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arxiv_dataset-50001402.2475 | Islands in graphs on surfaces
math.CO
An island in a graph is a set $X$ of vertices, such that each element of $X$
has few neighbors outside $X$. In this paper, we prove several bounds on the
size of islands in large graphs embeddable on fixed surfaces. As direct
consequences of our results, we obtain that:
(1) Every graph of genus $g$ can be colored from lists of size 5, in such a
way that each monochromatic component has size $O(g)$. Moreover all but $O(g)$
vertices lie in monochromatic components of size at most 3.
(2) Every triangle-free graph of genus $g$ can be colored from lists of size
3, in such a way that each monochromatic component has size $O(g)$. Moreover
all but $O(g)$ vertices lie in monochromatic components of size at most 10.
(3) Every graph of girth at least 6 and genus $g$ can be colored from lists
of size 2, in such a way that each monochromatic component has size $O(g)$.
Moreover all but $O(g)$ vertices lie in monochromatic components of size at
most 16.
While (2) is optimal up to the size of the components, we conjecture that the
size of the lists can be decreased to 4 in (1), and the girth can be decreased
to 5 in (3). We also study the complexity of minimizing the size of
monochromatic components in 2-colorings of planar graphs.
| arxiv topic:math.CO |
arxiv_dataset-50011402.2575 | Generalised shear coordinates on the moduli spaces of three-dimensional
spacetimes
math-ph gr-qc hep-th math.MP
We introduce coordinates on the moduli spaces of maximal globally hyperbolic
constant curvature 3d spacetimes with cusped Cauchy surfaces S. They are
derived from the parametrisation of the moduli spaces by the bundle of measured
geodesic laminations over Teichm\"uller space of S and can be viewed as
analytic continuations of the shear coordinates on Teichm\"uller space. In
terms of these coordinates the gravitational symplectic structure takes a
particularly simple form, which resembles the Weil-Petersson symplectic
structure in shear coordinates, and is closely related to the cotangent bundle
of Teichm\"uller space. We then consider the mapping class group action on the
moduli spaces and show that it preserves the gravitational symplectic
structure. This defines three distinct mapping class group actions on the
cotangent bundle of Teichm\"uller space, corresponding to different values of
the curvature.
| arxiv topic:math-ph gr-qc hep-th math.MP |
arxiv_dataset-50021402.2675 | Explaining the subpulse drift velocity of pulsar magnetosphere within
the space-charge limited flow model
astro-ph.SR astro-ph.HE
We try to explain the subpulse drift phenomena adopting the space-charge
limited flow (SCLF) model and comparing the plasma drift velocity in the inner
region of pulsar magnetospheres with the observed velocity of drifting
subpulses. We apply the approach described in a recent paper of van Leeuwen &
Timokhin (2012), where it was shown that the standard estimation of the
subpulse drift velocity through the total value of the scalar potential drop in
the inner gap gives inaccurate results, while the exact expression relating the
drift velocity to the gradient of the scalar potential should be used instead.
After considering a selected sample of sources taken from the catalog of
Weltevrede, Edwards & Stappers (2006) with coherently drifting subpulses and
reasonably known observing geometry, we show that their subpulse drift
velocities would correspond to the drift of the plasma located very close or
above the pair formation front. Moreover, a detailed analysis of PSR B0826-34
and PSR B0818-41 reveals that the variation of the subpulse separation with the
pulse longitude can be successfully explained by the dependence of the plasma
drift velocity on the angular coordinates.
| arxiv topic:astro-ph.SR astro-ph.HE |
arxiv_dataset-50031402.2775 | On data depth in infinite dimensional spaces
stat.ME
The concept of data depth leads to a center-outward ordering of multivariate
data, and it has been effectively used for developing various data analytic
tools. While different notions of depth were originally developed for finite
dimensional data, there have been some recent attempts to develop depth
functions for data in infinite dimensional spaces. In this paper, we consider
some notions of depth in infinite dimensional spaces and study their properties
under various stochastic models. Our analysis shows that some of the depth
functions available in the literature have degenerate behaviour for some
commonly used probability distributions in infinite dimensional spaces of
sequences and functions. As a consequence, they are not very useful for the
analysis of data satisfying such infinite dimensional probability models.
However, some modified versions of those depth functions as well as an infinite
dimensional extension of the spatial depth do not suffer from such degeneracy,
and can be conveniently used for analyzing infinite dimensional data.
| arxiv topic:stat.ME |
arxiv_dataset-50041402.2875 | Memory effects in chaotic advection of inertial particles
physics.flu-dyn nlin.CD
A systematic investigation of the effect of the history force on particle
advection is carried out for both heavy and light particles. General relations
are given to identify parameter regions where the history force is expected to
be comparable with the Stokes drag. As an illustrative example, a paradigmatic
two-dimensional flow, the von K\'arm\'an flow is taken. For small (but not
extremely small) particles all investigated dynamical properties turn out to
heavily depend on the presence of memory when compared to the memoryless case:
the history force generates a rather non-trivial dynamics that appears to
weaken (but not to suppress) inertial effects, it enhances the overall
contribution of viscosity. We explore the parameter space spanned by the
particle size and the density ratio, and find a weaker tendency for
accumulation in attractors and for caustics formation. The Lyapunov exponent of
transients becomes larger with memory. Periodic attractors are found to have a
very slow, $t^{-1/2}$ type convergence towards the asymptotic form. We find
that the concept of snapshot attractors is useful to understand this slow
convergence: an ensemble of particles converges exponentially fast towards a
snapshot attractor, which undergoes a slow shift for long times.
| arxiv topic:physics.flu-dyn nlin.CD |
arxiv_dataset-50051402.2975 | A study of low-metallicity DLAs at high redshift and C II* as a probe of
their physical conditions
astro-ph.GA astro-ph.CO
We present a detailed high spectral resolution (R $\sim$ 40000) study of five
high-z damped Lyman $\alpha$ systems (DLAs) and one sub-DLA detected along four
QSO sightlines. Four of these DLAs are very metal-poor with [Fe/H] $\le$ $-$2.
One of them, at z$_{abs}$ = 4.20287 towards J0953$-$0504, is the most
metal-poor DLA at z $>$ 4 known till date. This system shows no enhancement of
C over Fe and O, and standard Population II star yields can explain its
relative abundance pattern. The DLA at z$_{abs}$ = 2.34006 towards J0035$-$0918
has been claimed to be the most carbon-enhanced metal-poor DLA. However, we
show that thermal broadening is dominant in this system and, when this effect
is taken into account, the measured carbon enhancement ([C/Fe] = 0.45 $\pm$
0.19) becomes $\sim$ 10 times less than what was reported previously. The gas
temperature in this DLA is estimated to be in the range of 5000 $-$ 8000 K,
consistent with a warm neutral medium phase. From photoionization modelling of
two of the DLAs showing C II* absorption, we find that the metagalactic
background radiation alone is not sufficient to explain the observed C II*
cooling rate, and local heating sources, probably produced by in-situ star
formation, are needed. Cosmic ray heating is found to contribute $\gtrsim$ 60%
to the total heating in these systems. Using a sample of metal-poor DLAs with C
II* measurements, we conclude that the cosmic ray ionization rate is equal to
or greater than that seen in the Milky Way in $\sim$ 33% of the systems with C
II* detections.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-50061402.3075 | Decoherence of trapped bosons by buffer gas scattering: What length
scales matter?
quant-ph physics.atom-ph
We ask and answer a basic question about the length scales involved in
quantum decoherence: how far apart in space do two parts of a quantum system
have to be, before a common quantum environment decoheres them as if they were
entirely separate? We frame this question specifically in a cold atom context.
How far apart do two populations of bosons have to be, before an environment of
thermal atoms of a different species (`buffer gas') responds to their two
particle numbers separately? An initial guess for this length scale is the
thermal coherence length of the buffer gas; we show that a standard Born-Markov
treatment partially supports this guess, but predicts only inverse-square
saturation of decoherence rates with distance, and not the much more abrupt
Gaussian behavior of the buffer gas's first-order coherence. We confirm this
Born-Markov result with a more rigorous theory, based on an exact solution of a
two-scatterer scattering problem, which also extends the result beyond weak
scattering. Finally, however, we show that when interactions within the buffer
gas reservoir are taken into account, an abrupt saturation of the decoherence
rate does occur, exponentially on the length scale of the buffer gas's mean
free path.
| arxiv topic:quant-ph physics.atom-ph |
arxiv_dataset-50071402.3175 | Information-Geometric Equivalence of Transportation Polytopes
cs.IT math.CO math.IT
This paper deals with transportation polytopes in the probability simplex
(that is, sets of categorical bivariate probability distributions with
prescribed marginals). Information projections between such polytopes are
studied, and a sufficient condition is described under which these mappings are
homeomorphisms.
| arxiv topic:cs.IT math.CO math.IT |
arxiv_dataset-50081402.3275 | Automorphism groups of simplicial complexes of infinite type surfaces
math.GT
Let S be any orientable surface of infinite genus with a finite number of
boundary components. In this work we consider the curve complex C(S), the
nonseparating curve complex N(S) and the Schmutz graph G(S) of S. When all the
topological ends of S carry genus, we show that all elements in the
automorphism groups Aut(C(S)), Aut(N(S)) and Aut(G(S)) are geometric, i.e.
these groups are naturally isomorphic to the extended mapping class group
MCG*(S) of the infinite surface S. Finally, we study rigidity phenomena within
Aut(C(S)) and Aut(N(S))
| arxiv topic:math.GT |
arxiv_dataset-50091402.3375 | Spatial Information in Large-Scale Neural Recordings
q-bio.NC
A central issue in neural recording is that of distinguishing the activities
of many neurons. Here, we develop a framework, based on Fisher information, to
quantify how separable a neuron's activity is from the activities of nearby
neurons. We (1) apply this framework to model information flow and spatial
distinguishability for several electrical and optical neural recording methods,
(2) provide analytic expressions for information content, and (3) demonstrate
potential applications of the approach. This method generalizes to many
recording devices that resolve objects in space and thus may be useful in the
design of next-generation scalable neural recording systems.
| arxiv topic:q-bio.NC |
arxiv_dataset-50101402.3475 | Structural heterogeneity and its role in determining properties of
disordered solids
cond-mat.soft
We construct a new order parameter from the normal modes of vibration, based
on the consideration of energy equipartition, to quantify the structural
heterogeneity in disordered solids. The order parameter exhibits strong spatial
correlations with low-temperature single particle dynamics and local structural
entropy. To characterize the role of particles with the most defective local
structures identified by the order parameter, we pin them and study how
properties of disordered solids respond to the pinning. It turns out that these
particles are responsible to the quasilocalized low-frequency vibration,
instability, softening, and nonaffinity of disordered solids.
| arxiv topic:cond-mat.soft |
arxiv_dataset-50111402.3575 | Optimal Hour-Ahead Bidding in the Real-Time Electricity Market with
Battery Storage using Approximate Dynamic Programming
math.OC
There is growing interest in the use of grid-level storage to smooth
variations in supply that are likely to arise with increased use of wind and
solar energy. Energy arbitrage, the process of buying, storing, and selling
electricity to exploit variations in electricity spot prices, is becoming an
important way of paying for expensive investments into grid-level storage.
Independent system operators such as the NYISO (New York Independent System
Operator) require that battery storage operators place bids into an hour-ahead
market (although settlements may occur in increments as small as 5 minutes,
which is considered near "real-time"). The operator has to place these bids
without knowing the energy level in the battery at the beginning of the hour,
while simultaneously accounting for the value of leftover energy at the end of
the hour. The problem is formulated as a dynamic program. We describe and
employ a convergent approximate dynamic programming (ADP) algorithm that
exploits monotonicity of the value function to find a revenue-generating
bidding policy; using optimal benchmarks, we empirically show the computational
benefits of the algorithm. Furthermore, we propose a distribution-free variant
of the ADP algorithm that does not require any knowledge of the distribution of
the price process (and makes no assumptions regarding a specific real-time
price model). We demonstrate that a policy trained on historical real-time
price data from the NYISO using this distribution-free approach is indeed
effective.
| arxiv topic:math.OC |
arxiv_dataset-50121402.3675 | Common boundary regular fixed points for holomorphic semigroups in
strongly convex domains
math.CV math.DS
Let $D$ be a bounded strongly convex domain with smooth boundary in $\mathbb
C^N$. Let $(\phi_t)$ be a continuous semigroup of holomorphic self-maps of $D$.
We prove that if $p\in \partial D$ is an isolated boundary regular fixed point
for $\phi_{t_0}$ for some $t_0>0$, then $p$ is a boundary regular fixed point
for $\phi_t$ for all $t\geq 0$. Along the way we also study backward iteration
sequences for elliptic holomorphic self-maps of $D$.
| arxiv topic:math.CV math.DS |
arxiv_dataset-50131402.3775 | Spectral viscosity method with generalized Hermite functions for
nonlinear conservation laws
math.NA
In this paper, we propose new spectral viscosity methods based on the
generalized Hermite functions for the solution of nonlinear scalar conservation
laws in the whole line. It is shown rigorously that these schemes converge to
the unique entropy solution by using compensated compactness arguments, under
some conditions. The numerical experiments of the inviscid Burger's equation
support our result, and it verifies the reasonableness of the conditions.
| arxiv topic:math.NA |
arxiv_dataset-50141402.3875 | Hydrogen peroxide thermochemical oscillator as driver for primordial RNA
replication
q-bio.BM
This paper presents and tests a previously unrecognised mechanism for driving
a replicating molecular system on the prebiotic earth. It is proposed that
cell-free RNA replication in the primordial soup may have been driven by
self-sustained oscillatory thermochemical reactions. To test this hypothesis a
well-characterised hydrogen peroxide oscillator was chosen as the driver and
complementary RNA strands with known association and melting kinetics were used
as the substrate. An open flow system model for the self-consistent, coupled
evolution of the temperature and concentrations in a simple autocatalytic
scheme is solved numerically, and it is shown that thermochemical cycling
drives replication of the RNA strands. For the (justifiably realistic) values
of parameters chosen for the simulated example system, the mean amount of
replicant produced at steady state is 6.56 times the input amount, given a
constant supply of substrate species. The spontaneous onset of sustained
thermochemical oscillations via slowly drifting parameters is demonstrated, and
a scheme is given for prebiotic production of complementary RNA strands on rock
surfaces.
| arxiv topic:q-bio.BM |
arxiv_dataset-50151402.3975 | When does the Hawking into Unruh mapping for global embeddings work?
gr-qc hep-th
We discuss for which smooth global embeddings of a metric into a Minkowskian
spacetime the Hawking into Unruh mapping takes place. There is a series of
examples of global embeddings into the Minkowskian spacetime (GEMS) with such
mapping for physically interesting metrics. These examples use Fronsdal-type
embeddings for which timelines are hyperbolas. In the present work we show that
for some new embeddings (non Fronsdal-type) of the Schwarzschild and
Reissner-Nordstrom metrics there is no mapping. We give also the examples of
hyperbolic and non hyperbolic type embeddings for the de Sitter metric for
which there is no mapping. For the Minkowski metric where there is no Hawking
radiation we consider a non trivial embedding with hyperbolic timelines, hence
in the ambient space the Unruh effect takes place, and it follows that there is
no mapping too. The considered examples show that the meaning of the Hawking
into Unruh mapping for global embeddings remains still insufficiently clear and
requires further investigations.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-50161402.4075 | The applicability of FIR fine-structure lines as Star Formation Rate
tracers over wide ranges of metallicities and galaxy types
astro-ph.GA astro-ph.CO
We analyze the applicability of far-infrared fine-structure lines [CII] 158
micron, [OI] 63 micron and [OIII] 88 micron to reliably trace the star
formation rate (SFR) in a sample of low-metallicity dwarf galaxies from the
Herschel Dwarf Galaxy Survey and compare with a broad sample of galaxies of
various types and metallicities in the literature. We study the trends and
scatter in the relation between the SFR (as traced by GALEX FUV and MIPS 24
micron) and far-infrared line emission, on spatially resolved and global galaxy
scales, in dwarf galaxies. We assemble far-infrared line measurements from the
literature and infer whether the far-infrared lines can probe the SFR (as
traced by the total-infrared luminosity) in a variety of galaxy populations. In
metal-poor dwarfs, the [OI] and [OIII] lines show the strongest correlation
with the SFR with an uncertainty on the SFR estimates better than a factor of
2, while the link between [CII] emission and the SFR is more dispersed
(uncertainty factor of 2.6). The increased scatter in the SFR-L([CII]) relation
towards low metal abundances, warm dust temperatures, large filling factors of
diffuse, highly ionized gas suggests that other cooling lines start to dominate
depending on the density and ionization state of the gas. For the literature
sample, we evaluate the correlations for a number of different galaxy
populations. The [CII] and [OI] lines are considered to be reliable SFR tracers
in starburst galaxies, recovering the star formation activity within an
uncertainty of factor 2. [Abridged]
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-50171402.4175 | Perturbation Theory for Parent Hamiltonians of Matrix Product States
math-ph cond-mat.stat-mech math.MP quant-ph
This article investigates the stability of the ground state subspace of a
canonical parent Hamiltonian of a Matrix product state against local
perturbations. We prove that the spectral gap of such a Hamiltonian remains
stable under weak local perturbations even in the thermodynamic limit, where
the entire perturbation might not be bounded. Our discussion is based on
preceding work by D.A. Yarotsky that develops a perturbation theory for
relatively bounded quantum perturbation of classical Hamiltonians. We exploit a
renormalization procedure, which on large scale transforms the parent
Hamiltonian of a Matrix product state into a classical Hamiltonian plus some
perturbation. We can thus extend D.A. Yarotsky's results to provide a
perturbation theory for parent Hamiltonians of Matrix product states and
recover some of the findings of independent contributions by S. Michalakis et
al. [arXiv:1109.1588] and J. I. Cirac et al. [arXiv:1306.4003].
| arxiv topic:math-ph cond-mat.stat-mech math.MP quant-ph |
arxiv_dataset-50181402.4275 | Robust estimate of dynamo thresholds in the von K\'arm\'an sodium
experiment using the Extreme Value Theory
physics.flu-dyn physics.data-an
We apply a new threshold detection method based on the extreme value theory
to the von K\'arm\'an sodium (VKS) experiment data. The VKS experiment is a
successful attempt to get a dynamo magnetic field in a laboratory liquid-metal
experiment. We first show that the dynamo threshold is associated to a change
of the probability density function of the extreme values of the magnetic
field. This method does not require the measurement of response functions from
applied external perturbations, and thus provides a simple threshold estimate.
We apply our method to different configurations in the VKS experiment showing
that it yields a robust indication of the dynamo threshold as well as evidence
of hysteretic behaviors. Moreover, for the experimental configurations in which
a dynamo transition is not observed, the method provides a way to extrapolate
an interval of possible threshold values.
| arxiv topic:physics.flu-dyn physics.data-an |
arxiv_dataset-50191402.4375 | Higher order dark matter annihilations in the Sun and implications for
IceCube
hep-ph astro-ph.HE
Dark matter particles captured in the Sun would annihilate producing a
neutrino flux that could be detected at the Earth. In some channels, however,
the neutrino flux lies in the MeV range and is thus undetectable at IceCube,
namely when the dark matter particles annihilate into $e^+e^-$, $\mu^+\mu^-$ or
light quarks. On the other hand, the same interaction that mediates the
annihilations into light fermions also leads, via higher order effects, to the
production of weak gauge bosons (and in the case of quarks also gluons) that
generate a high energy neutrino flux potentially observable at IceCube. We
consider in this paper tree level annihilations into a fermion-antifermion pair
with the associated emission of one gauge boson and one loop annihilations into
two gauge bosons, and we calculate the limits on the scattering cross section
of dark matter particles with protons in scenarios where the dark matter
particle couples to electrons, muons or light quarks from the non-observation
of an excess of neutrino events in the direction of the Sun. We find that the
limits on the spin-dependent scattering cross section are, for some scenarios,
stronger than the limits from direct detection experiments.
| arxiv topic:hep-ph astro-ph.HE |
arxiv_dataset-50201402.4475 | Strong Coupling in Hyperbolic Metamaterials
physics.optics cond-mat.mes-hall
Nanoscale light-matter interaction in the weak-coupling regime has been
achieved with unique hyperbolic metamaterial modes possessing a high density of
states. Here, we show strong coupling between intersubband transitions (ISBTs)
of a multiple quantum well (MQW) slab and the bulk polariton modes of a
hyperbolic metamaterial (HMM). These HMM modes have large wave vectors (high-k
modes) and are normally evanescent in conventional materials. We analyze a
metal-dielectric practical multilayer HMM structure consisting of a highly
doped semiconductor acting as a metallic layer and an active multiple quantum
well dielectric slab. We observe delocalized metamaterial mode interaction with
the active materials distributed throughout the structure. Strong coupling and
characteristic anticrossing with a maximum Rabi splitting (RS) energy of up to
52 meV is predicted between the high-k mode of the HMMand the ISBT, a value
approximately 10.5 times greater than the ISBT linewidth and 4.5 times greater
than the material loss of the structure. The scalability and tunability of the
RS energy in an active semiconductor metamaterial device have potential
applications in quantum well infrared photodetectors and intersubband
light-emitting devices.
| arxiv topic:physics.optics cond-mat.mes-hall |
arxiv_dataset-50211402.4575 | 1SWASP J093010.78+533859.5: A Possible Hierarchical Quintuple System
astro-ph.SR
We present the observational results of this kind of rare object 1SWASP
J093010.78+533859.5, for which the doubly eclips- ing feature had been detected
previously from the SuperWASP photometric archive. Individual PSF photometry
for two objects with a separation of about 1.9 arcsec was performed for the
first time in this study. Our time-series photometric data confirms the finding
of Lohr et al. (2013) that the bright object A is an Algol-type detached
eclipsing binary and the fainter B is a W UMa-type contact eclipsing. Using the
high- resolution optical spectra, we obtained well-defined radial velocity
variations of system A. Furthermore, stationary spectral lines were detected
that must have originated from a further, previously unrecognized stellar
component. It was confirmed by the third object contribution from the light
curve analysis. No spectral feature of the system B was detected, probably due
to motion blur by long exposure time. We obtained the binary parameters and the
absolute dimensions of the systems A and B from light curve synthesis with and
without radial velocities, respectively. The primary and secondary components
of system A have a spectral type of K1 and K5 main sequences, respec- tively.
Two components of system B have nearly the same type of K3 main sequence. Light
variations for both binaries are satisfactorily modeled by using two-spot
models with one starspot on each component. We estimated the distances to
systems A and B individually. Two systems may have similar distances of about
70 pc and seem to be gravitationally bound with a separation of about 130 AU.
In conclusion, we suggest that 1SWASP J093010.78+533859.5 is a quintuple
stellar system with a hierarchical structure of a triple system A(ab)c and a
binary system B(ab).
| arxiv topic:astro-ph.SR |
arxiv_dataset-50221402.4675 | IEEE 802.11ah: The Wi-Fi Approach for M2M Communications
cs.NI
M2M communications are projected to be one of the fastest growing technology
segments of the IT sector in the next years. Sensor and actuator networks
connect communication machines and devices so that they automatically transmit
information, serving the growing demand for environmental data acquisition.
IEEE 802.11ah Task Group addresses the creation of a new standard for giving
response to the particular requirements of this type of networks: large number
of power-constrained stations, long transmission range, small and infrequent
data messages, low data-rates and non-critical delay. This article explores the
key features of this new standard under development, especially those related
to the reduction of energy consumption in the MAC Layer. In this direction, a
performance assessment of IEEE 802.11ah in four typical M2M scenarios has been
performed.
| arxiv topic:cs.NI |
arxiv_dataset-50231402.4775 | Higher homotopy excision and Blakers-Massey theorems for structured ring
spectra
math.AT
Working in the context of symmetric spectra, we prove higher homotopy
excision and higher Blakers-Massey theorems, and their duals, for algebras and
left modules over operads in the category of modules over a commutative ring
spectrum (e.g., structured ring spectra).
| arxiv topic:math.AT |
arxiv_dataset-50241402.4875 | Device-scale perpendicular alignment of colloidal nanorods
cond-mat.mtrl-sci
The self-assembly of nanocrystals enables new classes of materials whose
properties are controlled by the periodicities of the assembly, as well as by
the size, shape and composition of the nanocrystals. While self-assembly of
spherical nanoparticles has advanced significantly in the last decade, assembly
of rod-shaped nanocrystals has seen limited progress due to the requirement of
orientational order. Here, the parameters critically relevant to self-assembly
are systematically quantified using a combination of diffraction and
theoretical modeling; these highlight the importance of kinetics on
orientational order. Through drying-mediated self-assembly we achieve
unprecedented control over orientational order (up to 96% vertically oriented
rods on 1cm2 areas) on a wide range of substrates (ITO, PEDOT:PSS, Si3N4). This
opens new avenues for nanocrystal-based devices competitive with thin film
devices, as problems of granularity can be tackled through crystallographic
orientational control over macroscopic areas.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-50251402.4975 | Comparative study of non-Markovianity measures in exactly solvable one
and two qubit models
quant-ph
In this paper we present a detailed critical study of several recently
proposed non-Markovianity measures. We analyse their properties for single
qubit and two-qubit systems in both pure-dephasing and dissipative scenarios.
More specifically we investigate and compare their computability, their
physical meaning, their Markovian to non-Markovian crossover, and their
additivity properties with respect to the number of qubits. The bottom-up
approach that we pursue is aimed at identifying similarities and differences in
the behavior of non-Markovianity indicators in several paradigmatic open system
models. This in turn allows us to infer the leading traits of the variegated
phenomenon known as non-Markovian dynamics and, possibly, to grasp its physical
essence.
| arxiv topic:quant-ph |
arxiv_dataset-50261402.5075 | Starobinsky-Like Inflation in Dilaton-Brane Cosmology
hep-th astro-ph.CO gr-qc
We discuss how Starobinsky-like inflation may emerge from dilaton dynamics in
brane cosmology scenarios based on string theory, in which our universe is
represented as a three-brane. The effective potential may acquire a constant
term from a density of effectively point-like non-pertubative defects on the
brane. Higher-genus corrections generate corrections to the effective potential
that are exponentially damped at large field values, as in the Starobinsky
model, but at a faster rate, leading to a smaller prediction for the tensor-to
scalar perturbation ratio r. This may be compensated partially by logarithmic
deformations on the world-sheet due to recoil of the defects due to scattering
by string matter on the brane, which tend to enhance the tensor-to-scalar
ratio.
| arxiv topic:hep-th astro-ph.CO gr-qc |
arxiv_dataset-50271402.5175 | The QCD phase transition with physical-mass, chiral quarks
hep-lat
We report on the first lattice calculation of the QCD phase transition using
chiral fermions at physical values of the quark masses. This calculation uses
2+1 quark flavors, spatial volumes between (4 fm$)^3$ and (11 fm$)^3$ and
temperatures between 139 and 196 MeV . Each temperature was calculated using a
single lattice spacing corresponding to a temporal Euclidean extent of $N_t=8$.
The disconnected chiral susceptibility, $\chi_{\rm disc}$ shows a pronounced
peak whose position and height depend sensitively on the quark mass. We find no
metastability in the region of the peak and a peak height which does not change
when a 5 fm spatial extent is increased to 10 fm. Each result is strong
evidence that the QCD ``phase transition'' is not first order but a continuous
cross-over for $m_\pi=135$ MeV. The peak location determines a pseudo-critical
temperature $T_c = 155(1)(8)$ MeV. Chiral $SU(2)_L\times SU(2)_R$ symmetry is
fully restored above 164 MeV, but anomalous $U(1)_A$ symmetry breaking is
non-zero above $T_c$ and vanishes as $T$ is increased to 196 MeV.
| arxiv topic:hep-lat |
arxiv_dataset-50281402.5275 | VHDL Modeling of Intrusion Detection & Prevention System (IDPS) A Neural
Network Approach
cs.CR
The rapid development and expansion of World Wide Web and network systems
have changed the computing world in the last decade and also equipped the
intruders and hackers with new facilities for their destructive purposes. The
cost of temporary or permanent damages caused by unauthorized access of the
intruders to computer systems has urged different organizations to increasingly
implement various systems to monitor data flow in their network. The systems
are generally known as Intrusion Detection System (IDS).Our objective is to
implement an artificial network approach to the design of intrusion detection
and prevention system and finally convert the designed model to a VHDL (Very
High Speed Integrated Circuit Hardware Descriptive Language) code. This feature
enables the system to suggest proper actions against possible attacks. The
promising results of the present study show the potential applicability of ANNs
for developing practical IDSs.
| arxiv topic:cs.CR |
arxiv_dataset-50291402.5375 | Diffuse Interface Methods for Multiple Phase Materials: An Energetic
Variational Approach
math.AP physics.flu-dyn
In this paper, we introduce a diffuse interface model for describing the
dynamics of mixtures involving multiple (two or more) phases. The coupled
hydrodynamical system is derived through an energetic variational approach. The
total energy of the system includes the kinetic energy and the mixing
(interfacial) energies. The least action principle (or the principle of virtual
work) is applied to derive the conservative part of the dynamics, with a focus
on the reversible part of the stress tensor arising from the mixing energies.
The dissipative part of the dynamics is then introduced through a dissipation
function in the energy law, in line with the Onsager principle of least energy
dissipation. The final system, formed by a set of coupled time-dependent
partial differential equations, reflects a balance among various conservative
and dissipative forces and governs the evolution of velocity and phase fields.
To demonstrate the applicability of the proposed model, a few two-dimensional
simulations have been carried out, including (1) the force balance at the
three-phase contact line in equilibrium, (2) a rising bubble penetrating a
fluid-fluid interface, and (3) a solid particle falling in a binary fluid. The
effects of slip at solid surface have been examined in connection with contact
line motion and a pinch-off phenomenon.
| arxiv topic:math.AP physics.flu-dyn |
arxiv_dataset-50301402.5475 | Soft Consistency Reconstruction: A Robust 1-bit Compressive Sensing
Algorithm
cs.IT math.IT
A class of recovering algorithms for 1-bit compressive sensing (CS) named
Soft Consistency Reconstructions (SCRs) are proposed. Recognizing that CS
recovery is essentially an optimization problem, we endeavor to improve the
characteristics of the objective function under noisy environments. With a
family of re-designed consistency criteria, SCRs achieve remarkable
counter-noise performance gain over the existing counterparts, thus acquiring
the desired robustness in many real-world applications. The benefits of soft
decisions are exemplified through structural analysis of the objective
function, with intuition described for better understanding. As expected,
through comparisons with existing methods in simulations, SCRs demonstrate
preferable robustness against noise in low signal-to-noise ratio (SNR) regime,
while maintaining comparable performance in high SNR regime.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-50311402.5575 | High-accuracy absolute distance measurement by two-wavelength double
heterodyne interferometry with variable synthetic wavelengths
physics.ins-det physics.optics
We present an absolute distance measurement interferometer based on a two
wavelength interferometer and a variable synthetic wavelength technique. The
wavelength scanning range was 12 GHz, realized with a phase accuracy of 1.0
m{\lambda} by heterodyne detection at each measurement wavelength. This small
wavelength scanning range enabled the use of distributed feedback laser diodes
as an interferometer light source and a fast 20 ms wavelength scanning time by
injection current control. We demonstrated a measurement range of up to 1.5 m
and an accuracy better than 1.2 nm in comparison with a displacement
measurement interferometer, corresponding to a relative accuracy of 10-9. In
addition, we also proposed expanding the range of maximum measurement and
compensation of refractive index of air for linear colliders.
| arxiv topic:physics.ins-det physics.optics |
arxiv_dataset-50321402.5675 | The brief era of direct collapse black hole formation
astro-ph.CO
It has been proposed that the first, intermediate-mass ($\approx
10^{5-6}~M_\odot$) black holes might form through direct collapse of unpolluted
gas in atomic-cooling halos exposed to a strong Lyman-Werner (LW) or
near-infrared (NIR) radiation. As these systems are expected to be
Compton-thick, photons above 13.6 eV are largely absorbed and re-processed into
lower energy bands. It follows that direct collapse black holes (DCBHs) are
very bright in the LW/NIR bands, typically outshining small high-redshift
galaxies by more than 10 times. Once the first DCBHs form, they then trigger a
runaway process of further DCBH formation, producing a sudden rise in their
cosmic mass density. The universe enters the "DCBH era" at $z \approx 20$ when
a large fraction of atomic-cooling halos are experiencing DCBH formation. By
combining the clustering properties of the radiation sources with Monte Carlo
simulations we show that in this scenario the DCBH mass density rises from
$\sim 5$~$M_\odot$ Mpc$^{-3}$ at $z\sim 30$ to the peak value $\sim5\times10^5
M_\odot$ Mpc$^{-3}$ at $z \sim 14$ in our fiducial model. However, the
abundance of \textit{active} (accreting) DCBHs drops after $z \sim 14$, as gas
in the potential formation sites (unpolluted halos with virial temperature
slightly above $10^4$~K) is photoevaporated. This effect almost completely
suppresses DCBH formation after $z\sim 13$. The DCBH formation era lasts only
$\approx 150$ Myr, but it might crucially provide the seeds of the supermassive
black holes (SMBHs) powering $z\sim6$ quasars.
| arxiv topic:astro-ph.CO |
arxiv_dataset-50331402.5775 | New sum-product estimates for real and complex numbers
math.CO math.NT
A variation on the sum-product problem seeks to show that a set which is
defined by additive and multiplicative operations will always be large. In this
paper, we prove new results of this type. In particular, we show that for any
finite set $A$ of positive real numbers, it is true that
$$\left|\left\{\frac{a+b}{c+d}:a,b,c,d\in{A}\right\}\right|\geq{2|A|^2-1}.$$ As
a consequence of this result, it is also established that
$$|4^{k-1}A^{(k)}|:=|\underbrace{\underbrace{A\cdots{A}}_\textrm{k
times}+\cdots{+A\cdots{A}}}_\textrm{$4^{k-1}$ times}|\geq{|A|^k}.$$ Later on,
it is shown that both of these bounds hold in the case when $A$ is a finite set
of complex numbers, although with smaller multiplicative constants.
| arxiv topic:math.CO math.NT |
arxiv_dataset-50341402.5875 | Observation of strong-coupling pairing with weakened Fermi-surface
nesting at optimal hole doping in Ca$_{0.33}$Na$_{0.67}$Fe$_2$As$_2$
cond-mat.supr-con cond-mat.str-el
We report an angle-resolved photoemission investigation of optimally-doped
Ca$_{0.33}$Na$_{0.67}$Fe$_2$As$_2$. The Fermi surface topology of this compound
is similar to that of the well-studied Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$
material, except for larger hole pockets resulting from a higher hole
concentration per Fe atoms. We find that the quasi-nesting conditions are
weakened in this compound as compared to Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$. As
with Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ though, we observe nearly isotropic
superconducting gaps with Fermi surface-dependent magnitudes. A small variation
in the gap size along the momentum direction perpendicular to the surface is
found for one of the Fermi surfaces. Our superconducting gap results on all
Fermi surface sheets fit simultaneously very well to a global gap function
derived from a strong coupling approach, which contains only 2 global
parameters.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-50351402.5975 | Detecting floating black holes as they traverse the gas disk of the
Milky Way
astro-ph.GA
A population of intermediate-mass black holes (BHs) is predicted to be freely
floating in the Milky Way (MW) halo, due to gravitational wave recoil, ejection
from triple BH systems, or tidal stripping in the dwarf galaxies that merged to
make the MW. As these BHs traverse the gaseous MW disk, a bow shock forms,
producing detectable radio and mm/sub-mm synchrotron emission from accelerated
electrons. We calculate the synchrotron flux to be $\sim \rm 0.01-10\, mJy$ at
GHz frequency, detectable by Jansky Very Large Array, and $\sim 10-100\,\mu\rm
Jy$ at $\sim10^{10}-10^{12} \,\rm Hz$ frequencies, detectable by Atacama Large
Millimeter/sub-millimter Array. The discovery of the floating BH population
will provide insights on the formation and merger history of the MW as well as
on the evolution of massive BHs in the early Universe.
| arxiv topic:astro-ph.GA |
arxiv_dataset-50361402.6075 | Transverse magneto-optical Kerr effect in subwavelength dielectric
gratings
physics.optics
We demonstrate theoretically a large transverse magneto-optical Kerr effect
(TMOKE) in subwavelength gratings consisting of alternating magneto-insulating
and nonmagnetic dielectric nanostripes. The reflectivity of the grating reaches
$96\%$ at the frequencies corresponding to the maximum of the TMOKE response.
The combination of a large TMOKE response and high reflectivity is important
for applications in $3$D imaging, magneto-optical data storage, and magnonics.
| arxiv topic:physics.optics |
arxiv_dataset-50371402.6175 | Elastic Anomalies Associated with the Antiferroelectric Phase
Transitions of PbHfO3 Single Crystals
cond-mat.mtrl-sci
The temperature dependence of the elastic properties of antiferroelectric
PbHfO3 was investigated by Brillouin scattering. The two structural phase
transitions of antiferroelectric-antiferroelectric-paraelectric phases were
clearly identified by discontinuous changes in the acoustic mode frequencies
and the hypersonic damping. The substantial softening of the mode frequency
along with the remarkable increase in the acoustic damping observed in the
paraelectric phase indicated the formation of precursor noncentrosymmetric
(polar) clusters and their coupling to the acoustic waves. This was
corroborated by the observation of quasi-elastic central peaks, the intensity
of which grew upon cooling toward the Curie point. The obtained relaxation time
exhibited a slowing-down behavior, suggesting that the dynamics of precursor
clusters becomes more sluggish on approaching the phase transition temperature.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-50381402.6275 | Power broadening effects on Electromagnetically Induced Transparency in
$^{20}$Ne vapor
physics.optics physics.atom-ph quant-ph
We report here the first observation of electromagnetically induced
transparency (EIT) in $^{20}$Ne. The power broadening of the EIT linewidth is
measured as a function of neon pressure and RF excitation power. Doppler
effects on the EIT broadening are found even at low pressures and low
intensities, where the linewidth should be governed only by homogeneous
effects.
| arxiv topic:physics.optics physics.atom-ph quant-ph |
arxiv_dataset-50391402.6375 | Effects of Reagent Rotation and Vibration on H + OH (v,j) $\to$ O + H2
astro-ph.SR
The dynamics of the reaction H + OH $\to$ O (3P) + H2 have been studied in a
series of quasi-classical trajectory (QCT) calculations and transition state
theory (TST) methods using high quality 3A' and 3A'' potential energy surfaces
(PESs). Accurate OH (v, j) state resolved cross sections and rate constants on
both potential energy surfaces are presented and fitted for OH at (v = 0, j =
0-16) and (v = 1, j = 0-6). The cross sections were calculated for different
collisional energies (Ec), ranging from the threshold energy at each specific
rovibrational state up to 1.0 eV with step sizes of 0.1 eV or less. They
increase steeply with collision energy when the barrier to reaction can be
overcome, after which the cross sections stay nearly constant with energy.
State resolved rate constants in the temperature range 200-2500 K are presented
based on the cross sections. Total thermal rate constants were calculated by
summing the rates for reaction on the 3A' and 3A'' potential energy surfaces
weighted by 1/3 and taking into account the thermal populations of the
rovibrational states of the OH molecules. It is shown that the improved
canonical variational transition (CVT) treatments with the approximation of
zero-curvature tunneling (ZCT) or small-curvature tunneling (SCT) produce
results more in accord with the QCT results than the TST and CVT methods. The
reactions are governed by the direct reaction mechanism. The rate constants for
OH in excited vibrational and rotational states are orders of magnitude larger
than the thermal rate constants, which needs to be taken into account in
astrochemical models.
| arxiv topic:astro-ph.SR |
arxiv_dataset-50401402.6475 | Rupture cascades in a discrete element model of a porous sedimentary
rock
cond-mat.dis-nn physics.geo-ph
We investigate the scaling properties of the sources of crackling noise in a
fully-dynamic numerical model of sedimentary rocks subject to uniaxial
compression. The model is initiated by filling a cylindrical container with
randomly-sized spherical particles which are then connected by breakable beams.
Loading at a constant strain rate the cohesive elements fail and the resulting
stress transfer produces sudden bursts of correlated failures, directly
analogous to the sources of acoustic emissions in real experiments. The source
size, energy, and duration can all be quantified for an individual event, and
the population analyzed for their scaling properties, including the
distribution of waiting times between consecutive events. Despite the
non-stationary loading, the results are all characterized by power law
distributions over a broad range of scales in agreement with experiments. As
failure is approached temporal correlation of events emerge accompanied by
spatial clustering.
| arxiv topic:cond-mat.dis-nn physics.geo-ph |
arxiv_dataset-50411402.6575 | Magneto-elastic modes and lifetime of magnons in thin yttrium-iron
garnet films
cond-mat.str-el
We calculate the effects of the spin-lattice coupling on the magnon spectrum
of thin ferromagnetic films consisting of the magnetic insulator yttrium-iron
garnet. The magnon-phonon hybridisation generates a characteristic minimum in
the spin dynamic structure factor which quantitatively agrees with recent
Brillouin light scattering experiments. We also show that at room temperature
the phonon contribution to the magnon damping exhibits a rather complicated
momentum dependence: In the exchange regime the magnon damping is dominated by
Cherenkov type scattering processes, while in the long-wavelength dipolar
regime these processes are subdominant and the magnon damping is two orders of
magnitude smaller. We supplement our calculations by actual measurements of the
magnon relaxation in the dipolar regime. Our theory provides a simple
explanation of a recent experiment probing the different temperatures of the
magnon and phonon gases in yttrium-iron garnet.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-50421402.6675 | Matrix-F5 algorithms and tropical Gr\"obner bases computation
cs.SC math.AC
Let $K$ be a field equipped with a valuation. Tropical varieties over $K$ can
be defined with a theory of Gr\"obner bases taking into account the valuation
of $K$. Because of the use of the valuation, this theory is promising for
stable computations over polynomial rings over a $p$-adic fields.We design a
strategy to compute such tropical Gr\"obner bases by adapting the Matrix-F5
algorithm. Two variants of the Matrix-F5 algorithm, depending on how the
Macaulay matrices are built, are available to tropical computation with
respective modifications. The former is more numerically stable while the
latter is faster.Our study is performed both over any exact field with
valuation and some inexact fields like $\mathbb{Q}\_p$ or $\mathbb{F}\_q
\llbracket t \rrbracket.$ In the latter case, we track the loss in precision,
and show that the numerical stability can compare very favorably to the case of
classical Gr\"obner bases when the valuation is non-trivial. Numerical examples
are provided.
| arxiv topic:cs.SC math.AC |
arxiv_dataset-50431402.6775 | Analysis of Barcode sequence features to find anomalies due to
amplification Bias
cs.CE q-bio.QM
In this paper we aim at investigating whether barcode sequence features can
predict the read count ambiguities caused during PCR based next generation
sequencing techniques. The methodologies we used are mutual information based
motif discovery and Lasso regression technique using features generated from
the barcode sequence. The results indicate that there is a certain degree of
correlation between motifs discovered in the sequences and the read counts. Our
main contribution in this paper is a thorough investigation of the barcode
features that gave us useful information regarding the significance of the
sequence features and the sequence containing the discovered motifs in
prediction of read counts.
| arxiv topic:cs.CE q-bio.QM |
arxiv_dataset-50441402.6875 | Imaging single Rydberg electrons in a Bose-Einstein condensate
physics.atom-ph cond-mat.quant-gas quant-ph
The quantum mechanical states of electrons in atoms and molecules are
distinct orbitals, which are fundamental for our understanding of atoms,
molecules and solids. Electronic orbitals determine a wide range of basic
atomic properties, allowing also for the explanation of many chemical
processes. Here, we propose a novel technique to optically image the shape of
electron orbitals of neutral atoms using electron-phonon coupling in a
Bose-Einstein condensate. To validate our model we carefully analyze the impact
of a single Rydberg electron onto a condensate and compare the results to
experimental data. Our scheme requires only well-established experimental
techniques that are readily available and allows for the direct capture of
textbook-like spatial images of single electronic orbitals in a single shot
experiment.
| arxiv topic:physics.atom-ph cond-mat.quant-gas quant-ph |
arxiv_dataset-50451402.6975 | Heavy meson decay in three-mesons and FSI
hep-ph
The final state interaction (FSI) contribution to charged $D$ decay into
$K\pi\pi$ is computed within a light-front framework, considering $S$-wave
$K\pi$ interactions in $1/2$ and $3/2$ isospin states. The convergence of the
rescattering series is checked computing terms up to the third perturbative
order. The role of the resonances above $K^*_0(1430)$, and the contribution of
the $K\pi$ $3/2$ isospin channel to charged three-body $D$ decays, are studied
against the available phase-shift analysis.
| arxiv topic:hep-ph |
arxiv_dataset-50461402.7075 | Tests of In-Situ Formation Scenarios for Compact Multiplanet Systems
astro-ph.EP astro-ph.GA
Kepler has identified over 600 multiplanet systems, many of which have
several planets with orbital distances smaller than that of Mercury -- quite
different from the Solar System. Because these systems may be difficult to
explain in the paradigm of core accretion and disk migration, it has been
suggested that they formed in situ within protoplanetary disks with high solid
surface densities. The strong connection between giant planet occurrence and
stellar metallicity is thought to be linked to enhanced solid surface densities
in disks around metal-rich stars, so the presence of a giant planet can be a
detectable sign of planet formation in a high solid surface density disk. I
formulate quantitative predictions for the frequency of long-period giant
planets in these in situ models of planet formation by translating the proposed
increase in disk mass into an equivalent metallicity enhancement. I rederive
the scaling of giant planet occurrence with metallicity as P_gp =
0.05_{-0.02}^{+0.02} x 10^{(2.1 +/- 0.4) [M/H]} = 0.08_{-0.03}^{+0.02} x
10^{(2.3 +/- 0.4) [Fe/H]} and show that there is significant tension between
the frequency of giant planets suggested by the minimum mass extrasolar nebula
scenario and the observational upper limits. This fact suggests that high-mass
disks alone cannot explain the observed properties of the close-in Kepler
multiplanet systems and that migration is still a necessary contributor to
their formation. More speculatively, I combine the metallicity scaling of giant
planet occurrence with recently published small planet occurrence rates to
estimate the number of Solar System analogs in the Galaxy. I find that in the
Milky Way there are perhaps 4 x 10^6 true Solar System analogs with an FGK star
hosting both a terrestrial planet in the habitable zone and a long-period giant
planet companion.
| arxiv topic:astro-ph.EP astro-ph.GA |
arxiv_dataset-50471402.7175 | Rashba induced chirality switching of domain walls and suppression of
the Walker breakdown
cond-mat.mes-hall
In conventional domain wall systems the aim of a high domain wall velocity
may be hindered by the occurrence of a Walker breakdown at comparably low
current density. We show how a Rashba interaction can stabilize the domain wall
dynamics and thereby shift the Walker breakdown to higher current densities.
The Rashba interaction creates a field like spin torque, which breaks the
symmetry of the system and modifies the internal structure of the domain wall.
Besides a shift of the Walker breakdown it can additionally induce a chirality
switch of the domain wall at sufficient Rashba fields. The preferred chirality
may then be chosen by the direction of the current flow. Both, the suppression
of the Walker breakdown and the chirality switching, affect the domain wall
velocity. This is even more pronounced for short current pulses, where an
additional domain wall movement after the pulse in either positive or negative
direction can determine the final position of the domain wall.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-50481402.7275 | Silicene vs. ordered 2D silicide: the atomic and electronic structure of
the Si-$(\sqrt{19}\times\sqrt{19})R23.4^{\circ}$/Pt(111) surface
reconstruction
cond-mat.mtrl-sci
We discuss the possibility of a 2D ordered structure formed upon deposition
of Si on metal surfaces. We investigate the atomic and electronic structure of
the Si-$(\sqrt{19}\times\sqrt{19})R23.4^{\circ}$/Pt(111) surface reconstruction
by means of a set of experimental surface-science techniques supported by
theoretical calculations. The theory achieves a very good agreement with the
experimental results and corroborate beyond any doubt that this phase is a
surface alloy consisting of Si$_3$Pt tetramers that resembles a twisted Kagome
lattice. These findings render unlikely any formation of silicene or germanene
on Pt(111) and other transition metal surfaces.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-50491403.0001 | Link-Reliability Based Two-Hop Routing for Wireless Sensor Networks
cs.NI
Wireless Sensor Networks (WSNs) emerge as underlying infrastructures for new
classes of large scale net- worked embedded systems. However, WSNs system
designers must fulfill the Quality-of-Service (QoS) requirements imposed by the
applications (and users). Very harsh and dynamic physical environments and
extremely limited energy/computing/memory/communication node resources are
major obstacles for satisfying QoS metrics such as reliability, timeliness and
system lifetime. The limited communication range of WSN nodes, link asymmetry
and the characteristics of the physical environment lead to a major source of
QoS degradation in WSNs. This paper proposes a Link Reliability based Two-Hop
Routing protocol for wireless Sensor Networks (WSNs). The protocol achieves to
reduce packet deadline miss ratio while consid- ering link reliability, two-hop
velocity and power efficiency and utilizes memory and computational effective
methods for estimating the link metrics. Numerical results provide insights
that the protocol has a lower packet deadline miss ratio and longer sensor
network lifetime. The results show that the proposed protocol is a feasible
solution to the QoS routing problem in wireless sensor networks that support
real-time applications.
| arxiv topic:cs.NI |
arxiv_dataset-50501403.0101 | Recurrent events of synchrony in complex networks of pulse-coupled
oscillators
physics.bio-ph nlin.AO q-bio.NC
We present and analyze deterministic complex networks of pulse-coupled
oscillators that exhibits recurrent events comprised of an increase and a
decline in synchrony. Events emerging from the networks may form an oscillatory
behavior or may be separated by periods of asynchrony with varying duration.
The phenomenon is specific to spatial networks with both short- and long-ranged
connections and requires delayed interactions and refractoriness of
oscillators.
| arxiv topic:physics.bio-ph nlin.AO q-bio.NC |
arxiv_dataset-50511403.0201 | A Wilcoxon-Mann-Whitney type test for infinite dimensional data
stat.ME
The Wilcoxon-Mann-Whitney test is a robust competitor of the t-test in the
univariate setting. For finite dimensional multivariate data, several
extensions of the Wilcoxon-Mann-Whitney test have been shown to have better
performance than Hotelling's $T^{2}$ test for many non-Gaussian distributions
of the data. In this paper, we study a Wilcoxon-Mann-Whitney type test based on
spatial ranks for data in infinite dimensional spaces. We demonstrate the
performance of this test using some real and simulated datasets. We also
investigate the asymptotic properties of the proposed test and compare the test
with a wide range of competing tests.
| arxiv topic:stat.ME |
arxiv_dataset-50521403.0301 | Moment Determinacy of Powers and Products of Nonnegative Random
Variables
math.PR
We find conditions which guarantee moment (in)determinacy of powers and
products of nonnegative random variables. We establish new and general results
which are based either on the rate of growth of the moments of a random
variable or on conditions about the distribution itself. For the class of
generalized gamma random variables we show that the power and the product of
such variables share the same moment determinacy property. A similar statement
holds for half-logistic random variables. Besides answering new questions in
this area, we either extend some previously known results or provide new and
transparent proofs of existing results.
| arxiv topic:math.PR |
arxiv_dataset-50531403.0401 | Orbits and Manifolds near the Equilibrium Points around a Rotating
Asteroid
astro-ph.EP
We study the orbits and manifolds near the equilibrium points of a rotating
asteroid. The linearised equations of motion relative to the equilibrium points
in the gravitational field of a rotating asteroid, the characteristic equation
and the stable conditions of the equilibrium points are derived and discussed.
First, a new metric is presented to link the orbit and the geodesic of the
smooth manifold. Then, using the eigenvalues of the characteristic equation,
the equilibrium points are classified into 8 cases. A theorem is presented and
proved to describe the structure of the submanifold as well as the stable and
unstable behaviours of a massless particle near the equilibrium points. The
linearly stable, the non-resonant unstable, and the resonant equilibrium points
are discussed. There are three families of periodic orbits and four families of
quasi-periodic orbits near the linearly stable equilibrium point. For the
non-resonant unstable equilibrium points, there are four cases; for the
periodic orbit and the quasi-periodic orbit, the structures of the submanifold
and the subspace near the equilibrium points are studied for each case. For the
resonant equilibrium points, the dimension of the resonant manifold is greater
than four, and we find at least 1 family of periodic orbits near the resonant
equilibrium points. Besides, this theory is applied to asteroids 216 Kleopatra,
1620 Geographos, 4769 Castalia, and 6489 Golevka.
| arxiv topic:astro-ph.EP |
arxiv_dataset-50541403.0501 | Casimir Effect of Scalar Massive Field
quant-ph hep-th
The energy momentum tensor is used to introduce the Casimir force of the
massive scalar field acting on a nonpenetrating surface. This expression can be
used to evaluate the vacuum force by employing the appropriate field operators.
To simplify our formalism we also relates the vacuum force expression to the
imaginary part of the Green function via the fluctuation dissipation theorem
and Kubo formula. This allows one to evaluate the vacuum force without
resorting to the process of field quantization. These two approaches are used
to calculate the attractive force between two nonpenetrating plates. Special
attention is paid to the generalization of the formalism to D + 1 space-time
dimensions.
| arxiv topic:quant-ph hep-th |
arxiv_dataset-50551403.0601 | Phase Field Crystal Modeling as a Unified Atomistic Approach to Defect
Dynamics
cond-mat.mtrl-sci
Material properties controlled by evolving defect structures, such as
mechanical response, often involve processes spanning many length and time
scales which cannot be modeled using a single approach. We present a variety of
new results that demonstrate the ability of phase field crystal (PFC) models to
describe complex defect evolution phenomena on atomistic length scales and over
long, diffusive time scales. Primary emphasis is given to the unification of
conservative and non- conservative dislocation creation mechanisms in
three-dimensional FCC and BCC materials. These include Frank-Read-type glide
mechanisms involving closed dislocation loops or grain boundaries as well as
Bardeen-Herring-type climb mechanisms involving precipitates, inclusions,
and/or voids. Both source classes are naturally and simultaneously captured at
the atomistic level by PFC de- scriptions, with arbitrarily complex defect
configurations, types, and environments. An unexpected dipole-to-quadrupole
source transformation is identified, as well as various new and complex geomet-
rical features of loop nucleation via climb from spherical particles. Results
for the strain required to nucleate a dislocation loop from such a particle are
in agreement with analytic continuum theories. Other basic features of FCC and
BCC dislocation structure and dynamics are also outlined, and initial results
for dislocation-stacking fault tetrahedron interactions are presented. These
findings together highlight various capabilities of the PFC approach as a
coarse-grained atomistic tool for the study of three-dimensional crystal
plasticity.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-50561403.0701 | GraphChi-DB: Simple Design for a Scalable Graph Database System -- on
Just a PC
cs.DB
We propose a new data structure, Parallel Adjacency Lists (PAL), for
efficiently managing graphs with billions of edges on disk. The PAL structure
is based on the graph storage model of GraphChi (Kyrola et. al., OSDI 2012),
but we extend it to enable online database features such as queries and fast
insertions. In addition, we extend the model with edge and vertex attributes.
Compared to previous data structures, PAL can store graphs more compactly while
allowing fast access to both the incoming and the outgoing edges of a vertex,
without duplicating data. Based on PAL, we design a graph database management
system, GraphChi-DB, which can also execute powerful analytical graph
computation.
We evaluate our design experimentally and demonstrate that GraphChi-DB
achieves state-of-the-art performance on graphs that are much larger than the
available memory. GraphChi-DB enables anyone with just a laptop or a PC to work
with extremely large graphs.
| arxiv topic:cs.DB |
arxiv_dataset-50571403.0801 | Is getting the right answer just about choosing the right words? The
role of syntactically-informed features in short answer scoring
cs.CL
Developments in the educational landscape have spurred greater interest in
the problem of automatically scoring short answer questions. A recent shared
task on this topic revealed a fundamental divide in the modeling approaches
that have been applied to this problem, with the best-performing systems split
between those that employ a knowledge engineering approach and those that
almost solely leverage lexical information (as opposed to higher-level
syntactic information) in assigning a score to a given response. This paper
aims to introduce the NLP community to the largest corpus currently available
for short-answer scoring, provide an overview of methods used in the shared
task using this data, and explore the extent to which more
syntactically-informed features can contribute to the short answer scoring task
in a way that avoids the question-specific manual effort of the knowledge
engineering approach.
| arxiv topic:cs.CL |
arxiv_dataset-50581403.0901 | Tracking Back the Solar Wind to its Photospheric Footpoints from Wind
Observations -- A Statistical Study
astro-ph.SR
It is of great importance to track the solar wind back to its photospheric
source region and identify the related current sheets; this will provide key
information for investigating the origin and predictions of the solar wind. We
report a statistical study relating the photospheric footpoint motion and
in-situ observation of current sheets in the solar wind. We used the potential
force-free source--surface (PFSS) model and the daily synoptic charts to trace
the solar wind back from 1 AU, as observed by the Wind spacecraft, to the solar
surface. As the footpoints move along the solar surface we obtain a time series
of the jump times between different points. These jumps can be within a cell
and between adjacent cells. We obtained the distribution of the jump times and
the distribution for a subset of the jump times in which only jumps between
adjacent cells were counted. For both cases, the distributions clearly show two
populations. These distributions are compared with the distribution of in-situ
current sheets reported in an earlier work of Miao Peng and Li (2011). Its
implications on the origin of the current sheets are discussed.
| arxiv topic:astro-ph.SR |
arxiv_dataset-50591403.1001 | Cosmological constant in SUGRA models with Planck scale SUSY breaking
and degenerate vacua
hep-ph astro-ph.CO gr-qc hep-th
The empirical mass of the Higgs boson suggests small to vanishing values of
the quartic Higgs self--coupling and the corresponding beta function at the
Planck scale, leading to degenerate vacua. This leads us to suggest that the
measured value of the cosmological constant can originate from supergravity
(SUGRA) models with degenerate vacua. This scenario is realised if there are at
least three exactly degenerate vacua. In the first vacuum, associated with the
physical one, local supersymmetry (SUSY) is broken near the Planck scale while
the breakdown of the SU(2)_W\times U(1)_Y symmetry takes place at the
electroweak (EW) scale. In the second vacuum local SUSY breaking is induced by
gaugino condensation at a scale which is just slightly lower than \Lambda_{QCD}
in the physical vacuum. Finally, in the third vacuum local SUSY and EW symmetry
are broken near the Planck scale.
| arxiv topic:hep-ph astro-ph.CO gr-qc hep-th |
arxiv_dataset-50601403.1101 | Braided injections and double loop spaces
math.AT
We consider a framework for representing double loop spaces (and more
generally E-2 spaces) as commutative monoids. There are analogous commutative
rectifications of braided monoidal structures and we use this framework to
define iterated double deloopings. We also consider commutative rectifications
of E-infinity spaces and symmetric monoidal categories and we relate this to
the category of symmetric spectra.
| arxiv topic:math.AT |
arxiv_dataset-50611403.1201 | Correction of Arbitrary Errors in Population Inversion of Quantum
Systems by Universal Composite Pulses
quant-ph
We introduce universal broadband composite pulse sequences for robust
high-fidelity population inversion in two-state quantum systems, which
compensate deviations in any experimental parameter (e.g. pulse amplitude,
pulse duration, detuning from resonance, Stark shifts, unwanted frequency
chirp, etc.) and are applicable with any pulse shape. We demonstrate the
efficiency and universality of these composite pulses by experimental data on
rephasing of atomic coherences in a
$\text{Pr}^{3+}\text{:}\text{Y}_2\text{SiO}_5$ crystal.
| arxiv topic:quant-ph |
arxiv_dataset-50621403.1301 | Single photon emission from ZnO nanoparticles
cond-mat.mtrl-sci physics.optics
Room temperature single photon emitters are very important resources for
photonics and emerging quantum technologies. In this work we study single
photon emission from defect centers in 20 nm zinc oxide (ZnO) nanoparticles.
The emitters exhibit bright broadband fluorescence in the red spectral range
centered at 640 nm with polarized excitation and emission. The studied emitters
showed continuous blinking, however, bleaching can be suppressed using a
polymethyl methacrylate (PMMA) coating. Furthermore, hydrogen termination
increased the density of single photon emitters. Our results will contribute to
the identification of quantum systems in ZnO.
| arxiv topic:cond-mat.mtrl-sci physics.optics |
arxiv_dataset-50631403.1401 | The NLS equation in dimension one with spatially concentrated
nonlinearities: the pointlike limit
math-ph math.AP math.MP
In the present paper we study the following scaled nonlinear Schr\"odinger
equation (NLS) in one space dimension: \[ i\frac{d}{dt} \psi^{\varepsilon}(t)
=-\Delta\psi^{\varepsilon}(t) +
\frac{1}{\epsilon}V\left(\frac{x}{\epsilon}\right)|\psi^{\varepsilon}(t)|^{2\mu}\psi^{\varepsilon}(t)
\quad \quad \epsilon>0\ ,\quad V\in L^1(\mathbb{R},(1+|x|)dx) \cap
L^\infty(\mathbb{R}) \ . \] This equation represents a nonlinear Schr\"odinger
equation with a spatially concentrated nonlinearity. We show that in the limit
$\epsilon\to 0$, the weak (integral) dynamics converges in $H^1(\mathbb{R})$ to
the weak dynamics of the NLS with point-concentrated nonlinearity: \[
i\frac{d}{dt} \psi(t) =H_{\alpha}\psi(t) . \] where $H_{\alpha}$ is the
laplacian with the nonlinear boundary condition at the origin
$\psi'(t,0+)-\psi'(t,0-)=\alpha|\psi(t,0)|^{2\mu}\psi(t,0)$ and
$\alpha=\int_{\mathbb{R}}Vdx$. The convergence occurs for every $\mu\in
\mathbb{R}^+$ if $V \geq 0$ and for every $\mu\in (0,1)$ otherwise. The same
result holds true for a nonlinearity with an arbitrary number $N$ of
concentration points
| arxiv topic:math-ph math.AP math.MP |
arxiv_dataset-50641403.1501 | Sparse DOA Estimation of Wideband Sound Sources Using Circular Harmonics
cs.SD
Sparse signal models are in the focus of recent developments in narrowband
DOA estimation. Applying these methods to localizing audio sources, however, is
challenging due to the wideband nature of the signals. The common approach of
processing all frequency bands separately and fusing the results is costly and
can introduce errors in the solution. We show how these problems can be
overcome by decomposing the wavefield of a circular microphone array and using
circular harmonic coefficients instead of time-frequency data for sparse DOA
estimation. As a result, we present the super-resolution localization method
WASCHL (Wideband Audio Sparse Circular Harmonics Localizer) that is inherently
frequency-coherent and highly efficient from a computational point of view.
| arxiv topic:cs.SD |
arxiv_dataset-50651403.1601 | A bound on the number of edges in graphs without an even cycle
math.CO
We show that, for each fixed $k$, an $n$-vertex graph not containing a cycle
of length $2k$ has at most $80\sqrt{k}\log k\cdot n^{1+1/k}+O(n)$ edges.
| arxiv topic:math.CO |
arxiv_dataset-50661403.1701 | The transfer of resonance line polarization with partial frequency
redistribution and J-state interference
astro-ph.SR
The linear polarization signals produced by scattering processes in strong
resonance lines are rich in information on the magnetic and thermal structure
of the chromosphere and transition region of the Sun and of other stars. A
correct modeling of these signals requires accounting for partial frequency
redistribution effects, as well as for the impact of quantum interference
between different fine structure levels (J-state interference). In this paper,
we present a theoretical approach suitable for modeling the transfer of
resonance line polarization when taking these effects into account, along with
an accurate numerical method of solution of the problem's equations. We
consider a two-term atom with unpolarized lower term and infinitely sharp lower
levels, in the absence of magnetic fields. We show that by making simple formal
substitutions on the quantum numbers, the theoretical approach derived here for
a two-term atom can also be applied to describe a two-level atom with hyperfine
structure. An illustrative application to the MgII doublet around 2800A is
presented.
| arxiv topic:astro-ph.SR |
arxiv_dataset-50671403.1801 | Smooth manifolds with prescribed rational cohomology ring
math.GT
The Hirzebruch signature formula provides an obstruction to the following
realization question: given a rational Poincar\'e duality algebra
$\mathcal{A}$, does there exist a smooth manifold $M$ such that
$H^*(M;\mathbb{Q})=\mathcal{A}$?
This problem is especially interesting for rational truncated polynomial
algebras whose corresponding integral algebra is not realizable. For example,
there are number theoretic constraints on the dimension $n$ in which there
exists a closed smooth manifold $M^n$ with $H^*(M^n;\mathbb{Q})=
\mathbb{Q}[x]/\langle x^3\rangle$. We limit the possible existence dimension to
$n=8(2^a+2^b)$. For $n = 32$, such manifolds are not two-connected. We show
that the next smallest possible existence dimension is $n=128$. As there exists
no integral $\mathbb{O}P^m$ for $m>2$, the realization of the truncated
polynomial algebra $\mathbb{Q}[x]/\langle x^{m+1}\rangle, |x|=8$ is studied.
Similar considerations provide examples of topological manifolds which do not
have the rational homotopy type of a smooth closed manifold.
The appendix presents a recursive algorithm for efficiently computing the
coefficients of the L-polynomials which arise in the signature formula.
| arxiv topic:math.GT |
arxiv_dataset-50681403.1901 | NuSTAR Discovery of a cyclotron line in KS 1947+300
astro-ph.HE
We present a spectral analysis of three simultaneous NuSTAR and Swift/XRT
observations of the transient Be-neutron star binary KS 1947+300 taken during
its outburst in 2013/2014. These broad-band observations were supported by
Swift/XRT monitoring snap-shots every 3 days, which we use to study the
evolution of the spectrum over the outburst. We find strong changes of the
power-law photon index, which shows a weak trend of softening with increasing
X-ray flux. The neutron star shows very strong pulsations with a period of P ~
18.8 s. The 0.8-79 keV broad-band spectrum can be described by a power-law with
an exponential cutoff and a black-body component at low energies. During the
second observation we detect a cyclotron resonant scattering feature at 12.5
keV, which is absent in the phase-averaged spectra of observations 1 and 3.
Pulse phase-resolved spectroscopy reveals that the strength of the feature
changes strongly with pulse phase and is most prominent during the broad
minimum of the pulse profile. At the same phases the line also becomes visible
in the first and third observation at the same energy. This discovery implies
that KS 1947+300 has a magnetic field strength of B ~ 1.1e12 (1+z)G, which is
at the lower end of known cyclotron line sources.
| arxiv topic:astro-ph.HE |
arxiv_dataset-50691403.2001 | EEG Compression of Scalp Recordings based on Dipole Fitting
cs.IT math.IT
A novel technique for Electroencephalogram (EEG) compression is proposed in
this article. This technique models the intrinsic dependency inherent between
the different EEG channels. It is based on dipole fitting that is usually used
in order to find a solution to the classic problems in EEG analysis: inverse
and forward problems. The suggested compression system uses dipole fitting as a
first building block to provide an approximation of the recorded signals. Then,
(based on a smoothness factor,) appropriate coding techniques are suggested to
compress the residuals of the fitting process. Results show that this technique
works well for different types of recordings and is even able to provide near-
lossless compression for event-related potentials.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-50701403.2101 | The DFT and molecular dynamics multiscale study of the corrugation of
graphene on Ru(0001): the unexpected stability of the moire-buckled structure
cond-mat.mtrl-sci
Results from first principles density functional theory (DFT) calculations
and classical molecular dynamics (CMD) simulations are presented on
moire-corrugation of graphene (gr). We find that the moire-corrugated graphene
could be surprisingly stable against the perfectly flat gr-sheet as pointed out
by CMD simulations and DFT calculations. We also show that using the
cost-effective CMD approach one can simulate graphene on e.g. Ru(0001) with a
correct binding registry and reasonable corrugation and adhesion energy. A new
force field has been parameterized for the interface using an angular-dependent
Abell-Tersoff potential. The newly parameterized Abell-Tersoff interface
potential provides correct moire superstructures in accordance with scanning
tunnelling microscopy images and with DFT results. Based on ab initio DFT
calculations, we also find that the CMD moire superstructure can be used as a
preoptimized structure for DFT calculations and for further geometry
optimization. The nearly flat gr (the corrugation $\xi \approx 0.2$
$\hbox{\AA}$) on Ru(0001) is slightly energetically unfavorable vs. the
moire-corrugated gr-system ($\xi \approx 2.0$ $\hbox{\AA}$) as revealed by van
der Waals DFT structural relaxation.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-50711403.2201 | SMML estimators for linear regression and tessellations of hyperbolic
space
cs.IT math.IT
The strict minimum message length (SMML) principle links data compression
with inductive inference. The corresponding estimators have many useful
properties but they can be hard to calculate. We investigate SMML estimators
for linear regression models and we show that they have close connections to
hyperbolic geometry. When equipped with the Fisher information metric, the
linear regression model with $p$ covariates and a sample size of $n$ becomes a
Riemannian manifold, and we show that this is isometric to $(p+1)$-dimensional
hyperbolic space $\mathbb{H}^{p+1}$ equipped with a metric tensor which is $2n$
times the usual metric tensor on $\mathbb{H}^{p+1}$. A natural identification
then allows us to also view the set of sufficient statistics for the linear
regression model as a hyperbolic space. We show that the partition of an SMML
estimator corresponds to a tessellation of this hyperbolic space.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-50721403.2301 | Phase Retrieval using Lipschitz Continuous Maps
math.FA cs.IT math.IT stat.ML
In this note we prove that reconstruction from magnitudes of frame
coefficients (the so called "phase retrieval problem") can be performed using
Lipschitz continuous maps. Specifically we show that when the nonlinear
analysis map $\alpha:{\mathcal H}\rightarrow\mathbb{R}^m$ is injective, with
$(\alpha(x))_k=|<x,f_k>|^2$, where $\{f_1,\ldots,f_m\}$ is a frame for the
Hilbert space ${\mathcal H}$, then there exists a left inverse map
$\omega:\mathbb{R}^m\rightarrow {\mathcal H}$ that is Lipschitz continuous.
Additionally we obtain the Lipschitz constant of this inverse map in terms of
the lower Lipschitz constant of $\alpha$. Surprisingly the increase in
Lipschitz constant is independent of the space dimension or frame redundancy.
| arxiv topic:math.FA cs.IT math.IT stat.ML |
arxiv_dataset-50731403.2401 | Geometric generators for braid-like groups
math.GT
We study the problem of finding generators for the fundamental group G of a
space of the following sort: one removes a family of complex hyperplanes from n
dimensional complex vector space, or n dimensional complex hyperbolic space, or
the Hermitian symmetric space for O(2,n), and then takes the quotient by a
discrete group $P{\Gamma}$. The classical example is the braid group, but there
are many similar "braid-like" groups that arise in topology and algebraic
geometry. Our main result is that if $P{\Gamma}$ contains reflections in the
hyperplanes nearest the basepoint, and these reflections satisfy a certain
property, then G is generated by the analogues of the generators of the
classical braid group. We apply this to obtain generators for G in a particular
intricate example in complex hyperbolic space of dimension 13. The interest in
this example comes from a conjectured relationship between this braid-like
group and the monster simple group M, that gives geometric meaning to the
generators and relations in the Conway-Simons presentation of $(M \times M):2$.
| arxiv topic:math.GT |
arxiv_dataset-50741403.2501 | Application of AdS/CFT in Nuclear Physics
hep-th
We review some recent progress in studying the nuclear physics especially
nucleon-nucleon (NN) force within the gauge-gravity duality, in context of
noncritical string theory. Our main focus is on the holographic QCD model based
on the $AdS_6$ background. We explain the noncritical holography model and
obtain the vector-meson spectrum and pion decay constant. Also, we study the NN
interaction in this frame and calculate the nucleon-meson coupling constants. A
further topic covered is a toy model for calculating the light nuclei
potential. In particular, we calculate the light nuclei binding energies and
also excited energies of some available excited states. We compare our results
with the results of other nuclear models and also with the experimental data.
Moreover, we describe some other issues which are studied using the
gauge-gravity duality.
| arxiv topic:hep-th |
arxiv_dataset-50751403.2601 | Thermodynamics of the unified dark fluid with fast transition
gr-qc
In the so-called unified dark fluid models, the dark sector gets simplified
because dark matter and dark energy are replaced by a single fluid that behaves
as the former at early times and as the latter at late times. In this short
paper we analyze this class of models from the thermodynamic viewpoint. While
the second law of thermodynamics is satisfied, the first two derivatives of the
entropies of the apparent horizon and of the energy components suffer such a
sharp oscillation that doubts are raised about the soundness of this class of
models.
| arxiv topic:gr-qc |
arxiv_dataset-50761403.2701 | No Semiconjugacy to a Map of Constant Slope
math.DS
We study countably piecewise continuous, piecewise monotone interval maps. We
establish a necessary and sufficient criterion for the existence of a
nondecreasing semiconjugacy to a map of constant slope in terms of the
existence of an eigenvector of an operator acting on a space of measures. Then
we give sufficient conditions under which this criterion is not satisfied.
Finally, we give examples of maps not semiconjugate to a map of constant slope
via a nondecreasing map. Our examples are continuous and transitive.
| arxiv topic:math.DS |
arxiv_dataset-50771403.2801 | Astronomical Imagery: Considerations For a Contemporary Approach with
JPEG2000
astro-ph.IM
The new wide-field radio telescopes, such as: ASKAP, MWA, LOFAR, eVLA and
SKA; will produce spectral-imaging data-cubes (SIDC) of unprecedented size --
in the order of hundreds of Petabytes. Servicing such data as images to the
end-user in a traditional manner and formats is likely going to encounter
significant performance fallbacks. We discuss the requirements for extremely
large SIDCs, and in this light we analyse the applicability of the approach
taken in the JPEG2000 (ISO/IEC 15444) standards. We argue the case for the
adaptation of contemporary industry standards and technologies vs the
modification of legacy astronomy standards or the development new from scratch.
| arxiv topic:astro-ph.IM |
arxiv_dataset-50781403.2901 | Maximum Principles of Markov Regime-Switching Forward-Backward
Stochastic Differential Equations with Jumps and Partial Information
math.OC
This paper presents three versions of maximum principle for a stochastic
optimal control problem of Markov regime-switching forward-backward stochastic
differential equations with jumps (FBSDEJs). A general sufficient maximum
principle for optimal control for a system driven by a Markov regime-switching
forward and backward jump-diffusion model is developed. After, an equivalent
maximum principle is proved. Malliavin calculus is also employed to derive a
general stochastic maximum principle. The latter does not require concavity of
Hamiltonian. Applications of the stochastic maximum principle to non-concave
Hamiltonian and recursive utility maximization is also discussed.
| arxiv topic:math.OC |
arxiv_dataset-50791403.3001 | "The Gibbon of Math History". Who Invented the St. Petersburg Paradox?
Khinchin's resolution
math.HO
A sentence from Carl Boyer's A History of Mathematics can be interpreted so
that the full brothers Nicolaus II (02/06/1695 - 07/31/1726) and Daniel
Bernoulli (02/08/1700 - 03/17/1782) are the authors of the St. Petersburg
paradox. The paradox was formulated by their cousin Nicolaus I Bernoulli
(10/21/1687 - 11/29/1759). The author did not find evidences that Nicolaus II
and Daniel Bernoulli discussed the paradox. The key articles on the topic and
its history from Karl Menger and Paul Samuelson, and recent papers presenting
the time resolution miss Alexandr Khinchin's resolution of the paradox in his
paper "On Petersburg game." Matematicheskii sbornik, Volume 32, No 2, 1925, pp.
330 - 341. The C++ program khinchin.cpp simulates conditions of two Khinchin's
theorems and confirms his results providing concrete empirical dependencies of
the frequencies corresponding to geometric and arithmetic mean payments on the
number of Petersburg games.
| arxiv topic:math.HO |
arxiv_dataset-50801403.3101 | Topological Insulating Phases of Non-Abelian Anyonic Chains
cond-mat.str-el
Boundary conformal field theory is brought to bear on the study of
topological insulating phases of non-abelian anyonic chains. These
topologically non-trivial phases display protected anyonic end modes. We
consider antiferromagnetically coupled spin-1/2 su(2)$_k$ chains at any level
$k$, focusing on the most prominent examples; the case $k = 2$ describes Ising
anyons (equivalent to Majorana fermions) and $k = 3$ corresponds to Fibonacci
anyons. We prove that the braiding of these emergent anyons exhibits the same
braiding behavior as the physical quasiparticles. These results suggest a
`solid-state' topological quantum computation scheme in which the emergent
anyons are braided by simply tuning couplings of non-Abelian quasiparticles in
a fixed network.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-50811403.3201 | The rate of convergence of some Riemann-Stieltjes sums
math.CA
We give the rate of convergence of some optimal lower Riemann-Stieltjes sums
toward the integral.
| arxiv topic:math.CA |
arxiv_dataset-50821403.3301 | Amino acid metabolism conflicts with protein diversity
q-bio.PE q-bio.BM
The twenty protein coding amino acids are found in proteomes with different
relative abundances. The most abundant amino acid, leucine, is nearly an order
of magnitude more prevalent than the least abundant amino acid, cysteine. Amino
acid metabolic costs differ similarly, constraining their incorporation into
proteins. On the other hand, sequence diversity is necessary for protein
folding, function and evolution. Here we present a simple model for a
cost-diversity trade-off postulating that natural proteomes minimize amino acid
metabolic flux while maximizing sequence entropy. The model explains the
relative abundances of amino acids across a diverse set of proteomes. We found
that the data is remarkably well explained when the cost function accounts for
amino acid chemical decay. More than one hundred proteomes reach comparable
solutions to the trade-off by different combinations of cost and diversity.
Quantifying the interplay between proteome size and entropy shows that
proteomes can get optimally large and diverse.
| arxiv topic:q-bio.PE q-bio.BM |
arxiv_dataset-50831403.3401 | Coy Dark Matter and the anomalous magnetic moment
hep-ph astro-ph.CO astro-ph.HE
Coy Dark Matter removes the tension between the traditional WIMP paradigm of
Dark Matter and the latest exclusion bounds from direct detection experiments.
In this paper we present a leptophilic Coy Dark Matter model that, on top of
explaining the spatially extended 1-5 GeV $\gamma$-ray excess detected at the
Galactic Center, reconciles the measured anomalous magnetic moment of muon with
the corresponding Standard Model prediction. The annihilation channel of DM is
$\chi\chi \to \tau\bar\tau$ with the DM mass $m_\chi =
9.43\,(^{+.063}_{-0.52}\,{\rm stat.})\,(\pm 1.2 \,{\rm sys.})$ GeV given by
best-fit of the $\gamma$-ray excess. Fitting the measured anomalous magnetic
moment of the muon requires instead a pseudoscalar mediator with a minimal mass
$m_a = 12^{+7}_{-3}$ GeV.
| arxiv topic:hep-ph astro-ph.CO astro-ph.HE |
arxiv_dataset-50841403.3501 | Normal closure and injective normalizer of a group homomorphism
math.GR math.AT
Let $\varphi\colon\Gamma\to G$ be a homomorphism of groups. We consider
factorizations $\Gamma\xrightarrow{f} M\xrightarrow{g} G$ of $\varphi$ such
that either $g$ or $f$ are universal normal maps (namely, crossed modules).
These two factorizations are natural generalizations of the usual normal
closure and normalizer of a subgroup. Iterating these universal factorizations
yield towers related, on the one hand, to hypercentral group extensions,
Bousfield's localizations, and relative Schur multipliers. Dually, they extend
to a relative situation, the automorphisms tower of a centerless group. Our
constructions have strong ties to topological constructions.
| arxiv topic:math.GR math.AT |
arxiv_dataset-50851403.3601 | Phoretic self-propulsion at finite P\'eclet numbers
physics.flu-dyn cond-mat.soft physics.bio-ph
Phoretic self-propulsion is a unique example of force- and torque-free motion
on small scales. The classical framework describing the flow field around a
particle swimming by self-diffusiophoresis neglects the advection of the solute
field by the flow and assumes that the chemical interaction layer is thin
compared to the particle size. In this paper we quantify and characterize the
effect of solute advection on the phoretic swimming of a sphere. We first
rigorously derive the regime of validity of the thin-interaction layer
assumption at finite values of the P\'eclet number (Pe). Within this
assumption, we solve computationally the flow around Janus phoretic particles
and examine the impact of solute advection on propulsion and the flow created
by the particle. We demonstrate that although advection always leads to a
decrease of the swimming speed and flow stresslet at high values of the
P\'eclet number, an increase can be obtained at intermediate values of Pe. This
possible enhancement of swimming depends critically on the nature of the
chemical interactions between the solute and the surface. We then derive an
asymptotic analysis of the problem at small Pe allowing to rationalize our
computational results. Our computational and theoretical analysis is
accompanied by a parallel study of the role of reactive effects at the surface
of the particle on swimming (Damk\"ohler number).
| arxiv topic:physics.flu-dyn cond-mat.soft physics.bio-ph |
arxiv_dataset-50861403.3701 | Axisymmmetric empty space: light propagation, orbits and dark matter
gr-qc
This study presents a axisymmetric solution of the Einstein equations for
empty space. The geometry is studied by determining its Petrov classification
and Killing vectors. Light propagation, orbital motion and asymptotic and
Newtonian limits are also studied. Additionally, cosmological applications of
the geometry as an alternative model for the inflationary universe and as a
substitute for dark matter and quintessence are also outlined.
| arxiv topic:gr-qc |
arxiv_dataset-50871403.3801 | An extension of Tur\'an's Theorem, uniqueness and stability
math.CO
We determine the maximum number of edges of an $n$-vertex graph $G$ with the
property that none of its $r$-cliques intersects a fixed set $M\subset V(G)$.
For $(r-1)|M|\ge n$, the $(r-1)$-partite Turan graph turns out to be the unique
extremal graph. For $(r-1)|M|<n$, there is a whole family of extremal graphs,
which we describe explicitly. In addition we provide corresponding stability
results.
| arxiv topic:math.CO |
arxiv_dataset-50881403.3901 | New invariant relations for the generalized two-field gyrostat
nlin.SI
In the paper, we consider a completely integrable Hamiltonian system with
three degrees of freedom found by V.V.Sokolov and A.V.Tsiganov. This system is
known as the generalized two-field gyrostat. For the case of only gyroscopic
forces present, we find new invariant four-dimensional submanifolds such that
the induced dynamical systems are almost everywhere Hamiltonian with two
degrees of freedom.
| arxiv topic:nlin.SI |
arxiv_dataset-50891403.4001 | Static potentials on asymptotically flat manifolds
math.DG gr-qc
We consider the question whether a static potential on an asymptotically flat
3-manifold can have nonempty zero set which extends to the infinity. We prove
that this does not occur if the metric is asymptotically Schwarzschild with
nonzero mass. If the asymptotic assumption is relaxed to the usual assumption
under which the total mass is defined, we prove that the static potential is
unique up to scaling unless the manifold is flat. We also provide some
discussion concerning the rigidity of complete asymptotically flat 3-manifolds
without boundary that admit a static potential.
| arxiv topic:math.DG gr-qc |
arxiv_dataset-50901403.4101 | New criterion of asymptotic stability for delay systems with
time-varying structures and delays
math.CA
In this paper, we study asymptotic stability of the zero solution of a class
of differential systems governed by a scalar differential inequality with
time-varying structures and delays. We establish a new generalized Halanay
inequality for the asymptotic stability of the zero solution for such systems
under more relaxed conditions than the existing ones. We also apply the
theoretical results to the analysis of self synchronization in networks of
delayed differential systems and obtained a more general sufficient condition
for self synchronization.
| arxiv topic:math.CA |
arxiv_dataset-50911403.4201 | Graded polynomial identities and central polynomials of matrices over an
infinite integral domain
math.RA
Let $K$ be an infinite integral domain and $M_{n}(K)$ be the algebra of all
$n\times n$ matrices over $K$. This paper aims for the following goals:
Find a basis for the graded identities for elementary grading in $M_{n}(K)$
when the neutral component and diagonal coincide; Describe the
$\mathbb{Z}_{p}$-graded central polynomials of $M_{p}(K)$ when $p$ is a prime
number; Describe the $\mathbb{Z}$-graded central polynomials of $M_{n}(K)$.
| arxiv topic:math.RA |
arxiv_dataset-50921403.4301 | The power of choice combined with preferential attachment
math.PR math.CO
We prove almost sure convergence of the maximum degree in an evolving tree
model combining local choice and preferential attachment. At each step in the
growth of the graph, a new vertex is introduced. A fixed, finite number of
possible neighbors are sampled from the existing vertices with probability
proportional to degree. Of these possibilities, the vertex with the largest
degree is chosen. The maximal degree in this model has linear or near-linear
behavior. This contrasts sharply with what is seen in the same choice model
without preferential attachment. The proof is based showing the tree has a
persistent hub by comparison with the standard preferential attachment model,
as well as martingale and random walk arguments.
| arxiv topic:math.PR math.CO |
arxiv_dataset-50931403.4401 | On spinors, strings, integrable models and decomposed Yang-Mills theory
hep-th math-ph math.MP nlin.SI
This paper deals with various interrelations between strings and surfaces in
three dimensional ambient space, two dimensional integrable models and two
dimensional and four dimensional decomposed SU(2) Yang-Mills theories.
Initially, a spinor version of the Frenet equation is introduced in order to
describe the differential geometry of static three dimensional string-like
structures. Then its relation to the structure of the su(2) Lie algebra valued
Maurer-Cartan one-form is presented; while by introducing time evolution of the
string a Lax pair is obtained, as an integrability condition. In addition, it
is show how the Lax pair of the integrable nonlinear Schroedinger equation
becomes embedded into the Lax pair of the time extended spinor Frenet equation
and it is described how a spinor based projection operator formalism can be
used to construct the conserved quantities, in the case of the nonlinear
Schroedinger equation. Then the Lax pair structure of the time extended spinor
Frenet equation is related to properties of flat connections in a two
dimensional decomposed SU(2) Yang-Mills theory. In addition, the connection
between the decomposed Yang-Mills and the Gauss-Godazzi equation that describes
surfaces in three dimensional ambient space is presented. In that context the
relation between isothermic surfaces and integrable models is discussed.
Finally, the utility of the Cartan approach to differential geometry is
considered. In particular, the similarities between the Cartan formalism and
the structure of both two dimensional and four dimensional decomposed SU(2)
Yang-Mills theories are discussed, while the description of two dimensional
integrable models as embedded structures in the four dimensional decomposed
SU(2) Yang-Mills theory are presented.
| arxiv topic:hep-th math-ph math.MP nlin.SI |
arxiv_dataset-50941403.4501 | Social insect colony as a biological regulatory system: Information flow
in dominance networks
q-bio.PE physics.soc-ph
Social insects provide an excellent platform to investigate flow of
information in regulatory systems since their successful social organization is
essentially achieved by effective information transfer through complex
connectivity patterns among the colony members. Network representation of such
behavioural interactions offers a powerful tool for structural as well as
dynamical analysis of the underlying regulatory systems. In this paper, we
focus on the dominance interaction networks in the tropical social wasp
\textit{Ropalidia marginata} - a species where behavioural observations
indicate that such interactions are principally responsible for the transfer of
information between individuals about their colony needs, resulting in a
regulation of their own activities. Our research reveals that the dominance
networks of \textit{R. marginata} are structurally similar to a class of
naturally evolved information processing networks, a fact confirmed also by the
predominance of a specific substructure - the `feed-forward loop' - a key
functional component in many other information transfer networks. The dynamical
analysis through Boolean modeling confirms that the networks are sufficiently
stable under small fluctuations and yet capable of more efficient information
transfer compared to their randomized counterparts. Our results suggest the
involvement of a common structural design principle in different biological
regulatory systems and a possible similarity with respect to the effect of
selection on the organization levels of such systems. The findings are also
consistent with the hypothesis that dominance behaviour has been shaped by
natural selection to co-opt the information transfer process in such social
insect species, in addition to its primal function of mediation of reproductive
competition in the colony.
| arxiv topic:q-bio.PE physics.soc-ph |
arxiv_dataset-50951403.4601 | A perfect starburst cluster made in one go: the NGC 3603 young cluster
astro-ph.GA astro-ph.SR
Understanding how distinct, near-spherical gas-free clusters of very young,
massive stars shape out of vast, complex clouds of molecular hydrogen is one of
the biggest challenges in astrophysics. A popular thought dictates that a
single gas cloud fragments into many new-born stars which, in turn, energize
and rapidly expel the residual gas to form a gas-free cluster. This study
demonstrates that the above classical paradigm remarkably reproduces the
well-observed central, young cluster (HD 97950) of the Galactic NGC 3603
star-forming region, in particular, its shape, internal motion and the mass
distribution of stars, naturally and consistently follow from a single model
calculation. Remarkably, the same parameters (star formation efficiency, gas
expulsion time scale and delay) reproduce HD 97950 as were found to reproduce
the Orion Nebula Cluster, Pleiades and R136. The present results thereby
provide intriguing evidences of formation of star clusters through
single-starburst events followed by significant residual gas expulsion.
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-50961403.4701 | Betweenness Centrality in Some Classes of Graphs
math.CO
There are several centrality measures that have been introduced and studied
for real world networks. They account for the different vertex characteristics
that permit them to be ranked in order of importance in the network.
Betweenness centrality is a measure of the influence of a vertex over the flow
of information between every pair of vertices under the assumption that
information primarily flows over the shortest path between them. In this paper
we present betweenness centrality of some important classes of graphs.
| arxiv topic:math.CO |
arxiv_dataset-50971403.4801 | Coherence rephasing combined with spin-wave storage using chirped
control pulses
quant-ph
Photon-echo based optical quantum memory schemes often employ intermediate
steps to transform optical coherences to spin coherences for longer storage
times. We analyze a scheme that uses three identical chirped control pulses for
coherence rephasing in an inhomogeneously broadened ensemble of three-level
$\Lambda$-systems. The pulses induce a cyclic permutation of the atomic
populations in the adiabatic regime. Optical coherences created by a signal
pulse are stored as spin coherences at an intermediate time interval, and are
rephased for echo emission when the ensemble is returned to the initial state.
Echo emission during a possible partial rephasing when the medium is inverted
can be suppressed with an appropriate choice of control pulse wavevectors. We
demonstrate that the scheme works in an optically dense ensemble, despite
control pulse distortions during propagation. It integrates conveniently the
spin-wave storage step into memory schemes based on a second rephasing of the
atomic coherences.
| arxiv topic:quant-ph |
arxiv_dataset-50981403.4901 | On homogeneous warped product Einstein metrics
math.DG
In this article we study homogeneous warped product Einstein metrics and its
connections with homogeneous Ricci solitons. We show that homogeneous
$(\lambda,n+m)$-Einstein manifolds (which are the bases of homogeneous warped
product Einstein metrics) are one-dimensional extensions of algebraic solitons.
This answers a question from a paper of C. He, P. Petersen and W. Wylie, where
they prove the converse statement. Our proof is strongly based on their
results, but it also makes use of sharp tools from the theory of homogeneous
Ricci solitons. As an application, we obtain that any homogeneous warped
product Einstein metric with homogeneous base is diffeomorphic to a product of
homogeneous Einstein manifolds.
| arxiv topic:math.DG |
arxiv_dataset-50991403.5001 | k-Nearest Neighbor Classification over Semantically Secure Encrypted
Relational Data
cs.CR
Data Mining has wide applications in many areas such as banking, medicine,
scientific research and among government agencies. Classification is one of the
commonly used tasks in data mining applications. For the past decade, due to
the rise of various privacy issues, many theoretical and practical solutions to
the classification problem have been proposed under different security models.
However, with the recent popularity of cloud computing, users now have the
opportunity to outsource their data, in encrypted form, as well as the data
mining tasks to the cloud. Since the data on the cloud is in encrypted form,
existing privacy preserving classification techniques are not applicable. In
this paper, we focus on solving the classification problem over encrypted data.
In particular, we propose a secure k-NN classifier over encrypted data in the
cloud. The proposed k-NN protocol protects the confidentiality of the data,
user's input query, and data access patterns. To the best of our knowledge, our
work is the first to develop a secure k-NN classifier over encrypted data under
the semi-honest model. Also, we empirically analyze the efficiency of our
solution through various experiments.
| arxiv topic:cs.CR |
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