for asteroseismology
astro-ph.SR
We have studied solar cycle changes in the large frequency separations that
can be observed in Birmingham Solar Oscillations Network (BiSON) data. The
large frequency separation is often one of the first outputs from asteroseismic
studies because it can help constrain stellar properties like mass and radius.
We have used three methods for estimating the large separations: use of
individual p-mode frequencies, computation of the autocorrelation of
frequency-power spectra, and computation of the power spectrum of the power
spectrum. The values of the large separations obtained by the different methods
are offset from each other and have differing sensitivities to the realization
noise. A simple model was used to predict solar cycle variations in the large
separations, indicating that the variations are due to the well-known solar
cycle changes to mode frequency. However, this model is only valid over a
restricted frequency range. We discuss the implications of these results for
asteroseismology.
| arxiv topic:astro-ph.SR |
arxiv_dataset-24251102.1006 | On Approximating Four Covering and Packing Problems
cs.CC cs.DM cs.DS q-bio.PE
In this paper, we consider approximability issues of the following four
problems: triangle packing, full sibling reconstruction, maximum profit
coverage and 2-coverage. All of them are generalized or specialized versions of
set-cover and have applications in biology ranging from full-sibling
reconstructions in wild populations to biomolecular clusterings; however, as
this paper shows, their approximability properties differ considerably. Our
inapproximability constant for the triangle packing problem improves upon the
previous results; this is done by directly transforming the inapproximability
gap of Haastad for the problem of maximizing the number of satisfied equations
for a set of equations over GF(2) and is interesting in its own right. Our
approximability results on the full siblings reconstruction problems answers
questions originally posed by Berger-Wolf et al. and our results on the maximum
profit coverage problem provides almost matching upper and lower bounds on the
approximation ratio, answering a question posed by Hassin and Or.
| arxiv topic:cs.CC cs.DM cs.DS q-bio.PE |
arxiv_dataset-24261102.1106 | Target mass corrections to parity-violating DIS
hep-ph
We examine the implications of several parameterizations of so-called target
mass corrections (TMCs) for the physics of parity-violating deeply inelastic
scattering (DIS), especially at high values of the momentum fraction x. We
consider the role played by perturbative corrections in alpha_S in modifying
TMCs; we explicitly calculate these corrections at both the level of the
individual electroweak structure function (SF), as well as in the observables
of parity-violating DIS. TMCs augment an inventory of previously studied
corrections that become sizable at low Q^2 (finite-Q^2 corrections), and we
give special attention to the effects that might lead to the violation of the
approximate equality R^{gamma Z} = R^{gamma}.
| arxiv topic:hep-ph |
arxiv_dataset-24271102.1206 | LES of turbulent convection in solar-type stars and formation of
large-scale magnetic structures
astro-ph.SR physics.flu-dyn physics.plasm-ph
In this study we investigate the effects of turbulent convection on formation
of large-scale inhomogeneous magnetic structures by means of Large-Eddy
Simulation (LES) for convection in solar-type stars. The main idea of this
study is the implementation of a new subgrid-scale model for the effective
Lorentz force in a three-dimensional nonlinear radiative magnetohydrodynamics
(MHD) code developed for simulating the upper solar convection zone and lower
atmosphere. To this end we derived the energy budget equations, which include
the effects of the subgrid-scale turbulence on the Lorentz-force, and
implemented the new subgrid-scale turbulence model (TELF-Model) in a
three-dimensional nonlinear MHD LES code. Using imposed initial vertical and
horizontal uniform magnetic fields in LES with the TELF-Model, we have shown
that the magnetic flux tubes formation is started when the initial mean
magnetic field is larger than a threshold value (about 100 G). This is in
agreement with the theoretical studies by Rogachevskii and Kleeorin (2007). We
have determined the vertical profiles of the velocity and magnetic
fluctuations, total MHD energy and anisotropy of turbulent magneto-convection,
kinetic and current and cross helicities.
| arxiv topic:astro-ph.SR physics.flu-dyn physics.plasm-ph |
arxiv_dataset-24281102.1306 | Charmonium suppression at RHIC: Signature of a strongly-interacting QGP,
not a weakly interacting
hep-ph
Following a recent work on equation of state for strongly interacting
quark-gluon plasma [J. Phys. G: Nucl. Part. Phys. 32, 993 (2006)], we revisited
the equation of state by incorporating the non-perturbative effects in the
deconfined plasma phase. Our results on thermodynamic observables viz.
pressure, energy density, speed of sound etc. nicely fit with the lattice
equation of state for gluon, massless and as well massive flavored plasma.
Motivated by this agreement with lattice results, we have employed our equation
of state to estimate the quarkonium suppression in an expanding, dissipative
strongly interacting QGP produced in relativistic heavy-ion collisions and our
prediction matches exactly with the recent PHENIX data on the centrality
dependence of $J/\psi$ suppression in Au+Au collisions at BNL RHIC. We have
also predicted for the $\Upsilon$ suppression in Pb+Pb collisions at LHC energy
which could be tested in the ALICE experiments at CERN LHC.
| arxiv topic:hep-ph |
arxiv_dataset-24291102.1406 | Probing eV-mass scale axions with a Micromegas detector in the CAST
experiment
astro-ph.IM physics.data-an physics.ins-det
The CAST (CERN Axion Solar Telescope) experiment is searching for axions, an
hypothetical particle that emerges as a possible solution to the well known CP
violation problem in strong interactions. CAST is using a decommissioned LHC
dipole magnet able to track the Sun as a possible source of solar axions, and
to convert them to X-rays photons detectable with low background X-ray
detectors. CAST continues its data taking period scanning masses up to 1eV.
This thesis presents the data obtained with a Micromegas detector for the
scanned axion mass range up to 0.64eV. The working principle, characterization
and analysis of the Micromegas detectors operating in CAST are detailed in this
work. Moreover, the last detector data corresponding to the new data taking
period, with 3He gas inside the bores, was used to obtain a preliminar and
conservative upper limit on the axion-photon coupling for the new axion mass
range explored, g_{a\gamma} < 2.44 10^{-10} GeV^{-1}.
| arxiv topic:astro-ph.IM physics.data-an physics.ins-det |
arxiv_dataset-24301102.1506 | Why Cheating is Wrong
physics.ed-ph
Mathieu Bouville's "Why is cheating wrong?" (Studies in Philosophy and
Education, 29(1), 67-76, 2010) misses the mark by failing to consider the
longer term consequences of cheating on student character development and
longer term societal consequences of undermining professional expertise and
trust in disciplines where an earned degree is an essential part of
professional certification and qualifications. Educators who turn a blind eye
to student cheating are cheating the public by failing to deliver on the
promise of graduates who genuinely earned their degrees.
| arxiv topic:physics.ed-ph |
arxiv_dataset-24311102.1606 | Modular equations for some $\eta$-products
math.NT
The classical modular equations involve bivariate polynomials that can be
seen to be univariate with coefficients in the modular invariant $j$. Kiepert
found modular equations relating some $\eta$-quotients and the Weber functions
$\gamma_2$ and $\gamma_3$. In the present work, we extend this idea to double
$\eta$-quotients and characterize all the parameters leading to this kind of
equation. We give some properties of these equations, explain how to compute
them and give numerical examples.
| arxiv topic:math.NT |
arxiv_dataset-24321102.1706 | The Role of Exact Conditions in TDDFT
cond-mat.other
This chapter is devoted to exact conditions in time-dependent density
functional theory. Many conditions have been derived for the exact ground-state
density functional, and several have played crucial roles in the construction
of popular approximations. We believe that the reliability of the most
fundamental approximation of any density functional theory, the local density
approximation (LDA), is due to the exact conditions that it satisfies. Improved
approximations should satisfy at least those conditions that LDA satisfies,
plus others. (Which others is part of the art of functional approximation). In
the time-dependent case, as we shall see, the adiabatic LDA (ALDA) plays the
same role as LDA in the ground-state case, as it satisfies many exact
conditions. But we do not have a generally applicable improvement beyond ALDA
that includes nonlocality in time. For TDDFT, we have a surfeit of exact
conditions, but that only makes finding those that are useful to impose an even
more demanding task.
| arxiv topic:cond-mat.other |
arxiv_dataset-24331102.1806 | Electronic Structure of the Cuprate Superconducting and Pseudogap Phases
from Spectroscopic Imaging STM
cond-mat.supr-con cond-mat.str-el
We survey the use of spectroscopic imaging STM to probe the electronic
structure of underdoped cuprates. Two distinct classes of electronic states are
observed in both the d-wave superconducting (dSC) and the pseudogap (PG)
phases. The first class consists of the dispersive Bogoliubov quasiparticle
excitations of a homogeneous d-wave superconductor, existing below a lower
energy scale E=Delta0. We find that the Bogoliubov quasiparticle interference
signatures of delocalized Cooper pairing are restricted to a k-space arc which
terminates near the lines connecting k=\pm(pi/a0,0) to k=\pm(pi/a0). This arc
shrinks continuously with decreasing hole density such that Luttinger's theorem
could be satisfied if it represents the front side of a hole-pocket which is
bounded behind by the lines between k=\pm(pi/a0,0) and k=\pm(0,pi/a0). In both
phases the only broken symmetries detected for the |E|<Delta0 states are those
of a d-wave superconductor. The second class of states occurs proximate to the
pseudogap energy scale E=Delta1. Here the non-dispersive electronic structure
breaks the expected 90o-rotational symmetry of electronic structure within each
unit cell, at least down to 180o-rotational symmetry. This Q=0 electronic
symmetry breaking was first detected as an electronic inequivalence at the two
oxygen sites within each unit cell by using a measure of nematic (C2) symmetry.
Incommensurate non-dispersive conductance modulations, locally breaking both
rotational and translational symmetries, coexist with this intra-unit-cell
electronic symmetry breaking at E=Delta1. Their characteristic wavevector Q is
determined by the k-space points where Bogoliubov quasiparticle interference
terminates and therefore changes continuously with doping. The distinct broken
electronic symmetry states (Q=0 and finite Q) coexisting at E~Delta1 are found
to be indistinguishable in the dSC and PG phases.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-24341102.1906 | Key Polynomials
math.AG math.AC
The notion of key polynomials was first introduced in 1936 by S. Maclane in
the case of discrete rank 1 valuations. . Let K -> L be a field extension and
{\nu} a valuation of K. The original motivation for introducing key polynomials
was the problem of describing all the extensions {\mu} of {\nu} to L. Take a
valuation {\mu} of L extending the valuation {\nu}. In the case when {\nu} is
discrete of rank 1 and L is a simple algebraic extension of K Maclane
introduced the notions of key polynomials for {\mu} and augmented valuations
and proved that {\mu} is obtained as a limit of a family of augmented
valuations on the polynomial ring K[x].
In a series of papers, M. Vaqui\'e generalized MacLane's notion of key
polynomials to the case of arbitrary valuations {\nu} (that is, valuations
which are not necessarily discrete of rank 1).
In the paper Valuations in algebraic field extensions, published in the
Journal of Algebra in 2007, F.J. Herrera Govantes, M.A. Olalla Acosta and M.
Spivakovsky develop their own notion of key polynomials for extensions (K,
{\nu}) -> (L, {\mu}) of valued fields, where {\nu} is of archimedian rank 1
(not necessarily discrete) and give an explicit description of the limit key
polynomials.
Our purpose in this paper is to clarify the relationship between the two
notions of key polynomials already developed by vaqui\'e and by F.J. Herrera
Govantes, M.A. Olalla Acosta and M. Spivakovsky.
| arxiv topic:math.AG math.AC |
arxiv_dataset-24351102.2006 | High resolution stopwatch for cents
physics.pop-ph physics.ed-ph physics.ins-det
A very low-cost, easy-to-make stopwatch is presented to support various
experiments in mechanics. The high-resolution stopwatch is based on two
photodetectors connected directly to the microphone input of the sound card. A
dedicated free open-source software has been developed and made available to
download. The efficiency is demonstrated by a free fall experiment.
| arxiv topic:physics.pop-ph physics.ed-ph physics.ins-det |
arxiv_dataset-24361102.2106 | Vertical current induced domain wall motion in MgO-based magnetic tunnel
junction with low current densities
cond-mat.mtrl-sci
Shifting electrically a magnetic domain wall (DW) by the spin transfer
mechanism is one of the future ways foreseen for the switching of spintronic
memories or registers. The classical geometries where the current is injected
in the plane of the magnetic layers suffer from a poor efficiency of the
intrinsic torques acting on the DWs. A way to circumvent this problem is to use
vertical current injection. In that case, theoretical calculations attribute
the microscopic origin of DW displacements to the out-of-plane (field-like)
spin transfer torque. Here we report experiments in which we controllably
displace a DW in the planar electrode of a magnetic tunnel junction by vertical
current injection. Our measurements confirm the major role of the out-of-plane
spin torque for DW motion, and allow to quantify this term precisely. The
involved current densities are about 100 times smaller than the one commonly
observed with in-plane currents. Step by step resistance switching of the
magnetic tunnel junction opens a new way for the realization of spintronic
memristive devices.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-24371102.2206 | On infrared and ultraviolet divergences of cosmological perturbations
astro-ph.CO gr-qc hep-th
We study a consistent infrared and ultraviolet regularization scheme for the
cosmological perturbations. The infrared divergences are cured by assuming that
the Universe undergoes a transition between a non-singular pre-inflationary,
radiation-dominated phase and a slow-roll inflationary evolution. The
ultraviolet divergences are eliminated via adiabatic subtraction. A consistent
regularization of the field fluctuations through this transition is obtained by
performing a mode matching for both the gauge invariant Mukhanov variable and
its adiabatic expansion. We show that these quantities do not generate
ultraviolet divergences other than the standard ones, when evolving through the
matching time. We also show how the de Witt-Schwinger expansion, which can be
used to construct the counter-terms regularizing the ultraviolet divergences,
ceases to be valid well before horizon exit of the scales of interest. Thus,
such counter-terms should not be used beyond the time of the horizon exit so it
is unlikely that the observed power spectrum is modified by adiabatic
subtraction as claimed in the literature. However, the infrared regularization
might have an impact on the observed spectrum, and we briefly discuss this
possibility.
| arxiv topic:astro-ph.CO gr-qc hep-th |
arxiv_dataset-24381102.2306 | Determination of the bandgap and split-off band of wurtzite GaAs
cond-mat.mes-hall
GaAs nanowires with a 100% wurtzite structure are synthesized by the
vapor-liquid-solid method in a molecular beam epitaxy system, using gold as a
catalyst. We use resonant Raman spectroscopy and photoluminescence to determine
the position of the crystal-field split-off band of hexagonal wurtzite GaAs.
The temperature dependence of this transition enables us to extract the value
at 0 K, which is 1.982 eV. Our photoluminescence excitation spectroscopy
measurements are consistent with a band gap of GaAs wurtzite below 1.523 eV.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-24391102.2406 | Chiral spin states in polarized kagome spin systems with spin-orbit
coupling
cond-mat.str-el
We study quantum spin systems with a proper combination of geometric
frustration, spin-orbit coupling and ferromagnetism. We argue that such a
system is likely to be in a chiral spin state, a fractional quantum Hall (FQH)
state for bosonic spin degrees of freedom. The energy scale of the bosonic FQH
state is of the same order as the spin-orbit coupling and ferromagnetism ---
overall much higher than the energy scale of FQH states in semiconductors.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-24401102.2506 | Opportunistic Relaying for Space-Time Coded Cooperation with Multiple
Antenna Terminals
cs.IT math.IT
We consider a wireless relay network with multiple antenna terminals over
Rayleigh fading channels, and apply distributed space-time coding (DSTC) in
amplify-and-forward (A&F) mode. The A&F scheme is used in a way that each relay
transmits a scaled version of the linear combination of the received symbols.
It turns out that, combined with power allocation in the relays, A&F DSTC
results in an opportunistic relaying scheme, in which only the best relay is
selected to retransmit the source's space-time coded signal. Furthermore,
assuming the knowledge of source-relay CSI at the source node, we design an
efficient power allocation which outperforms uniform power allocation across
the source antennas. Next, assuming M-PSK or M-QAM modulations, we analyze the
performance of the proposed cooperative diversity transmission schemes in a
wireless relay networks with the multiple-antenna source and destination. We
derive the probability density function (PDF) of the received SNR at the
destination. Then, the PDF is used to determine the symbol error rate (SER) in
Rayleigh fading channels. We derived closed-form approximations of the average
SER in the high SNR scenario, from which we find the diversity order of system
RminfNs;Ndg, where R, Ns, and Nd are the number of the relays, source antennas,
and destination antennas, respectively. Simulation results show that the
proposed system obtain more than 6 dB gain in SNR over A&F MIMO DSTC for BER
10^{-4}, when R = 2, Ns = 2, and Nd = 1.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-24411102.2606 | On irreducible representations of compact $p$-adic analytic groups
math.RT math.NT math.RA
We prove that the canonical dimension of a coadmissible representation of a
semisimple $p$-adic Lie group in a $p$-adic Banach space is either zero or at
least half the dimension of a non-zero coadjoint orbit. To do this we establish
analogues for $p$-adically completed enveloping algebras of Bernstein's
inequality for modules over Weyl algebras, the Beilinson-Bernstein localisation
theorem and Quillen's Lemma about the endomorphism ring of a simple module over
an enveloping algebra.
| arxiv topic:math.RT math.NT math.RA |
arxiv_dataset-24421102.2706 | Blind source separation of convolutive mixtures of non circular linearly
modulated signals with unknown baud rates
cs.IT math.IT
This paper addresses the problem of blind separation of convolutive mixtures
of BPSK and circular linearly modulated signals with unknown (and possibly
different) baud rates and carrier frequencies. In previous works, we
established that the Constant Modulus Algorithm (CMA) is able to extract a
source from a convolutive mixture of circular linearly modulated signals. We
extend the analysis of the extraction capabilities of the CMA when the mixing
also contains BPSK signals. We prove that if the various source signals do not
share any non zero cyclic frequency nor any non conjugate cyclic frequencies,
the local minima of the constant modulus cost function are separating filters.
Unfortunately, the minimization of the Godard cost function generally fails
when considering BPSK signals that have the same rates and the same carrier
frequencies. This failure is due to the existence of non-separating local
minima of the Godard cost function. In order to achieve the separation, we
propose a simple modification of the Godard cost function which only requires
knowledge of the BPSK sources frequency offsets at the receiver side. We
provide various simulations of realistic digital communications scenarios that
support our theoretical statements.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-24431102.2806 | The Nuclear Science References (NSR) Database and Web Retrieval System
physics.data-an cs.DL
The Nuclear Science References (NSR) database together with its associated
Web interface, is the world's only comprehensive source of easily accessible
low- and intermediate-energy nuclear physics bibliographic information for more
than 200,000 articles since the beginning of nuclear science. The
weekly-updated NSR database provides essential support for nuclear data
evaluation, compilation and research activities. The principles of the database
and Web application development and maintenance are described. Examples of
nuclear structure, reaction and decay applications are specifically included.
The complete NSR database is freely available at the websites of the National
Nuclear Data Center http://www.nndc.bnl.gov/nsr and the International Atomic
Energy Agency http://www-nds.iaea.org/nsr.
| arxiv topic:physics.data-an cs.DL |
arxiv_dataset-24441102.2906 | A Tight Lower Bound on Distributed Random Walk Computation
cs.DC cs.DS
We consider the problem of performing a random walk in a distributed network.
Given bandwidth constraints, the goal of the problem is to minimize the number
of rounds required to obtain a random walk sample. Das Sarma et al. [PODC'10]
show that a random walk of length $\ell$ on a network of diameter $D$ can be
performed in $\tilde O(\sqrt{\ell D}+D)$ time. A major question left open is
whether there exists a faster algorithm, especially whether the multiplication
of $\sqrt{\ell}$ and $\sqrt{D}$ is necessary.
In this paper, we show a tight unconditional lower bound on the time
complexity of distributed random walk computation. Specifically, we show that
for any $n$, $D$, and $D\leq \ell \leq (n/(D^3\log n))^{1/4}$, performing a
random walk of length $\Theta(\ell)$ on an $n$-node network of diameter $D$
requires $\Omega(\sqrt{\ell D}+D)$ time. This bound is {\em unconditional},
i.e., it holds for any (possibly randomized) algorithm. To the best of our
knowledge, this is the first lower bound that the diameter plays a role of
multiplicative factor. Our bound shows that the algorithm of Das Sarma et al.
is time optimal.
Our proof technique introduces a new connection between {\em bounded-round}
communication complexity and distributed algorithm lower bounds with $D$ as a
trade-off parameter, strengthening the previous study by Das Sarma et al.
[STOC'11]. In particular, we make use of the bounded-round communication
complexity of the pointer chasing problem. Our technique can be of independent
interest and may be useful in showing non-trivial lower bounds on the
complexity of other fundamental distributed computing problems.
| arxiv topic:cs.DC cs.DS |
arxiv_dataset-24451102.3006 | Unipotent Schottky bundles on Riemann surfaces and complex tori
math.AG math.DG
We study a natural map from representations of a free (resp. free abelian)
group of rank g in GL_r(C), to holomorphic vector bundles of degree zero over a
compact Riemann surface X of genus g (resp. complex torus X of dimension g).
This map defines what is called a Schottky functor. Our main result is that
this functor induces an equivalence between the category of unipotent
representations of Schottky groups and the category of unipotent vector bundles
on X. We also show that, over a complex torus, any vector or principal bundle
with a flat holomorphic connection is Schottky.
| arxiv topic:math.AG math.DG |
arxiv_dataset-24461102.3106 | Multi-linear iterative K-Sigma-semialgebras
cs.DM cs.FL
We consider $K$-semialgebras for a commutative semiring $K$ that are at the
same time $\Sigma$-algebras and satisfy certain linearity conditions. When each
finite system of guarded polynomial fixed point equations has a unique solution
over such an algebra, then we call it an iterative multi-linear
$K$-$\Sigma$-semialgebra. Examples of such algebras include the algebras of
$\Sigma$-tree series over an alphabet $A$ with coefficients in $K$, and the
algebra of all rational tree series. We show that for many commutative
semirings $K$, the rational $\Sigma$-tree series over $A$ with coefficients in
$K$ form the free multi-linear iterative $K$-$\Sigma$-semialgebra on $A$.
| arxiv topic:cs.DM cs.FL |
arxiv_dataset-24471102.3206 | The First Limits on the Ultra-high Energy Neutrino Fluence from
Gamma-ray Bursts
astro-ph.HE
We set the first limits on the ultra-high energy (UHE) neutrino fluence at
energies greater than 10^9 GeV from gamma-ray bursts (GRBs) based on data from
the second flight of the ANtarctic Impulsive Transient Antenna (ANITA). During
the 31 day flight of ANITA-II, 26 GRBs were recorded by Swift or Fermi. Of
these, we analyzed the 12 GRBs which occurred during quiet periods when the
payload was away from anthropogenic activity. In a blind analysis, we observe 0
events on a total background of 0.0044 events in the combined prompt window for
all 12 low-background bursts. We also observe 0 events from the remaining 14
bursts. We place a 90% confidence level limit on the E^-4 prompt neutrino
fluence of 2.5x10^17 GeV^3/cm^2 between 10^8 and 10^12 GeV from GRB090107A.
This is the first reported limit on the UHE neutrino fluence from GRBs above
10^9 GeV, and the strongest limit above 10^8 GeV.
| arxiv topic:astro-ph.HE |
arxiv_dataset-24481102.3306 | Efficient Error-Correcting Geocoding
cs.IR cs.DS
We study the problem of resolving a perhaps misspelled address of a location
into geographic coordinates of latitude and longitude. Our data structure
solves this problem within a few milliseconds even for misspelled and
fragmentary queries. Compared to major geographic search engines such as Google
or Bing we achieve results of significantly better quality.
| arxiv topic:cs.IR cs.DS |
arxiv_dataset-24491102.3406 | Mixing Times for the Mean-Field Blume-Capel Model via Aggregate Path
Coupling
math.PR math-ph math.MP
In this paper we investigate the relationship between the mixing times of the
Glauber dynamics of a statistical mechanical system with its thermodynamic
equilibrium structure. For this we consider the mean-field Blume-Capel model,
one of the simplest statistical mechanical models that exhibits the following
intricate phase transition structure: within a two dimensional parameter space
there exists a curve at which the model undergoes a second-order, continuous
phase transition, a curve where the model undergoes a first-order,
discontinuous phase transition, and a tricritical point which separates the two
curves. We determine the interface between the regions of slow and rapid
mixing. In order to completely determine the region of rapid mixing, we employ
a novel extension of the path coupling method, successfully proving rapid
mixing even in the absence of contraction between neighboring states.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-24501102.3506 | Quenching of superconductivity by Co doping in K0.8Fe2Se2
cond-mat.supr-con cond-mat.str-el
We synthesized a series of K0.8Fe2-xCoxSe2 samples with nominal compositions
0\leq x\leq 0.035 and investigated their physical properties. The results show
that the superconductivity in K0.8Fe2-xCoxSe2 is quenched down to 5 K by 0.5
at. % Co doping, the fastest quenching rate ever-reported. The role played here
by Co is in contrast with the one in FeAs based superconductors where Co
usually induces superconductivity from parent compounds. Such a rapid quenching
favors a localized 3d model against the itinerant one for iron pnictide
superconductors.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-24511102.3606 | Ferromagnetic instability and finite-temperature properties of
two-dimensional electron systems with van Hove singularities
cond-mat.str-el
We study a ferromagnetic tendency in the two-dimensional Hubbard model near
van Hove filling by using a functional renormalization-group method. We compute
temperature dependences of magnetic susceptibilities including incommensurate
magnetism. The ferromagnetic tendency is found to occur in a dome-shaped region
around van Hove filling with an asymmetric property: incommensurate magnetism
is favored near the edge of the dome above van Hove filling whereas a
first-order-like transition to the ferromagnetic ground state is expected below
van Hove filling. The dome-shaped phase diagram is well captured in the Stoner
theory by invoking a smaller Coulomb interaction. Triplet p-wave
superconductivity tends to develop at low temperatures inside the dome and
extends more than the ferromagnetic region above van Hove filling.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-24521102.3706 | Bumpy Black Holes in Alternate Theories of Gravity
gr-qc
We generalize the bumpy black hole framework to allow for alternative theory
deformations. We construct two model-independent parametric deviations from the
Kerr metric: one built from a generalization of the quasi-Kerr and bumpy
metrics and one built directly from perturbations of the Kerr spacetime in
Lewis-Papapetrou form. We find the conditions that these "bumps" must satisfy
for there to exist an approximate second-order Killing tensor so that the
perturbed spacetime still possesses three constants of the motion (a deformed
energy, angular momentum and Carter constant) and the geodesic equations can be
written in first-order form. We map these parameterized metrics to each other
via a diffeomorphism and to known analytical black hole solutions in
alternative theories of gravity. The parameterized metrics presented here serve
as frameworks for the systematic calculation of extreme-mass ratio inspiral
waveforms in parameterized non-GR theories and the investigation of the
accuracy to which space-borne gravitational wave detectors can constrain such
deviations.
| arxiv topic:gr-qc |
arxiv_dataset-24531102.3806 | Factorisation breaking in diffractive dijet photoproduction at HERA?
hep-ph hep-ex
Recent experimental data on dijet cross sections in diffractive
photoproduction at HERA collider are analysed with an emphasis on QCD
factorisation breaking effects. The possible sources of the contradiction in
conclusions of H1 and ZEUS collaborations such as different hadronisation
corrections and different phase space of both analyses are studied.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-24541102.3906 | Renormalization Group Functions of \phi^4 Theory from High-Temperature
Expansions
hep-ph cond-mat.stat-mech hep-lat hep-th math-ph math.MP
It has been previously shown that calculation of renormalization group (RG)
functions of the scalar \phi^4 theory reduces to the analysis of thermodynamic
properties of the Ising model. Using high-temperature expansions for the
latter, RG functions of four-dimensional theory can be calculated for arbitrary
coupling constant g with an accuracy 10^{-4} for the Gell-Mann - Low function
\beta(g) and an accuracy 10^{-3} - 10^{-2} for anomalous dimensions. Expansions
of RG functions up to the 13th order in g^{-1/2} are obtained.
| arxiv topic:hep-ph cond-mat.stat-mech hep-lat hep-th math-ph math.MP |
arxiv_dataset-24551102.4006 | Exact diagonalization: the Bose-Hubbard model as an example
cond-mat.stat-mech math-ph math.MP quant-ph
We take the Bose-Hubbard model to illustrate exact diagonalization techniques
in a pedagogical way. We follow the road of first generating all the basis
vectors, then setting up the Hamiltonian matrix with respect to this basis, and
finally using the Lanczos algorithm to solve low lying eigenstates and
eigenvalues. Emphasis is placed on how to enumerate all the basis vectors and
how to use the hashing trick to set up the Hamiltonian matrix or matrices
corresponding to other quantities. Although our route is not necessarily the
most efficient one in practice, the techniques and ideas introduced are quite
general and may find use in many other problems.
| arxiv topic:cond-mat.stat-mech math-ph math.MP quant-ph |
arxiv_dataset-24561102.4106 | An Overview of IEEE 802.15.6 Standard
cs.NI
Wireless Body Area Networks (WBAN) has emerged as a key technology to provide
real-time health monitoring of a patient and diagnose many life threatening
diseases. WBAN operates in close vicinity to, on, or inside a human body and
supports a variety of medical and non-medical applications. IEEE 802 has
established a Task Group called IEEE 802.15.6 for the standardization of WBAN.
The purpose of the group is to establish a communication standard optimized for
low-power in-body/on-body nodes to serve a variety of medical and non-medical
applications. This paper explains the most important features of the new IEEE
802.15.6 standard. The standard defines a Medium Access Control (MAC) layer
supporting several Physical (PHY) layers. We briefly overview the PHY and MAC
layers specifications together with the bandwidth efficiency of IEEE 802.15.6
standard. We also discuss the security paradigm of the standard.
| arxiv topic:cs.NI |
arxiv_dataset-24571102.4206 | Brane inflation in background supergravity
hep-th astro-ph.CO gr-qc hep-ph
We propose a model of inflation in the framework of brane cosmology driven by
background supergravity. Starting from bulk supergravity we construct the
inflaton potential on the brane and employ it to investigate for the
consequences to inflationary paradigm. To this end, we derive the expressions
for the important parameters in brane inflation, which are somewhat different
from their counterparts in standard cosmology, using the one loop radiative
corrected potential. We further estimate the observable parameters and find
them to fit well with recent observational data by confronting with WMAP7 using
CAMB. We also analyze the typical energy scale of brane inflation with our
model, which resonates well with present estimates from cosmology and standard
model of particle physics.
| arxiv topic:hep-th astro-ph.CO gr-qc hep-ph |
arxiv_dataset-24581102.4306 | Anomalous diffusion in a symbolic model
cond-mat.stat-mech physics.comp-ph
We address this work to investigate some statistical properties of symbolic
sequences generated by a numerical procedure in which the symbols are repeated
following a power law probability density. In this analysis, we consider that
the sum of n symbols represents the position of a particle in erratic movement.
This approach revealed a rich diffusive scenario characterized by non-Gaussian
distributions and, depending on the power law exponent and also on the
procedure used to build the walker, we may have superdiffusion, subdiffusion or
usual diffusion. Additionally, we use the continuous-time random walk framework
to compare with the numerical data, finding a good agreement. Because of its
simplicity and flexibility, this model can be a candidate to describe real
systems governed by power laws probabilities densities.
| arxiv topic:cond-mat.stat-mech physics.comp-ph |
arxiv_dataset-24591102.4406 | A Markov chain on the symmetric group which is Schubert positive?
math.CO math.PR
We study a multivariate Markov chain on the symmetric group with remarkable
enumerative properties. We conjecture that the stationary distribution of this
Markov chain can be expressed in terms of positive sums of Schubert
polynomials.
This Markov chain is a multivariate generalization of a Markov chain
introduced by the first author in the study of random affine Weyl group
elements.
| arxiv topic:math.CO math.PR |
arxiv_dataset-24601102.4506 | The effect of magnetic activity saturation in chromospheric flux-flux
relationships
astro-ph.SR astro-ph.GA
We present a homogeneous study of chromospheric and coronal flux-flux
relationships using a sample of 298 late-type dwarf active stars with spectral
types F to M. The chromospheric lines were observed simultaneously in each star
to avoid spread due to long term variability. Unlike other works, we subtract
the basal chromospheric contribution in all the spectral lines studied. For the
first time, we quantify the departure of dMe stars from the general relations.
We show that dK and dKe stars also deviate from the general trend. Studying the
flux-colour diagrams we demonstrate that the stars deviating from the general
relations are those with saturated X-ray emission and that those stars also
present saturation in the H$\alpha$ line. Using several age spectral
indicators, we show that they are younger stars than those following the
general relationships. The non-universality of flux-flux relationships found in
this work should be taken into account when converting between fluxes in
different chromospheric activity indicators.
| arxiv topic:astro-ph.SR astro-ph.GA |
arxiv_dataset-24611102.4606 | An Ultra-Steep Spectrum Radio Relic in the Galaxy Cluster Abell 2443
astro-ph.CO
We present newly discovered radio emission in the galaxy cluster Abell 2443
which is (1) diffuse, (2) extremely steep spectrum, (3) offset from the cluster
center, (4) of irregular morphology and (5) not clearly associated with any of
the galaxies within the cluster. The most likely explanation is that this
emission is a cluster radio relic, associated with a cluster merger. We present
deep observations of Abell 2443 at multiple low frequencies (1425, 325 and 74
MHz) which help characterize the spectrum and morphology of this relic. Based
on the curved spectral shape of the relic emission and the presence of small
scale structure, we suggest that this new source is likely a member of the
radio phoenix class of radio relics.
| arxiv topic:astro-ph.CO |
arxiv_dataset-24621102.4706 | Enhancement of thermal photon production in event-by-event hydrodynamics
hep-ph
Thermal photon emission is widely believed to reflect properties of the
earliest, hottest evolution stage of the medium created in ultra-relativistic
heavy-ion collisions. Previous computations of photon emission have been
carried out using a hydrodynamical medium description with smooth, averaged
initial conditions. Recently, more sophisticated hydrodynamical models which
calculate observables by averaging over many evolutions with event-by-event
fluctuating initial conditions (IC) have been developed. Given their direct
connection to the early time dynamics, thermal photon emission appears an ideal
observable to probe fluctuations in the medium initial state. In this work, we
demonstrate that including fluctuations in the IC may lead to an enhancement of
the thermal photon yield of about a factor of 2 in the region $2 < p_T < 4$
GeV/$c$ (where thermal photon production dominates the direct photon yield)
compared to a scenario using smooth, averaged IC. Consequently, a much better
agreement with PHENIX data is found. This can be understood in terms of the
strong temperature dependence of thermal photon production, translating into a
sensitivity to the presence of 'hotspots' in an event and thus establishing
thermal photons as a suitable probe to characterize IC fluctuations.
| arxiv topic:hep-ph |
arxiv_dataset-24631102.4806 | Generation of Multi-Color Attosecond X-Ray Radiation Through Modulation
Compression
physics.acc-ph
In this paper, we propose a scheme to generate tunable multi-color attosecond
coherent X-ray radiation for future light source applications. This scheme uses
an energy chirped electron beam, a laser modulators, a laser chirper and two
bunch compressors to generate a multi-spike prebunched kilo-Ampere current
electron beam from a few tens Ampere electron beam out of a linac. Such an
electron beam transports through a series of undulator radiators and bunch
compressors to generate multi-color coherent X-ray radiation. As an
illustration, we present an example to generate two attosecond pulses with
$2.2$ nm and $3$ nm coherent X-ray radiation wavelength and more than $200$ MW
peak power using a $30$ Ampere $200$ nm laser seeded electron beam.
| arxiv topic:physics.acc-ph |
arxiv_dataset-24641102.4906 | Dark Matter in Inert Triplet Models
hep-ph
We study the inert triplet models, in which the standard model (SM) is
extended to have a new SU(2)L triplet scalar (Y=0 or 2) with an Z2 symmetry. We
show that the neutral component of the triplet can be a good dark matter
candidate. In particular, for the hypercharge Y=0 triplet model, the WMAP data
favors the region where the dark matter mass is around 5.5 TeV, which is also
consistent with the direct detection experiments. In contrast, for the Y=2
model, although dark matter with its mass around 2.8 TeV is allowed by WMAP, it
is excluded by the direct detection experiments because the spin-independent
cross section is enhanced by the Z mediated tree-level scattering process.
| arxiv topic:hep-ph |
arxiv_dataset-24651102.5006 | Two state scattering problem to Multi-channel scattering problem:
Analytically solvable model
quant-ph
Starting from few simple examples we have proposed a general method for
finding an exact analytical solution for the two state scattering problem in
presence of a delta function coupling. We have also extended our model to deal
with general one dimensional multi-channel scattering problems.
| arxiv topic:quant-ph |
arxiv_dataset-24661102.5106 | Time Reversal in Neutrino Oscillations
hep-ph
We estimate the time reversal violations for neutrino oscillations in matter
for typical experimental energies and baselines. We examine the present status
of experiments on neutrino oscillations, propose experiments for TRV, and
discuss the future.
| arxiv topic:hep-ph |
arxiv_dataset-24671102.5206 | The Domination Number of Grids
cs.DM
In this paper, we conclude the calculation of the domination number of all
$n\times m$ grid graphs. Indeed, we prove Chang's conjecture saying that for
every $16\le n\le m$, $\gamma(G_{n,m})=\lfloor\frac{(n+2)(m+2)}{5}\rfloor -4$.
| arxiv topic:cs.DM |
arxiv_dataset-24681102.5306 | Achlioptas process phase transitions are continuous
math.PR math.CO
It is widely believed that certain simple modifications of the random graph
process lead to discontinuous phase transitions. In particular, starting with
the empty graph on $n$ vertices, suppose that at each step two pairs of
vertices are chosen uniformly at random, but only one pair is joined, namely,
one minimizing the product of the sizes of the components to be joined. Making
explicit an earlier belief of Achlioptas and others, in 2009, Achlioptas,
D'Souza and Spencer [Science 323 (2009) 1453-1455] conjectured that there
exists a $\delta>0$ (in fact, $\delta\ge1/2$) such that with high probability
the order of the largest component "jumps" from $o(n)$ to at least $\delta n$
in $o(n)$ steps of the process, a phenomenon known as "explosive percolation."
We give a simple proof that this is not the case. Our result applies to all
"Achlioptas processes," and more generally to any process where a fixed number
of independent random vertices are chosen at each step, and (at least) one edge
between these vertices is added to the current graph, according to any (online)
rule. We also prove the existence and continuity of the limit of the rescaled
size of the giant component in a class of such processes, settling a number of
conjectures. Intriguing questions remain, however, especially for the product
rule described above.
| arxiv topic:math.PR math.CO |
arxiv_dataset-24691102.5406 | Isotropic properties of the photonic band gap in quasicrystals with
low-index contrast
physics.optics
We report on the formation and development of the photonic band gap in
two-dimensional 8-, 10- and 12-fold symmetry quasicrystalline lattices of low
index contrast. Finite size structures made of dielectric cylindrical rods were
studied and measured in the microwave region, and their properties compared
with a conventional hexagonal crystal. Band gap characteristics were
investigated by changing the direction of propagation of the incident beam
inside the crystal. Various angles of incidence from 0 \degree to 30\degree
were used in order to investigate the isotropic nature of the band gap. The
arbitrarily high rotational symmetry of aperiodically ordered structures could
be practically exploited to manufacture isotropic band gap materials, which are
perfectly suitable for hosting waveguides or cavities.
| arxiv topic:physics.optics |
arxiv_dataset-24701102.5506 | Quantum criticality in a Mott pn-junction in an armchair carbon nanotube
cond-mat.mes-hall
In an armchair carbon nanotube pn junction the p- and n- regions are
separated by a region of a Mott insulator, which can backscatter electrons only
in pairs. We predict a quantum-critical behavior in such a pn junction.
Depending on the junction's built-in electric field E, its conductance G scales
either to zero or to the ideal value G=4e^2/h as the temperature T is lowered.
The two types of the G(T) dependence indicate the existence, at some special
value of E, of an intermediate quantum critical point with a finite conductance
G<4e^2/h. This makes the pn junction drastically different from a simple
barrier in a Luttinger liquid.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-24711102.5606 | Ornstein-Uhlenbeck type processes with heavy distribution tails
math.PR math.ST stat.TH
We consider a transformed Ornstein-Uhlenbeck process model that can be a good
candidate for modelling real-life processes characterized by a combination of
time-reverting behaviour with heavy distribution tails. We begin with
presenting the results of an exploratory statistical analysis of the log prices
of a major Australian public company, demonstrating several key features
typical of such time series. Motivated by these findings, we suggest a simple
transformed Ornstein-Uhlenbeck process model and analyze its properties showing
that the model is capable of replicating our empirical findings. We also
discuss three different estimators for the drift coefficient in the underlying
(unobservable) Ornstein-Uhlenbeck process which is the key descriptor of
dependence in the process.
| arxiv topic:math.PR math.ST stat.TH |
arxiv_dataset-24721102.5706 | Observed Binary Fraction Sets Limits on the Extent of Collisional
Grinding in the Kuiper Belt
astro-ph.EP
The size distribution in the cold classical Kuiper belt can be approximated
by two idealized power laws: one with steep slope for radii R>R* and one with
shallow slope for R<R*, where R*~25-50 km. Previous works suggested that the
SFD roll-over at R* can be the result of extensive collisional grinding in the
Kuiper belt that led to the catastrophic disruption of most bodies with R<R*.
Here we use a new code to test the effect of collisions in the Kuiper belt. We
find that the observed roll-over could indeed be explained by collisional
grinding provided that the initial mass in large bodies was much larger than
the one in the present Kuiper belt, and was dynamically depleted. In addition
to the size distribution changes, our code also tracks the effects of
collisions on binary systems. We find that it is generally easier to dissolve
wide binary systems, such as the ones existing in the cold Kuiper belt today,
than to catastrophically disrupt objects with R~R*. Thus, the binary survival
sets important limits on the extent of collisional grinding in the Kuiper belt.
We find that the extensive collisional grinding required to produce the SFD
roll-over at R* would imply a strong gradient of the binary fraction with R and
separation, because it is generally easier to dissolve binaries with small
components and/or those with wide orbits. The expected binary fraction for R<R*
is <0.1. The present observational data do not show such a gradient. Instead,
they suggest a large binary fraction of ~0.4 for R=30-40 km. This may indicate
that the roll-over was not produced by disruptive collisions, but is instead a
fossil remnant of the KBO formation process.
| arxiv topic:astro-ph.EP |
arxiv_dataset-24731103.0032 | On factorizations in perturbative quantum gravity
hep-th
Some features of Einstein gravity are most easily understood from string
theory but are not manifest at the level of the usual Lagrangian formulation.
One example is the factorization of gravity amplitudes into gauge theory
amplitudes. Based on the recently constructed `double field theory' and a
geometrical frame-like formalism developed by Siegel, we provide a framework of
perturbative Einstein gravity coupled to a 2-form and a dilaton in which, as a
consequence of T-duality, the Feynman rules factorize to all orders in
perturbation theory. We thereby establish the precise relation between the
field variables in different formulations and discuss the Lagrangian that, when
written in terms of these variables, makes a left-right factorization manifest.
| arxiv topic:hep-th |
arxiv_dataset-24741103.0132 | Quantum Action Principle for Covariant Systems. Bosonic string
quant-ph gr-qc
A new form of covariant quantum theory based on a quantum version of the
action principle is considered for the case of a free bosonic string. The
central idea of the new approach is to delay conditions of stationarity of the
classical action with respect to Lagrangian multipliers up to the quantum level
where delayed conditions of stationarity are imposed on a quantum action.
Physical states of the ordinary covariant quantum theory are replaced by well
defined stationary states as those which obey quantum action principle. The
stationary states have well defined energies.
| arxiv topic:quant-ph gr-qc |
arxiv_dataset-24751103.0232 | The defect variance of random spherical harmonics
math-ph math.MP math.PR
The defect of a function $f:M\rightarrow \mathbb{R}$ is defined as the
difference between the measure of the positive and negative regions. In this
paper, we begin the analysis of the distribution of defect of random Gaussian
spherical harmonics. By an easy argument, the defect is non-trivial only for
even degree and the expected value always vanishes. Our principal result is
obtaining the asymptotic shape of the defect variance, in the high frequency
limit. As other geometric functionals of random eigenfunctions, the defect may
be used as a tool to probe the statistical properties of spherical random
fields, a topic of great interest for modern Cosmological data analysis.
| arxiv topic:math-ph math.MP math.PR |
arxiv_dataset-24761103.0332 | Directed Coulomb explosion effect on proton acceleration by an intense
laser pulse from a double-layer target
physics.plasm-ph physics.acc-ph
We examine ion acceleration by irradiating a hundred TW laser pulse on a
double-layer target. It is shown analytically and by three-dimensional
particle-in-cell simulations that higher energy protons are obtained by using
material with a high charge-to-mass ratio in the first layer of a double-layer
target, because a strong Coulomb explosion occurs in such a material. As a
result, the protons keep accelerating for a longer time. Using the optimal
conditions for the target, it is shown that high energy and high quality
protons can be generated.
| arxiv topic:physics.plasm-ph physics.acc-ph |
arxiv_dataset-24771103.0432 | The role of attractive forces in viscous liquids
cond-mat.stat-mech
We present evidence from computer simulation that the slowdown of relaxation
of a standard Lennard-Jones glass-forming liquid and that of its reduction to a
model with truncated pair potentials without attractive tails is quantitatively
and qualitatively different in the viscous regime. The pair structure of the
two models is however very similar. This finding, which appears to contradict
the common view that the physics of dense liquids is dominated by the steep
repulsive forces between atoms, is characterized in detail, and its
consequences are explored. Beyond the role of attractive forces themselves, a
key aspect in explaining the differences in the dynamical behavior of the two
models is the truncation of the interaction potentials beyond a cutoff at
typical interatomic distance. This leads us to question the ability of the
jamming scenario to describe the physics of glass-forming liquids and polymers.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-24781103.0532 | Observations of Dispersion Cancellation of Entangled Photon Pairs
quant-ph
An experimental study of the dispersion cancellation occurring in
frequency-entangled photon pairs is presented. The approach uses time-resolved
up conversion of the pairs, which has temporal resolution at the fs level, and
group-delay dispersion sensitivity of $\approx \ 20 \, \mathrm{fs}^2$ under
experimental conditions. The cancellation is demonstrated with dispersion
stronger than $\pm 10^3 \, \mathrm{fs}^2$ in the signal $(-)$ and idler $(+)$
modes. The observations represent the generation, compression, and
characterization of ultrashort biphotons with correlation width as small as 6.8
times the degenerate optical period.
| arxiv topic:quant-ph |
arxiv_dataset-24791103.0632 | An Agent Based Architecture (Using Planning) for Dynamic and Semantic
Web Services Composition in an EBXML Context
cs.AI
The process-based semantic composition of Web Services is gaining a
considerable momentum as an approach for the effective integration of
distributed, heterogeneous, and autonomous applications. To compose Web
Services semantically, we need an ontology. There are several ways of inserting
semantics in Web Services. One of them consists of using description languages
like OWL-S. In this paper, we introduce our work which consists in the
proposition of a new model and the use of semantic matching technology for
semantic and dynamic composition of ebXML business processes.
| arxiv topic:cs.AI |
arxiv_dataset-24801103.0732 | Collapse and revival of oscillations in a parametrically excited
Bose-Einstein condensate in combined harmonic and optical lattice trap
cond-mat.quant-gas
In this work, we study parametric resonances in an elongated cigar-shaped BEC
in a combined harmonic trap and a time dependent optical lattice by using
numerical and analytical techniques. We show that there exists a relative
competition between the harmonic trap which tries to spatially localize the BEC
and the time varying optical lattice which tries to delocalize the BEC. This
competition gives rise to parametric resonances (collapse and revival of the
oscillations of the BEC width). Parametric resonances disappear when one of the
competing factors i.e strength of harmonic trap or the strength of optical
lattice dominates. Parametric instabilities (exponential growth of Bogoliubov
modes) arise for large variations in the strength of the optical lattice.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-24811103.0832 | A gradient estimate for solutions to parabolic equations with
discontinuous coefficients
math.AP
Li-Vogelius and Li-Nirenberg gave a gradient estimate for solutions of
strongly elliptic equations and systems of divergence forms with piecewise
smooth coefficients, respectively. The discontinuities of the coefficients are
assumed to be given by manifolds of codimension 1, which we called them
manifolds of discontinuities. Their gradient estimate is independent of the
distances between manifolds of discontinuities. In this paper, we gave a
parabolic version of their results. That is, we gave a gradient estimate for
parabolic equations of divergence forms with piecewise smooth coefficients. The
coefficients are assumed to be independent of time and their discontinuities
are likewise the previous elliptic equations. As an application of this
estimate, we also gave a pointwise gradient estimate for the fundamental
solution of a parabolic operator with piecewise smooth coefficients. The both
gradient estimates are independent of the distances between manifolds of
discontinuities.
| arxiv topic:math.AP |
arxiv_dataset-24821103.0932 | A Monomial Basis for the Holomorphic Functions on $c_{0}$
math.CV
We show that both $(\mathcal{H}(c_{0}),\tau_{\omega})$ and
$(\mathcal{H}_{b}(c_{0}),\tau_{b})$ have a monomial Schauder basis.
| arxiv topic:math.CV |
arxiv_dataset-24831103.1032 | Subharmonicity of the modulus of quasiregular harmonic mappings
math.FA
In this note we determine all numbers $q\in \mathbf R$ such that $|u|^q$ is a
subharmonic function, provided that $u$ is a $K-$quasiregular harmonic mappings
in an open subset $\Omega$ of the Euclidean space $\mathbf R^n$.
| arxiv topic:math.FA |
arxiv_dataset-24841103.1132 | Holographic multiverse and the measure problem
hep-th
We discuss the duality, conjectured in earlier work, between the wave
function of the multiverse and a 3D Euclidean theory on the future boundary of
spacetime. In particular, we discuss the choice of the boundary metric and the
relation between the UV cutoff scale xi on the boundary and the hypersurfaces
Sigma on which the wave function is defined in the bulk. We propose that in the
limit of xi going to 0 these hypersurfaces should be used as cutoff surfaces in
the multiverse measure. Furthermore, we argue that in the inflating regions of
spacetime with a slowly varying Hubble rate H the hypersurfaces Sigma are
surfaces of constant comoving apparent horizon (CAH). Finally, we introduce a
measure prescription (called CAH+) which appears to have no pathological
features and coincides with the constant CAH cutoff in regions of slowly
varying H.
| arxiv topic:hep-th |
arxiv_dataset-24851103.1232 | Efficient algorithms for highly compressed data: The Word Problem in
Higman's group is in P
math.GR
Power circuits are data structures which support efficient algorithms for
highly compressed integers. Using this new data structure it has been shown
recently by Myasnikov, Ushakov and Won that the Word Problem of the one-relator
Baumslag group is in P. Before that the best known upper bound has been
non-elementary. In the present paper we provide new results for power circuits
and we give new applications in algorithmic algebra and algorithmic group
theory: 1. We define a modified reduction procedure on power circuits which
runs in quadratic time thereby improving the known cubic time complexity. The
improvement is crucial for our other results. 2. We improve the complexity of
the Word Problem for the Baumslag group to cubic time thereby providing the
first practical algorithm for that problem. 3. The main result is that the Word
Problem of Higman's group is decidable in polynomial time. The situation for
Higman's group is more complicated than for the Baumslag group and forced us to
advance the theory of power circuits.
| arxiv topic:math.GR |
arxiv_dataset-24861103.1332 | Differential Operators on the free algebras
math.RA math.RT
Following the definitions of the algebras of differential operators,
$\beta$-differential operators, and the quantum differential operators on a
noncommutative (graded) algebra given in \cite{LR}, we describe these operators
on the free associative algebra. We further study their properties.
| arxiv topic:math.RA math.RT |
arxiv_dataset-24871103.1432 | Vectorial Feedback with Carry Registers and Memory requirements
cs.IT cs.CR math.IT
In \cite{marjane2010}, we have introduced vectorial conception of FCSR's in
Fibonacci mode. This conception allows us to easily analyze FCSR's over binary
finite fields $\mathbb{F}_{2^{n}}$ for $n\geq 2$. In \cite{allailou2010}, we
describe and study the corresponding Galois mode and use it to design a new
stream cipher. In this paper, we introduce the Ring mode for vectorial FCSR,
explain the analysis of such Feedback registers and illustrate with a simple
example.
| arxiv topic:cs.IT cs.CR math.IT |
arxiv_dataset-24881103.1532 | Ionizing feedback from massive stars in massive clusters: Fake bubbles
and untriggered star formation
astro-ph.SR
We use Smoothed Particle Hydrodynamics to simulate the formation of a massive
(10^6Msun) stellar cluster system formed from the gravitational collapse of a
turbulent molecular cloud. We investigate the hierarchical clustering
properties of our model system and we study the influence of the photoionizing
radiation produced by the system's multiple O-type stars on the evolution of
the protocluster. We find that dense gas near the ionizing sources prevents the
radiation from eroding the filaments in which most of the star formation occurs
and that instead, ionized gas fills pre-existing voids and bubbles originally
created by the turbulent velocity field.
| arxiv topic:astro-ph.SR |
arxiv_dataset-24891103.1632 | Monopoles, strings and dark matter
hep-ph
We develop a scenario whereby monopoles in a hidden sector yield a decaying
dark matter candidate of interest for the PAMELA and FERMI $e^\pm$ excesses.
The monopoles are not completely hidden due to a very small kinetic mixing and
a hidden photon mass. The latter also causes the monopoles and anti-monopoles
to be connected by strings. The resulting long-lived objects eventually decay
to hidden photons which tend to escape galactic cores before decaying. The mass
scales are those of the hidden photon ($\approx 500$ MeV), the monopole
($\approx 3$ TeV) and the mixing scale (close to the Planck scale). A gauge
coupling in the hidden sector is the only other parameter. This coupling must
be strong and this results in light point-like monopoles and light thin
strings.
| arxiv topic:hep-ph |
arxiv_dataset-24901103.1732 | Semi-Global Approximate stabilization of an infinite dimensional quantum
stochastic system
math.OC cs.SY math-ph math.FA math.MP
In this paper we study the semi-global (approximate) state feedback
stabilization of an infinite dimensional quantum stochastic system towards a
target state. A discrete-time Markov chain on an infinite-dimensional Hilbert
space is used to model the dynamics of a quantum optical cavity. We can choose
an (unbounded) strict Lyapunov function that is minimized at each time-step in
order to prove (weak-$\ast$) convergence of probability measures to a final
state that is concentrated on the target state with (a pre-specified)
probability that may be made arbitrarily close to 1. The feedback parameters
and the Lyapunov function are chosen so that the stochastic flow that describes
the Markov process may be shown to be tight (concentrated on a compact set with
probability arbitrarily close to 1). We then use Prohorov's theorem and
properties of the Lyapunov function to prove the desired convergence result.
| arxiv topic:math.OC cs.SY math-ph math.FA math.MP |
arxiv_dataset-24911103.1832 | PT-symmetry breaking in complex nonlinear wave equations and their
deformations
math-ph hep-th math.MP quant-ph
We investigate complex versions of the Korteweg-deVries equations and an Ito
type nonlinear system with two coupled nonlinear fields. We systematically
construct rational, trigonometric/hyperbolic, elliptic and soliton solutions
for these models and focus in particular on physically feasible systems, that
is those with real energies. The reality of the energy is usually attributed to
different realisations of an antilinear symmetry, as for instance PT-symmetry.
It is shown that the symmetry can be spontaneously broken in two alternative
ways either by specific choices of the domain or by manipulating the parameters
in the solutions of the model, thus leading to complex energies. Surprisingly
the reality of the energies can be regained in some cases by a further breaking
of the symmetry on the level of the Hamiltonian. In many examples some of the
fixed points in the complex solution for the field undergo a Hopf bifurcation
in the PT-symmetry breaking process. By employing several different variants of
the symmetries we propose many classes of new invariant extensions of these
models and study their properties. The reduction of some of these models yields
complex quantum mechanical models previously studied.
| arxiv topic:math-ph hep-th math.MP quant-ph |
arxiv_dataset-24921103.1932 | Towards Detecting The 2175-{\AA} Dust Feature Associated With Strong
High Redshift Mg {\ss}II Absorption Lines
astro-ph.CO
We report detections of 39 2175-{\AA} dust extinction bump candidates
associated with strong Mg II absorption lines at z$\sim$ 1--1.8 on quasar
spectra in Sloan Digital Sky Survey (SDSS) DR3. These strong Mg II absorption
line systems are detected among 2,951 strong Mg II absorbers with the rest
equivalent width $W_r\lambda2796 >$ 1.0{\AA} at $1.0 < z < 1.86$, which is part
of a full sample of 7,421 strong Mg II absorbers compiled by Prochter et al.
(2006). The redshift range of the absorbers is chosen to allow the 2175-{\AA}
extinction features to be completely covered within the SDSS spectrograph
operation wavelength range. An upper limit of the background quasar emission
redshift at z$=$2.1 is set to prevent the Ly$\alpha$ forest lines from
contaminating the sensitive spectral region for the 2175-{\AA} bump
measurements. The FM90 (Fitzpatrick & Massa 1990) parameterization is applied
to model the Optical/UV extinction curve in the rest frame of Mg II absorbers
of the 2175-{\AA} bump candidates. The simulation technique developed by Jiang
et al. (2010a, b) is used to derive the statistical significance of the
candidate 2175-{\AA} bumps. A total of 12 absorbers are detected with
2175-{\AA} bumps at a 5$\sigma$ level of statistical significance, 10 are
detected at a 4$\sigma$ level and 17 are detected at a 3$\sigma$ level. Most of
the candidate bumps in this work are similar to the relatively weak 2175-{\AA}
bumps observed in the Large Magellanic Clouds (LMC) LMC2 supershell rather than
the strong ones observed in the Milky Way (MW). This sample has greatly
increased the total number of 2175-{\AA} extinction bumps measured on SDSS
quasar spectra. Follow-up observations may rule out some of possible false
detections and reveal the physical and chemical natures of 2175-{\AA} quasar
absorbers.
| arxiv topic:astro-ph.CO |
arxiv_dataset-24931103.2032 | Raman-assisted Rabi resonances in two-mode cavity QED
quant-ph
The dynamics of a vibronic system in a lossy two-mode cavity is studied, with
the first mode being resonant to the electronic transition and the second one
being nearly resonant due to Raman transitions. We derive analytical solutions
for the dynamics of this system. For a properly chosen detuning of the second
mode from the exact Raman resonance, we obtain conditions that are closely
related to the phenomenon of Rabi resonance as it is well known in laser
physics. Such resonances can be observed in the spontaneous emission spectra,
where the spectrum of the second mode in the case of weak Raman coupling is
enhanced substantially.
| arxiv topic:quant-ph |
arxiv_dataset-24941103.2132 | No Confirmed New Isolated Neutron Stars In The SDSS Data Release 4
astro-ph.SR
We report on follow-up observations of candidate X-ray bright, radio-quiet
isolated neutron stars (INSs) identified from correlations of the ROSAT All-Sky
Survey (RASS) and the Sloan Digital Sky Survey (SDSS) Data Release 4 in
Ag\"ueros et al. (2006). We obtained Chandra X-ray Telescope exposures for 13
candidates in order to pinpoint the source of X-ray emission in optically blank
RASS error circles. These observations eliminated 12 targets as good INS
candidates. We discuss subsequent observations of the remaining candidate with
the XMM-Newton X-ray Observatory, the Gemini North Observatory, and the Apache
Point Observatory. We identify this object as a likely extragalactic source
with an unusually high log(fX/fopt) ~ 2.4. We also use an updated version of
the population synthesis models of Popov et al. (2010) to estimate the number
of RASS-detected INSs in the SDSS Data Release 7 footprint. We find that these
models predict ~3-4 INSs in the 11,000 square deg imaged by SDSS, which is
consistent with the number of known INSs that fall within the survey footprint.
In addition, our analysis of the four new INS candidates identified by Turner
et al. (2010) in the SDSS footprint implies that they are unlikely to be
confirmed as INSs; together, these results suggest that new INSs are not likely
to be found from further correlations of the RASS and SDSS.
| arxiv topic:astro-ph.SR |
arxiv_dataset-24951103.2232 | Filtering and analyzing mobile qubit information via
Rashba-Dresselhaus-Aharonov-Bohm interferometers
cond-mat.mes-hall quant-ph
Spin-1/2 electrons are scattered through one or two diamond-like loops, made
of quantum dots connected by one-dimensional wires, and subject to both an
Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. With
some symmetry between the two branches of each diamond, and with appropriate
tuning of the electric and magnetic fields (or of the diamond shapes) this
device completely blocks electrons with one polarization, and allows only
electrons with the opposite polarization to be transmitted. The directions of
these polarizations are tunable by these fields, and do not depend on the
energy of the scattered electrons. For each range of fields one can tune the
site and bond energies of the device so that the transmission of the fully
polarized electrons is close to unity. Thus, these devices perform as ideal
spin filters, and these electrons can be viewed as mobile qubits; the device
writes definite quantum information on the spinors of the outgoing electrons.
The device can also read the information written on incoming polarized
electrons: the charge transmission through the device contains full information
on this polarization. The double-diamond device can also act as a realization
of the Datta-Das spin field-effect transistor.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-24961103.2332 | Relativistic Continuum Quasiparticle Random Phase Approximation in
Spherical Nuclei
nucl-th
We have calculated the strength distributions of the dipole response in
spherical nuclei, ranging all over the periodic table. The calculations were
performed within two microscopic models: the discretized quasiparticle random
phase approximation (QRPA) and the quasiparticle continuum RPA, which takes
into account the coupling of the single-particle continuum in an exact way.
Pairing correlations are treated with the BCS model. In the calculations, two
density functionals were used, namely the functional PC-F1 and the functional
DD-PC1. Both are based on relativistic point coupling Lagrangians. It is
explicitly shown that this model is capable of reproducing the giant as well as
the pygmy dipole resonance for open-shell nuclei in a high level of
quantitative agreement with the available experimental observations.
| arxiv topic:nucl-th |
arxiv_dataset-24971103.2432 | Baryon Properties from Continuum-QCD
nucl-th hep-lat hep-ph nucl-ex
We provide an inkling of recent progress in hadron physics made using QCD's
Dyson-Schwinger equations, reviewing: the notion of in-hadron condensates and a
putative solution of a gross problem with the cosmological constant; a
symmetry-preserving computation that simultaneously correlates the masses of
meson and baryon ground- and excited-states, and contributes to a resolution of
the conundrum of the Roper resonance; and a prediction for the Q^2-dependence
of u- and d-quark Dirac and Pauli form factors in the proton, which exposes the
critical role played by diquark correlations within the nucleon.
| arxiv topic:nucl-th hep-lat hep-ph nucl-ex |
arxiv_dataset-24981103.2532 | Fast transport of Bose-Einstein condensates
quant-ph
We propose an inverse method to accelerate without final excitation the
adiabatic transport of a Bose Einstein condensate. The method, applicable to
arbitrary potential traps, is based on a partial extension of the
Lewis-Riesenfeld invariants, and provides transport protocols that satisfy
exactly the no-excitation conditions without constraints or approximations.
This inverse method is complemented by optimizing the trap trajectory with
respect to different physical criteria and by studying the effect of noise.
| arxiv topic:quant-ph |
arxiv_dataset-24991103.2632 | Breaking parameter degeneracy in interacting dark energy models from
observations
astro-ph.CO gr-qc hep-ph hep-th
We study the interacting dark energy model with time varying dark energy
equation of state. We examine the stability in the perturbation formalism and
the degeneracy among the coupling between dark sectors, the time-dependent dark
energy equation of state and dark matter abundance in the cosmic microwave
background radiation. Further we discuss the possible ways to break such
degeneracy by doing global fitting using the latest observational data and we
get a tight constraint on the interaction between dark sectors.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
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