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arxiv_dataset-36001207.6786 | Towards higher-spin holography in ambient space of any dimension
hep-th
We derive the propagators for higher-spin master fields in anti-de Sitter
space of arbitrary dimension. A method is developed to construct the
propagators directly without solving any differential equations. The use of the
ambient space, where AdS is represented as a hyperboloid and its conformal
boundary as a projective light-cone, simplifies the approach and makes a direct
contact between boundary-to-bulk propagators and two-point functions of
conserved currents.
| arxiv topic:hep-th |
arxiv_dataset-36011207.6886 | Estimation of Huesler-Reiss distributions and Brown-Resnick processes
stat.ME math.PR
Estimation of extreme-value parameters from observations in the max-domain of
attraction (MDA) of a multivariate max-stable distribution commonly uses
aggregated data such as block maxima. Since we expect that additional
information is contained in the non-aggregated, single "large" observations, we
introduce a new approach of inference based on a multivariate
peaks-over-threshold method. We show that for any process in the MDA of the
frequently used H\"usler-Reiss model or its spatial extension, the
Brown-Resnick process, suitably defined conditional increments asymptotically
follow a multivariate Gaussian distribution. This leads to computationally
efficient estimates of the H\"usler-Reiss parameter matrix. Further, the
results enable parametric inference for Brown-Resnick processes. A simulation
study compares the performance of the new estimators to other commonly used
methods. As an application, we fit a non-isotropic Brown-Resnick process to the
extremes of 12 year data of daily wind speed measurements.
| arxiv topic:stat.ME math.PR |
arxiv_dataset-36021207.6986 | Two Embedding Theorems for Data with Equivalences under Finite Group
Action
cs.DS cs.IT math.IT
There is recent interest in compressing data sets for non-sequential
settings, where lack of obvious orderings on their data space, require notions
of data equivalences to be considered. For example, Varshney & Goyal (DCC,
2006) considered multiset equivalences, while Choi & Szpankowski (IEEE Trans.
IT, 2012) considered isomorphic equivalences in graphs. Here equivalences are
considered under a relatively broad framework - finite-dimensional,
non-sequential data spaces with equivalences under group action, for which
analogues of two well-studied embedding theorems are derived: the Whitney
embedding theorem and the Johnson-Lindenstrauss lemma. Only the canonical data
points need to be carefully embedded, each such point representing a set of
data points equivalent under group action. Two-step embeddings are considered.
First, a group invariant is applied to account for equivalences, and then
secondly, a linear embedding takes it down to low-dimensions. Our results
require hypotheses on discriminability of the applied invariant, such notions
related to seperating invariants (Dufresne, 2008), and completeness in pattern
recognition (Kakarala, 1992). In the latter theorem, the embedding complexity
depends on the size of the canonical part, which may be significantly smaller
than the whole data set, up to a factor equal to the size the group.
| arxiv topic:cs.DS cs.IT math.IT |
arxiv_dataset-36031207.7086 | M-Horizons
hep-th
We solve the Killing spinor equations and determine the near horizon
geometries of M-theory that preserve at least one supersymmetry. The M-horizon
spatial sections are 9-dimensional manifolds with a Spin(7) structure
restricted by geometric constraints which we give explicitly. We also provide
an alternative characterization of the solutions of the Killing spinor
equation, utilizing the compactness of the horizon section and the field
equations, by proving a Lichnerowicz type of theorem which implies that the
zero modes of a Dirac operator coupled to 4-form fluxes are Killing spinors. We
use this, and the maximum principle, to solve the field equations of the theory
for some special cases and present some examples.
| arxiv topic:hep-th |
arxiv_dataset-36041207.7186 | Pr magnetism and its interplay with the Fe spin density wave in PrFeAsO
cond-mat.supr-con
We have studied the magnetism of the Pr3+ ions in PrFeAsO_1-xF_x (x = 0;
0.15) and its interaction with the Fe magnetic order (for x = 0). Specific heat
data confirm the presence of a first excited crystal electric field (CEF) level
around 3.5 meV in the undoped compound PrFeAsO. This finding is in agreement
with recent neutron scattering experiments. The doped compound is found to have
a much lower first CEF splitting of about 2.0 meV. The Pr ordering in PrFeAsO
gives rise to large anomalies in the specific heat and the thermal expansion
coefficient. In addition, a field-induced transition is found at low
temperatures that is most pronounced for the magnetostriction coefficient. This
transition, which is absent in the doped compound, is attributed to a reversal
of the Fe spin canting as the antiferromagnetic Pr order is destroyed by the
external magnetic field.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-36051207.7286 | Rotation invariant Minkowski classes of convex bodies
math.MG math.DG math.FA
A Minkowski class is a closed subset of the space of convex bodies in
Euclidean space Rn which is closed under Minkowski addition and non-negative
dilatations. A convex body in Rn is universal if the expansion of its support
function in spherical harmonics contains non-zero harmonics of all orders. If K
is universal, then a dense class of convex bodies M has the following property.
There exist convex bodies T1; T2 such that M + T1 = T2, and T1; T2 belong to
the rotation invariant Minkowski class generated by K. It is shown that every
convex body K which is not centrally symmetric has a linear image, arbitrarily
close to K, which is universal. A modified version of the result holds for
centrally symmetric convex bodies. In this way, a result of S. Alesker is
strengthened, and at the same time given a more elementary proof.
| arxiv topic:math.MG math.DG math.FA |
arxiv_dataset-36061208.0028 | On Bayesian credible sets in restricted parameter space problems and
lower bounds for frequentist coverage
math.ST stat.TH
For estimating a lower bounded parametric function in the framework of
Marchand and Strawderman (2006), we provide through a unified approach a class
of Bayesian confidence intervals with credibility $1-\alpha$ and frequentist
coverage probability bounded below by $\frac{1-\alpha}{1+\alpha}$. In cases
where the underlying pivotal distribution is symmetric, the findings represent
extensions with respect to the specification of the credible set achieved
through the choice of a {\it spending function}, and include Marchand and
Strawderman's HPD procedure result. For non-symmetric cases, the determination
of a such a class of Bayesian credible sets fills a gap in the literature and
includes an "equal-tails" modification of the HPD procedure. Several examples
are presented demonstrating wide applicability.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-36071208.0128 | A finiteness theorem for Galois representations of function fields over
finite fields (after Deligne)
math.AG math.NT
Revised: just some typos, reorganized a bit the article. It will be published
in the VIASM Annual meeting, Hanoi.
We give a detailed account of Deligne's letter to Drinfeld dated June 18,
2011, in which he shows that there are finitely many irreducible lisse $\bar
\Q_\ell$-sheaves with bounded ramification, up to isomorphism and up to twist,
on a smooth variety defined over a finite field. The proof relies on
Lafforgue's Langlands correspondence over curves. In addition, Deligne shows
the existence of affine moduli of finite type over $\mathbb{Q}$. A corollary of
Deligne's finiteness theorem is the existence of a number field which contains
all traces of the Frobenii at closed points, which was the main result of his
recent article and which answers positively his own conjecture from Weil II.
| arxiv topic:math.AG math.NT |
arxiv_dataset-36081208.0228 | Initial Version of State Transition Algorithm
math.OC cs.NE
In terms of the concepts of state and state transition, a new algorithm-State
Transition Algorithm (STA) is proposed in order to probe into classical and
intelligent optimization algorithms. On the basis of state and state
transition, it becomes much simpler and easier to understand. As for continuous
function optimization problems, three special operators named rotation,
translation and expansion are presented. While for discrete function
optimization problems, an operator called general elementary transformation is
introduced. Finally, with 4 common benchmark continuous functions and a
discrete problem used to test the performance of STA, the experiment shows that
STA is a promising algorithm due to its good search capability.
| arxiv topic:math.OC cs.NE |
arxiv_dataset-36091208.0328 | Percolation through Voids around Overlapping Spheres, a Dynamically
based Finite Size Scaling Analysis
cond-mat.dis-nn
The percolation threshold for flow or conduction through voids surrounding
randomly placed spheres is rigorously calculated. With large scale Monte Carlo
simulations, we give a rigorous continuum treatment to the geometry of the
impenetrable spheres and the spaces between them. To properly exploit finite
size scaling, we examine multiple systems of differing sizes, with suitable
averaging over disorder, and extrapolate to the thermodynamic limit. An order
parameter based on the statistical sampling of stochastically driven dynamical
excursions and amenable to finite size scaling analysis is defined, calculated
for various system sizes, and used to determine the critical volume fraction
phi_{c} = 0.0317 +/- 0.0004 and the correlation length exponent nu = 0.92 +/-
0.05.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-36101208.0428 | Recent developments in U(3) ChPT: meson-meson scattering and finite
energy sum rules
hep-ph
We discuss the meson-meson scattering and finite energy sum rule(FESR), based
on the one-loop calculation within U(3) chiral perturbation theory. First we
obtain the pertinent resonance spectroscopy from the unitarized partial wave
scattering amplitudes. Then we investigate how well the FESR can be satisfied
in the physical situation at Nc=3. Further discussions on the extrapolation of
Nc are also given.
| arxiv topic:hep-ph |
arxiv_dataset-36111208.0528 | Families of contact 3-manifolds with arbitrarily large Stein fillings
math.GT math.SG
We show that there are vast families of contact 3-manifolds each member of
which admits infinitely many Stein fillings with arbitrarily big euler
characteristics and arbitrarily small signatures ---which disproves a
conjecture of Stipsicz and Ozbagci. To produce our examples, we set a framework
which generalizes the construction of Stein structures on allowable Lefschetz
fibrations over the 2-disk to those over any orientable base surface, along
with the construction of contact structures via open books on 3-manifolds to
spinal open books introduced in [24].
| arxiv topic:math.GT math.SG |
arxiv_dataset-36121208.0628 | Ancestral Inference from Functional Data: Statistical Methods and
Numerical Examples
stat.ML q-bio.PE q-bio.QM
Many biological characteristics of evolutionary interest are not scalar
variables but continuous functions. Here we use phylogenetic Gaussian process
regression to model the evolution of simulated function-valued traits. Given
function-valued data only from the tips of an evolutionary tree and utilising
independent principal component analysis (IPCA) as a method for dimension
reduction, we construct distributional estimates of ancestral function-valued
traits, and estimate parameters describing their evolutionary dynamics.
| arxiv topic:stat.ML q-bio.PE q-bio.QM |
arxiv_dataset-36131208.0728 | The effect of frame dragging on the iron K alpha line in X-ray binaries
astro-ph.HE
The clear characteristic timescale picked out by the low frequency
quasi-periodic oscillations (QPOs) seen in many black hole and neutron star
binaries has the potential to provide a very powerful diagnostic of the inner
regions of the accretion flow. However, this potential cannot be realised
without a quantitative model for the QPO. We have recently shown that the same
truncated disc/hot inner flow geometry which is used to interpret the spectral
transitions can also directly produce the QPO from Lense-Thirring (vertical)
precession of the hot inner flow. This correctly predicts both the frequency
and spectrum of the QPO, and the tight correlation of these properties with the
total spectrum of the source via a changing truncation radius between the disc
and hot flow. This model predicts a unique iron line signature as a vertically
tilted flow illuminates different azimuths of the disc as it precesses. The
iron line arising from this rotating illumination is blue shifted when the flow
irradiates the approaching region of the spinning disc and red shifted when the
flow irradiates the receding region of the disc. This gives rise to a
characteristic rocking of the iron line on the QPO frequency which is a
necessary (and probably sufficient) test of a Lense-Thirring origin. This is
also an independent test of disc truncation models for the low/hard state, as
vertical precession cannot occur if there is a disc in the midplane.
We show that it may be possible to observe this effect using archival data
from the Rossi X-ray timing explorer (RXTE) or XMM Newton. However, a clean
test requires a combination of moderate resolution and good statistics, such as
would be available from a long XMM-Newton observation or with data from the
proposed ESA mission LOFT.
| arxiv topic:astro-ph.HE |
arxiv_dataset-36141208.0828 | Are Lines From Unassociated Gamma-Ray Sources Evidence For Dark Matter
Annihilation?
astro-ph.HE astro-ph.GA hep-ph
Very recently, it was pointed out that there exists a population of gamma-ray
sources without associations at other wavelengths which exhibit spectral
features consistent with mono-energetic lines at energies of approximately 111
and 129 GeV. Given recent evidence of similar gamma-ray lines from the Inner
Galaxy, it is tempting to interpret these unassociated sources as nearby dark
matter subhalos, powered by ongoing annihilations. In this paper, we study the
spectrum, luminosity, and angular distribution of these sources, with the
intention of testing the hypothesis that they are, in fact, dark matter
subhalos. We find that of the 12 sources containing at least one prospective
line photon, only 2 exhibit an overall gamma-ray spectrum which is consistent
with that predicted from dark matter annihilations (2FGL J2351.6-7558 and 2FGL
J0555.9-4348). After discounting the 10 clearly non-dark matter sources, the
statistical significance of the remaining two prospective line photons is
negligible. That being said, we cannot rule out the possibility that either or
both of these sources are dark matter subhalos; their overall luminosity and
galactic latitude distribution are not inconsistent with a dark matter origin.
| arxiv topic:astro-ph.HE astro-ph.GA hep-ph |
arxiv_dataset-36151208.0928 | Surface codes: Towards practical large-scale quantum computation
quant-ph
This article provides an introduction to surface code quantum computing. We
first estimate the size and speed of a surface code quantum computer. We then
introduce the concept of the stabilizer, using two qubits, and extend this
concept to stabilizers acting on a two-dimensional array of physical qubits, on
which we implement the surface code. We next describe how logical qubits are
formed in the surface code array and give numerical estimates of their
fault-tolerance. We outline how logical qubits are physically moved on the
array, how qubit braid transformations are constructed, and how a braid between
two logical qubits is equivalent to a controlled-NOT. We then describe the
single-qubit Hadamard, S and T operators, completing the set of required gates
for a universal quantum computer. We conclude by briefly discussing physical
implementations of the surface code. We include a number of appendices in which
we provide supplementary information to the main text.
| arxiv topic:quant-ph |
arxiv_dataset-36161208.1028 | Progress in the mathematical theory of quantum disordered systems
math-ph math.MP quant-ph
We review recent progress in the mathematical theory of quantum disordered
systems: the Anderson transition (joint work with Domingos Marchetti), the
(quantum and classical) Edwards-Anderson (EA) spin glass model and return to
equilibrium for a class of spin glass models, which includes the EA model
initially in a very large transverse magnetic field.
| arxiv topic:math-ph math.MP quant-ph |
arxiv_dataset-36171208.1128 | Coupling of magnetic and ferroelectric hysteresis by a multi-component
magnetic structure in Mn2GeO4
cond-mat.mtrl-sci cond-mat.other
The olivine compound Mn2GeO4 is shown to feature both a ferroelectric
polarization and a ferromagnetic magnetization that are directly coupled and
point along the same direction. We show that a spin spiral generates
ferroelectricity (FE), and a canted commensurate order leads to weak
ferromagnetism (FM). Symmetry suggests that the direct coupling between the FM
and FE is mediated by Dzyaloshinskii-Moriya interactions that exist only in the
ferroelectric phase, controlling both the sense of the spiral rotation and the
canting of the commensurate structure. Our study demonstrates how
multi-component magnetic structures found in magnetically-frustrated materials
like Mn2GeO4 provide a new route towards functional materials that exhibit
coupled FM and FE.
| arxiv topic:cond-mat.mtrl-sci cond-mat.other |
arxiv_dataset-36181208.1228 | Two Millisecond Pulsars Discovered by the PALFA Survey and a Shapiro
Delay Measurement
astro-ph.SR
We present two millisecond pulsar discoveries from the PALFA survey of the
Galactic plane with the Arecibo telescope. PSR J1955+2527 is an isolated pulsar
with a period of 4.87 ms, and PSR J1949+3106 has a period of 13.14 ms and is in
a 1.9-day binary system with a massive companion. Their timing solutions, based
on 4 years of timing measurements with the Arecibo, Green Bank, Nan\c{c}ay and
Jodrell Bank telescopes, allow precise determination of spin and astrometric
parameters, including precise determinations of their proper motions. For PSR
J1949+3106, we can clearly detect the Shapiro delay. From this we measure the
pulsar mass to be 1.47(+0.43/-0.31) solar masses, the companion mass to be
0.85(+0.14/-0.11) solar masses and the orbital inclination to be i =
79.9(+1.6/-1.9) degrees, where uncertainties correspond to +/- 1-\sigma\
confidence levels. With continued timing, we expect to also be able to detect
the advance of periastron for the J1949+3106 system. This effect, combined with
the Shapiro delay, will eventually provide very precise mass measurements for
this system and a test of general relativity.
| arxiv topic:astro-ph.SR |
arxiv_dataset-36191208.1328 | Structure and rotations of the Hoyle state
nucl-th astro-ph.SR hep-lat nucl-ex
The excited state of the 12C nucleus known as the "Hoyle state" constitutes
one of the most interesting, difficult and timely challenges in nuclear
physics, as it plays a key role in the production of carbon via fusion of three
alpha particles in red giant stars. In this letter, we present ab initio
lattice calculations which unravel the structure of the Hoyle state, along with
evidence for a low-lying spin-2 rotational excitation. For the 12C ground state
and the first excited spin-2 state, we find a compact triangular configuration
of alpha clusters. For the Hoyle state and the second excited spin-2 state, we
find a "bent-arm" or obtuse triangular configuration of alpha clusters. We also
calculate the electromagnetic transition rates between the low-lying states of
12C.
| arxiv topic:nucl-th astro-ph.SR hep-lat nucl-ex |
arxiv_dataset-36201208.1428 | Perturbative algebraic quantum field theory
math-ph hep-th math.MP
These notes are based on the course given by Klaus Fredenhagen at the Les
Houches Winter School in Mathematical Physics (January 29 - February 3, 2012)
and the course "QFT for mathematicians" given by Katarzyna Rejzner in Hamburg
for the Research Training Group 1670 (February 6 -11, 2012). Both courses were
meant as an introduction to modern approach to perturbative quantum field
theory and are aimed both at mathematicians and physicists.
| arxiv topic:math-ph hep-th math.MP |
arxiv_dataset-36211208.1528 | The Inherent Structure Landscape Connection Between Liquids, Granular
materials and the Jamming Phase Diagram
cond-mat.soft cond-mat.stat-mech
We provide a comprehensive picture of the jamming phase diagram by connecting
the athermal, granular ensemble of jammed states and the equilibrium fluid
through the inherent structure paradigm for a system hard discs confined to a
narrow channel. The J-line is shown to be divided into packings that are
thermodynamically accessible from the equilibrium fluid and inaccessible
packings. The J-point is found to occur at the transition between these two
sets of packings and is located at the maximum the inherent structure
distribution. A general thermodynamic argument suggests that the density of the
states at the configurational entropy maximum represents a lower bound on the
J-point density in hard sphere systems. Finally, we find that the granular and
fluid systems only occupy the same set of inherent structures, under the same
thermodynamic conditions, at two points, corresponding to zero and infinite
pressures, where they sample the J-point states and the most dense packing
respectively.
| arxiv topic:cond-mat.soft cond-mat.stat-mech |
arxiv_dataset-36221208.1628 | Investigation of smooth wave fronts using SLM-based phase retrieval and
a phase diffuser
physics.optics
A phase retrieval technique using a spatial light modulator (SLM) and a phase
diffuser for a fast reconstruction of smooth wave fronts is demonstrated
experimentally. Diffuse illumination of a smooth test object with the aid of a
phase diffuser (maximum phase shift, Df = 0.85p) results in a significant
diversity in the intensity measurements which, in turn, is beneficial for a
non-stagnating iterative phase reconstruction. The use of the SLM enables
accurate and fast speckle intensity recording and active correction of
misalignments in the setup. The effectiveness of the technique is demonstrated
in the optical testing of lenses.
| arxiv topic:physics.optics |
arxiv_dataset-36231208.1728 | Statistical Analysis of Autoregressive Fractionally Integrated Moving
Average Models
stat.CO stat.AP stat.ME
In practice, several time series exhibit long-range dependence or persistence
in their observations, leading to the development of a number of estimation and
prediction methodologies to account for the slowly decaying autocorrelations.
The autoregressive fractionally integrated moving average (ARFIMA) process is
one of the best-known classes of long-memory models. In the package afmtools
for R, we have implemented some of these statistical tools for analyzing ARFIMA
models. In particular, this package contains functions for parameter
estimation, exact autocovariance calculation, predictive ability testing, and
impulse response function, amongst others. Finally, the implemented methods are
illustrated with applications to real-life time series.
| arxiv topic:stat.CO stat.AP stat.ME |
arxiv_dataset-36241208.1828 | Tunable metal-insulator transitions in bilayer graphene by thermal
annealing
cond-mat.mtrl-sci cond-mat.mes-hall
Tunable and highly reproducible metal-insulator transitions have been
observed in bilayer graphene upon thermal annealing at 400 K under high vacuum
conditions. Before annealing, the sample is metallic in the whole temperature
regime of study. Upon annealing, the conductivity changes from metallic to that
of an insulator and the transition temperature is a function of annealing time.
The pristine metallic state can be reinstated by exposing to air thereby
inducing changes in the electronic properties by adsorbing water vapor, which
makes graphene a technologically promising material for sensor applications.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-36251208.1928 | Simulation of quantum zero-point effects in water using a
frequency-dependent thermostat
cond-mat.stat-mech cond-mat.mtrl-sci cond-mat.soft physics.chem-ph physics.comp-ph
Molecules like water have vibrational modes with a zero-point energy well
above room temperature. As a consequence, classical molecular dynamics
simulations of their liquids largely underestimate the energy of modes with a
higher zero-point temperature, which translates into an underestimation of
covalent interatomic distances due to anharmonic effects. Zero-point effects
can be recovered using path integral molecular dynamics simulations, but these
are computationally expensive, making their combination with ab initio
molecular dynamics simulations a challenge. As an alternative to path integral
methods, from a computationally simple perspective, one would envision the
design of a thermostat capable of equilibrating and maintaining the different
vibrational modes at their corresponding zero-point temperatures. Recently,
Ceriotti et al. (Phys. Rev. Lett. 102 020601 (2009)) introduced a framework to
use a custom-tailored Langevin equation with correlated noise that can be used
to include quantum fluctuations in classical molecular dynamics simulations.
Here we show that it is possible to use the generalized Langevin equation with
suppressed noise in combination with Nose-Hoover thermostats to efficiently
impose a zero-point temperature on independent modes in liquid water. Using our
simple and inexpensive method, we achieve excellent agreement for all atomic
pair correlation functions compared to the path integral molecular dynamics
simulation.
| arxiv topic:cond-mat.stat-mech cond-mat.mtrl-sci cond-mat.soft physics.chem-ph physics.comp-ph |
arxiv_dataset-36261208.2028 | Cosmic bulk flows on 50 {h}^{-1}Mpc scales: A Bayesian hyper-parameter
method and multishells likelihood analysis
astro-ph.CO
It has been argued recently that the galaxy peculiar velocity field provides
evidence of excessive power on scales of $50\hmpc$, which seems to be
inconsistent with the standard $\Lambda$CDM cosmological model. We discuss
several assumptions and conventions used in studies of the large-scale bulk
flow to check whether this claim is robust under a variety of conditions.
Rather than using a composite catalogue we select samples from the SN, ENEAR,
SFI++ and A1SN catalogues, and correct for Malmquist bias in each according to
the IRAS PSCz density field. We also use slightly different assumptions about
the small-scale velocity dispersion and the parameterisation of the matter
power spectrum when calculating the variance of the bulk flow. By combining the
likelihood of individual catalogues using a Bayesian hyper-parameter method, we
find that the joint likelihood of the amplitude parameter gives
$\sigma_8=0.65^{+0.47}_{-0.35}(\pm 1 \sigma)$, which is entirely consistent
with the $\Lambda$CDM model. In addition, the bulk flow magnitude ($v \sim 310
\kms$) and direction, $(l,b)\sim (280^{\circ} \pm 8^{\circ}, 5.1^{\circ} \pm
6^{\circ})$, found by each of the catalogues are all consistent with each
other, and with the bulk flow results from most previous studies. Furthermore,
the bulk flow velocities in different shells of the surveys constrain
$\sigma_{8}$--$\Omega_{\rm{m}}$ to be
($1.01^{+0.26}_{-0.20},0.31^{+0.28}_{-0.14}$, SFI++) and
($1.04^{+0.32}_{-0.24},0.28^{+0.30}_{-0.14}$, ENEAR), which is consistent with
{\it WMAP} 7-year best-fit values. We finally discuss the differences between
our conclusions and those of the studies claiming the largest bulk flows.
| arxiv topic:astro-ph.CO |
arxiv_dataset-36271208.2128 | Brain tumor MRI image classification with feature selection and
extraction using linear discriminant analysis
cs.CV cs.LG
Feature extraction is a method of capturing visual content of an image. The
feature extraction is the process to represent raw image in its reduced form to
facilitate decision making such as pattern classification. We have tried to
address the problem of classification MRI brain images by creating a robust and
more accurate classifier which can act as an expert assistant to medical
practitioners. The objective of this paper is to present a novel method of
feature selection and extraction. This approach combines the Intensity,
Texture, shape based features and classifies the tumor as white matter, Gray
matter, CSF, abnormal and normal area. The experiment is performed on 140 tumor
contained brain MR images from the Internet Brain Segmentation Repository. The
proposed technique has been carried out over a larger database as compare to
any previous work and is more robust and effective. PCA and Linear Discriminant
Analysis (LDA) were applied on the training sets. The Support Vector Machine
(SVM) classifier served as a comparison of nonlinear techniques Vs linear ones.
PCA and LDA methods are used to reduce the number of features used. The feature
selection using the proposed technique is more beneficial as it analyses the
data according to grouping class variable and gives reduced feature set with
high classification accuracy.
| arxiv topic:cs.CV cs.LG |
arxiv_dataset-36281208.2228 | Bohr-Sommerfeld Quantization of Space
gr-qc math-ph math.MP
We introduce semiclassical methods into the study of the volume spectrum in
loop gravity. The classical system behind a 4-valent spinnetwork node is a
Euclidean tetrahedron. We investigate the tetrahedral volume dynamics on phase
space and apply Bohr-Sommerfeld quantization to find the volume spectrum. The
analysis shows a remarkable quantitative agreement with the volume spectrum
computed in loop gravity. Moreover, it provides new geometrical insights into
the degeneracy of this spectrum and the maximum and minimum eigenvalues of the
volume on intertwiner space.
| arxiv topic:gr-qc math-ph math.MP |
arxiv_dataset-36291208.2328 | Suppression of backward scattering of Dirac fermions in iron pnictides
Ba(Fe$_{1-x}$Ru$_x$As)$_2$
cond-mat.supr-con cond-mat.str-el
We report electronic transport of Dirac cones when Fe is replaced by Ru,
which has an isoelectronic electron configuration to Fe, using single crystals
of Ba(Fe$_{1-x}$Ru$_x$As)$_2$. The electronic transport of parabolic bands is
shown to be suppressed by scattering due to the crystal lattice distortion and
the impurity effect of Ru, while that of the Dirac cone is not significantly
reduced due to the intrinsic character of Dirac cones. It is clearly shown from
magnetoresistance and Hall coefficient measurements that the inverse of average
mobility, proportional to cyclotron effective mass, develops as the square root
of the carrier number (n) of the Dirac cones. This is the unique character of
the Dirac cone linear dispersion relationship. Scattering of Ru on the Dirac
cones is discussed in terms of the estimated mean free path using experimental
parameters.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-36301208.2428 | Accelerating cellular automata simulations using AVX and CUDA
cs.DC physics.comp-ph physics.flu-dyn
We investigated various methods of parallelization of the
Frish-Hasslacher-Pomeau (FHP) cellular automata algorithm for modeling fluid
flow. These methods include SSE, AVX, and POSIX Threads for central processing
units (CPUs) and CUDA for graphics processing units (GPUs). We present
implementation details of the FHP algorithm based on AVX/SSE and CUDA
technologies. We found that (a) using AVX or SSE is necessary to fully utilize
the potential of modern CPUs; (b) CPUs and GPUs are comparable in terms of
computational and economic efficiency only if the CPU code uses AVX or SSE
instructions; (c) AVX does not offer any substantial improvement relative to
SSE.
| arxiv topic:cs.DC physics.comp-ph physics.flu-dyn |
arxiv_dataset-36311208.2528 | A search for RCB stars in globular clusters
astro-ph.GA
There are only about 65 R Coronae Borealis stars known in our Galaxy, and
none in globular clusters. As these stars are thought to result from the merger
of two white dwarfs, one would expect the higher stellar density of globular
clusters to favor their formation. We have searched for such stars in Galactic
globular clusters, as their presence in a specific category of clusters might
provide more clues as to their formation. We selected from the WISE all-Sky
source catalog all the stars within the tidal radius of the 150 globular
clusters within 50 kpc, which is the distance to which RCB stars are detectable
by WISE. The total number of stars selected in this way was 635989. We then
successively applied the eight selection criteria of Tisserand (2012) satisfied
by RCB stars to the dereddened photometric WISE and 2MASS data. Only three
stars satisfying the conditions were found in the field of three globular
clusters. The star in the field of Liller 1 is most probably a protostar. For
the two other candidates, the absence of photometry in the visible range did
not allow us to establish their nature with certainty. We further identified
one dust-enshrouded star that only satisfied the first selection criteria, and
used DUSTY to determine that it is a star of temperature 4800K enshrouded in a
dusty envelope with a temperature 300 K and an opacity in the visible of 0.59.
It is probably an Xray binary star with a dusty accretion disk. We found no RCB
stars truly belonging to a globular cluster, thus providing a constraint on
their formation mechanism.
| arxiv topic:astro-ph.GA |
arxiv_dataset-36321208.2628 | The generalized second law of thermodynamics in f(R) gravity for various
choices of scale factor
physics.gen-ph gr-qc
The present study is aimed at investigating the validity of the generalized
second law (GSL) of thermodynamics in $f(\cal R)$ gravity. Choosing $f(\cal
R)=R+\xi R^{\mu}+\zeta R^{-\nu}$ [following Phys Rev D, 68, 123512 (2003)] we
have computed the time derivatives of total entropy for various choices of
scale factor pertaining to emergent, intermediate and logamediate scenarios of
the universe. We have taken into account the radii of hubble, apparent,
particle and event horizons while computing the time derivatives of entropy
under various situations being considered. After analyzing through the plots of
time derivative of total entropy against cosmic time it is observed that the
derivative always stays at positive level that indicate the validity of GSL of
thermodynamics in the $f(\cal R)$ gravity irrespective of the choices of scale
factor and enveloping horizon.
| arxiv topic:physics.gen-ph gr-qc |
arxiv_dataset-36331208.2728 | Dispersionless integrable systems in 3D and Einstein-Weyl geometry
math-ph math.DG math.MP nlin.SI
For several classes of second order dispersionless PDEs, we show that the
symbols of their formal linearizations define conformal structures which must
be Einstein-Weyl in 3D (or self-dual in 4D) if and only if the PDE is
integrable by the method of hydrodynamic reductions. This demonstrates that the
integrability of these dispersionless PDEs can be seen from the geometry of
their formal linearizations.
| arxiv topic:math-ph math.DG math.MP nlin.SI |
arxiv_dataset-36341208.2828 | Local approximation of superharmonic and superparabolic functions in
nonlinear potential theory
math.AP
We prove that arbitrary superharmonic functions and superparabolic functions
related to the $p$-Laplace and the $p$-parabolic equations are locally obtained
as limits of supersolutions with desired convergence properties of the
corresponding Riesz measures. As an application we show that a family of
uniformly bounded supersolutions to the $p$-parabolic equation contains a
subsequence that converges to a supersolution.
| arxiv topic:math.AP |
arxiv_dataset-36351208.2928 | Valence-band structure of ferromagnetic semiconductor (InGaMn)As
cond-mat.mtrl-sci
To clarify the whole picture of the valence-band structures of prototype
ferromagnetic semiconductors (III,Mn)As (III: In and Ga), we perform systematic
experiments of the resonant tunneling spectroscopy on [(In_0.53Ga_0.47)_1-x
Mn_x]As (x=0.06-0.15) and In_0.87Mn_0.13As grown on AlAs/ In_0.53Ga_0.47As:Be/
p+InP(001). We show that the valence band of InGaMnAs almost remains unchanged
from that of the host semiconductor InGaAs, that the Fermi level exists in the
band gap, and that the p-d exchange splitting in the valence band is negligibly
small in (InGaMn)As. In the In0.87Mn0.13As sample, although the resonant peaks
are very weak due to the large strain induced by the lattice mismatch between
InP and InMnAs, our results also indicate that the Fermi level exists in the
band gap and that the p-d exchange splitting in the valence band is negligibly
small. These results are quite similar to those of GaMnAs obtained by the same
method, meaning that there are no holes in the valence band, and that the
impurity-band holes dominate the transport and magnetism both in the InGaMnAs
and In_0.87Mn_0.13As films. This band picture of (III,Mn)As is remarkably
different from that of II-VI-based diluted magnetic semiconductors.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-36361208.3028 | Radiating Kerr-Newman black hole in $f(R)$ gravity
gr-qc
We derive an exact radiating Kerr-Newman like black hole solution, with
constant curvature $R=R_0$ imposed, to {\it metric} $f(R)$ gravity via complex
transformations suggested by Newman-Janis. This generates a geometry which is
precisely that of radiating Kerr-Newman-de Sitter / anti-de Sitter with the
$f(R)$ gravity contributing an $R_0$ cosmological-like term. The structure of
three horizon-like surfaces, {\it viz.} timelike limit surface, apparent
horizon and event horizon, are determined. We demonstrate the existence of an
additional cosmological horizon, in $f(R)$ gravity model, apart from the
regular black hole horizons that exist in the analogous general relativity
case. In particular, the known stationary Kerr-Newman black hole solutions of
$f(R)$ gravity and general relativity are retrieved. We find that the timelike
limit surface becomes less prolate with $R_0$ thereby affecting the shape of
the corresponding ergosphere.
| arxiv topic:gr-qc |
arxiv_dataset-36371208.3128 | Consistent explanations of tunneling and photoemission data in cuprate
superconductors: No evidence for magnetic pairing
cond-mat.supr-con
We have analyzed scanning tunneling spectra of two electron-doped cuprates
Pr0.88LaCe0.12CuO4 (Tc = 21 K and 24 K) and compared them with tunneling
spectrum of hole-doped La1.84Sr0.16CuO4 and effective electron-boson spectral
function of hole-doped La1.97Sr0.03CuO4 (extracted from angle-resolved
photoemission spectrum). We have also analyzed tunneling spectra and
angle-resolved photoemission spectra for hole-doped Bi2Sr2CaCu2O8. These
results unambiguously rule out magnetic pairing mechanism in both electron- and
hole-doped cuprates and support polaronic/bipolaronic superconductivity in
hole-doped Bi2Sr2CaCu2O8.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-36381208.3228 | Model of the Human Sleep Wake System
math.DS physics.bio-ph q-bio.NC
A model and analysis of the human sleep/wake system is presented. The model
is derived using the known neuronal groups, and their various projections,
involved with sleep and wake. Inherent in the derivation is the existence of a
slow time scale associated with homeostatic regulation, and a faster time scale
associated with the dynamics within the sleep phase. A significant feature of
the model is that it does not contain a periodic forcing term, common in other
models, reflecting the fact that sleep/wake is not dependent upon a diurnal
stimulus. Once derived, the model is analyzed using a linearized stability
analysis. We then use experimental data from normal sleep-wake systems and
orexin knockout systems to verify the physiological validity of the equations.
| arxiv topic:math.DS physics.bio-ph q-bio.NC |
arxiv_dataset-36391208.3328 | Asymptotics of Maxwell time in the plate-ball problem
math.OC
The problem on rolling of a sphere on a plane without slipping or twisting is
considered. One should roll the sphere from one contact configuration to
another so that the length of the curve traced by the contact point in the
plane was the shortest possible. Asymptotics of Maxwell time for rolling of the
sphere along small amplitude sinusoids is studied. Two-sided estimate for this
asymptotics is obtained.
| arxiv topic:math.OC |
arxiv_dataset-36401208.3428 | Comparative Bi-stochastizations and Associated
Clusterings/Regionalizations of the 1995-2000 U. S. Intercounty Migration
Network
cs.SI physics.soc-ph stat.AP
Wang, Li and Konig have recently compared the cluster-theoretic properties of
bi-stochasticized symmetric data similarity (e. g. kernel) matrices, produced
by minimizing two different forms of Bregman divergences. We extend their
investigation to non-symmetric matrices, specifically studying the 1995-2000 U.
S. 3,107 x 3,107 intercounty migration matrix. A particular bi-stochastized
form of it had been obtained (arXiv:1207.0437), using the well-established
Sinkhorn-Knopp (SK) (biproportional) algorithm--which minimizes the
Kullback-Leibler form of the divergence. This matrix has but a single entry
equal to (the maximal possible value of) 1. Highly contrastingly, the
bi-stochastic matrix obtained here, implementing the Wang-Li-Konig-algorithm
for the minimum of the alternative, squared-norm form of the divergence, has
2,707 such unit entries. The corresponding 3,107-vertex, 2,707-link directed
graph has 2,352 strong components. These consist of 1,659 single/isolated
counties, 654 doublets (thirty-one interstate in nature), 22 triplets (one
being interstate), 13 quartets (one being interstate), three quintets and one
septet. Not manifest in these graph-theoretic results, however, are the
five-county states of Hawaii and Rhode Island and the eight-county state of
Connecticut. These--among other regional configurations--appealingly emerged as
well-defined entities in the SK-based strong-component hierarchical clustering.
| arxiv topic:cs.SI physics.soc-ph stat.AP |
arxiv_dataset-36411208.3528 | Highly-charged ions as a basis of optical atomic clockwork of
exceptional accuracy
physics.atom-ph physics.optics quant-ph
We propose a novel class of atomic clocks based on highly charged ions. We
consider highly-forbidden laser-accessible transitions within the $4f^{12}$
ground-state configurations of highly charged ions. Our evaluation of
systematic effects demonstrates that these transitions may be used for building
exceptionally accurate atomic clocks which may compete in accuracy with
recently proposed nuclear clock.
| arxiv topic:physics.atom-ph physics.optics quant-ph |
arxiv_dataset-36421208.3628 | Studying Neutrino Directionality with Double Chooz
physics.ins-det hep-ex
The first results from Double Chooz with 100 days of data measured
$\sin^2(2\theta_{13}) = 0.086 \pm 0.051$. Backgrounds contribute significantly
to the systematic uncertainty budget. Using the incoming neutrino
directionality we will attempt to further separate the inverse beta decay
signal from backgrounds. The CHOOZ experiment completed a similar analysis and
found that the neutrino source can be located to within a cone of half-aperture
of 18 degrees at the 68% C.L. We study the possible improvement of this result
by Double Chooz.
| arxiv topic:physics.ins-det hep-ex |
arxiv_dataset-36431208.3728 | Online Learning with Predictable Sequences
stat.ML cs.LG
We present methods for online linear optimization that take advantage of
benign (as opposed to worst-case) sequences. Specifically if the sequence
encountered by the learner is described well by a known "predictable process",
the algorithms presented enjoy tighter bounds as compared to the typical worst
case bounds. Additionally, the methods achieve the usual worst-case regret
bounds if the sequence is not benign. Our approach can be seen as a way of
adding prior knowledge about the sequence within the paradigm of online
learning. The setting is shown to encompass partial and side information.
Variance and path-length bounds can be seen as particular examples of online
learning with simple predictable sequences.
We further extend our methods and results to include competing with a set of
possible predictable processes (models), that is "learning" the predictable
process itself concurrently with using it to obtain better regret guarantees.
We show that such model selection is possible under various assumptions on the
available feedback. Our results suggest a promising direction of further
research with potential applications to stock market and time series
prediction.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-36441208.3828 | The Big Trip and Wheeler-DeWitt equation
gr-qc
Of all the possible ways to describe the behavior of the universe that has
undergone a big trip the Wheeler-DeWitt equation should be the most accurate --
provided, of course, that we employ the correct formulation. In this article we
start by discussing the standard formulation introduced by Gonz\'alez-D\'iaz
and Jimenez-Madrid, and show that it allows for a simple yet efficient method
of the solution's generation, which is based on the Moutard transformation.
Next, by shedding the unnecessary restrictions, imposed on aforementioned
standard formulation we introduce a more general form of the Wheeler-DeWitt
equation. One immediate prediction of this new formula is that for the universe
the probability to emerge right after the big trip in a state with $w=w_0$ will
be maximal if and only if $w_0=-1/3$.
| arxiv topic:gr-qc |
arxiv_dataset-36451208.3928 | Time-reversal anomaly and Josephson effect in time-reversal invariant
topological superconductors
cond-mat.supr-con
Topological superconductors are gapped superconductors with protected
Majorana surface/edge states on the boundary. In this paper, we study the
Josephson coupling between time-reversal invariant topological superconductors
and s-wave superconductors. The Majorana edge/surface states of time-reversal
invariant topological superconductors in all physical dimensions 1, 2, 3 have a
generic topological property which we named as time-reversal anomaly. Due to
the time-reversal anomaly, the Josephson coupling prefers a nonzero phase
difference between topological and trivial superconductors. The nontrivial
Josesphon coupling leads to a current-flux relation with a half period in a
SQUID geometry, and also a half period Fraunhofer effect in dimension higher
than one. We also show that an in-plane magnetic field restores the ordinary
Josephson coupling, as a sharp signature that the proposed effect is a
consequence of the unique time-reversal property of the topological
edge/surface states. Our proposal provides a general approach to experimentally
verify whether a superconductor is topological or not.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-36461208.4028 | Quantum Gravity effect on the Quark-Gluon Plasma
hep-ph hep-th quant-ph
The Generalized Uncertainty Principle (GUP), which has been predicted by
various theories of quantum gravity near the Planck scale is implemented on
deriving the thermodynamics of ideal Quark-Gluon Plasma (QGP) consisting of two
massless quark flavors at the hadron-QGP phase equilibrium and at a vanishing
chemical potential. The effective degrees of freedom and MIT bag pressure are
utilized to distinguish between the hadronic and partonic phases. We find that
GUP makes a non-negligible contribution to all thermodynamic quantities,
especially at high temperatures. The asymptotic behavior of corresponding QGP
thermodynamic quantities characterized by the Stephan-Boltzmann limit would be
approached, when the GUP approach is taken into consideration.
| arxiv topic:hep-ph hep-th quant-ph |
arxiv_dataset-36471208.4128 | Appendix A: Adequacy of representations of finite groups of Lie type
math.GR math.NT
Thorne introduced the notion of adequate representations as a weakening of
the big representations used by Wiles and Taylor and others. In this appendix
to Dieulefait's paper, Automorphy of Symm5(GL(2)) and base change, we show that
certain representations of SL(2,q) are adequate. This is used by Dieulefait to
prove results about Hecke eigenforms of level 1 and newforms. We also prove
some general results about adequacy for representations of finite groups of Lie
type in the natural characteristic.
| arxiv topic:math.GR math.NT |
arxiv_dataset-36481208.4228 | Electronics and Optics of Graphene Nanoflakes: Edge Functionalization
and Structural Distortions
cond-mat.mes-hall
The effects of edge covalent functionalization on the structural, electronic
and optical properties of elongated armchair graphene nanoflakes (AGNFs) are
analyzed in detail for a wide range of terminations, within the ramework of
Hartree-Fock-based semi-empirical methods. The chemical features of the
functional groups, their distribution and the resulting system symmetry are
identified as the key factors that determine the modification of structural and
optoelectronic features. While the electronic gap is always reduced in presence
of substituents, functionalization-induced distortions contribute to the
observed lowering by about 35-55%. This effect is paired with a red shift of
the first optical peak, corresponding to about 75% of the total optical gap
reduction. Further, the functionalization pattern and the specific features of
the edge-substituent bond are found to influence the strength and the character
of the low energy excitations. All these effects are discussed for flakes of
different width, representing the three families of AGNFs.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-36491208.4328 | Collapsing topology of isolated singularities
math.MG math.AG math.LO
We proof here the existence of a topological thick and thin decomposition of
any closed definable thick isolated singularity germ in the spirit of the
recently discovered metric thick and thin decomposition of complex normal
surface singularities of [10]. Our thin zone catches exactly the homology of
the family of the links collapsing faster than linearly. Simultaneously we
introduce a class of rigid homeomorphisms more general than bi-Lipschitz ones,
which map the topological thin zone onto the topological thin zone of its
image. As a consequence of this point of view for the class of singularities we
consider we exhibit an equivalent description of the notion of separating sets
in terms of this fast contracting homology
| arxiv topic:math.MG math.AG math.LO |
arxiv_dataset-36501208.4428 | A Rellich Type Theorem for Discrete Schr{\"o}dinger Operators
math.SP
An analogue of Rellich's theorem is proved for discrete Laplacian on square
lattice, and applied to show unique continuation property on certain domains as
well as non-existence of embedded eigenvalues for discrete Schr{\"o}dinger
operators.
| arxiv topic:math.SP |
arxiv_dataset-36511208.4528 | On Dynamical Cournot Game on a Graph
cs.GT
Cournot dynamical game is studied on a graph. The stability of the system is
studied. Prisoner's dilemma game is used to model natural gas transmission.
| arxiv topic:cs.GT |
arxiv_dataset-36521208.4628 | The Ordering Ambiguity
quant-ph
The kinetic energy operator of a quantum particle with position dependent
mass and the associated ordering ambiguity is revisited. We introduce a new
form of this operator which is a continues or discreet superposition of the
acceptable values for the ordering parameters.
| arxiv topic:quant-ph |
arxiv_dataset-36531208.4728 | Non-destructive testing of carbon reinforced plastics by means of phase
retrieval
physics.optics
In this work, the SLM-based phase retrieval system will be used to inspect
carbon reinforced plastics samples (CFRP) under applying a thermal load. For
this purpose, the system is used to capture a sequence of 8 spatially separated
recording planes, where the distance between subsequent planes equals 2 mm. For
detecting the hidden failures two sets of intensity observations are recorded.
The first set for the initial state and the second set is captured after
applying the load. To recover the phase information associated with the two
states, the captured intensities have been subjected to an iterative algorithm
based on the method of generalized projection.
| arxiv topic:physics.optics |
arxiv_dataset-36541208.4828 | A coherent and passive one dimensional quantum memory
quant-ph cond-mat.mes-hall
We show that the state of a flying qubit may be transferred to a chain of
identical, (near) ferromagnetically polarised, but non-interacting, static
spin-1/2 particles in a passive way. During this process the flying qubit is
coherently polarised, emerging in the direction of the majority static spins.
We also show that this process is reversible for at least two flying qubits
injected sequentially and thus has the potential to be exploited as a passive
quantum memory to encode the flying qubits without the necessity of resetting
between successive encoding operations. We show that the quantum information
may be spread over many static spins in the memory chain, making the mechanism
resistent to spin decoherence and other imperfections. Among some potential
architectures, we discuss implementing the memory in a photonic waveguide
embedded with quantum dots, which is resilient to various possible errors.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-36551208.4928 | Boundary regularity criteria for suitable weak solutions of the
magnetohydrodynamic equations
math.AP
We present some new regularity criteria for suitable weak solutions of
magnetohydrodynamic equations near boundary in dimension three. We prove that
suitable weak solutions are H\"older continuous near boundary provided that
either the scaled $L^{p,q}_{x,t}$-norm of the velocity with $3/p+2/q\le 2$,
$2<q<\infty$, or the scaled $L^{p,q}_{x,t}$-norm of the vorticity with
$3/p+2/q\le 3$, $2<q<\infty$ are sufficiently small near the boundary.
| arxiv topic:math.AP |
arxiv_dataset-36561208.5028 | A 1D microphysical cloud model for Earth, and Earth-like exoplanets.
Liquid water and water ice clouds in the convective troposphere
astro-ph.EP physics.ao-ph
One significant difference between the atmospheres of stars and exoplanets is
the presence of condensed particles (clouds or hazes) in the atmosphere of the
latter.
The main goal of this paper is to develop a self-consistent microphysical
cloud model for 1D atmospheric codes, which can reproduce some observed
properties of Earth, such as the average albedo, surface temperature, and
global energy budget. The cloud model is designed to be computationally
efficient, simple to implement, and applicable for a wide range of atmospheric
parameters for planets in the habitable zone.
We use a 1D, cloud-free, radiative-convective, and photochemical equilibrium
code originally developed by Kasting, Pavlov, Segura, and collaborators as
basis for our cloudy atmosphere model. The cloud model is based on models used
by the meteorology community for Earth's clouds. The free parameters of the
model are the relative humidity and number density of condensation nuclei, and
the precipitation efficiency. In a 1D model, the cloud coverage cannot be
self-consistently determined, thus we treat it as a free parameter.
We apply this model to Earth (aerosol number density 100 cm^-3, relative
humidity 77 %, liquid cloud fraction 40 %, and ice cloud fraction 25 %) and
find that a precipitation efficiency of 0.8 is needed to reproduce the albedo,
average surface temperature and global energy budget of Earth. We perform
simulations to determine how the albedo and the climate of a planet is
influenced by the free parameters of the cloud model. We find that the
planetary climate is most sensitive to changes in the liquid water cloud
fraction and precipitation efficiency.
The advantage of our cloud model is that the cloud height and the droplet
sizes are self-consistently calculated, both of which influence the climate and
albedo of exoplanets.
| arxiv topic:astro-ph.EP physics.ao-ph |
arxiv_dataset-36571208.5128 | Three-dimensional topological lattice models with surface anyons
cond-mat.str-el
We study a class of three dimensional exactly solvable models of topological
matter first put forward by Walker and Wang [arXiv:1104.2632v2]. While these
are not models of interacting fermions, they may well capture the topological
behavior of some strongly correlated systems. In this work we give a full
pedagogical treatment of a special simple case of these models, which we call
the 3D semion model: We calculate its ground state degeneracies for a variety
of boundary conditions, and classify its low-lying excitations. While point
defects in the bulk are confined in pairs connected by energetic strings, the
surface excitations are more interesting: the model has deconfined point
defects pinned to the boundary of the lattice, and these exhibit semionic
braiding statistics. The surface physics is reminiscent of a $\nu=1/2$ bosonic
fractional quantum Hall effect in its topological limit, and these
considerations help motivate an effective field theoretic description for the
lattice models as variants of $bF$ theories. Our special example of the 3D
semion model captures much of the behavior of more general `confined
Walker-Wang models'. We contrast the 3D semion model with the closely related
3D version of the toric code (a lattice gauge theory) which has deconfined
point excitations in the bulk and we discuss how more general models may have
some confined and some deconfined excitations. Having seen that there exist
lattice models whose surfaces have the same topological order as a bosonic
fractional quantum Hall effect on a confining bulk, we construct a lattice
model whose surface has similar topological order to a fermionic quantum hall
effect. We find that in these models a fermion is always deconfined in the
three dimensional bulk.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-36581208.5228 | Existence and uniqueness for Mean Field Equations on multiply connected
domains at the critical parameter
math.AP
We consider the mean field equation: (1) \Delta u+\rho\frac{e^u}{\int_\Omega
e^u}=0 & \hbox{in} \;\Omega, u=0 & \hbox{on}\;\partial\Omega, where
$\Omega\subset \mathbb{R}^2$ is an open and bounded domain of class $C^1$. In
his 1992 paper, Suzuki proved that if $\Omega$ is a simply-connected domain,
then equation (1) admits a unique solution for $\rho\in[0,8\pi)$. This result
for $\Omega$ a simply-connected domain has been extended to the case
$\rho=8\pi$ by Chang, Chen and the second author. However, the uniqueness
result for $\Omega$ a multiply-connected domain has remained a long standing
open problem which we solve positively here for $\rho\in[0,8\pi]$. To obtain
this result we need a new version of the classical Bol's inequality suitable to
be applied on multiply-connected domains.
Our second main concern is the existence of solutions for (1) when
$\rho=8\pi$. We a obtain necessary and sufficient condition for the solvability
of the mean field equation at $\rho=8\pi$ which is expressed in terms of the
Robin's function $\gamma$ for $\Omega$. For example, if equation (1) has no
solution at $\rho=8\pi$, then $\gamma$ has a unique nondegenerate maximum
point. As a by product of our results we solve the long-standing open problem
of the equivalence of canonical and microcanonical ensembles in the Onsager's
statistical description of two-dimensional turbulence on multiply-connected
domains.
| arxiv topic:math.AP |
arxiv_dataset-36591208.5328 | The Higgs boson mass in a natural MSSM with nonuniversal gaugino masses
at the GUT scale
hep-ph
We identify a parameter region where the mass of the lightest CP-even Higgs
boson resides in $124.4-126.8$ GeV, and at the same time the degree of tuning a
Higgsino-mass parameter (so-called $\mu$-parameter) is relaxed above 10% in the
minimal supersymmetric standard model (MSSM) with soft supersymmetry breaking
terms, by solving the full set of one-loop renormalization group equations
numerically. It is found that certain nonuniversal values of gaugino-mass
parameters at the so-called grand unification theory (GUT) scale $\sim 10^{16}$
GeV are important ingredients for the MSSM to predict, without a severe
fine-tuning, the Higgs boson mass $\sim 125$ GeV indicated by recent
observations at the Large Hadron Collider. We also show a typical superparticle
spectrum in this parameter region.
| arxiv topic:hep-ph |
arxiv_dataset-36601208.5428 | Disentangling effects of collision geometry and symmetry energy in U+U
collisions
nucl-th nucl-ex
Effects of the collision geometry on experimental observables that are known
to be sensitive to the high-density behavior of nuclear symmetry energy are
examined in U+U collisions at 0.52 GeV/nucleon using an isospin- and
momentum-dependent interaction within the framework of IBUU transport model. It
is found that the neutron-proton differential flow in tip-tip collisions and
the difference of neutron and proton elliptic flow in body-body collisions are
more sensitive to the symmetry energy at supra-saturation densities compared
with collisions of spherical nuclei of the same masses. In addition, the n/p
ratio of pre-equilibrium nucleons is found to be slightly more sensitive to the
symmetry energy in tip-tip collisions, and the collision geometry affects the
\pi^-/\pi^+ ratio significantly.
| arxiv topic:nucl-th nucl-ex |
arxiv_dataset-36611208.5528 | Coded Path Protection Part 2: Design, Implementation, and Performance
cs.NI
In Part 1 of this paper, we introduced a coding-based proactive network
protection scheme, named Coded Path Protection (CPP). In CPP, a backup stream
of the primary data is encoded with other data streams, resulting in capacity
savings. In addition to being a systematic approach of building valid coding
structures, CPP is an optimal and simple capacity placement and coding group
formation algorithm. It converts the sharing structure of any solution of a
Shared Path Protection (SPP) technique into a coding structure with minimum
extra capacity. In this Part 2 of the paper, we describe the implementation of
our algorithm using Integer Linear Programming (ILP), its timing and
synchronization requirements, and implementation issues in networks. We present
simulation results which confirm that CPP provides faster link failure recovery
than SPP while it incurs marginal extra capacity beyond that of SPP.
| arxiv topic:cs.NI |
arxiv_dataset-36621208.5628 | Phonon-induced dephasing of chromium colour centres in diamond
cond-mat.mes-hall quant-ph
We report on the coherence properties of single photons from chromium-based
colour centres in diamond. We use field-correlation and spectral lineshape
measurements to reveal the interplay between slow spectral wandering and fast
dephasing mechanisms as a function of temperature. We show that the zero-phonon
transition frequency and its linewidth follow a power-law dependence on
temperature indicating that the dominant fast dephasing mechanisms for these
centres are direct electron-phonon coupling and phonon-modulated Coulomb
coupling to nearby impurities. Further, the observed reduction in the quantum
yield for photon emission as a function of temperature is consistent with the
opening of additional nonradiative channels through thermal activation to
higher energy states predominantly and indicates a near-unity quantum
efficiency at 4 K.
| arxiv topic:cond-mat.mes-hall quant-ph |
arxiv_dataset-36631208.5728 | Fast, Efficient Calculations of the Two-Body Matrix Elements of the
Transition Operators for Neutrinoless Double Beta Decay
nucl-th hep-ph nucl-ex
To extract information about the neutrino properties from the study of
neutrinoless double-beta (0\nu\beta\beta) decay one needs a precise computation
of the nuclear matrix elements (NMEs) associated with this process. Approaches
based on the Shell Model (ShM) are among the nuclear structure methods used for
their computation. ShM better incorporates the nucleon correlations, but have
to face the problem of the large model spaces and computational resources. The
goal is to develop a new, fast algorithm and the associated computing code for
efficient calculation of the two-body matrix elements (TBMEs) of the
0\nu\beta{\beta} decay transition operator, which are necessary to calculate
the NMEs. This would allow us to extend the ShM calculations for double-beta
decays to larger model spaces, of about 9-10 major harmonic oscillator shells.
The improvement of our code consists in a faster calculation of the radial
matrix elements. Their computation normally requires the numerical evaluation
of two-dimensional integrals: one over the coordinate space and the other over
the momentum space. By rearranging the expressions of the radial matrix
elements, the integration over the coordinate space can be performed
analytically, thus the computation reduces to sum up a small number of
integrals over momentum. Our results for the NMEs are in a good agreement with
similar results from literature, while we find a significant reduction of the
computation time for TBMEs, by a factor of about 30, as compared with our
previous code that uses two-dimensional integrals.
| arxiv topic:nucl-th hep-ph nucl-ex |
arxiv_dataset-36641208.5828 | CoFeB Thickness Dependence of Thermal Stability Factor in CoFeB/MgO
Perpendicular Magnetic Tunnel Junctions
cond-mat.mtrl-sci
Thermal stability factor (delta) of recording layer was studied in
perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions (p-MTJs) with
various CoFeB recording layer thicknesses and junction sizes. In all series of
p-MTJs with different thicknesses, delta is virtually independent of the
junction sizes of 48-81 nm in diameter. The values of delta increase linearly
with increasing the recording layer thickness. The slope of the linear fit is
explained well by a model based on nucleation type magnetization reversal.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-36651208.5928 | The Supernova Remnant G296.7-0.9 in X-rays
astro-ph.HE
Aims: We present a detailed study of the supernova remnant (SNR) G296.7-0.9
in the 0.2-12 keV X-ray band.
Methods: Using data from XMM-Newton we performed a spectro-imaging analysis
of G296.7-0.9 in order to deduce the basic parameters of the remnant and to
search for evidence of a young neutron star associated with it.
Results: In X-rays the remnant is characterized by a bright arc located in
the south-west direction. Its X-ray spectrum can best be described by an
absorbed non-equilibrium collisional plasma model with a hydrogen density of
N_H=1.24_{-0.05}^{+0.07} x 10^{22} cm^{-2} and a plasma temperature of
6.2^{+0.9}_{-0.8} million Kelvin. The analysis revealed a remnant age of 5800
to 7600 years and a distance of 9.8_{-0.7}^{+1.1} kpc. The latter suggests a
spatial connection with a close-by HII region. We did not find evidence for a
young neutron star associated with the remnant.
| arxiv topic:astro-ph.HE |
arxiv_dataset-36661208.6028 | Design of Low Noise Amplifiers Using Particle Swarm Optimization
cs.NE
This short paper presents a work on the design of low noise microwave
amplifiers using particle swarm optimization (PSO) technique. Particle Swarm
Optimization is used as a method that is applied to a single stage amplifier
circuit to meet two criteria: desired gain and desired low noise. The aim is to
get the best optimized design using the predefined constraints for gain and low
noise values. The code is written to apply the algorithm to meet the desired
goals and the obtained results are verified using different simulators. The
results obtained show that PSO can be applied very efficiently for this kind of
design problems with multiple constraints.
| arxiv topic:cs.NE |
arxiv_dataset-36671208.6128 | QCD studies and discoveries with e+e- colliders and future perspectives
hep-ex
Observations of new charmonium(-like) and bottomonium(-like) states
(sometimes refered to as "XYZ" states) at e+e- colliders have changed our
picture of quarkonia systems as QCD bound states. Potential models with a
linear confinement ansatz, which were able to predict many conventional states
with an accuracy of ~1 MeV, absolutely fail in describing many of the new
states. Symmetries play an important role e.g. in the determination of the
quantum numbers (such as charge conjugation in the radiative decays) or in
trying to explain surprising properties such as isospin violation. It will also
be discussed, how future experiments (Panda, Belle II) can help to understand
the nature of these states.
| arxiv topic:hep-ex |
arxiv_dataset-36681208.6228 | The distribution function of the distance between two random points in a
right-angled triangle
math.PR
In this paper we obtain the density function and the distribution function of
the distance between two uniformly and independently distributed random points
in any right-angled triangle. The density function is derived from the chord
length distribution function using Piefke's formula. We conclude results for
random distances between two congruent right-angled triangles together forming
a rectangle.
| arxiv topic:math.PR |
arxiv_dataset-36691208.6328 | Direct and inverse theorems of approximation theory for a generalised
modulus of smoothness
math.FA
An asymmetric operator of generalised translation is introduced in this
paper. Using this operator, we define a generalised modulus of smoothness and
prove direct and inverse theorems of approximation theory for it.
| arxiv topic:math.FA |
arxiv_dataset-36701208.6428 | A Hardware Time Manager Implementation for the Xenomai Real-Time Kernel
of Embedded Linux
cs.OS cs.AR cs.PF
Nowadays, the use of embedded operating systems in different embedded
projects is subject to a tremendous growth. Embedded Linux is becoming one of
those most popular EOSs due to its modularity, efficiency, reliability, and
cost. One way to make it hard real-time is to include a real-time kernel like
Xenomai. One of the key characteristics of a Real-Time Operating System (RTOS)
is its ability to meet execution time deadlines deterministically. So, the more
precise and flexible the time management can be, the better it can handle
efficiently the determinism for different embedded applications. RTOS time
precision is characterized by a specific periodic interrupt service controlled
by a software time manager. The smaller the period of the interrupt, the better
the precision of the RTOS, the more it overloads the CPU, and though reduces
the overall efficiency of the RTOS. In this paper, we propose to drastically
reduce these overheads by migrating the time management service of Xenomai into
a configurable hardware component to relieve the CPU. The hardware component is
implemented in a Field Programmable Gate Array coupled to the CPU. This work
was achieved in a Master degree project where students could apprehend many
fields of embedded systems: RTOS programming, hardware design, performance
evaluation, etc.
| arxiv topic:cs.OS cs.AR cs.PF |
arxiv_dataset-36711208.6528 | Quantum Monte Carlo study of inhomogeneous neutron matter
nucl-th
We present an ab-initio study of neutron drops. We use Quantum Monte Carlo
techniques to calculate the energy up to 54 neutrons in different external
potentials, and we compare the results with Skyrme forces. We also calculate
the rms radii and radial densities, and we find that a re-adjustment of the
gradient term in Skyrme is needed in order to reproduce the properties of these
systems given by the ab-initio calculation. By using the ab-initio results for
neutron drops for close- and open-shell configurations, we suggest how to
improve Skyrme forces when dealing with systems with large isospin-asymmetries
like neutron-rich nuclei.
| arxiv topic:nucl-th |
arxiv_dataset-36721209.0036 | Supporting Structured Browsing for Full-Text Scientific Research Reports
cs.DL
Scientific research is highly structured and some of that structure is
reflected in research reports. Traditional scientific research reports are
yielding to interactive documents which expose their internal structure and are
richly linked to other materials. In these changes, there are opportunities to
take advantage of the structure in scientific research reports which previously
have not been systematically captured. Thus, we explore ways of capturing more
of the structure of research in reports about the research and we use that
structure to support the development of a new generation of document browsers
which include novel interaction widgets. We apply the browsers incorporating
the conceptual modeling framework to full-text research reports from the Public
Library of Science (PLoS). In addition, we describe the application of
model-oriented constructs to facilitating highly interlinked digital libraries.
| arxiv topic:cs.DL |
arxiv_dataset-36731209.0136 | Incremental Control Synthesis in Probabilistic Environments with
Temporal Logic Constraints
cs.RO cs.LO
In this paper, we present a method for optimal control synthesis of a plant
that interacts with a set of agents in a graph-like environment. The control
specification is given as a temporal logic statement about some properties that
hold at the vertices of the environment. The plant is assumed to be
deterministic, while the agents are probabilistic Markov models. The goal is to
control the plant such that the probability of satisfying a syntactically
co-safe Linear Temporal Logic formula is maximized. We propose a
computationally efficient incremental approach based on the fact that temporal
logic verification is computationally cheaper than synthesis. We present a
case-study where we compare our approach to the classical non-incremental
approach in terms of computation time and memory usage.
| arxiv topic:cs.RO cs.LO |
arxiv_dataset-36741209.0236 | Cross-Bifix-Free Codes Within a Constant Factor of Optimality
cs.IT math.CO math.IT
A cross-bifix-free code is a set of words in which no prefix of any length of
any word is the suffix of any word in the set. Cross-bifix-free codes arise in
the study of distributed sequences for frame synchronization. We provide a new
construction of cross-bifix-free codes which generalizes the construction in
Bajic (2007) to longer code lengths and to any alphabet size. The codes are
shown to be nearly optimal in size. We also establish new results on Fibonacci
sequences, that are used in estimating the size of the cross-bifix-free codes.
| arxiv topic:cs.IT math.CO math.IT |
arxiv_dataset-36751209.0336 | Testing the CGC in proton-lead collisions at the LHC
hep-ph
I present a brief review of present CGC phenomenological applications and of
the physics prospects for the forthcoming proton-lead run at the LHC
| arxiv topic:hep-ph |
arxiv_dataset-36761209.0436 | Determination of the charm-quark mass in the MS-bar scheme using charm
production data from deep inelastic scattering at HERA
hep-ph hep-ex
We determine the charm-quark mass mc(mc) in the MS-bar scheme using
measurements of charm production in deep-inelastic ep scattering at HERA in the
kinematic range of photon virtuality from 5 to 1000 GeV squared and Bjorken
scaling variable from 0.0001 to 0.5. The extraction of charm quark mass from
this process with space-like kinematics provides complementary information to
results from hadronic processes. The QCD analysis of the HERA data yields a
value of mc(mc) of 1.27 plus minus 0.05(exp) plus 0.06 minus 0.01(scale) GeV at
next-to-leading order and mc(mc) of 1.36 plus minus 0.04(exp) plus 0.04 minus
0.00 (scale) plus minus 0.1(theory) GeV at approximate next-to-next-to-leading
order. The results are consistent with and of comparable precision as the world
average.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-36771209.0536 | Thermalization via Heat Radiation of an Individual Object Thinner than
the Thermal Wavelength
quant-ph cond-mat.stat-mech
Modeling and investigating the thermalization of microscopic objects with
arbitrary shape from first principles is of fundamental interest and may lead
to technical applications. Here, we study, over a large temperature range, the
thermalization dynamics due to far-field heat radiation of an individual,
deterministically produced silica fiber with a predetermined shape and a
diameter smaller than the thermal wavelength. The temperature change of the
subwavelength-diameter fiber is determined through a measurement of its optical
path length in conjunction with an ab initio thermodynamic model of the fiber
structure. Our results show excellent agreement with a theoretical model that
considers heat radiation as a volumetric effect and takes the emitter shape and
size relative to the emission wavelength into account.
| arxiv topic:quant-ph cond-mat.stat-mech |
arxiv_dataset-36781209.0636 | Disentangling the EMC Effect
nucl-ex hep-ph nucl-th
The deep inelastic scattering cross section for scattering from bound
nucleons differs from that of free nucleons.This phenomena, first discovered 30
years ago, is known as the EMC effect and is still not fully understood. Recent
analysis of world data showed that the strength of the EMC effect is linearly
correlated with the relative amount of Two-Nucleon Short Range Correlated pairs
(2N-SRC) in nuclei. The latter are pairs of nucleons whose wave functions
overlap, giving them large relative momentum and low center of mass momentum,
where high and low is relative to the Fermi momentum of the nucleus. The
observed correlation indicates that the EMC effect, like 2N-SRC pairs, is
related to high momentum nucleons in the nucleus. This paper reviews previous
studies of the EMC-SRC correlation and studies its robustness. It also presents
a planned experiment aimed at studying the origin of this EMC-SRC correlation.
| arxiv topic:nucl-ex hep-ph nucl-th |
arxiv_dataset-36791209.0736 | On Set Size Distribution Estimation and the Characterization of Large
Networks via Sampling
math.ST cs.IT cs.SI math.IT stat.TH
In this work we study the set size distribution estimation problem, where
elements are randomly sampled from a collection of non-overlapping sets and we
seek to recover the original set size distribution from the samples. This
problem has applications to capacity planning, network theory, among other
areas. Examples of real-world applications include characterizing in-degree
distributions in large graphs and uncovering TCP/IP flow size distributions on
the Internet. We demonstrate that it is hard to estimate the original set size
distribution. The recoverability of original set size distributions presents a
sharp threshold with respect to the fraction of elements that remain in the
sets. If this fraction remains below a threshold, typically half of the
elements in power-law and heavier-than-exponential-tailed distributions, then
the original set size distribution is unrecoverable. We also discuss practical
implications of our findings.
| arxiv topic:math.ST cs.IT cs.SI math.IT stat.TH |
arxiv_dataset-36801209.0836 | Structure formation in a nonlocally modified gravity model
astro-ph.CO gr-qc
We study a nonlocally modified gravity model proposed by Deser and Woodard
which gives an explanation for current cosmic acceleration. By deriving and
solving the equations governing the evolution of the structure in the Universe,
we show that this model predicts a pattern of growth that differs from standard
general relativity (+dark energy) at the 10-30% level. These differences will
be easily probed by the next generation of galaxy surveys, so the model should
be tested shortly.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-36811209.0936 | The Andre-Oort conjecture
math.NT
In this paper we prove, assuming the Generalized Riemann Hypothesis, the
Andr?e-Oort conjecture on the Zariski closure of sets of special points in a
Shimura variety. In the case of sets of special points satisfying an additional
assumption, we prove the conjecture without assuming the GRH.
| arxiv topic:math.NT |
arxiv_dataset-36821209.1036 | Bessel Integrals, Periods and Zeta Numbers
math-ph math.MP
We present a summary of recent and older results on Bessel integrals and
their relation with zeta numbers.
| arxiv topic:math-ph math.MP |
arxiv_dataset-36831209.1136 | Some results on large cardinals and the continuum function
math.LO
Given a Woodin cardinal $\delta$, I show that if $F$ is any Easton function
with $F"\delta\subseteq\delta$ and $\GCH$ holds, then there is a
cofinality-preserving forcing extension in which $2^\gamma= F(\gamma)$ for each
regular cardinal $\gamma<\delta$, and in which $\delta$ remains Woodin.
I also present a new example in which forcing a certain behavior of the
continuum function on the regular cardinals, while preserving a given large
cardinal, requires large cardinal strength beyond that of the original large
cardinal under consideration. Specifically, I prove that the existence of a
$\lambda$-supercompact cardinal $\kappa$ such that $\GCH$ fails at $\lambda$ is
equiconsistent with the existence of a cardinal $\kappa$ that is
$\lambda$-supercompact and $\lambda^{++}$-tall.
I generalize a theorem on measurable cardinals due to Levinski, which says
that given a measurable cardinal, there is a forcing extension preserving the
measurability of $\kappa$ in which $\kappa$ is the least regular cardinal at
which $\GCH$ holds. Indeed, I show that Levinski's result can be extended to
many other large cardinal contexts. This work paves the way for many additional
results, analogous to the results stated above for Woodin cardinals and
partially supercompact cardinals.
| arxiv topic:math.LO |
arxiv_dataset-36841209.1236 | Coordination of autonomic functionalities in communications networks
cs.NI cs.SY
Future communication networks are expected to feature autonomic (or
self-organizing) mechanisms to ease deployment (self-configuration), tune
parameters automatically (self-optimization) and repair the network
(self-healing). Self-organizing mechanisms have been designed as stand-alone
entities, even though multiple mechanisms will run in parallel in operational
networks. An efficient coordination mechanism will be the major enabler for
large scale deployment of self-organizing networks. We model self-organizing
mechanisms as control loops, and study the conditions for stability when
running control loops in parallel. Based on control theory and Lyapunov
stability, we propose a coordination mechanism to stabilize the system, which
can be implemented in a distributed fashion. The mechanism remains valid in the
presence of measurement noise via stochastic approximation. Instability and
coordination in the context of wireless networks are illustrated with two
examples and the influence of network geometry is investigated. We are
essentially concerned with linear systems, and the applicability of our results
for non-linear systems is discussed.
| arxiv topic:cs.NI cs.SY |
arxiv_dataset-36851209.1336 | Detection of Weak Force using a Bose-Einstein Condensate
cond-mat.quant-gas quant-ph
We investigate the possibility of detecting a weak coherent force by means of
a hybrid optomechanical quantum device formed by a Bose Einstein Condensate
(BEC) confined in a high quality factor optical cavity with an oscillatory end
mirror. We show using the stochastic cooling technique that the atomic two-body
interaction can be utilized to cool the mirror and achieve position squeezing
essential for making sensitive measurements of weak forces. We further show
that the atomic two-body interaction can also increase the signal to noise
ratio (SNR) and decrease the noise of the off-resonant stationary spectral
measurements.
| arxiv topic:cond-mat.quant-gas quant-ph |
arxiv_dataset-36861209.1436 | Satisfaction, Restriction and Amalgamation of Constraints in the
Framework of M-Adhesive Categories
cs.LO
Application conditions for rules and constraints for graphs are well-known in
the theory of graph transformation and have been extended already to M-adhesive
transformation systems. According to the literature we distinguish between two
kinds of satisfaction for constraints, called general and initial satisfaction
of constraints, where initial satisfaction is defined for constraints over an
initial object of the base category. Unfortunately, the standard definition of
general satisfaction is not compatible with negation in contrast to initial
satisfaction.
Based on the well-known restriction of objects along type morphisms, we study
in this paper restriction and amalgamation of application conditions and
constraints together with their solutions. In our main result, we show
compatibility of initial satisfaction for positive constraints with restriction
and amalgamation, while general satisfaction fails in general.
Our main result is based on the compatibility of composition via pushouts
with restriction, which is ensured by the horizontal van Kampen property in
addition to the vertical one that is generally satisfied in M-adhesive
categories.
| arxiv topic:cs.LO |
arxiv_dataset-36871209.1536 | Negativity and quantum discord in Davies environments
quant-ph
We investigate the time evolution of negativity and quantum discord for a
pair of non-interacting qubits with one being weakly coupled to a decohering
Davies--type Markovian environment. At initial time of preparation, the qubits
are prepared in one of the maximally entangled pure Bell states. In the
limiting case of pure decoherence (i.e. pure dephasing), both, the quantum
discord and negativity decay to zero in the long time limit. In presence of a
manifest dissipative dynamics, the entanglement negativity undergoes a sudden
death at finite time while the quantum discord relaxes continuously to zero
with increasing time. We find that in dephasing environments the decay of the
negativity is more propitious with increasing time; in contrast, the evolving
decay of the quantum discord proceeds weaker for dissipative environments.
Particularly, the slowest decay of the quantum discord emerges when the energy
relaxation time matches the dephasing time.
| arxiv topic:quant-ph |
arxiv_dataset-36881209.1636 | Galaxy And Mass Assembly (GAMA): The mass-metallicity relationship
astro-ph.CO
Context: The mass-metallicity relationship (MMR) of star-forming galaxies is
well-established, however there is still some disagreement with respect to its
exact shape and its possible dependence on other observables. Aims: We measure
the MMR in the Galaxy And Mass Assembly (GAMA) survey. We compare our measured
MMR to that measured in the Sloan Digital Sky Survey (SDSS) and study the
dependence of the MMR on various selection criteria to identify potential
causes for disparities seen in the literature. Methods: We use strong emission
line ratio diagnostics to derive oxygen abundances. We then apply a range of
selection criteria for the minimum signal-to-noise in various emission lines,
as well as the apparent and absolute magnitude to study variations in the
inferred MMR. Results: The shape and position of the MMR can differ
significantly depending on the metallicity calibration and selection used.
After selecting a robust metallicity calibration amongst those tested, we find
that the mass-metallicity relation for redshifts 0.061< z<0.35 in GAMA is in
reasonable agreement with that found in the SDSS despite the difference in the
luminosity range probed. Conclusions: In view of the significant variations of
the MMR brought about by reasonable changes in the sample selection criteria
and method, we recommend that care be taken when comparing the MMR from
different surveys and studies directly. We also conclude that there could be a
modest level of evolution over 0.06<z<0.35 within the GAMA sample.
| arxiv topic:astro-ph.CO |
arxiv_dataset-36891209.1736 | Evidence for anisotropic polar nanoregions in relaxor PMN: A neutron
study of the elastic constants and anomalous TA phonon damping
cond-mat.mtrl-sci
We use neutron scattering to characterize the acoustic phonons in the relaxor
PMN and demonstrate the presence of an anisotropic damping mechanism directly
related to short-range, polar correlations. For a large range of temperatures
above Tc ~ 210, K, where dynamic polar correlations exist, acoustic phonons
propagating along [1\bar{1}0] and polarized along [110] (TA2 phonons) are
overdamped and softened across most of the Brillouin zone. By contrast,
acoustic phonons propagating along [100] and polarized along [001] (TA1
phonons) are overdamped and softened for only a limited range of wavevectors.
The anisotropy and temperature dependence of the acoustic phonon energy
linewidth are directly correlated with the elastic diffuse scattering,
indicating that polar nanoregions are the cause of the anomalous behavior. The
damping and softening vanish for q -> 0, i.e. for long-wavelength acoustic
phonons, which supports the notion that the anomalous damping is a result of
the coupling between the relaxational component of the diffuse scattering and
the harmonic TA phonons. Therefore, these effects are not due to large changes
in the elastic constants with temperature because the elastic constants
correspond to the long-wavelength limit. We compare the elastic constants we
measure to those from Brillouin scattering and to values reported for pure PT.
We show that while the values of C44 are quite similar, those for C11 and C12
are significantly less in PMN and result in a softening of (C11-C12) over PT.
There is also an increased elastic anisotropy (2C44/(C11-C12)) versus that in
PT. These results suggest an instability to TA2 acoustic fluctuations in
relaxors. We discuss our results in the context of the debate over the
"waterfall" effect and show that they are inconsistent with TA-TO phonon
coupling or other models that invoke the presence of a second optic mode.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-36901209.1836 | Experimental implementation of a Kochen-Specker set of quantum tests
quant-ph
The conflict between classical and quantum physics can be identified through
a series of yes-no tests on quantum systems, without it being necessary that
these systems be in special quantum states. Kochen-Specker (KS) sets of yes-no
tests have this property and provide a quantum-versus-classical advantage that
is free of the initialization problem that affects some quantum computers.
Here, we report the first experimental implementation of a complete KS set that
consists of 18 yes-no tests on four-dimensional quantum systems and show how to
use the KS set to obtain a state-independent quantum advantage. We first
demonstrate the unique power of this KS set for solving a task while avoiding
the problem of state initialization. Such a demonstration is done by showing
that, for 28 different quantum states encoded in the orbital-angular-momentum
and polarization degrees of freedom of single photons, the KS set provides an
impossible-to-beat solution. In a second experiment, we generate maximally
contextual quantum correlations by performing compatible sequential
measurements of the polarization and path of single photons. In this case,
state independence is demonstrated for 15 different initial states. Maximum
contextuality and state independence follow from the fact that the sequences of
measurements project any initial quantum state onto one of the KS set's
eigenstates. Our results show that KS sets can be used for quantum-information
processing and quantum computation and pave the way for future developments.
| arxiv topic:quant-ph |
arxiv_dataset-36911209.1936 | On the Son-Yamamoto relation in the soft-wall holographic model of QCD
hep-ph
We study the vertex function of two vector and one axial-vector operators in
the soft-wall holographic model of QCD. In particular, we discuss the possible
relation, introduced by Son and Yamamoto, between the structure function $w_T$
describing such a vertex when one of the two vector currents represents an
on-shell soft photon and the the two-point $\Pi_\perp^{VV}-\Pi_\perp^{AA}$
correlation function.
| arxiv topic:hep-ph |
arxiv_dataset-36921209.2036 | Three-dimensional quantum photonic elements based on single nitrogen
vacancy-centres in laser-written microstructures
quant-ph physics.optics
A fully integrated quantum optical technology requires active quantum systems
incorporated into resonant optical microstructures and inter-connected in three
dimensions via photonic wires. Nitrogen vacancy-centres (NV-centres) in diamond
which are excellent photostable room temperature single-photon emitters are
ideal candidates for that purpose. Extensive research efforts to couple
NV-centres to photonic structures such as optical microresonators,
microcavities, and waveguides have been pursued. Strategies for integration
range from top-down fabrication via etching of diamond membranes to
sophisticated bottom-up assembly of hybrid structures using diamond
nanocrystals where the latter approach allows for deterministic coupling.
Recently, another approach based on the incorporation of nanodiamonds in soft
glass optical fibres via a melting process has been introduced. Here, we
utilize two-photon direct laser writing (DLW) to fabricate fully
three-dimensional (3D) structures from a photoresist mixed with a solution of
nanodiamonds containing NV-centres. For the first time, this approach
facilitates building integrated 3D quantum photonic elements of nearly
arbitrary shapes.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-36931209.2136 | Can habitable planets form in clustered environments?
astro-ph.SR astro-ph.EP
We present observational evidence of environmental effects on the formation
and evolution of planetary systems. We combine catalogues of resolved
protoplanetary discs (PPDs) and young stellar objects in the solar
neighbourhood to analyse the PPD size distribution as a function of ambient
stellar density. By running Kolmogorov-Smirnov tests between the PPD radii at
different densities, we find empirical evidence, at the >97% confidence level,
for a change in the PPD radius distribution at ambient stellar densities \Sigma
> 10^{3.5} pc^{-2}. This coincides with a simple theoretical estimate for the
truncation of PPDs or planetary systems by dynamical encounters. If this
agreement is causal, the ongoing disruption of PPDs and planetary systems
limits the possible existence of planets in the habitable zone, with shorter
lifetimes at higher host stellar masses and ambient densities. Therefore,
habitable planets are not likely to be present in long-lived stellar clusters,
and may have been ejected altogether to form a population of unbound,
free-floating planets. We conclude that, while highly suggestive, our results
should be verified through other methods. Our simple model shows that
truncations should lead to a measurable depletion of the PPD mass function that
can be detected with ALMA observations of the densest nearby and young
clusters.
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-36941209.2236 | On two multistable extensions of stable L\'evy motion and their
semimartingale representation
math.PR
We compare two definitions of multistable L\'evy motions. Such processes are
extensions of classical L\'evy motion where the stability index is allowed to
vary in time. We show that the two multistable L\'evy motions have distinct
properties: in particular, one is a pure-jump Markov process, while the other
one satisfies neither of these properties. We prove that both are
semimartingales and provide semimartingale decompositions.
| arxiv topic:math.PR |
arxiv_dataset-36951209.2336 | Connectedness of the moduli of Sp(2p,2q)-Higgs bundles
math.AG
Using the Morse-theoretic techniques introduced by Hitchin, we prove that the
moduli space of $\Sp(2p,2q)$-Higgs bundles over a compact Riemann surface of
genus $g\geq 2$ is connected. In particular, this implies that the moduli space
of representations of the fundamental group of the surface in $\Sp(2p,2q)$ is
connected.
| arxiv topic:math.AG |
arxiv_dataset-36961209.2436 | Gamma Ray Bursts: recent results and connections to very high energy
Cosmic Rays and Neutrinos
astro-ph.HE hep-ph
Gamma-ray bursts are the most concentrated explosions in the Universe. They
have been detected electromagnetically at energies up to tens of GeV, and it is
suspected that they could be active at least up to TeV energies. It is also
speculated that they could emit cosmic rays and neutrinos at energies reaching
up to the $10^{18}-10^{20}$ eV range. Here we review the recent developments in
the photon phenomenology in the light of \swift and \fermi satellite
observations, as well as recent IceCube upper limits on their neutrino
luminosity. We discuss some of the theoretical models developed to explain
these observations and their possible contribution to a very high energy cosmic
ray and neutrino background.
| arxiv topic:astro-ph.HE hep-ph |
arxiv_dataset-36971209.2536 | Omnipresent long-period intensity oscillations in open coronal
structures
astro-ph.SR
Quasi-periodic propagating disturbances in coronal structures have been
interpreted as slow magneto-acoustic waves and/or periodic upflows. Here we aim
to understand their nature from the observed properties using a three-hour
imaging sequence from AIA/SDO in two different temperature channels. We also
compare the characteristics with a simple wave model. We searched for
propagating disturbances in open-loop structures at three different locations;
a fan loop-structure off-limb, an on-disk plume-like structure and the
plume/interplume regions in the north pole of the sun. In each of the subfield
regions chosen to cover these structures, the time series at each pixel
location was subjected to wavelet analysis to find the different periodicities.
We then constructed powermaps in three different period ranges. We also
constructed space-time maps for the on-disk plume structure to estimate the
propagation speeds in different channels. We find propagating disturbances in
all three structures. Powermaps indicate that the power in the long-period
range is significant up to comparatively longer distances along the loop than
that in the shorter periods. This nature is observed in all three structures. A
detailed analysis on the on-disk plume structure gives consistently higher
propagation speeds in the 193 \AA channel and also reveals spatial damping
along the loop. The amplitude and the damping length values are lower in hotter
channels, indicating their acoustic dependence. These properties can be
explained very well with a propagating slow-wave model. We suggest that these
disturbances are more likely to be caused by propagating slow magneto-acoustic
waves than by high-speed quasi-periodic upflows. We find that intensity
oscillations in longer periods are omnipresent at larger heights even in active
regions.
| arxiv topic:astro-ph.SR |
arxiv_dataset-36981209.2636 | The dust energy balance in the edge-on spiral galaxy NGC 4565
astro-ph.CO
We combine new dust continuum observations of the edge-on spiral galaxy NGC
4565 in all Herschel/SPIRE (250, 350, 500 micron) wavebands, obtained as part
of the Herschel Reference Survey, and a large set of ancillary data (Spitzer,
SDSS, GALEX) to analyze its dust energy balance. We fit a radiative transfer
model for the stars and dust to the optical maps with the fitting algorithm
FitSKIRT. To account for the observed UV and mid-infrared emission, this
initial model was supplemented with both obscured and unobscured star-forming
regions. Even though these star-forming complexes provide an additional heating
source for the dust, the far-infrared/submillimeter emission long wards of 100
micron is underestimated by a factor of 3-4. This inconsistency in the dust
energy budget of NGC 4565 suggests that a sizable fraction (two-thirds) of the
total dust reservoir (Mdust ~ 2.9e+8 Msun) consists of a clumpy distribution
with no associated young stellar sources. The distribution of those dense dust
clouds would be in such a way that they remain unresolved in current
far-infrared/submillimeter observations and hardly comtribute to the
attenuation at optical wavelengths. More than two-thirds of the dust heating in
NGC 4565 is powered by the old stellar population, with localized embedded
sources supplying the remaining dust heating in NGC 4565. The results from this
detailed dust energy balance study in NGC 4565 is consistent with that of
similar analyses of other edge-on spirals.
| arxiv topic:astro-ph.CO |
arxiv_dataset-36991209.2736 | The Ensemble Kalman Filter for Inverse Problems
math.OC
The Ensemble Kalman filter (EnKF) was introduced by Evensen in 1994 [10] as a
novel method for data assimilation: state estimation for noisily observed
time-dependent problems. Since that time it has had enormous impact in many
application domains because of its robustness and ease of implementation, and
numerical evidence of its accuracy. In this paper we propose the application of
an iterative ensemble Kalman method for the solution of a wide class of inverse
problems. In this context we show that the estimate of the unknown function
that we obtain with the ensemble Kalman method lies in a subspace A spanned by
the initial ensemble. Hence the resulting error may be bounded above by the
error found from the best approximation in this subspace. We provide numerical
experiments which compare the error incurred by the ensemble Kalman method for
inverse problems with the error of the best approximation in A, and with
variants on traditional least-squares approaches, restricted to the subspace A.
In so doing we demonstrate that the ensemble Kalman method for inverse problems
provides a derivative-free optimization method with comparable accuracy to that
achieved by traditional least-squares approaches. Furthermore, we also
demonstrate that the accuracy is of the same order of magnitude as that
achieved by the best approximation. Three examples are used to demonstrate
these assertions: inversion of a compact linear operator; inversion of
piezometric head to determine hydraulic conductivity in a Darcy model of
groundwater flow; and inversion of Eulerian velocity measurements at positive
times to determine the initial condition in an incompressible fluid.
| arxiv topic:math.OC |
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