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arxiv_dataset-25001103.2732 | d = 11 Supergravity on almost flat R^4 times a compact hyperbolic
7-manifold, and the dip and bump seen in ATLAS-CONF-2010-088
hep-th gr-qc hep-ex hep-ph
Rough estimates are presented to show that the bump at 1.7 to 1.9 TeV seen in
ATLAS-CONF-2010-088 could arise from about 10^{30} approximately degenerate
Kaluza-Klein states of the d = 11 supergravity multiplet in the s channel, that
could arise from compactification of d = 11 supergravity on a 7-manifold with a
compact hyperbolic Cartesian factor of intrinsic volume around 10^{34} and
curvature radius an inverse TeV. A first hypothesis that the modes in the bump
arise from a large degeneracy that restores agreement between the spectral
staircase and the Weyl asymptotic formula immediately above the spectral gap
gives a number of modes that is too large by a factor of around 60000. An
alternative hypothesis that the modes in the bump arise from harmonic forms on
the compact 7-manifold that are classically massless and acquire approximately
equal masses from the leading quantum corrections to the CJS action naturally
explains the slight reduction on a logarithmic scale in the number of modes
relative to the first hypothesis, and predicts that the bump is spin 0 if the
compact hyperbolic factor of large intrinsic volume is 7-dimensional, and a
mixture of spins 0 and 1 if it is 5-dimensional or 3-dimensional. Even
dimensions probably give too many modes. A provisional solution of the
quantum-corrected d = 11 Einstein equations on a compact hyperbolic 7-manifold
times 4 almost flat extended dimensions whose de Sitter radius can easily be as
large as the observed value is considered, and a Horava-Witten boundary is
introduced to accommodate the Standard Model fields.
| arxiv topic:hep-th gr-qc hep-ex hep-ph |
arxiv_dataset-25011103.2832 | Autotagging music with conditional restricted Boltzmann machines
cs.LG cs.IR cs.SD
This paper describes two applications of conditional restricted Boltzmann
machines (CRBMs) to the task of autotagging music. The first consists of
training a CRBM to predict tags that a user would apply to a clip of a song
based on tags already applied by other users. By learning the relationships
between tags, this model is able to pre-process training data to significantly
improve the performance of a support vector machine (SVM) autotagging. The
second is the use of a discriminative RBM, a type of CRBM, to autotag music. By
simultaneously exploiting the relationships among tags and between tags and
audio-based features, this model is able to significantly outperform SVMs,
logistic regression, and multi-layer perceptrons. In order to be applied to
this problem, the discriminative RBM was generalized to the multi-label setting
and four different learning algorithms for it were evaluated, the first such
in-depth analysis of which we are aware.
| arxiv topic:cs.LG cs.IR cs.SD |
arxiv_dataset-25021103.2932 | Nonlinear wave interaction and spin models in the MHD regime
physics.plasm-ph
Here we consider the influence on the electron spin in the MHD regime.
Recently developed models which include spin-velocity correlations are taken as
a starting point. A theoretical argument is presented, suggesting that in the
MHD regime a single fluid electron model with spin correlations is equivalent
to a model with spin-up and spin-down electrons constituting different fluids,
but where the spin-velocity correlations are omitted. Three wave interaction of
2 shear Alfven waves and a compressional Alfven wave is then taken as a model
problem to evaluate the asserted equivalence. The theoretical argument turns
out to be supported, as the predictions of the two models agree completely.
Furthermore, the three wave coupling coefficients obey the Manley-Rowe
relations, which give further support to the soundness of the models and the
validity of the assumptions made in the derivation. Finally we point out that
the proposed two-fluid model can be incorporated in standard Particle-In-Cell
schemes with only minor modifications.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-25031103.3032 | Why Can't We Predict RNA Structure At Atomic Resolution?
q-bio.BM physics.bio-ph physics.chem-ph
No existing algorithm can start with arbitrary RNA sequences and return the
precise, three-dimensional structures that ensures their biological function.
This chapter outlines current algorithms for automated RNA structure prediction
(including our own FARNA-FARFAR), highlights their successes, and dissects
their limitations, using a tetraloop and the sarcin/ricin motif as examples.
The barriers to future advances are considered in light of three particular
challenges: improving computational sampling, reducing reliance on
experimentally solved structures, and avoiding coarse-grained representations
of atomic-level interactions. To help meet these challenges and better
understand the current state of the field, we propose an ongoing community-wide
CASP-style experiment for evaluating the performance of current structure
prediction algorithms.
| arxiv topic:q-bio.BM physics.bio-ph physics.chem-ph |
arxiv_dataset-25041103.3132 | On the discrete spectrum of two-particle discrete Schr\"odinger
operators
math.FA
In the present paper our aim is to explore some spectral properties of the
family two-particle discrete Schr\"odinger operators
$h^{\mathrm{d}}(k)=h^{\mathrm{d}}_0(k)+ \mathbf{v},$ $k\in \T^\mathrm{d},$ on
the $\mathrm{d}$ dimensional lattice $\Z^{\mathrm{d}},$ $\mathrm{d}\geq 1,$ $k$
being the two-particle quasi-momentum. Under some condition in the case $k\in
\T^{\mathrm{d}}\setminus (-\pi,\pi)^{\mathrm{d}},$ we establish necessary and
sufficient conditions for existence of infinite discrete spectrum of the
operator $h^{\mathrm{d}}(k)$.
| arxiv topic:math.FA |
arxiv_dataset-25051103.3232 | Isolated Vortex and Vortex Lattice in a Holographic p-wave
Superconductor
hep-th cond-mat.str-el cond-mat.supr-con
Using the holographic gauge-gravity duality, we find a solution for an
isolated vortex and a vortex lattice in a 2+1 dimensional p-wave
superconductor, which is described by the boundary theory dual to an SU(2)
gauge theory in 3+1 dimensional anti-de Sitter space. Both $p_x+ip_y$ and
$p_x-ip_y$ components of the superconducting order parameter, as well as the
effects of a magnetic field on these components, are considered. The isolated
vortex solution is studied, and it is found that the two order parameter
components have different amplitudes due to the time reversal symmetry
breaking. The vortex lattice for large magnetic fields is also studied, where
it is argued that only one order parameter component will be nonzero
sufficiently close to the upper critical field. The upper critical field
exhibits a characteristic upward curvature, reflecting the effects of
field-induced correlations captured by the holographic theory. The free energy
is calculated perturbatively in this region of the phase diagram, and it is
shown that the triangular vortex lattice is the thermodynamically preferred
solution.
| arxiv topic:hep-th cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-25061103.3332 | Confidentiality & Authentication Mechanism for Biometric Information
Transmitted over Low Bandwidth & Unreliable channel
cs.CR
The security of bio-metric information - finger print, retina mapping, DNA
mapping and some other chemical and biological modified genes related
information - transfer through low bandwidth and unreliable or covert channel
is challenging task. Therefore, Security of biometric information is essential
requirement in this fast developing communication world. Thus, in this paper,
we propose efficient and effective mechanism for confidentiality and
authentication for biometric information transmitted by using arithmetic
encoding representation over low bandwidth and unreliable channel. It enhances
the speed of encryption, decryption and authentication process. It uses
arithmetic encoding scheme and public key cryptography e.g. modified version of
RSA algorithm called RSA-2 algorithm.
| arxiv topic:cs.CR |
arxiv_dataset-25071103.3432 | Sensing electric fields using single diamond spins
quant-ph cond-mat.mtrl-sci physics.atom-ph
The ability to sensitively detect charges under ambient conditions would be a
fascinating new tool benefitting a wide range of researchers across
disciplines. However, most current techniques are limited to low-temperature
methods like single-electron transistors (SET), single-electron electrostatic
force microscopy and scanning tunnelling microscopy. Here we open up a new
quantum metrology technique demonstrating precision electric field measurement
using a single nitrogen-vacancy defect centre(NV) spin in diamond. An AC
electric field sensitivity reaching ~ 140V/cm/\surd Hz has been achieved. This
corresponds to the electric field produced by a single elementary charge
located at a distance of ~ 150 nm from our spin sensor with averaging for one
second. By careful analysis of the electronic structure of the defect centre,
we show how an applied magnetic field influences the electric field sensing
properties. By this we demonstrate that diamond defect centre spins can be
switched between electric and magnetic field sensing modes and identify
suitable parameter ranges for both detector schemes. By combining magnetic and
electric field sensitivity, nanoscale detection and ambient operation our study
opens up new frontiers in imaging and sensing applications ranging from
material science to bioimaging.
| arxiv topic:quant-ph cond-mat.mtrl-sci physics.atom-ph |
arxiv_dataset-25081103.3532 | 4D Wavelet-Based Regularization for Parallel MRI Reconstruction: Impact
on Subject and Group-Levels Statistical Sensitivity in fMRI
stat.ME cs.CV physics.med-ph
Parallel MRI is a fast imaging technique that enables the acquisition of
highly resolved images in space. It relies on $k$-space undersampling and
multiple receiver coils with complementary sensitivity profiles in order to
reconstruct a full Field-Of-View (FOV) image. The performance of parallel
imaging mainly depends on the reconstruction algorithm, which can proceed
either in the original $k$-space (GRAPPA, SMASH) or in the image domain
(SENSE-like methods). To improve the performance of the widely used SENSE
algorithm, 2D- or slice-specific regularization in the wavelet domain has been
efficiently investigated. In this paper, we extend this approach using
3D-wavelet representations in order to handle all slices together and address
reconstruction artifacts which propagate across adjacent slices. The extension
also accounts for temporal correlations that exist between successive scans in
functional MRI (fMRI). The proposed 4D reconstruction scheme is fully
\emph{unsupervised} in the sense that all regularization parameters are
estimated in the maximum likelihood sense on a reference scan. The gain induced
by such extensions is first illustrated on EPI image reconstruction but also
measured in terms of statistical sensitivity during a fast event-related fMRI
protocol. The proposed 4D-UWR-SENSE algorithm outperforms the SENSE
reconstruction at the subject and group-levels (15 subjects) for different
contrasts of interest and using different parallel acceleration factors on
$2\times2\times3$mm$^3$ EPI images.
| arxiv topic:stat.ME cs.CV physics.med-ph |
arxiv_dataset-25091103.3632 | The geometry of Hrushovski constructions, II. The strongly minimal case
math.LO
We investigate the isomorphism types of combinatorial geometries arising from
Hrushovski's flat strongly minimal structures and answer some questions from
Hrushovski's original paper.
| arxiv topic:math.LO |
arxiv_dataset-25101103.3732 | Subclasses of Normal Helly Circular-Arc Graphs
cs.DM
A Helly circular-arc model M = (C,A) is a circle C together with a Helly
family \A of arcs of C. If no arc is contained in any other, then M is a proper
Helly circular-arc model, if every arc has the same length, then M is a unit
Helly circular-arc model, and if there are no two arcs covering the circle,
then M is a normal Helly circular-arc model. A Helly (resp. proper Helly, unit
Helly, normal Helly) circular-arc graph is the intersection graph of the arcs
of a Helly (resp. proper Helly, unit Helly, normal Helly) circular-arc model.
In this article we study these subclasses of Helly circular-arc graphs. We show
natural generalizations of several properties of (proper) interval graphs that
hold for some of these Helly circular-arc subclasses. Next, we describe
characterizations for the subclasses of Helly circular-arc graphs, including
forbidden induced subgraphs characterizations. These characterizations lead to
efficient algorithms for recognizing graphs within these classes. Finally, we
show how do these classes of graphs relate with straight and round digraphs.
| arxiv topic:cs.DM |
arxiv_dataset-25111103.3832 | A New Dynamic Round Robin and SRTN Algorithm with Variable Original Time
Slice and Intelligent Time Slice for Soft Real Time Systems
cs.OS
The main objective of the paper is to improve the Round Robin (RR) algorithm
using dynamic ITS by coalescing it with Shortest Remaining Time Next (SRTN)
algorithm thus reducing the average waiting time, average turnaround time and
the number of context switches. The original time slice has been calculated for
each process based on its burst time.This is mostly suited for soft real time
systems where meeting of deadlines is desirable to increase its performance.
The advantage is that processes that are closer to their remaining completion
time will get more chances to execute and leave the ready queue. This will
reduce the number of processes in the ready queue by knocking out short jobs
relatively faster in a hope to reduce the average waiting time, turn around
time and number of context switches. This paper improves the algorithm [8] and
the experimental analysis shows that the proposed algorithm performs better
than algorithm [6] and [8] when the processes are having an increasing order,
decreasing order and random order of burst time.
| arxiv topic:cs.OS |
arxiv_dataset-25121103.3932 | Ambiguity Sparse Processes
stat.ME math.ST stat.TH
This paper introduces the class of ambiguity sparse processes, containing
subsets of popular nonstationary time series such as locally stationary,
cyclostationary and uniformly modulated processes. The class also contains
aggregations of the aforementioned processes. Ambiguity sparse processes are
defined for a fixed sampling regime, in terms of a given number of sample
points and a fixed sampling period. The framework naturally allows us to treat
heterogeneously nonstationary processes, and to develop methodology for
processes that have growing but controlled complexity with increasing sample
sizes and shrinking sampling periods. Expressions for the moments of the sample
ambiguity function are derived for ambiguity sparse processes. These properties
inspire an Empirical Bayes shrinkage estimation procedure. The representation
of the covariance structure of the process in terms of a time-frequency
representation is separated from the estimation of these second order
properties. The estimated ambiguity function is converted into an estimate of
the time-varying moments of the process, and from these moments, any bilinear
representation can be calculated with reduced estimation risk. Any of these
representations can be used to understand the time-varying spectral content of
the signal. The choice of representation is discussed. Parameters of the
shrinkage procedure quantify the performance of the proposed estimation.
| arxiv topic:stat.ME math.ST stat.TH |
arxiv_dataset-25131103.4032 | All non-classical correlations can be activated into distillable
entanglement
quant-ph cond-mat.stat-mech math-ph math.MP
We devise a protocol in which general non-classical multipartite correlations
produce a physically relevant effect, leading to the creation of bipartite
entanglement. In particular, we show that the relative entropy of quantumness,
which measures all non-classical correlations among subsystems of a quantum
system, is equivalent to and can be operationally interpreted as the minimum
distillable entanglement generated between the system and local ancillae in our
protocol. We emphasize the key role of state mixedness in maximizing
non-classicality: Mixed entangled states can be arbitrarily more non-classical
than separable and pure entangled states.
| arxiv topic:quant-ph cond-mat.stat-mech math-ph math.MP |
arxiv_dataset-25141103.4132 | Limits on Dark Radiation, Early Dark Energy, and Relativistic Degrees of
Freedom
astro-ph.CO
Recent cosmological data analyses hint at the presence of an extra
relativistic energy component in the early universe. This component is often
parametrized as an excess of the effective neutrino number N_{eff} over the
standard value of 3.046. The excess relativistic energy could be an indication
for an extra (sterile) neutrino, but early dark energy and barotropic dark
energy also contribute to the relativistic degrees of freedom. We examine the
capabilities of current and future data to constrain and discriminate between
these explanations, and to detect the early dark energy density associated with
them. We found that while early dark energy does not alter the current
constraints on N_{eff}, a dark radiation component, such as that provided by
barotropic dark energy models, can substantially change current constraints on
N_{eff}, bringing its value back to agreement with the theoretical prediction.
Both dark energy models also have implications for the primordial mass fraction
of Helium Y_p and the scalar perturbation index n_s. The ongoing Planck
satellite mission will be able to further discriminate between sterile
neutrinos and early dark energy.
| arxiv topic:astro-ph.CO |
arxiv_dataset-25151103.4232 | Rydberg atoms in one-dimensional optical lattices
cond-mat.quant-gas quant-ph
We experimentally realize Rydberg excitations in Bose-Einstein condensates of
rubidium atoms loaded into quasi one-dimensional traps and in optical lattices.
Our results for condensates expanded to different sizes in the one-dimensional
trap agree well with the intuitive picture of a chain of Rydberg excitations.
We also find that the Rydberg excitations in the optical lattice do not destroy
the phase coherence of the condensate, and our results in that system agree
with the picture of localized collective Rydberg excitations including
nearest-neighbour blockade.
| arxiv topic:cond-mat.quant-gas quant-ph |
arxiv_dataset-25161103.4332 | Real-time feedback control of a mesoscopic superposition
quant-ph cond-mat.mes-hall
We show that continuous real-time feedback can be used to track, control, and
protect a mesoscopic superposition of two spatially separated wave-packets. The
feedback protocol is enabled by an approximate state-estimator, and requires
two continuous measurements, performed simultaneously. For nanomechanical and
superconducting resonators, both measurements can be implemented by coupling
the resonators to superconducting qubits.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-25171103.4432 | Dynamic Modeling and Simulation of a Real World Billiard
nlin.CD physics.comp-ph
Gravitational billiards provide an experimentally accessible arena for
testing formulations of nonlinear dynamics. We present a mathematical model
that captures the essential dynamics required for describing the motion of a
realistic billiard for arbitrary boundaries. Simulations of the model are
applied to parabolic, wedge and hyperbolic billiards that are driven
sinusoidally. Direct comparisons are made between the model's predictions and
previously published experimental data. It is shown that the data can be
successfully modeled with a simple set of parameters without an assumption of
exotic energy dependence.
| arxiv topic:nlin.CD physics.comp-ph |
arxiv_dataset-25181103.4532 | A Carbon-Cycle Based Stochastic Cellular Automata Climate Model
nlin.CG nlin.AO
In this article a stochastic cellular automata model is examined, which has
been developed to study a "small" world, where local changes may noticeably
alter global characteristics. This is applied to a climate model, where global
temperature is determined by an interplay between atmospheric carbon dioxide
and carbon stored by plant life. The latter can be relased by forest fires,
giving rise to significant changes of global conditions within short time.
| arxiv topic:nlin.CG nlin.AO |
arxiv_dataset-25191103.4632 | Hubble expansion and structure formation in the "running FLRW model" of
the cosmic evolution
astro-ph.CO gr-qc hep-ph hep-th
A new class of FLRW cosmological models with time-evolving fundamental
parameters should emerge naturally from a description of the expansion of the
universe based on the first principles of quantum field theory and string
theory. Within this general paradigm, one expects that both the gravitational
Newton's coupling, G, and the cosmological term, Lambda, should not be strictly
constant but appear rather as smooth functions of the Hubble rate. This
scenario ("running FLRW model") predicts, in a natural way, the existence of
dynamical dark energy without invoking the participation of extraneous scalar
fields. In this paper, we perform a detailed study of these models in the light
of the latest cosmological data, which serves to illustrate the
phenomenological viability of the new dark energy paradigm as a serious
alternative to the traditional scalar field approaches. By performing a joint
likelihood analysis of the recent SNIa data, the CMB shift parameter, and the
BAOs traced by the Sloan Digital Sky Survey, we put tight constraints on the
main cosmological parameters. Furthermore, we derive the theoretically
predicted dark-matter halo mass function and the corresponding redshift
distribution of cluster-size halos for the "running" models studied. Despite
the fact that these models closely reproduce the standard LCDM Hubble
expansion, their normalization of the perturbation's power-spectrum varies,
imposing, in many cases, a significantly different cluster-size halo redshift
distribution. This fact indicates that it should be relatively easy to
distinguish between the "running" models and the LCDM cosmology using realistic
future X-ray and Sunyaev-Zeldovich cluster surveys.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
arxiv_dataset-25201103.4732 | A Theoretical Study of the Magnetically Deformed Inner Crust Matter of
Magnetars
astro-ph.SR
We have studied various physical properties of magnetically deformed atoms
and the associated matter, replacing the atoms by the deformed Wigner-Seitz
(WS) cells at the crustal region of strongly magnetized neutron stars
(magnetars). A relativistic version of Thomas-Fermi (TF) model in presence of
strong magnetic field in cylindrical coordinates is used to study the
properties of such matter.
| arxiv topic:astro-ph.SR |
arxiv_dataset-25211103.4832 | Characterization process of emission sources of spin entangled pairs
with several species
quant-ph
Normally, sources of entangled pairs generate several species of them. This
work proposes a characterization algorithm for relatively general bipartite
entangled states, generating several standard Bell states with controlled
population as output.
| arxiv topic:quant-ph |
arxiv_dataset-25221103.4932 | Equilibrium rotation of a vortex bundle terminating on a lateral wall
cond-mat.other
The paper investigates possibility of equilibrium solid-body rotation of a
vortex bundle diverging at some height from a cylinder axis and terminating on
a lateral wall of a container. Such a bundle arises when vorticity expands up
from a container bottom eventually filling the whole container. The analysis
starts from a single vortex, then goes to a vortex sheet, and finally addresses
a multi-layered crystal vortex bundle. The equilibrium solid-body rotation of
the vortex bundle requires that the thermodynamic potentials in the
vortex-filled and in the vortex-free parts of the container are equal providing
the absence of a force on the vortex front separating the two parts. The paper
considers also a weakly non-equilibrium state when the bundle and the container
rotate with different angular velocities and the vortex front propagates with
the velocity determined by friction between vortices and the container or the
normal liquid moving together with the container.
| arxiv topic:cond-mat.other |
arxiv_dataset-25231103.5032 | Near-field examination of perovskite-based superlenses and
superlens-enhanced probe-object coupling
physics.optics
A planar slab of negative index material works as a superlens with
sub-diffraction-limited imaging resolution, since propagating waves are focused
and, moreover, evanescent waves are reconstructed in the image plane. Here, we
demonstrate a superlens for electric evanescent fields with low losses using
perovskites in the mid-infrared regime. The combination of near-field
microscopy with a tunable free-electron laser allows us to address precisely
the polariton modes, which are critical for super-resolution imaging. We
spectrally study the lateral and vertical distributions of evanescent waves
around the image plane of such a lens, and achieve imaging resolution of
wavelength/14 at the superlensing wavelength. Interestingly, at certain
distances between the probe and sample surface, we observe a maximum of these
evanescent fields. Comparisons with numerical simulations indicate that this
maximum originates from an enhanced coupling between probe and object, which
might be applicable for multifunctional circuits, infrared spectroscopy, and
thermal sensors.
| arxiv topic:physics.optics |
arxiv_dataset-25241103.5132 | Orbifold techniques in degeneration formulas
math.AG math.SG
We give an approach for relative and degenerate Gromov--Witten invariants,
inspired by that of Jun Li but replacing predeformable maps by transversal maps
to a twisted target. The main advantage is a significant simplification in the
definition of the obstruction theory. We reprove in our language the
degeneration formula, extending it to the orbifold case.
| arxiv topic:math.AG math.SG |
arxiv_dataset-25251103.5232 | A unified approach to $q$-special functions of the Laplace type
math.CA
We propose a unified approach to $q$-special functions, which are
degenerations of basic hypergeometric functions ${}_2\phi_1(a,b;c;q,x)$. We
obtain a list of seven different class of $q$-special functions: ${}_2\phi_1,
{}_1\phi_1$, two different types of the $q$-Bessel functions, the
$q$-Hermite-Weber functions, two different types of the $q$-Airy functions. We
show that there exist a relation between two types of the $q$-Airy functions.
| arxiv topic:math.CA |
arxiv_dataset-25261103.5332 | On the chromospheric activity of stars with planets
astro-ph.EP
Context. Signatures of chromospheric activity enhancement have been found for
a dozen stars, pointing to a possible star-planet interaction. Nevertheless in
the coronal activity regime, there is no conclusive observational evidence for
such an interaction. Does star-planet interaction manifest itself only for a
few particular cases, without having a major effect on stars with planets in
general? Aims. We aim to add additional observational constraints to support or
reject the major effects of star-planet interactions in stellar activity, based
on CaII chromospheric emission flux. Methods. We performed a statistical
analysis of CaII emission flux of stars with planets, as well as a comparison
between CaII and X-ray emission fluxes, searching for dependencies on planetary
parameters. Results. In the present sample of stars with planets, there are no
significant correlations between chromospheric activity indicator log(R'HK) and
planetary parameters. Further, the distribution of the chromospheric activity
indicator for stars without planets is not distinguishable from the one with
planets.
| arxiv topic:astro-ph.EP |
arxiv_dataset-25271103.5432 | How to display science since images have no mass
physics.ed-ph
Education, science, in fact the whole society, extensively use images.
Between us and the world are the visual displays. Screens, small and large,
individual or not, are everywhere. Images are increasingly the 2D substrate of
our virtual interaction with reality. However images will never support a
complete representation of the reality. Three-dimensional representations will
not change that. Images are primarily a spatial representation of our world
dedicated to our sight. Key aspects such as energy and the associated forces
are not spatially materialized. In classical physics, interaction description
is based on Newton equations with trajectory and force as the dual central
concepts. Images can in real time show all aspects of trajectories but not the
associated dynamical aspects described by forces and energies. Contrary to the
real world, the world of images opposes no constrain, nor resistance to our
actions. Only the physical quantities, that do not contain mass in their
dimension can be satisfactory represented by images. Often symbols such as
arrows are introduced to visualize the force vectors.
| arxiv topic:physics.ed-ph |
arxiv_dataset-25281103.5532 | Diffusive Transport Enhanced by Thermal Velocity Fluctuations
cond-mat.mes-hall
We study the contribution of advection by thermal velocity fluctuations to
the effective diffusion coefficient in a mixture of two indistinguishable
fluids. The enhancement of the diffusive transport depends on the system size L
and grows as \ln(L/L_0) in quasi two-dimensional systems, while in three
dimensions it scales as L_0^{-1}-L^{-1}, where L_0 is a reference length. The
predictions of a simple fluctuating hydrodynamics theory are compared to
results from particle simulations and a finite-volume solver and excellent
agreement is observed. Our results conclusively demonstrate that the nonlinear
advective terms need to be retained in the equations of fluctuating
hydrodynamics when modeling transport in small-scale finite systems.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-25291103.5632 | Hydrokinetic predictions for femtoscopy scales in A+A collisions in the
light of recent ALICE LHC results
nucl-th hep-ph
A study of energy behavior of the pion spectra and interferometry scales is
carried out for the top SPS, RHIC and for LHC energies within the hydrokinetic
approach. The main mechanisms that lead to the paradoxical, at first sight,
dependence of the interferometry scales with an energy growth, in particular, a
decrease $R_{out}/R_{side}$ ratio, are exposed. The hydrokinetic predictions
for the HBT radii at LHC energies are compared with the recent results of the
ALICE experiment.
| arxiv topic:nucl-th hep-ph |
arxiv_dataset-25301103.5732 | A remark of Ruzsa's construction of an infinite Sidon set
math.NT math.CO
A Sidon set is a set of the positive integers such that the sums of two pairs
is not repeated. I. Ruzsa gave a probabilistic construction of an infinite
Sidon set. In this work we present the details of a simplified proof of this
construction as suggested in a paper of I. Ruzsa and J. Cilleruelo (Real and
-padic Sidon sequences, Acta Sci. Math (Szeged) 70 (2004), 505-510).
| arxiv topic:math.NT math.CO |
arxiv_dataset-25311103.5832 | Classification of complete N=2 supersymmetric theories in 4 dimensions
hep-th
We define the notion of a complete N=2 supersymmetric theory in 4 dimensions
as a UV complete theory for which all the BPS central charges can be
arbitrarily varied as we vary its Coulomb branch parameters, masses, and
coupling constants. We classify all such theories whose BPS spectrum can be
obtained via a quiver diagram. This is done using the 4d/2d correspondence and
by showing that such complete N=2 theories map to quivers of finite mutation
type. The list of such theories is given by the (generalized) Gaiotto theories
consisting of two 5-branes wrapping Riemann surfaces with punctures, as well as
11 additional exceptional cases, which we identify.
| arxiv topic:hep-th |
arxiv_dataset-25321103.5932 | High temperature unfolding simulations of a single stranded DNA i-motif
physics.bio-ph cond-mat.soft physics.comp-ph
We present the results of high temperature 500 K Molecular Dynamics
simulations of the DNA i-motif. The essential dynamics and the main unfolding
pathways are compared to a biased metadynamics simulation at 300 K. Our results
indicate a remarkable agreement of the concerted motion at both temperatures.
The transition can be described by a few number of eigenvectors indicating a
simple unfolding process. Two main mechanisms for the unfolding pathway at 500
K can be detected which are in good agreement to the results of the biased
simulation at 300 K.
| arxiv topic:physics.bio-ph cond-mat.soft physics.comp-ph |
arxiv_dataset-25331103.6032 | A VLBA survey of the core shift effect in AGN jets I. Evidence for
dominating synchrotron opacity
astro-ph.CO
The effect of a frequency dependent shift of the VLBI core position (known as
the "core shift") was predicted more than three decades ago and has since been
observed in a few sources, but often within a narrow frequency range. This
effect has important astrophysical and astrometric applications. To achieve a
broader understanding of the core shift effect and the physics behind it, we
conducted a dedicated survey with NRAO's Very Long Baseline Array (VLBA). We
used the VLBA to image 20 pre-selected sources simultaneously at nine
frequencies in the 1.4-15.4 GHz range. The core position at each frequency was
measured by referencing it to a bright, optically thin feature in the jet. A
significant core shift has been successfully measured in each of the twenty
sources observed. The median value of the core shift is found to be 1.21 mas if
measured between 1.4 and 15.4 GHz, and 0.24 mas between 5.0 and 15.4 GHz. The
core position, r, as a function of frequency, n, is found to be consistent with
an r n^-1 law. This behavior is predicted by the Blandford & Koenigl model of a
purely synchrotron self-absorbed conical jet in equipartition. No systematic
deviation from unity of the power law index in the r(n) relation has been
convincingly detected. We conclude that neither free-free absorption nor
gradients in pressure and/or density in the jet itself and in the ambient
medium surrounding the jet play a significant role in the sources observed
within the 1.4-15.4 GHz frequency range. These results support the
interpretation of the parsec-scale core as a continuous Blandford-Koenigl type
jet with smooth gradients of physical properties along it.
| arxiv topic:astro-ph.CO |
arxiv_dataset-25341103.6132 | On Quillen's calculation of graded $K$-theory
math.KT
We adapt Quillen's calculation of graded K-groups of
Z-graded rings with support in N to graded
K-theory, allowing gradings in a product Z \times G with G an arbitrary
group. This in turn allows us to use inductions and calculate graded K-theory
of Z^m-graded rings. Here Z is the ring of integers and N positive natural
numbers.
| arxiv topic:math.KT |
arxiv_dataset-25351103.6232 | On a Loomis-Whitney Type Inequality for Permutationally Invariant
Unconditional Convex Bodies
math.FA
For a permutationally invariant unconditional convex body K in R^n we define
a finite sequence (K_j), j = 1, ..., n of projections of the body K to the
space spanned by first j vectors of the standard basis of R^n. We prove that
the sequence of volumes (|K_1|, ..., |K_n|) is log-concave.
| arxiv topic:math.FA |
arxiv_dataset-25361104.0046 | Review of minimum-bias jet systematics at RHIC
nucl-ex
Jets are studied in A-A collisions at RHIC and LHC with the goal to
understand how they are affected by the medium and how they affect the medium.
It is widely believed that hard-scattered partons lose energy when propagating
through a medium before hadronizing. Partons losing enough energy may not even
make it out of the medium as identifiable jets (although the momentum will be
shared among whatever particles are emitted). "Full" jet reconstruction
attempts to determine the partonic energy loss as well as possible changes in
jet shape. Heavy ion collisions typically produce many unrelated particles
within the jet "cone," and subtraction of this background introduces
significant uncertainties. A variety of techniques using high-$p_t$ particles,
assumed to be leading particles from jet fragmentation, look for disappearance
of jets and attenuation of jets relative to the reaction plane, as well as
medium modifications such as Mach cones. Those techniques have considerable
uncertainty due to subtraction of $v_2$. In this paper we discuss minimum-bias
jets observed at RHIC using two-particle correlations. We find that jets
produced in p-p collisions have interesting properties. Peripheral A-A
collisions look like p-p collision. As we select more central collisions the
number of jets increases following binary collision scaling until at a
system-dependent centrality the number of particles associated with jets
increases substantially above this scaling. Near this transition centrality the
jet aspect ratio---elongated transverse to the beam direction for low-energy
jets produced in p-p collisions---becomes highly elongated along the beam
direction in A-A collisions.
| arxiv topic:nucl-ex |
arxiv_dataset-25371104.0146 | A low-Reynolds-number treadmilling swimmer near a semi-infinite wall
physics.bio-ph nlin.CD physics.flu-dyn
We investigate the behavior of a treadmilling microswimmer in a
two-dimensional unbounded domain with a semi-infinite no-slip wall. The wall
can also be regarded as a probe or pipette inserted into the flow. We solve the
governing evolution equations in an analytical form and numerically calculate
trajectories of the swimmer for several different initial positions and
orientations. We then compute the probability that the treadmilling organism
can escape the vicinity of the wall. We find that many trajectories in a
'wedge' around the wall are likely to escape. This suggests that inserting a
probe or pipette in a suspension of organism may push away treadmilling
swimmers.
| arxiv topic:physics.bio-ph nlin.CD physics.flu-dyn |
arxiv_dataset-25381104.0246 | The effects of a hot gaseous halo in galaxy major mergers
astro-ph.GA
Cosmological hydrodynamical simulations as well as observations indicate that
spiral galaxies are comprised of five different components: dark matter halo,
stellar disc, stellar bulge, gaseous disc and gaseous halo. While the first
four components have been extensively considered in numerical simulations of
binary galaxy mergers, the effect of a hot gaseous halo has usually been
neglected even though it can contain up to 80% of the total gas within the
galaxy virial radius. We present a series of hydrodynamic simulations of major
mergers of disc galaxies, that for the first time include a diffuse, rotating,
hot gaseous halo. Through cooling and accretion, the hot halo can dissipate and
refuel the cold gas disc before and after a merger. This cold gas can
subsequently form stars, thus impacting the morphology and kinematics of the
remnant. Simulations of isolated systems with total mass M~10^12Msun show a
nearly constant star formation rate of ~5Msun/yr if the hot gaseous halo is
included, while the star formation rate declines exponentially if it is
neglected. We conduct a detailed study of the star formation efficiency during
mergers and find that the presence of a hot gaseous halo reduces the starburst
efficiency (e=0.5) compared to simulations without a hot halo (e=0.68).
Moreover we find cases where the stellar mass of the merger remnant is lower
than the sum of the stellar mass of the two progenitor galaxies when evolved in
isolation. This suggests a revision to semi-analytic galaxy formation models
which assume that a merger always leads to enhanced star formation. We show
that adding the hot gas component has a significant effect on the kinematics
and internal structure of the merger remnants, like an increased abundance of
fast rotators and an r^(1/4) surface brightness profile at small scales.
| arxiv topic:astro-ph.GA |
arxiv_dataset-25391104.0346 | Stability of equatorial circular geodesics in static axially symmetric
spacetimes
gr-qc
A general study of the stability of equatorial circular orbits in static
axially symmetric gravitating systems is presented. Important circular
geodesics as the marginally stable orbit, the marginally bounded orbit and the
photon orbit are analyzed. We found general expressions for the radius,
specific energy, specific angular momentum and the radius of the marginally
stable orbit, both for null and timelike circular geodesics. Solutions
expressed in cylindrical coordinates, oblate spheroidal coordinates, and
prolate spheroidal coordinates are considered. We show that all null circular
orbits are unstable and that there are not marginally stable null geodesics,
whereas that for timelike geodesics the orbits can be unbounded, bounded or
circulars.
| arxiv topic:gr-qc |
arxiv_dataset-25401104.0446 | Reconstruction of Binary Functions and Shapes from Incomplete Frequency
Information
cs.IT math.IT math.OC
The characterization of a binary function by partial frequency information is
considered. We show that it is possible to reconstruct binary signals from
incomplete frequency measurements via the solution of a simple linear
optimization problem. We further prove that if a binary function is spatially
structured (e.g. a general black-white image or an indicator function of a
shape), then it can be recovered from very few low frequency measurements in
general. These results would lead to efficient methods of sensing,
characterizing and recovering a binary signal or a shape as well as other
applications like deconvolution of binary functions blurred by a low-pass
filter. Numerical results are provided to demonstrate the theoretical
arguments.
| arxiv topic:cs.IT math.IT math.OC |
arxiv_dataset-25411104.0546 | Thermodynamic Geometry of the Born-Infeld-anti-de Sitter black holes
gr-qc hep-th
Thermodynamic geometry is applied to the Born-Infeld-anti-de Sitter black
hole (BIAdS) in the four dimensions, which is a nonlinear generalization of the
Reissner-Norstr\"Aom-AdS black hole (RNAdS). We compute the Weinhold as well as
the Ruppeiner scalar curvature and find that the singular points are not the
same with the ones obtained using the heat capacity. Legendre-invariant metric
proposed by Quevedo and the metric obtained by using the free energy as the
thermodynamic potential are obtained and the corresponding scalar curvatures
diverge at the Davies points.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-25421104.0646 | Realizable homotopy colimits
math.AG math.AT math.CT math.KT
In this paper we prove that for any model category, the Bousfield-Kan
construction of the homotopy colimit is the absolute left derived functor of
the colimit. This is achieved by showing that the Bousfield-Kan homotopy
colimit is moreover a realizable homotopy colimit, defined by means of a
suitable 2-category of relative categories. In addition, in the case of exact
coproducts, we characterize the realizable homotopy colimits that satisfy a
cofinality property as those given by a formula following the pattern of
Bousfield-Kan construction: they are the composition of a "geometric
realization" with the simplicial replacement.
| arxiv topic:math.AG math.AT math.CT math.KT |
arxiv_dataset-25431104.0746 | Quantifier Elimination over Finite Fields Using Gr\"obner Bases
cs.SC cs.LO
We give an algebraic quantifier elimination algorithm for the first-order
theory over any given finite field using Gr\"obner basis methods. The algorithm
relies on the strong Nullstellensatz and properties of elimination ideals over
finite fields. We analyze the theoretical complexity of the algorithm and show
its application in the formal analysis of a biological controller model.
| arxiv topic:cs.SC cs.LO |
arxiv_dataset-25441104.0846 | Coronal mass ejections associated with LDE flares of slow rise phase
astro-ph.SR
It is well known, that there is temporal relationship between CMEs and
associated flares. The duration of the acceleration phase is related to the
duration of the rise phase of a flare. We investigated CMEs associated with
long duration flares of slow rise phase (slow LDE). These CMEs are
characterized by high velocity (v>1000 km/s) during the propagation phase and
low average acceleration during the main, prolongated, acceleration phase. The
CMEs are accelerated until the height $> 5 R_\odot$, which is higher value than
in typical impulsive CMEs. CMEs associated with slow LDEs have characteristics
of both classes of CMEs, i.e. CMEs associated with flares and CMEs associated
with eruptive prominences.
| arxiv topic:astro-ph.SR |
arxiv_dataset-25451104.0946 | Early star catalogues of the southern sky: De Houtman, Kepler (Second
and Third Classes), and Halley
astro-ph.IM
De Houtman in 1603, Kepler in 1627 and Halley in 1679 published the earliest
modern catalogues of the southern sky. We provide machine-readable versions of
these catalogues, make some comparisons between them, and briefly discuss their
accuracy on the basis of comparison with data from the modern Hipparcos
Catalogue. We also compare our results for De Houtman with those by Knobel
(1917) finding good overall agreement. About half of the about 200 new stars
(with respect to Ptolemaios) added by De Houtman are in twelve new
constellations, half in old constellations like Centaurus, Lupus and Argo. The
right ascensions and declinations given by De Houtman have error distributions
with widths of about 40 arcmin, the longitudes and latitudes given by Kepler
have error distributions with widths of about 45 arcmin. Halley improves on
this by more than an order of magnitude to widths of about 3 arcmin, and all
entries in his catalogue can be identified. The measurement errors of Halley
are due to a systematic deviation of his sextant (increasing with angle to 2
arcmin at 60 degrees) and random errors of 0.7 arcmin. The position errors in
the catalogue of Halley are dominated by the position errors in the reference
stars, which he took from Brahe.
| arxiv topic:astro-ph.IM |
arxiv_dataset-25461104.1046 | Shaping interactions between polar molecules with far-off-resonant light
physics.atom-ph cond-mat.quant-gas physics.chem-ph physics.optics
We show that dressing polar molecules with a far-off-resonant optical field
leads to new types of intermolecular potentials, which undergo a crossover from
the inverse-power to oscillating behavior depending on the intermolecular
distance, and whose parameters can be tuned by varying the laser intensity and
wavelength. We present analytic expressions for the potential energy surfaces,
thereby providing direct access to the parameters of an optical field required
to design intermolecular interactions experimentally.
| arxiv topic:physics.atom-ph cond-mat.quant-gas physics.chem-ph physics.optics |
arxiv_dataset-25471104.1146 | An Open-System Quantum Simulator with Trapped Ions
quant-ph
The control of quantum systems is of fundamental scientific interest and
promises powerful applications and technologies. Impressive progress has been
achieved in isolating the systems from the environment and coherently
controlling their dynamics, as demonstrated by the creation and manipulation of
entanglement in various physical systems. However, for open quantum systems,
engineering the dynamics of many particles by a controlled coupling to an
environment remains largely unexplored. Here we report the first realization of
a toolbox for simulating an open quantum system with up to five qubits. Using a
quantum computing architecture with trapped ions, we combine multi-qubit gates
with optical pumping to implement coherent operations and dissipative
processes. We illustrate this engineering by the dissipative preparation of
entangled states, the simulation of coherent many-body spin interactions and
the quantum non-demolition measurement of multi-qubit observables. By adding
controlled dissipation to coherent operations, this work offers novel prospects
for open-system quantum simulation and computation.
| arxiv topic:quant-ph |
arxiv_dataset-25481104.1246 | Jordan-H\"older decomposition of regular $(a, b)$-modules
math.CV
A classical result of singularity theory states that the spectrum of an
isolated hypersurface singularity is symmetric with respect to $n/2$, where $n$
is the dimension of the enclosing space. We prove a similar result for the
Jordan-H\"older composition series of the $(a,b)$-module associated to an
isolated hypersurface singularity.
| arxiv topic:math.CV |
arxiv_dataset-25491104.1346 | Extended Drude model and role of interband transitions in the
mid-infrared spectra of pnictides
cond-mat.supr-con
We analyze the outcomes of an extended-Drude-model approach to the optical
spectra of pnictides, where the multiband nature of the electronic excitations
requires a careful analysis of the role of interband processes in the optical
conductivity.Through a direct comparison between model calculations of the
intraband optical spectra and experimental data, we show that interband
transitions,whose relevance is shown by first-principle calculations,give a non
negligible contribution already in the infrared region. This leads to a
substantial failure of the extended-Drude-model analysis on the measured
optical data without subtraction of interband contributions.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-25501104.1446 | Dynamics of Simple Balancing Models with State Dependent Switching
Control
math.DS
Time-delayed control in a balancing problem may be a nonsmooth function for a
variety of reasons. In this paper we study a simple model of the control of an
inverted pendulum by either a connected movable cart or an applied torque for
which the control is turned off when the pendulum is located within certain
regions of phase space. Without applying a small angle approximation for
deviations about the vertical position, we see structurally stable periodic
orbits which may be attracting or repelling. Due to the nonsmooth nature of the
control, these periodic orbits are born in various discontinuity-induced
bifurcations. Also we show that a coincidence of switching events can produce
complicated periodic and aperiodic solutions.
| arxiv topic:math.DS |
arxiv_dataset-25511104.1546 | Physical Simulation of Inarticulate Robots
cs.RO
In this note we study the structure and the behavior of inarticulate robots.
We introduce a robot that moves by successive revolvings. The robot's structure
is analyzed, simulated and discussed in detail.
| arxiv topic:cs.RO |
arxiv_dataset-25521104.1646 | Jet Substructure Without Trees
hep-ph hep-ex
We present an alternative approach to identifying and characterizing jet
substructure. An angular correlation function is introduced that can be used to
extract angular and mass scales within a jet without reference to a clustering
algorithm. This procedure gives rise to a number of useful jet observables. As
an application, we construct a top quark tagging algorithm that is competitive
with existing methods.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-25531104.1746 | Potential barrier of Graphene edges
cond-mat.mtrl-sci cond-mat.mes-hall
We calculated row resolved density of states, charge distribution and work
function of graphene's zigzag and armchair edge (either clean or terminated
alternatively with H, O or OH group). The zigzag edge saturated via OH group
has the lowest work function of 3.76 eV, while the zigzag edge terminated via O
has the highest work function of 7.74 eV. The angle-dependent potential barrier
on the edge is fitted to a multi-pole model and is explained by the charge
distribution.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-25541104.1846 | Determining the validity of solutions of the meanfield Bogoliubov-de
Gennes equation
quant-ph cond-mat.quant-gas
We provide a general methodology to directly determine the validity of the
meanfield Bogoliubov-de Gennes equation. In particular we apply this
methodology to the case of two component interacting ultracold Fermi gases. As
an example, we consider the case of population imbalance, between the two
components, in the strongly attractive interacting regime, where meanfield
results predict Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states. For these
states we find at finite temperatures that the assumptions used to derive the
Bogoliubov-de Gennes equation are invalid.
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-25551104.1946 | Coverage, Continuity and Visual Cortical Architecture
q-bio.NC physics.bio-ph
The primary visual cortex of many mammals contains a continuous
representation of visual space, with a roughly repetitive aperiodic map of
orientation preferences superimposed. It was recently found that orientation
preference maps (OPMs) obey statistical laws which are apparently invariant
among species widely separated in eutherian evolution. Here, we examine whether
one of the most prominent models for the optimization of cortical maps, the
elastic net (EN) model, can reproduce this common design. The EN model
generates representations which optimally trade of stimulus space coverage and
map continuity. While this model has been used in numerous studies, no
analytical results about the precise layout of the predicted OPMs have been
obtained so far. We present a mathematical approach to analytically calculate
the cortical representations predicted by the EN model for the joint mapping of
stimulus position and orientation. We find that in all previously studied
regimes, predicted OPM layouts are perfectly periodic. An unbiased search
through the EN parameter space identifies a novel regime of aperiodic OPMs with
pinwheel densities lower than found in experiments. In an extreme limit,
aperiodic OPMs quantitatively resembling experimental observations emerge.
Stabilization of these layouts results from strong nonlocal interactions rather
than from a coverage-continuity-compromise. Our results demonstrate that
optimization models for stimulus representations dominated by nonlocal
suppressive interactions are in principle capable of correctly predicting the
common OPM design. They question that visual cortical feature representations
can be explained by a coverage-continuity-compromise.
| arxiv topic:q-bio.NC physics.bio-ph |
arxiv_dataset-25561104.2046 | SU(5)xSU(5) unification revisited
hep-ph
The idea of grand unification in a minimal supersymmetric SU(5)xSU(5)
framework is revisited. It is shown that the unification of gauge couplings
into a unique coupling constant can be achieved at a high-energy scale
compatible with proton decay constraints. This requires the addition of a
minimal particle content at intermediate energy scales. In particular, the
introduction of the SU(2)_L triplets belonging to the (15,1)+(\bar{15},1)
representations, as well as of the scalar triplet \Sigma_3 and octet \Sigma_8
in the (24,1) representation, turns out to be crucial for unification. The
masses of these intermediate particles can vary over a wide range, and even lie
in the TeV region. In contrast, the exotic vector-like fermions must be heavy
enough and have masses above 10^10 GeV. We also show that, if the SU(5)xSU(5)
theory is embedded into a heterotic string scenario, it is not possible to
achieve gauge coupling unification with gravity at the perturbative string
scale.
| arxiv topic:hep-ph |
arxiv_dataset-25571104.2146 | Reply to "Comment on 'Isotope effect in multi-band and multi-channel
attractive systems and inverse isotope effect in iron-based superconductors'"
cond-mat.supr-con
The Comment insists on the following: in our model it is assumed that the
effective interactions have specific energy ranges within the single band with
a cutoff at \omega_1 for the phononic part and a range from \omega_1 to
\omega_2 in the AF channel. Our reply is that we assume that V_i(k,k')\neq 0 if
|\xi_k|<\omega_i and |\xi_{k'}|<\omega_i, and otherwise V_i(k,k')= 0 (i=1,2),
as stated in our paper. This is the model of BCS type with two attractive
interactions, and this assumption is the characteristic of the BCS
approximation. The claim "the integration limits have been modified such that
the AF channel mediated pairing sets in where the ph-channel pairing terminates
and is limited at an energy given by \omega_j=\omega_{AF}" in the Comment is
wrong. We describe the model and the method to solve the gap equation in more
detail.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-25581104.2246 | Magnetic Connectivity between Active Regions 10987, 10988, and 10989 by
Means of Nonlinear Force-Free Field Extrapolation
astro-ph.SR
Extrapolation codes for modelling the magnetic field in the corona in
cartesian geometry do not take the curvature of the Sun's surface into account
and can only be applied to relatively small areas, \textit{e.g.}, a single
active region. We apply a method for nonlinear force-free coronal magnetic
field modelling of photospheric vector magnetograms in spherical geometry which
allows us to study the connectivity between multi-active regions. We use vector
magnetograph data from the Synoptic Optical Long-term Investigations of the Sun
survey (SOLIS)/Vector Spectromagnetograph(VSM) to model the coronal magnetic
field, where we study three neighbouring magnetically connected active regions
(ARs: 10987, 10988, 10989) observed on 28, 29, and 30 March 2008, respectively.
We compare the magnetic field topologies and the magnetic energy densities and
study the connectivities between the active regions(ARs). We have studied the
time evolution of magnetic field over the period of three days and found no
major changes in topologies as there was no major eruption event. From this
study we have concluded that active regions are much more connected
magnetically than the electric current.
| arxiv topic:astro-ph.SR |
arxiv_dataset-25591104.2346 | A quantum mechanical model of the upper bounds of the cascading
contribution to the second hyperpolarizability
physics.optics physics.chem-ph quant-ph
Microscopic cascading of second-order nonlinearities between two molecules
has been proposed to yield an enhanced third-order molecular nonlinear-optical
response. In this contribution, we investigate the two-molecule cascaded second
hyperpolarizability and show that it will never exceed the fundamental limit of
a single molecule with the same number of electrons as the two-molecule system.
We show the apparent divergence behavior of the cascading contribution to the
second hyperpolarizability vanishes when properly taking into account the
intermolecular interactions. Although cascading can never lead to a larger
nonlinear-optical response than a single molecule, it provides alternative
molecular design configurations for creating materials with large third-order
susceptibilities that may be difficult to design into a single molecule.
| arxiv topic:physics.optics physics.chem-ph quant-ph |
arxiv_dataset-25601104.2446 | A rotating three component perfect fluid source and its junction with
empty space-time
gr-qc
The Kerr solution for empty space-time is presented in an ellipsoidally
symmetric coordinate system and it is used to produce generalised ellipsoidal
metrics appropriate for the generation of rotating interior solutions of
Einstein's equations. It is shown that these solutions are the familiar static
perfect fluid cases commonly derived in curvature coordinates but now endowed
with rotation. The resulting solutions are also discussed in the context of
T-solutions of Einstein's equations and the vacuum T-solution outside a
rotating source is presented. The interior source for these solutions is shown
not to be a perfect fluid but rather an anisotropic three component perfect
fluid for which the energy momentum tensor is derived. The Schwarzschild
interior solution is given as an example of the approach.
| arxiv topic:gr-qc |
arxiv_dataset-25611104.2546 | The diamond Nitrogen-Vacancy center as a probe of random fluctuations in
a nuclear spin ensemble
cond-mat.mes-hall
New schemes that exploit the unique properties of Nitrogen-Vacancy (NV)
centers in diamond are presently being explored as a platform for
high-resolution magnetic sensing. Here we focus on the ability of a NV center
to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, we
conduct comparative experiments where the NV spin evolves under the influence
of surrounding 13C nuclei or, alternatively, in the presence of asynchronous AC
fields engineered to emulate bath fluctuations. Our study reveals substantial
differences that underscore the limitations of the semi-classical picture when
interpreting and predicting the outcome of experiments designed to probe small
nuclear spin ensembles. In particular, our study elucidates the NV center
response to bath fluctuations under common pulse sequences, and explores a
detection protocol designed to probe time correlations of the nuclear spin bath
dynamics. Further, we show that the presence of macroscopic nuclear spin order
is key to the emergence of semi-classical spin magnetometry.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-25621104.2646 | Quantum Percolation Transition from Graphene to Graphane: Graph
Theoretical Approach
cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.stat-mech
Graphane is obtained by perfectly hydrogenating graphene. There exists an
intermediate material, partially hydrogenated graphene (which we call
\textit{hydrographene}), interpolating from pure graphene to pure graphane. It
has various intriguing electronic and magnetic properties. We investigate a
metal-insulator transition, employing a quantum-site percolation model together
with a graph theoretical approach. Hydrographene is an exceptional case in
which electronic properties cannot be determined solely by the density of
states at the Fermi energy. Though there are plenty of zero energy state in
wide range of hydrogenation density, most of them are insulating states. We
also demonstrate that it shows a bulk ferromagnetic property based on the Lieb
theory.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.stat-mech |
arxiv_dataset-25631104.2746 | Thermal Casimir drag in fluctuating classical fields
cond-mat.stat-mech cond-mat.soft
A uniformly moving inclusion which locally suppresses the fluctuations of a
classical thermally excited field is shown to experience a drag force which
depends on the dynamics of the field. It is shown that in a number of cases the
linear friction coefficient is dominated by short distance fluctuations and
takes a very simple form. Examples where this drag can occur are for stiff
objects, such as proteins, nonspecifically bound to more flexible ones such as
polymers and membranes.
| arxiv topic:cond-mat.stat-mech cond-mat.soft |
arxiv_dataset-25641104.2846 | On graviton non-Gaussianities during inflation
hep-th astro-ph.CO
We consider the most general three point function for gravitational waves
produced during a period of exactly de Sitter expansion. The de Sitter
isometries constrain the possible shapes to only three: two preserving parity
and one violating parity. These isometries imply that these correlation
functions should be conformal invariant. One of the shapes is produced by the
ordinary gravity action. The other shape is produced by a higher derivative
correction and could be as large as the gravity contribution. The parity
violating shape does not contribute to the bispectrum [1106.3228, 1108.0175],
even though it is present in the wavefunction. We also introduce a spinor
helicity formalism to describe de Sitter gravitational waves with circular
polarization. These results also apply to correlation functions in Anti-de
Sitter space. They also describe the general form of stress tensor correlation
functions, in momentum space, in a three dimensional conformal field theory.
Here all three shapes can arise, including the parity violating one.
| arxiv topic:hep-th astro-ph.CO |
arxiv_dataset-25651104.2946 | The ground state energy of the frustrated ferromagnetic spin chain near
the transition point
cond-mat.str-el
The one-dimensional quantum spin-1/2 model with nearest-neighbor
ferromagnetic and next-nearest-neighbor antiferromagnetic interaction is
considered. The Hamiltonian is first bosonized by using the linear spin wave
approximation, and then is treated by using the Green's function approach. An
integral expression of the quantum correction to the classical ground state
energy is derived. The critical behavior of the ground state energy in the
vicinity of the transition point from the ferromagnetic to the singlet ground
state is analyzed by numerical calculation, and the result is $-8\gamma^2$.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-25661104.3046 | Asymptotic behaviour of the number of the Eulerian circuits
math.CO
We determine the asymptotic behaviour of the number of the Eulerian circuits
in undirected simple graphs with large algebraic connectivity (the
second-smallest eigenvalue of the Laplacian matrix). We also prove some new
properties of the Laplacian matrix.
| arxiv topic:math.CO |
arxiv_dataset-25671104.3146 | Localizing Sagittarius A* and M87 on Microarcsecond Scales with
Millimeter VLBI
astro-ph.HE
With the advent of the Event Horizon Telescope (EHT), a
millimeter/sub-millimeter very-long baseline interferometer (VLBI), it has
become possible to image a handful of black holes with sub-horizon resolutions.
However, these images do not translate into microarcsecond absolute positions
due to the lack of absolute phase information when an external phase reference
is not used. Due to the short atmospheric coherence time at these wavelengths,
nodding between the source and phase reference is impractical. However, here we
suggest an alternative scheme which makes use of the fact that many of the VLBI
stations within the EHT are arrays in their own right. With this we show that
it should be possible to absolutely position the supermassive black holes at
the centers of the Milky Way (Sgr A*) and M87 relative to nearby objects with
precisions of roughly 1 microarcsecond. This is sufficient to detect the
perturbations to Sgr A*'s position resulting from interactions with the stars
and stellar-mass black holes in the Galactic cusp on year timescales, and
severely constrain the astrophysically relevant parameter space for an orbiting
intermediate mass black hole, implicated in some mechanisms for producing the
young massive stars in the Galactic center. For M87, it allows the registering
of millimeter images, in which the black hole may be identified by its
silhouette against nearby emission, and existing larger scale radio images,
eliminating present ambiguities in the nature of the radio core and
inclination, opening angle, and source of the radio jet.
| arxiv topic:astro-ph.HE |
arxiv_dataset-25681104.3246 | Hybrid Quantum Annealing for Clustering Problems
cond-mat.dis-nn cond-mat.stat-mech quant-ph
We develop a hybrid type of quantum annealing in which we control temperature
and quantum field simultaneously. We study the efficiency of proposed quantum
annealing and find a good schedule of changing thermal fluctuation and quantum
fluctuation. In this paper, we focus on clustering problems which are important
topics in information science and engineering. We obtain the better solution of
the clustering problem than the standard simulated annealing by proposed
quantum annealing.
| arxiv topic:cond-mat.dis-nn cond-mat.stat-mech quant-ph |
arxiv_dataset-25691104.3346 | Dielectric screening in two-dimensional insulators: Implications for
excitonic and impurity states in graphane
cond-mat.mes-hall
For atomic thin layer insulating materials we provide an exact analytic form
of the two-dimensional screened potential. In contrast to three-dimensional
systems where the macroscopic screening can be described by a static dielectric
constant in 2D systems the macroscopic screening is non local (q-dependent)
showing a logarithmic divergence for small distances and reaching the
unscreened Coulomb potential for large distances. The cross-over of these two
regimes is dictated by 2D layer polarizability that can be easily computed by
standard first-principles techniques. The present results have strong
implications for describing gap-impurity levels and also exciton binding
energies. The simple model derived here captures the main physical effects and
reproduces well, for the case of graphane, the full many-body GW plus
Bethe-Salpeter calculations. As an additional outcome we show that the impurity
hole-doping in graphane leads to strongly localized states, what hampers
applications in electronic devices. In spite of the inefficient and nonlocal
two-dimensional macroscopic screening we demonstrate that a simple
$\mathbf{k}\cdot\mathbf{p}$ approach is capable to describe the electronic and
transport properties of confined 2D systems.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-25701104.3446 | Patterned Deposition of Particles in Spatio-temporally Driven Lattices
nlin.CD
We present and analyze mechanisms for the patterned deposition of particles
in a spatio-temporally driven lattice. The working principle is based on the
breaking of the spatio-temporal translation symmetry, which is responsible for
the equivalence of all lattice sites, by applying modulated phase shifts to the
lattice sites. The patterned trapping of the particles occurs in confined
chaotic seas, created via the ramping of the height of the lattice potential.
Complex density profiles on the length scale of the complete lattice can be
obtained by a quasi-continuous, spatial deformation of the chaotic sea in a
frequency modulated lattice.
| arxiv topic:nlin.CD |
arxiv_dataset-25711104.3546 | Viscosity calculated in simulations of strongly-coupled dusty plasmas
with gas friction
physics.plasm-ph cond-mat.soft
A two-dimensional strongly-coupled dusty plasma is modeled using Langevin and
frictionless molecular dynamical simulations. The static viscosity $\eta$ and
the wave-number-dependent viscosity $\eta(k)$ are calculated from the
microscopic shear in the random motion of particles. A recently developed
method of calculating the wave-number-dependent viscosity $\eta(k)$ is
validated by comparing the results of $\eta(k)$ from the two simulations. It is
also verified that the Green-Kubo relation can still yield an accurate measure
of the static viscosity $\eta$ in the presence of a modest level of friction as
in dusty plasma experiments.
| arxiv topic:physics.plasm-ph cond-mat.soft |
arxiv_dataset-25721104.3646 | Two-Center Integrals for r_{ij}^{n} Polynomial Correlated Wave Functions
math-ph cond-mat.str-el math.MP quant-ph
All integrals needed to evaluate the correlated wave functions with
polynomial terms of inter-electronic distance are included. For this form of
the wave function, the integrals needed can be expressed as a product of
integrals involving at most four electrons.
| arxiv topic:math-ph cond-mat.str-el math.MP quant-ph |
arxiv_dataset-25731104.3746 | Dressed Wilson Loops on S^2
hep-th
We present a new, two-parameter family of string solutions corresponding to
the holographic duals of specific 1/8-BPS Wilson loops on S^2 in N = 4
supersymmetric Yang-Mills theory. The solutions are obtained using the dressing
method on the known longitude solution in the context of the auxiliary
sigma-model on S^3 put forth in arXiv:0905.0665[hep-th]. We verify that the
regularized area of the worldsheets are consistent with expectations.
| arxiv topic:hep-th |
arxiv_dataset-25741104.3846 | New Measure of the Dissipation Region in Collisionless Magnetic
Reconnection
astro-ph.SR physics.plasm-ph physics.space-ph
A new measure to identify a small-scale dissipation region in collisionless
magnetic reconnection is proposed. The energy transfer from the electromagnetic
field to plasmas in the electron's rest frame is formulated as a
Lorentz-invariant scalar quantity. The measure is tested by two-dimensional
particle-in-cell simulations in typical configurations: symmetric and
asymmetric reconnection, with and without the guide field. The innermost region
surrounding the reconnection site is accurately located in all cases. We
further discuss implications for nonideal MHD dissipation.
| arxiv topic:astro-ph.SR physics.plasm-ph physics.space-ph |
arxiv_dataset-25751104.3946 | Anomalous spectral scaling of light emission rates in low dimensional
metallic nanostructures
physics.optics
The strength of light emission near metallic nanostructures can scale
anomalously with frequency and dimensionality. We find that light-matter
interactions in plasmonic systems confined in two dimensions (e.g., near metal
nanowires) strengthen with decreasing frequency owing to strong mode
confinement away from the surface plasmon frequency. The anomalous scaling also
applies to the modulation speed of plasmonic light sources, including lasers,
with modulation bandwidths growing at lower carrier frequencies. This allows
developing optical devices that exhibit simultaneously femto-second response
times at the nano-meter scale, even at longer wavelengths into the mid IR,
limited only by non-local effects and reversible light-matter coupling.
| arxiv topic:physics.optics |
arxiv_dataset-25761104.4046 | Long range magnetic ordering in Na$_2$IrO$_3$
cond-mat.mtrl-sci
We report a combined experimental and theoretical investigation of the
magnetic structure of the honeycomb lattice magnet Na$_2$IrO$_3$, a strong
candidate for a realization of a gapless spin-liquid. Using resonant x-ray
magnetic scattering at the Ir L$_3$-edge, we find 3D long range
antiferromagnetic order below T$_N$=13.3 K. From the azimuthal dependence of
the magnetic Bragg peak, the ordered moment is determined to be predominantly
along the {\it a}-axis. Combining the experimental data with first principles
calculations, we propose that the most likely spin structure is a novel
"zig-zag" structure.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-25771104.4146 | Ultra stable and very low noise signal source using a cryocooled
sapphire oscillator for VLBI
physics.ins-det astro-ph.IM
Here we present the design and implementation of a novel frequency
synthesizer based on low phase noise digital dividers and a direct digital
synthesizer. The synthesis produces two low noise accurate and tunable signals
at 10 MHz and 100 MHz. We report on the measured residual phase noise and
frequency stability of the synthesizer, and estimate the total frequency
stability, which can be expected from the synthesizer seeded with a signal near
11.2 GHz from an ultra-stable cryocooled sapphire oscillator.
The synthesizer residual single sideband phase noise, at 1 Hz offset, on 10
MHz and 100 MHz signals, respectively, were measured to be -135 dBc/Hz and -130
dBc/Hz. Their intrinsic frequency stability contributions, on the 10 MHz and
100 MHz signals, respectively, were measured as sigma_y = 9 x 10^-15 and
sigma_y = 2.2 x 10^-15, at 1 s integration time.
The Allan Deviation of the total fractional frequency noise on the 10 MHz and
100 MHz signals derived from the synthesizer with the cryocooled sapphire
oscillator, may be estimated as sigma_y = 5.2 x 10^-15 \tau ^-1 + 3.6 x 10^-15
\tau ^-1/2 + 4 x 10^-16 and sigma_y = 2 x 10^-15 \tau ^-1/2 + 3 x 10^-16,
respectively, for 1 s < \tau < 10^4 s.
We also calculate the coherence function, (a figure of merit in VLBI) for
observation frequencies of 100 GHz, 230 GHz and 345 GHz, when using the
cryocooled sapphire oscillator and an hydrogen maser. The results show that the
cryocooled sapphire oscillator offers a significant advantage at frequencies
above 100 GHz.
| arxiv topic:physics.ins-det astro-ph.IM |
arxiv_dataset-25781104.4246 | ^{59}Co-Nuclear Quadrupole Resonance and Nuclear Magnetic Resonance
studies on YCoGe --- Comparison between YCoGe and UCoGe ---
cond-mat.str-el cond-mat.supr-con
We have performed ^{59}Co-nuclear quadrupole resonance (NQR) and nuclear
magnetic resonance (NMR) studies on YCoGe, which is a reference compound of
ferromagnetic superconductor UCoGe, in order to investigate the magnetic
properties at the Co site. Magnetic and superconducting transitions were not
observed down to 0.3 K, but a conventional metallic behavior was found in
YCoGe, although its crystal structure is similar to that of UCoGe. From the
comparison between experimental results of two compounds, the ferromagnetism
and superconductivity observed in UCoGe originate from the U-5f electrons.
| arxiv topic:cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-25791104.4346 | Fourier Transform Representation of the Extended Fermi-Dirac and
Bose-Einstein Functions with Applications to the Family of the Zeta and
Related Functions
math-ph math.CA math.MP
On the one hand the Fermi-Dirac and Bose-Einstein functions have been
extended in such a way that they are closely related to the Riemann and other
zeta functions. On the other hand the Fourier transform representation of the
gamma and generalized gamma functions proved useful in deriving various
integral formulae for these functions. In this paper we use the Fourier
transform representation of the extended functions to evaluate integrals of
products of these functions. In particular we evaluate some integrals
containing the Riemann and Hurwitz zeta functions, which had not been evaluated
before.
| arxiv topic:math-ph math.CA math.MP |
arxiv_dataset-25801104.4446 | A Note on Angular Momentum Commutators in Light-Cone Formulation of Open
Bosonic String Theory
hep-th
We recalculate in a systematic and pedagogical way one of the most important
results of Bosonic open string theory in the light-cone formulation, namely the
[J^{-i},J^{-j}] commutators, which together with Lorentz covariance, famously
yield the critical dimension D=26 and the normal order constant a=1. We use
traditional transverse oscillator mode expansions (avoiding the elegant but
more advanced language of operator product expansions). We streamline the proof
by introducing a novel bookkeeping/regularization parameter \kappa to avoid
splitting into creation and annihilation parts, and to avoid sandwiching
between bras and kets.
| arxiv topic:hep-th |
arxiv_dataset-25811104.4546 | Implications of the gauge-fixing in Loop Quantum Cosmology
gr-qc hep-th
The restriction to invariant connections in a Friedmann-Robertson-Walker
space-time is discussed via the analysis of the Dirac brackets associated with
the corresponding gauge fixing. This analysis allows us to establish the proper
correspondence between reduced and un-reduced variables. In this respect, it is
outlined how the holonomy-flux algebra coincides with the one of Loop Quantum
Gravity if edges are parallel to simplicial vectors and the quantization of the
model is performed via standard techniques by restricting admissible paths.
Within this scheme, the discretization of the area spectrum is emphasized.
Then, the role of the diffeomorphisms generator in reduced phase-space is
investigated and it is clarified how it implements homogeneity on quantum
states, which are defined over cubical knots. Finally, the perspectives for a
consistent dynamical treatment are discussed.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-25821104.4646 | Local Optimality Certificates for LP Decoding of Tanner Codes
cs.IT math.CO math.IT
We present a new combinatorial characterization for local optimality of a
codeword in an irregular Tanner code. The main novelty in this characterization
is that it is based on a linear combination of subtrees in the computation
trees. These subtrees may have any degree in the local code nodes and may have
any height (even greater than the girth). We expect this new characterization
to lead to improvements in bounds for successful decoding.
We prove that local optimality in this new characterization implies
ML-optimality and LP-optimality, as one would expect. Finally, we show that is
possible to compute efficiently a certificate for the local optimality of a
codeword given an LLR vector.
| arxiv topic:cs.IT math.CO math.IT |
arxiv_dataset-25831104.4746 | Lasserre Hierarchy, Higher Eigenvalues, and Approximation Schemes for
Quadratic Integer Programming with PSD Objectives
cs.CC cs.DS
We present an approximation scheme for optimizing certain Quadratic Integer
Programming problems with positive semidefinite objective functions and global
linear constraints. This framework includes well known graph problems such as
Minimum graph bisection, Edge expansion, Uniform sparsest cut, and Small Set
expansion, as well as the Unique Games problem. These problems are notorious
for the existence of huge gaps between the known algorithmic results and
NP-hardness results. Our algorithm is based on rounding semidefinite programs
from the Lasserre hierarchy, and the analysis uses bounds for low-rank
approximations of a matrix in Frobenius norm using columns of the matrix.
For all the above graph problems, we give an algorithm running in time
$n^{O(r/\epsilon^2)}$ with approximation ratio
$\frac{1+\epsilon}{\min\{1,\lambda_r\}}$, where $\lambda_r$ is the $r$'th
smallest eigenvalue of the normalized graph Laplacian $\mathcal{L}$. In the
case of graph bisection and small set expansion, the number of vertices in the
cut is within lower-order terms of the stipulated bound. Our results imply
$(1+O(\epsilon))$ factor approximation in time $n^{O(r^\ast/\epsilon^2)}$ where
$r^\ast$ is the number of eigenvalues of $\mathcal{L}$ smaller than
$1-\epsilon$.
For Unique Games, we give a factor $(1+\frac{2+\epsilon}{\lambda_r})$
approximation for minimizing the number of unsatisfied constraints in
$n^{O(r/\epsilon)}$ time. This improves an earlier bound for solving Unique
Games on expanders, and also shows that Lasserre SDPs are powerful enough to
solve well-known integrality gap instances for the basic SDP.
We also give an algorithm for independent sets in graphs that performs well
when the Laplacian does not have too many eigenvalues bigger than $1+o(1)$.
| arxiv topic:cs.CC cs.DS |
arxiv_dataset-25841104.4846 | A Schauder and Riesz Basis Criterion for Non-Self-Adjoint Schr\"odinger
Operators with Periodic and Antiperiodic Boundary Conditions
math.SP math.CA math.FA
Under the assumption that $V \in L^2([0,\pi]; dx)$, we derive necessary and
sufficient conditions for (non-self-adjoint) Schr\"odinger operators
$-d^2/dx^2+V$ in $L^2([0,\pi]; dx)$ with periodic and antiperiodic boundary
conditions to possess a Riesz basis of root vectors (i.e., eigenvectors and
generalized eigenvectors spanning the range of the Riesz projection associated
with the corresponding periodic and antiperiodic eigenvalues). We also discuss
the case of a Schauder basis for periodic and antiperiodic Schr\"odinger
operators $-d^2/dx^2+V$ in $L^p([0,\pi]; dx)$, $p \in (1,\infty)$.
| arxiv topic:math.SP math.CA math.FA |
arxiv_dataset-25851104.4946 | Radio-Optical-Gamma-Ray properties of MOJAVE AGN detected by Fermi/LAT
astro-ph.CO
Aims. We use a sample of 83 core-dominated active galactic nuclei (AGN)
selected from the MOJAVE (Monitoring of Jets in AGN with VLBA Experiments)
radio-flux-limited sample and detected with the Fermi Large Area Telescope
(LAT) to study the relations between non-simultaneous radio, optical, and
gamma-ray measurements. Methods. We perform a multi-band statistical analysis
to investigate the relations between the emissions in different bands and
reproduce these relations by modeling of the spectral energy distributions of
blazars. Results. There is a significant correlation between the gamma-ray
luminosity and the optical nuclear and radio (15 GHz) luminosities of blazars.
We report a well defined positive correlation between the gamma-ray luminosity
and the radio-optical loudness for quasars and BL Lacertae type objects (BL
Lacs). A strong positive correlation is found between the radio luminosity and
the gamma-ray-optical loudness for quasars, while a negative correlation
between the optical luminosity and the gamma-ray-radio loudness is present for
BL Lacs. Modeling of these correlations with a simple leptonic jet model for
blazars indicates that variations of the accretion disk luminosity (and hence
the jet power) is able to reproduce the trends observed in most of the
correlations. To reproduce all observed correlations, variations of several
parameters, such as the accretion power, jet viewing angle, Lorentz factor, and
magnetic field of the jet, are required.
| arxiv topic:astro-ph.CO |
arxiv_dataset-25861104.5046 | Environmentally Driven Global Evolution of Galaxies
astro-ph.CO astro-ph.HE
Utilizing high-resolution large-scale galaxy formation simulations of the
standard cold dark matter model, we examine global trends in the evolution of
galaxies due to gravitational shock heating by collapse of large halos and
large-scale structure. We find two major global trends. (1) The mean specific
star formation rate (sSFR) at a given galaxy mass is a monotonically increasing
function with increasing redshift. (2) The mean sSFR at a given redshift is a
monotonically increasing function of decreasing galaxy mass that steepens with
decreasing redshift. The general dimming trend with time merely reflects the
general decline of gas inflow rate with increasing time. The differential
evolution of galaxies of different masses with redshift is a result of
gravitational shock heating of gas due to formation of large halos (groups and
clusters) and large-scale structure that move a progressively larger fraction
of galaxies and their satellites into environments where gas has too high an
entropy to cool to continue feeding resident galaxies. Overdense regions where
larger halos are preferentially located begin to be heated earlier and have
higher temperatures than lower density regions at any given time, causing sSFR
of larger galaxies to fall below the general dimming trend at higher redshift
than less massive galaxies and galaxies with high sSFR to gradually shift to
lower density environments at lower redshift. We find that several noted cosmic
downsizing phenomena are different manifestations of these general trends. We
also find that the great migration of galaxies from blue cloud to red sequence
as well as color-density relation, among others, may arise naturally in this
picture.
| arxiv topic:astro-ph.CO astro-ph.HE |
arxiv_dataset-25871104.5146 | Scaling Behaviors and Novel Creep Motion of Flux Lines under AC Driving
cond-mat.supr-con cond-mat.stat-mech
We performed Langevin dynamics simulations for the \textit{ac} driven flux
lines in a type II superconductor with random point-like pinning centers.
Scaling properties of flux-line velocity with respect to instantaneous driving
force of small frequency and around the critical \textit{dc} depinning force
are revealed successfully, which provides precise estimates on dynamic critical
exponents. From the scaling function we derive a creep law associated with the
activation by the regular shaking. The effective energy barrier vanishes at the
critical dc depinning point in a square-root way when the instantaneous driving
force increases. The frequency plays a similar role of temperature in
conventional creep motions, but in a nontrivial way governed by the critical
exponents. We have also performed systematic finite-size scaling analysis for
flux-line velocity in transient processes with \textit{dc} driving, which
provide estimates on critical exponents in good agreement with those derived
with ac driving. The scaling law is checked successfully.
| arxiv topic:cond-mat.supr-con cond-mat.stat-mech |
arxiv_dataset-25881104.5246 | How well can we estimate a sparse vector?
cs.IT math.IT math.ST stat.TH
The estimation of a sparse vector in the linear model is a fundamental
problem in signal processing, statistics, and compressive sensing. This paper
establishes a lower bound on the mean-squared error, which holds regardless of
the sensing/design matrix being used and regardless of the estimation
procedure. This lower bound very nearly matches the known upper bound one gets
by taking a random projection of the sparse vector followed by an $\ell_1$
estimation procedure such as the Dantzig selector. In this sense, compressive
sensing techniques cannot essentially be improved.
| arxiv topic:cs.IT math.IT math.ST stat.TH |
arxiv_dataset-25891104.5346 | Synthetic line and continuum linear-polarisation signatures of
axisymmetric type II supernova ejecta
astro-ph.SR
We present synthetic single-line and continuum linear-polarisation signatures
due to electron scattering in axially-symmetric Type II supernovae (SNe) which
we calculate using a Monte Carlo and a long-characteristic radiative-transfer
code. Aspherical ejecta are produced by prescribing a latitudinal scaling or
stretching of SN ejecta inputs obtained from 1-D non-LTE time-dependent
calculations. We study polarisation signatures as a function of inclination,
shape factor, wavelength, line identity, post-explosion time. At early times,
cancellation and optical-depth effects make the polarisation intrinsically low,
causing complicated sign reversals with inclination or continuum wavelength,
and across line profiles. While the line polarisation is positive (negative)
for an oblate (prolate) morphology at the peak and in the red wing, the
continuum polarisation may be of any sign. These complex polarisation
variations are produced not just by the asymmetric distribution of scatterers
but also of the flux. Our early-time signatures are in contradiction with
predictions for a centrally illuminated aspherical nebula, although this
becomes a better approximation at nebular times. For a fixed asymmetry, our
synthetic continuum polarisation is generally low, may evolve non-monotonically
during the plateau phase, but it systematically rises as the ejecta become
optically thin. Changes in polarization over time do not necessarily imply a
change in the asymmetry of the ejecta. The SN structure (e.g.,
density/ionization) critically influences the level of polarisation.
Importantly, a low polarisation (<0.5%) at early times does not necessarily
imply a low degree of asymmetry as usually assumed. Asphericity influences
line-profile morphology and the luminosity, which may compromise the accuracy
of SN characteristics inferred from these.
| arxiv topic:astro-ph.SR |
arxiv_dataset-25901104.5446 | Relativistic analyses of quasielastic neutrino cross sections at
MiniBooNE kinematics
nucl-th hep-ph
Two relativistic approaches are considered to evaluate the quasielastic
double-differential and integrated neutrino-nucleus cross sections. One, based
on the relativistic impulse approximation, relies on the microscopic
description of nuclear dynamics using relativistic mean field theory, and
incorporates a description of the final-state interactions. The second is based
on the superscaling behavior exhibited by electron scattering data and its
applicability, due to the universal character of the scaling function, to the
analysis of neutrino scattering reactions. The role played by the vector
meson-exchange currents in the two-particle two-hole sector is also
incorporated and the results obtained are compared with the recent data for
neutrinos measured by the MiniBooNE Collaboration.
| arxiv topic:nucl-th hep-ph |
arxiv_dataset-25911104.5546 | Optimal coding for the deletion channel with small deletion probability
cs.IT math.IT
The deletion channel is the simplest point-to-point communication channel
that models lack of synchronization. Input bits are deleted independently with
probability d, and when they are not deleted, they are not affected by the
channel. Despite significant effort, little is known about the capacity of this
channel, and even less about optimal coding schemes. In this paper we develop a
new systematic approach to this problem, by demonstrating that capacity can be
computed in a series expansion for small deletion probability. We compute three
leading terms of this expansion, and find an input distribution that achieves
capacity up to this order. This constitutes the first optimal coding result for
the deletion channel.
The key idea employed is the following: We understand perfectly the deletion
channel with deletion probability d=0. It has capacity 1 and the optimal input
distribution is i.i.d. Bernoulli(1/2). It is natural to expect that the channel
with small deletion probabilities has a capacity that varies smoothly with d,
and that the optimal input distribution is obtained by smoothly perturbing the
i.i.d. Bernoulli(1/2) process. Our results show that this is indeed the case.
We think that this general strategy can be useful in a number of capacity
calculations.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-25921104.5646 | Persistence for Circle Valued Maps
math.AT cs.CG cs.DS
We study circle valued maps and consider the persistence of the homology of
their fibers. The outcome is a finite collection of computable invariants which
answer the basic questions on persistence and in addition encode the topology
of the source space and its relevant subspaces. Unlike persistence of real
valued maps, circle valued maps enjoy a different class of invariants called
Jordan cells in addition to bar codes. We establish a relation between the
homology of the source space and of its relevant subspaces with these
invariants and provide a new algorithm to compute these invariants from an
input matrix that encodes a circle valued map on an input simplicial complex.
| arxiv topic:math.AT cs.CG cs.DS |
arxiv_dataset-25931105.0035 | Base-Station Selections for QoS Provisioning Over Distributed Multi-User
MIMO Links in Wireless Networks
cs.IT math.IT
We propose the QoS-aware BS-selection and the corresponding
resource-allocation schemes for downlink multi-user transmissions over the
distributed multiple-input-multiple-output (MIMO) links, where multiple
location-independent base-stations (BS), controlled by a central server,
cooperatively transmit data to multiple mobile users. Our proposed schemes aim
at minimizing the BS usages and reducing the interfering range of the
distributed MIMO transmissions, while satisfying diverse statistical delay-QoS
requirements for all users, which are characterized by the delay-bound
violation probability and the effective capacity technique. Specifically, we
propose two BS-usage minimization frameworks to develop the QoS-aware
BS-selection schemes and the corresponding wireless resource-allocation
algorithms across multiple mobile users. The first framework applies the joint
block-diagonalization (BD) and probabilistic transmission (PT) to implement
multiple access over multiple mobile users, while the second one employs
time-division multiple access (TDMA) approach to control multiple users' links.
We then derive the optimal BS-selection schemes for these two frameworks,
respectively. In addition, we further discuss the PT-only based BS-selection
scheme. Also conducted is a set of simulation evaluations to comparatively
study the average BS-usage and interfering range of our proposed schemes and to
analyze the impact of QoS constraints on the BS selections for distributed MIMO
transmissions.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-25941105.0135 | An Invariance Principle of G-Brownian Motion for the Law of the Iterated
Logarithm under G-expectation
math.PR
The classical law of the iterated logarithm (LIL for short)as fundamental
limit theorems in probability theory play an important role in the development
of probability theory and its applications. Strassen (1964) extended LIL to
large classes of functional random variables, it is well known as the
invariance principle for LIL which provide an extremely powerful tool in
probability and statistical inference. But recently many phenomena show that
the linearity of probability is a limit for applications, for example in
finance, statistics. As while a nonlinear expectation--- G-expectation has
attracted extensive attentions of mathematicians and economists, more and more
people began to study the nature of the G-expectation space. A natural question
is: Can the classical invariance principle for LIL be generalized under
G-expectation space? This paper gives a positive answer. We present the
invariance principle of G-Brownian motion for the law of the iterated logarithm
under G-expectation.
| arxiv topic:math.PR |
arxiv_dataset-25951105.0235 | Coexistence of Magnetic Order and Two-dimensional Superconductivity at
LaAlO$_3$/SrTiO$_3$ Interfaces
cond-mat.mtrl-sci cond-mat.mes-hall
A two dimensional electronic system with novel electronic properties forms at
the interface between the insulators LaAlO$_3$ and SrTiO$_3$. Samples
fabricated until now have been found to be either magnetic or superconducting,
depending on growth conditions. We combine transport measurements with
high-resolution magnetic torque magnetometry and report here evidence of
magnetic ordering of the two-dimensional electron liquid at the interface. The
magnetic ordering exists from well below the superconducting transition to up
to 200 K, and is characterized by an in-plane magnetic moment. Our results
suggest that there is either phase separation or coexistence between magnetic
and superconducting states. The coexistence scenario would point to an
unconventional superconducting phase in the ground state.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-25961105.0335 | Sharp Hardy inequalities in the half space with trace remainder term
math.AP
In this paper we deal with a class of inequalities which interpolate the
Kato's inequality and the Hardy's inequality in the half space. Starting from
the classical Hardy's inequality in the half space $\rnpiu
=\R^{n-1}\times(0,\infty)$, we show that, if we replace the optimal constant
$\frac{(n-2)^2}{4}$ with a smaller one $\frac{(\beta-2)^2}{4}$, $2\le \beta
<n$, then we can add an extra trace-term equals to that one that appears in the
Kato's inequality. The constant in the trace remainder term is optimal and it
tends to zero when $\beta$ goes to $n$, while it is equal to the optimal
constant in the Kato's inequality when $\beta=2$.
| arxiv topic:math.AP |
arxiv_dataset-25971105.0435 | A merger mystery: no extended radio emission in the merging cluster
Abell 2146
astro-ph.CO
We present a new 400ks Chandra X-ray observation and a GMRT radio observation
at 325MHz of the merging galaxy cluster Abell 2146. The Chandra observation
reveals detailed structure associated with the major merger event including the
Mach M=2.1+/-0.2 bow shock located ahead of the dense subcluster core and the
first known example of an upstream shock (M=1.6+/-0.1). Surprisingly, the deep
GMRT observation at 325MHz does not detect any extended radio emission
associated with either shock front. All other merging galaxy clusters with
X-ray detected shock fronts, including the Bullet cluster, Abell 520, Abell 754
and Abell 2744, and clusters with candidate shock fronts have detected radio
relics or radio halo edges coincident with the shocks. We consider several
possible factors which could affect the formation of radio relics, including
the shock strength and the presence of a pre-existing electron population, but
do not find a favourable explanation for this result. We calculate a 3sigma
upper limit of 13mJy on extended radio emission, which is significantly below
the radio power expected by the observed P_{radio}-L_{X} correlation for
merging systems. The lack of an extended radio halo in Abell 2146 maybe due to
the low cluster mass relative to the majority of merging galaxy clusters with
detected radio halos.
| arxiv topic:astro-ph.CO |
arxiv_dataset-25981105.0535 | Divergences in QFT on the Noncommutative Minkowski Space with
Grosse-Wulkenhaar potential
hep-th
We study quantum field theory on the two-dimensional Noncommutative Minkoswki
space with a Grosse-Wulkenhaar potential. We explicitly construct the retarded
propagator and show that it is not a tempered distribution. This leads to
problems when trying to define planar products of such distributions, as they
appear in the Yang-Feldman series. At and above the self-dual point, these can
no longer be defined, not even at different points. This shows that we do not
deal with an ordinary ultraviolet divergence.
| arxiv topic:hep-th |
arxiv_dataset-25991105.0635 | Multiclass multiserver queueing system in the Halfin-Whitt heavy traffic
regime. Asymptotics of the stationary distribution
math.PR
We consider a heterogeneous queueing system consisting of one large pool of
$O(r)$ identical servers, where $r\to\infty$ is the scaling parameter. The
arriving customers belong to one of several classes which determines the
service times in the distributional sense. The system is heavily loaded in the
Halfin-Whitt sense, namely the nominal utilization is $1-a/\sqrt{r}$ where
$a>0$ is the spare capacity parameter. Our goal is to obtain bounds on the
steady state performance metrics such as the number of customers waiting in the
queue $Q^r(\infty)$. While there is a rich literature on deriving process level
(transient) scaling limits for such systems, the results for steady state are
primarily limited to the single class case.
This paper is the first one to address the case of heterogeneity in the
steady state regime. Moreover, our results hold for any service policy which
does not admit server idling when there are customers waiting in the queue. We
assume that the interarrival and service times have exponential distribution,
and that customers of each class may abandon while waiting in the queue at a
certain rate (which may be zero). We obtain upper bounds of the form
$O(\sqrt{r})$ on both $Q^r(\infty)$ and the number of idle servers. The bounds
are uniform w.r.t. parameter $r$ and the service policy. In particular, we show
that $\limsup_r E \exp(\theta r^{-1/2}Q^r(\infty))<\infty$. Therefore, the
sequence $r^{-1/2}Q^r(\infty)$ is tight and has a uniform exponential tail
bound. We further consider the system with strictly positive abandonment rates,
and show that in this case every weak limit $\hat{Q}(\infty)$ of
$r^{-1/2}Q^r(\infty)$ has a sub-Gaussian tail. Namely $E[\exp(\theta
(\hat{Q}(\infty))^2)]<\infty$, for some $\theta>0$.
| arxiv topic:math.PR |
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