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arxiv_dataset-43001305.2732 | An efficient algorithm for learning with semi-bandit feedback
cs.LG
We consider the problem of online combinatorial optimization under
semi-bandit feedback. The goal of the learner is to sequentially select its
actions from a combinatorial decision set so as to minimize its cumulative
loss. We propose a learning algorithm for this problem based on combining the
Follow-the-Perturbed-Leader (FPL) prediction method with a novel loss
estimation procedure called Geometric Resampling (GR). Contrary to previous
solutions, the resulting algorithm can be efficiently implemented for any
decision set where efficient offline combinatorial optimization is possible at
all. Assuming that the elements of the decision set can be described with
d-dimensional binary vectors with at most m non-zero entries, we show that the
expected regret of our algorithm after T rounds is O(m sqrt(dT log d)). As a
side result, we also improve the best known regret bounds for FPL in the full
information setting to O(m^(3/2) sqrt(T log d)), gaining a factor of sqrt(d/m)
over previous bounds for this algorithm.
| arxiv topic:cs.LG |
arxiv_dataset-43011305.2832 | Decoupling of Fourier Reconstruction System for Shifts of Several
Signals
math.CA
We consider the problem of ``algebraic reconstruction'' of linear
combinations of shifts of several signals $f_1,\ldots,f_k$ from the Fourier
samples. For each $r=1,\ldots,k$ we choose sampling set $S_r$ to be a subset of
the common set of zeroes of the Fourier transforms ${\cal F}(f_\l), \ \l \ne
r$, on which ${\cal F}(f_r)\ne 0$. We show that in this way the reconstruction
system is reduced to $k$ separate systems, each including only one of the
signals $f_r$. Each of the resulting systems is of a ``generalized Prony''
form. We discuss the problem of unique solvability of such systems, and provide
some examples.
| arxiv topic:math.CA |
arxiv_dataset-43021305.2932 | A first look at transition amplitudes in (2+1)-dimensional causal
dynamical triangulations
gr-qc hep-lat hep-th
We study a lattice regularization of the gravitational path integral--causal
dynamical triangulations--for (2+1)-dimensional Einstein gravity with positive
cosmological constant in the presence of past and future spacelike boundaries
of fixed intrinsic geometries. For spatial topology of a 2-sphere, we determine
the form of the Einstein-Hilbert action supplemented by the
Gibbons-Hawking-York boundary terms within the Regge calculus of causal
triangulations. Employing this action we numerically simulate a variety of
transition amplitudes from the past boundary to the future boundary. To the
extent that we have so far investigated them, these transition amplitudes
appear consistent with the gravitational effective action previously found to
characterize the ground state of quantum spacetime geometry within the
Euclidean de Sitter-like phase. Certain of these transition amplitudes
convincingly demonstrate that the so-called stalks present in this phase are
numerical artifacts of the lattice regularization, seemingly indicate that the
quantization technique of causal dynamical triangulations differs in detail
from that of the no-boundary proposal of Hartle and Hawking, and possibly
represent the first numerical simulations of portions of temporally unbounded
quantum spacetime geometry within the causal dynamical triangulations approach.
We also uncover tantalizing evidence suggesting that Lorentzian not Euclidean
de Sitter spacetime dominates the ground state on sufficiently large scales.
| arxiv topic:gr-qc hep-lat hep-th |
arxiv_dataset-43031305.3032 | Universal Superfluid Transition and Transport Properties of
Two-Dimensional Dirty Bosons
cond-mat.quant-gas
We study the phase diagram of two-dimensional, interacting bosons in the
presence of a correlated disorder in continuous space, using large-scale finite
temperature quantum Monte Carlo simulations. We show that the superfluid
transition is strongly protected against disorder. It remains of the
Berezinskii-Kosterlitz-Thouless type up to disorder strengths comparable to the
chemical potential. Moreover, we study the transport properties in the strong
disorder regime where a zero-temperature Bose-glass phase is expected. We show
that the conductance exhibits a thermally activated behavior vanishing only at
zero temperature. Our results point towards the existence of Bose bad-metal
phase as a precursor of the Bose-glass phase.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-43041305.3132 | Conformal supergravity in three dimensions: New off-shell formulation
hep-th
We propose a new off-shell formulation for N-extended conformal supergravity
in three spacetime dimensions. Our construction is based on the gauging of the
N-extended superconformal algebra in superspace. Covariant constraints are
imposed such that the algebra of covariant derivatives is given in terms of a
single curvature superfield which turns out to be the super Cotton tensor. An
immediate corollary of this construction is that the curved superspace is
conformally flat if and only if the super Cotton tensor vanishes. Upon
degauging of certain local symmetries, our formulation is shown to reduce to
the conventional one with the local structure group SL(2,R) x SO(N).
| arxiv topic:hep-th |
arxiv_dataset-43051305.3232 | Linear and nonlinear Anderson localization in a curved potential
physics.optics cond-mat.quant-gas nlin.PS
We investigate disorder induced localization in the presence of nonlinearity
and curvature. We numerically analyze the time-resolved three-dimensional
expansion of a wave-packet in a bended cigar shaped potential with a focusing
Kerr-like interaction term and Gaussian disorder. We report on a
self-consistent analytical theory in which randomness, nonlinearity and
geometry are determined by a single scaling parameter, and show that curvature
enhances localization.
| arxiv topic:physics.optics cond-mat.quant-gas nlin.PS |
arxiv_dataset-43061305.3332 | In-vivo magnetic resonance imaging of hyperpolarized silicon particles
cond-mat.mes-hall cond-mat.mtrl-sci physics.med-ph
Silicon-based micro and nanoparticles have gained popularity in a wide range
of biomedical applications due to their biocompatibility and biodegradability
in-vivo, as well as a flexible surface chemistry, which allows drug loading,
functionalization and targeting. Here we report direct in-vivo imaging of
hyperpolarized 29Si nuclei in silicon microparticles by MRI. Natural physical
properties of silicon provide surface electronic states for dynamic nuclear
polarization (DNP), extremely long depolarization times, insensitivity to the
in-vivo environment or particle tumbling, and surfaces favorable for
functionalization. Potential applications to gastrointestinal, intravascular,
and tumor perfusion imaging at sub-picomolar concentrations are presented.
These results demonstrate a new background-free imaging modality applicable to
a range of inexpensive, readily available, and biocompatible Si particles.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci physics.med-ph |
arxiv_dataset-43071305.3432 | G - functors arising from categorical group actions on abelian
categories
math.CT math.KT math.QA
A Mackey type decomposition for group actions on abelian categories is
described. This allows us to define new Mackey functors which associates to any
subgroup the $K$-theory of the corresponding equivariantized abelian category.
In the case of an action by tensor autoequivalences the Mackey functor at the
level of Grothendieck rings has a Green functor structure. As an application we
give a description of the Grothendieck rings of equivariantized fusion
categories under group actions by tensor autoequivalences on graded fusion
categories.
| arxiv topic:math.CT math.KT math.QA |
arxiv_dataset-43081305.3532 | Temporal networks of face-to-face human interactions
physics.soc-ph cs.SI
The ever increasing adoption of mobile technologies and ubiquitous services
allows to sense human behavior at unprecedented levels of details and scale.
Wearable sensors are opening up a new window on human mobility and proximity at
the finest resolution of face-to-face proximity. As a consequence, empirical
data describing social and behavioral networks are acquiring a longitudinal
dimension that brings forth new challenges for analysis and modeling. Here we
review recent work on the representation and analysis of temporal networks of
face-to-face human proximity, based on large-scale datasets collected in the
context of the SocioPatterns collaboration. We show that the raw behavioral
data can be studied at various levels of coarse-graining, which turn out to be
complementary to one another, with each level exposing different features of
the underlying system. We briefly review a generative model of temporal contact
networks that reproduces some statistical observables. Then, we shift our focus
from surface statistical features to dynamical processes on empirical temporal
networks. We discuss how simple dynamical processes can be used as probes to
expose important features of the interaction patterns, such as burstiness and
causal constraints. We show that simulating dynamical processes on empirical
temporal networks can unveil differences between datasets that would otherwise
look statistically similar. Moreover, we argue that, due to the temporal
heterogeneity of human dynamics, in order to investigate the temporal
properties of spreading processes it may be necessary to abandon the notion of
wall-clock time in favour of an intrinsic notion of time for each individual
node, defined in terms of its activity level. We conclude highlighting several
open research questions raised by the nature of the data at hand.
| arxiv topic:physics.soc-ph cs.SI |
arxiv_dataset-43091305.3632 | Low temperature structural effects in the (TMTSF)$_2$PF$_6$ and AsF$_6$
Bechgaard salts
cond-mat.str-el
We present a detailed low-temperature investigation of the statics and
dynamics of the anions and methyl groups in the organic conductors
(TMTSF)$_2$PF$_6$ and (TMTSF)$_2$AsF$_6$ (TMTSF :
tetramethyl-tetraselenafulvalene). The 4 K neutron scattering structure
refinement of the fully deuterated (TMTSF)$_2$PF$_6$-D12 salt allows locating
precisely the methyl groups at 4 K. This structure is compared to the one of
the fully hydrogenated (TMTSF)$_2$PF$_6$-H12 salt previously determined at the
same temperature. Surprisingly it is found that deuteration corresponds to the
application of a negative pressure of 5 x 10$^2$ MPa to the H12 salt. Accurate
measurements of the Bragg intensity show anomalous thermal variations at low
temperature both in the deuterated PF$_6$ and AsF$_6$ salts. Two different
thermal behaviors have been distinguished. Low-Bragg-angle measurements reflect
the presence of low-frequency modes at characteristic energies {\theta}$_E$ =
8.3 K and {\theta}$_E$ = 6.7 K for the PF$_6$-D12 and AsF$_6$-D12 salts,
respectively. These modes correspond to the low-temperature methyl group
motion. Large-Bragg-angle measurements evidence an unexpected structural change
around 55 K which probably corresponds to the linkage of the anions to the
methyl groups via the formation of F...D-CD2 bonds observed in the 4 K
structural refinement. Finally we show that the thermal expansion coefficient
of (TMTSF)$_2$PF$_6$ is dominated by the librational motion of the PF$_6$
units. We quantitatively analyze the low-temperature variation of the lattice
expansion via the contribution of Einstein oscillators, which allows us to
determine for the first time the characteristic frequency of the PF6
librations: {\theta}$_E$ = 50 K and {\theta}$_E$ = 76 K for the PF$_6$-D12 and
PF$_6$-H12 salts, respectively.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-43101305.3732 | Excitation spectrum in two-dimensional superfluid 4He
cond-mat.other cond-mat.stat-mech
In this work we perform an ab-initio study of an ideal two-dimensional sample
of 4He atoms, a model for 4He films adsorbed on several kinds of substrates.
Starting from a realistic hamiltonian we face the microscopic study of the
excitation phonon-roton spectrum of the system at zero temperature. Our
approach relies on Path Integral Ground State Monte Carlo projection methods,
allowing to evaluate exactly the dynamical density correlation functions in
imaginary time, and this gives access to the dynamical structure factor of the
system S(q,omega), containing information about the excitation spectrum E(q),
resulting in sharp peaks in S(q,omega). The actual evaluation of S(q,omega)
requires the inversion of the Laplace transform in ill-posed conditions, which
we face via the Genetic Inversion via Falsification of Theories technique. We
explore the full density range from the region of spinodal decomposition to the
freezing density, i.e. 0.0321 A^-2 - 0.0658 A^-2. In particular we follow the
density dependence of the excitation spectrum, focusing on the low wave--vector
behavior of E(q), the roton dispersion, the strength of single quasi--particle
peak, Z(q), and the static density response function, chi(q). As the density
increases, the dispersion E(q) at low wave--vector changes from a super-linear
(anomalous dispersion) trend to a sub-linear (normal dispersion) one,
anticipating the crystallization of the system; at the same time the
maxon-roton structure, which is barely visible at low density, becomes well
developed at high densities and the roton wave vector has a strong density
dependence. Connection is made with recent inelastic neutron scattering results
from highly ordered silica nanopores partially filled with 4He.
| arxiv topic:cond-mat.other cond-mat.stat-mech |
arxiv_dataset-43111305.3832 | Thermal Conductivity Inhibition in Phonon Engineered Core-Shell
Cross-Section Modulated Si/Ge Nanowires
cond-mat.mes-hall
We have shown theoretically that a combination of cross-section modulation
and acoustic mismatch in the core-shell Si/Ge nanowires can lead to a drastic
reduction of the thermal conductivity. Our calculations, which utilized two
different models - five-parameter Born-von Karman and six-parameter
valence-force field - for the lattice vibrations, indicate that the room
temperature thermal conductivity of Si/Ge cross-section modulated nanowires is
almost three orders of magnitude lower than that of bulk Si. Thermal flux in
the modulated nanowires is suppressed by an order of magnitude in comparison
with generic Si nanowires. The effect is explained by modification of the
phonon spectra in modulated nanowires leading to decrease of the phonon group
velocities and localization of certain phonon modes in narrow or wide nanowire
segments. The thermal conductivity inhibition is achieved in nanowires without
additional surface roughness and, thus, potentially reducing degradation of the
electron transport. Our results suggest that the acoustically mismatched
cross-section modulated nanowires are promising candidates for thermoelectric
applications.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-43121305.3932 | Inferring the Origin Locations of Tweets with Quantitative Confidence
cs.SI cs.HC cs.LG
Social Internet content plays an increasingly critical role in many domains,
including public health, disaster management, and politics. However, its
utility is limited by missing geographic information; for example, fewer than
1.6% of Twitter messages (tweets) contain a geotag. We propose a scalable,
content-based approach to estimate the location of tweets using a novel yet
simple variant of gaussian mixture models. Further, because real-world
applications depend on quantified uncertainty for such estimates, we propose
novel metrics of accuracy, precision, and calibration, and we evaluate our
approach accordingly. Experiments on 13 million global, comprehensively
multi-lingual tweets show that our approach yields reliable, well-calibrated
results competitive with previous computationally intensive methods. We also
show that a relatively small number of training data are required for good
estimates (roughly 30,000 tweets) and models are quite time-invariant
(effective on tweets many weeks newer than the training set). Finally, we show
that toponyms and languages with small geographic footprint provide the most
useful location signals.
| arxiv topic:cs.SI cs.HC cs.LG |
arxiv_dataset-43131305.4032 | Radiative Mechanisms in GRB prompt emission
astro-ph.HE
Motivated by the Fermi gamma-ray space telescope results, in recent years
immense efforts were given to understanding the mechanism that leads to the
prompt emission observed. The failure of the optically thin emission models
(synchrotron and synchrotron self Compton) increased interest in alternative
models. Optically thick models, while having several advantages, also face
difficulty in capturing several key observables. Theoretical efforts are
focused in two main directions: (1) mechanisms that act to broaden the Planck
spectrum; and (2) combining the optically thin and optically thick models to a
hybrid model that could explain the key observables.
| arxiv topic:astro-ph.HE |
arxiv_dataset-43141305.4132 | Risk-minimization and hedging claims on a jump-diffusion market model,
Feynman-Kac Theorem and PIDE
q-fin.PR
At first, we solve a problem of finding a risk-minimizing hedging strategy on
a general market with ratings. Next, we find a solution to this problem on
Markovian market with ratings on which prices are influenced by additional
factors and rating, and behavior of this system is described by SDE driven by
Wiener process and compensated Poisson random measure and claims depend on
rating. To find a tool to calculate hedging strategy we prove a Feynman-Kac
type theorem. This result is of independent interest and has many applications,
since it enables to calculate some conditional expectations using related
PIDE's. We illustrate our theory on two examples of market. The first is a
general exponential L\'{e}vy model with stochastic volatility, and the second
is a generalization of exponential L\'{e}vy model with regime-switching.
| arxiv topic:q-fin.PR |
arxiv_dataset-43151305.4232 | Embedding Riemannian Manifolds by the Heat Kernel of the Connection
Laplacian
math.DG math.SP math.ST stat.ML stat.TH
Given a class of closed Riemannian manifolds with prescribed geometric
conditions, we introduce an embedding of the manifolds into $\ell^2$ based on
the heat kernel of the Connection Laplacian associated with the Levi-Civita
connection on the tangent bundle. As a result, we can construct a distance in
this class which leads to a pre-compactness theorem on the class under
consideration.
| arxiv topic:math.DG math.SP math.ST stat.ML stat.TH |
arxiv_dataset-43161305.4332 | Quasilinear and Hessian type equations with exponential reaction and
measure data
math.AP
We prove existence results concerning equations of the type
$-\Delta_pu=P(u)+\mu$ for $p>1$ and $F_k[-u]=P(u)+\mu$ with $1\leq
k<\frac{N}{2}$ in a bounded domain $\Omega$ or the whole $\mathbb{R}^N$, where
$\mu$ is a positive Radon measure and $P(u)\sim e^{au^\beta}$ with $a>0$ and
$\beta\geq 1$. Sufficient conditions for existence are expressed in terms of
the fractional maximal potential of $\mu$. Two-sided estimates on the solutions
are obtained in terms of some precise Wolff potentials of $\mu$. Necessary
conditions are obtained in terms of Orlicz capacities. We also establish
existence results for a general Wolff potential equation under the form $u={\bf
W}_{\alpha,p}^R[P(u)]+f$ in $\mathbb{R}^N$, where $0
| arxiv topic:math.AP |
arxiv_dataset-43171305.4432 | Adsorption of cytosine and aza derivatives of cytidine on Au single
crystal surfaces
physics.chem-ph cond-mat.mtrl-sci
The adsorption of cytosine on the Au(111) and Au(110) surfaces has been
studied using both aqueous deposition and evaporation in vacuum to prepare the
samples. Soft X-ray photoelectron spectroscopy (XPS) and near edge X-ray
absorption fine structure spectroscopy (NEXAFS) were used to determine the
electronic structure and orientation of the adsorbates. In addition, three
derivatives of cytosine, 6-azacytosine, 6-azacytidine and 5- azacytidine, were
studied. Monolayer films of the latter three samples were adsorbed on Au(111)
from aqueous solution, and the nature of bonding was determined. Spectra have
been interpreted in the light of published calculations of free cytosine
molecules and new ab initio calculations of the other compounds. Surface core
level shifts of Au 4f imply that all of these compounds are chemisorbed.
Cytosine adsorbs as a single tautomer, but in two chemical states with
different surface-molecule bonding. For deposition in vacuum, a flat-lying
molecular state bonded through the N(3) atom of the pyrimidine ring dominates,
but a second state is also present. For deposition from solution, the second
state dominates, with the molecular plane no longer parallel to the surface.
This state also bonds through the N(3) atom, but in addition interacts with the
surface via the amino group. Two tautomers of 6-azacytosine were observed, and
they and 6-azacytidine adsorb with similar geometries, chemically bonding via
the azacytosine ring. The ribose ring does not appear to perturb the adsorption
of azacytidine compared with azacytosine. The azacytosine ring is nearly but
not perfectly parallel to the surface, like 5-azacytidine, which adsorbs as an
imino tautomer. ...
| arxiv topic:physics.chem-ph cond-mat.mtrl-sci |
arxiv_dataset-43181305.4532 | Strongly representable algebras
math.LO
We give a simpler proof of a result of Hodkinson in the context of a blow and
blur up construction argueing that the idea at heart is similar to that adopted
by Andr\'eka et all \cite{sayed}. The idea is to blow up a finite structure,
replacing each 'colour or atom' by infinitely many, using blurs to represent
the resulting term algebra, but the blurs are not enough to blur the structure
of the finite structure in the complex algebra. A reverse of this process
exists in the literature, it builds algebras with infinite blurs converging to
one with finite blurs. This idea due to Hirsch and Hodkinson, uses
probabilistic methods of Erdos to construct a sequence of graphs with infinite
chromatic number one that is 2 colourable. This construction, which works for
both relation and cylindric algebras, further shows that the class of strongly
representable atom structures is not elementary. We will generalize such a
result for any class of algebras between diagonal free algebras and polyadic
algebras with and without equality, then we further discuss possibilities for
the infinite dimensional case.
Finally, we suggest a very plausible equivalence, and that is: If $n>2$, is
finite, and $\A\in \CA_n$ is countable and atomic, then $\Cm\At\A$ is
representable if and only if $\A\in \Nr_n\CA_{\omega}$. We could prove one
side.
| arxiv topic:math.LO |
arxiv_dataset-43191305.4632 | The Process of Mobile Spectrum Allocation and its impact on Electronic
Commerce and Mobile Commerce
cs.CY cs.GT
Spectrum being a very scarce natural resource of a country has to be
judicially used for the purpose of nation building and the allocation process
to telecom operators should be very transparent and ethical. There are various
ways of how spectrum can be allocated and there is no best way that can be
adopted universally. The market situation, Government policies, competition etc
determine the price of the spectrum and this is purely a regulatory or a
government decision to sell spectrum to telecom companies. The different
allocation methods, their implications with case studies across the globe is
analysed and presented in this paper. The reason why spectrum allocation should
be fair and transparent and the cost should be reasonable is analysed and
described.
| arxiv topic:cs.CY cs.GT |
arxiv_dataset-43201305.4732 | Enabling Self-Powered Autonomous Wireless Sensors with New-Generation
I2C-RFID Chips
cs.OH
A self-powered autonomous RFID device with sensing and computing capabilities
is presented in this paper. Powered by an RF energy-harvesting circuit enhanced
by a DC-DC voltage booster in silicon-on-insulator (SOI) technology, the device
relies on a microcontroller and a new generation I2C-RFID chip to wirelessly
deliver sensor data to standard RFID EPC Class-1 Generation-2 (Gen2) readers.
When the RF power received from the interrogating reader is -14 dBm or higher,
the device, fabricated on an FR4 substrate using low-cost discrete components,
is able to produce 2.4-V DC voltage to power its circuitry. The experimental
results demonstrate the effectiveness of the device to perform reliable sensor
data transmissions up to 5 meters in fully-passive mode. To the best of our
knowledge, this represents the longest read range ever reported for passive UHF
RFID sensors compliant with the EPC Gen2 standard.
| arxiv topic:cs.OH |
arxiv_dataset-43211305.4832 | Secure Biometrics: Concepts, Authentication Architectures and Challenges
cs.CR cs.IT math.IT
BIOMETRICS are an important and widely used class of methods for identity
verification and access control. Biometrics are attractive because they are
inherent properties of an individual. They need not be remembered like
passwords, and are not easily lost or forged like identifying documents. At the
same time, bio- metrics are fundamentally noisy and irreplaceable. There are
always slight variations among the measurements of a given biometric, and,
unlike passwords or identification numbers, biometrics are derived from
physical characteristics that cannot easily be changed. The proliferation of
biometric usage raises critical privacy and security concerns that, due to the
noisy nature of biometrics, cannot be addressed using standard cryptographic
methods. In this article we present an overview of "secure biometrics", also
referred to as "biometric template protection", an emerging class of methods
that address these concerns.
| arxiv topic:cs.CR cs.IT math.IT |
arxiv_dataset-43221305.4932 | Warm Ionized Gas Revealed in the Magellanic Bridge Tidal Remnant:
Constraining the Baryon Content and the Escaping Ionizing Photons around
Dwarf Galaxies
astro-ph.GA
The Magellanic System includes some of the nearest examples of galaxies
disturbed by galaxy interactions. These interactions have redistributed much of
their gas into the halos of the Milky Way and the Magellanic Clouds. We present
Wisconsin H-alpha Mapper kinematically resolved observations of the warm
ionized gas in the Magellanic Bridge over the velocity range of +100 to +300
km/s in the local standard-of-rest reference frame. These observations include
the first full H-alpha intensity map and the corresponding intensity-weighted
mean velocity map of the Magellanic Bridge across (l, b) = (281.5, -30.0) to
(302.5, -46.7). Using the H-alpha emission from the SMC-Tail and the Bridge we
estimate that the mass of the ionized material is between (0.7-1.7)x10^8 times
the mass of the Sun, compared to 3.3x10^8 times the mass of the Sun for the
neutral mass over the same region. The diffuse Bridge is significantly more
ionized than the SMC-Tail, with an ionization fraction of 36-52% compared to
5-24% for the Tail. The H-alpha emission has a complex multiple-component
structure with a velocity distribution that could trace the sources of
ionization or distinct ionized structures. We find that incident radiation from
the extragalactic background and the Milky Way alone are insufficient to
produced the observed ionization in the Magellanic Bridge and present a model
for the escape fraction of the ionizing photons from both the Small and Large
Magellanic Clouds. With this model, we place an upper limit of 4.0% for the
average escape fraction of ionizing photons from the LMC and an upper limit of
5.5% for the SMC. These results, combined with the findings of a half a dozen
results for dwarf galaxies in different environments, provide compelling
evidence that only a small percentage of the ionizing photons escape from dwarf
galaxies in the present epoch to influence their surroundings.
| arxiv topic:astro-ph.GA |
arxiv_dataset-43231305.5032 | Binary shuffle bases for quasi-symmetric functions
math.CO
We construct bases of quasi-symmetric functions whose product rule is given
by the shuffle of binary words, as for multiple zeta values in their integral
representations, and then extend the construction to the algebra of free
quasi-symmetric functions colored by positive integers. As a consequence, we
show that the fractions introduced in [Guo and Xie, Ramanujan Jour. 25 (2011)
307-317] provide a realization of this algebra by rational moulds extending
that of free quasi-symmetric functions given in [Chapoton et al., Int. Math.
Res. Not. IMRN 2008, no. 9, Art. ID rnn018].
| arxiv topic:math.CO |
arxiv_dataset-43241305.5132 | Distributed Power Control Network and Green Building Test-bed for Demand
Response in Smart Grid
cs.SY
It is known that demand and supply power balancing is an essential method to
operate power delivery system and prevent blackouts caused by power shortage.
In this paper, we focus on the implementation of demand response strategy to
save power during peak hours by using Smart Grid. It is obviously impractical
with centralized power control network to realize the real-time control
performance, where a single central controller measures the huge metering data
and sends control command back to all customers. For that purpose, we propose a
new architecture of hierarchical distributed power control network which is
scalable regardless of the network size. The sub-controllers are introduced to
partition the large system into smaller distributed clusters where low-latency
local feedback power control loops are conducted to guarantee control
stability. Furthermore, sub-controllers are stacked up in an hierarchical
manner such that data are fed back layer-by-layer in the inbound while in the
outbound control responses are decentralized in each local sub-controller for
realizing the global objectives. Numerical simulations in a realistic scenario
of up to 5000 consumers show the effectiveness of the proposed scheme to
achieve a desired 10% peak power saving by using off-the-shelf wireless devices
with IEEE802.15.4g standard. In addition, a small scale power control system
for green building test-bed is implemented to demonstrate the potential use of
the proposed scheme for power saving in real life.
| arxiv topic:cs.SY |
arxiv_dataset-43251305.5232 | A Semiparametric Estimator for Long-Range Dependent Multivariate
Processes
math.ST stat.TH
In this paper we propose a generalization of a class of Gaussian
Semiparametric Estimators (GSE) of the fractional differencing parameter for
long-range dependent multivariate time series. We generalize a known GSE-type
estimator by introducing some modifications at the objective function level
regarding the process' spectral density matrix estimator. We study large sample
properties of the estimator without assuming Gaussianity as well as hypothesis
testing. The class of models considered here satisfies simple conditions on the
spectral density function, restricted to a small neighborhood of the zero
frequency. This includes, but is not limited to, the class of VARFIMA models. A
simulation study to assess the finite sample properties of the proposed
estimator is presented and supports its competitiveness. We also present an
empirical application to an exchange rate data.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-43261305.5332 | Heavy-to-light chromomagentic matrix element
hep-ph
We report the computation of the matrix element of the chromomagnetic
operator of the flavour changing neutral current (FCNC)-type between a $B$- or
$D$-meson state and a light hadron and off-shell photon. The computation is
carried out by using the method of light-cone sum rules (LCSR). It is found
that the matrix element exhibits a large strong phase for which we give a long
distance interpretation. The analytic structure of the correlation function in
use admits a complex anomalous threshold on the physical sheet, the meaning and
handling of which within the sum rule approach is discussed. We compare our
results to QCD factorisation for which spectator photon emission is end-point
divergent.
| arxiv topic:hep-ph |
arxiv_dataset-43271305.5432 | Decay constants of heavy-light vector mesons from QCD sum rules
hep-ph hep-lat
We revisit QCD sum rules for the decay constants of heavy-light mesons. In
the sum rules for the vector mesons B^*_(s) and D^*_(s) we improve the accuracy
of OPE, taking into account the O(alpha_s^2) terms in the perturbative part and
calculating the O(alpha_s) corrections to the quark-condensate contribution.
With this accuracy, we obtain the ratios of decay constants: f_B^*/f_B=1.02
+0.07 -0.03, f_D^*/f_D=1.20 +0.10 -0.07. The sum rule predictions for the decay
constants of pseudoscalar mesons are updated with the results f_B=(207 +17 -9)
MeV, f_B_s=(242 +17 -12) MeV, f_D=(201 +12 -13) MeV, f_D_s=(238 +13 -23) MeV.
In order to assess the sensitivity of our calculation to the form of the sum
rule, we consider alternative versions such as the power moments and Borel sum
rules with different weights of the spectral density. We also investigated the
heavy quark limit of the sum rules for vector and pseudoscalar mesons,
estimating the violations of the heavy-quark spin and flavour symmetry.
| arxiv topic:hep-ph hep-lat |
arxiv_dataset-43281305.5532 | Ligand Discrimination in Myoglobin from Linear-Scaling DFT+U
physics.chem-ph cond-mat.str-el physics.bio-ph q-bio.BM
Myoglobin modulates the binding of diatomic molecules to its heme group via
hydrogen-bonding and steric interactions with neighboring residues, and is an
important benchmark for computational studies of biomolecules. We have
performed calculations on the heme binding site and a significant proportion of
the protein environment (more than 1000 atoms) using linear-scaling density
functional theory and the DFT+U method to correct for self-interaction errors
associated with localized 3d states. We confirm both the hydrogen-bonding
nature of the discrimination effect (3.6 kcal/mol) and assumptions that the
relative strain energy stored in the protein is low (less than 1 kcal/mol). Our
calculations significantly widen the scope for tackling problems in drug design
and enzymology, especially in cases where electron localization, allostery or
long-ranged polarization influence ligand binding and reaction.
| arxiv topic:physics.chem-ph cond-mat.str-el physics.bio-ph q-bio.BM |
arxiv_dataset-43291305.5632 | Photometric study of an Eclipsing Binary in Praesepe
astro-ph.SR
We present CCD photometric observations of an eclipsing binary in the
direction of the open cluster Praesepe using the 2 m telescope of IUCAA
Girawali Observatory, India. Though the system was classified as an eclipsing
binary by Pepper et al.(2008),detail investigations were lacking. The
photometric solutions using the Wilson-Devinney code suggest that it is a
W-type W UMa system and interestingly, the system parameters were similar to
another contact binary system SW Lac.
| arxiv topic:astro-ph.SR |
arxiv_dataset-43301305.5732 | Formation of stationary electronic states in finite homogeneous
molecular chains
cond-mat.other
Evolution of an arbitrary initial distribution of a quantummechanical
particle in a uniform molecular chain is simulated by a system of coupled
quantumclassical dynamical equations with dissipation. Stability of a uniform
distribution of the particle over the chain is studied. An asymptotical
expression is obtained for the time in which a localized state is formed. The
validity of the expression is checked by direct computational experiments. It
is shown that the time of soliton and multisoliton type states formation
depends strongly on the initial phase of the particle's wave function. It is
shown that in multisoliton states objects with a fractional electron charge
which can be observed experimentally are realized. The results obtained are
applied to synthetic uniform polynucleotide molecular chains.
| arxiv topic:cond-mat.other |
arxiv_dataset-43311305.5832 | Efficient Single Photon Absorption by Optimized Superconducting Nanowire
Geometries
cond-mat.supr-con physics.optics quant-ph
We report on simulation results that shows optimum photon absorption by
superconducting nanowires can happen at a fill-factor that is much less than
100%. We also present experimental results on high performance of our
superconducting nanowire single photon detectors realized using NbTiN on
oxidized silicon.
| arxiv topic:cond-mat.supr-con physics.optics quant-ph |
arxiv_dataset-43321305.5932 | Solid-fluid dynamics of yield-stress fluids
cond-mat.soft physics.flu-dyn
On the example of two-phase continua experiencing stress induced solid-fluid
phase transitions we explore the use of the Euler structure in the formulation
of the governing equations. The Euler structure guarantees that solutions of
the time evolution equations possessing it are compatible with mechanics and
with thermodynamics. The former compatibility means that the equations are
local conservation laws of the Godunov type and the latter compatibility means
that the entropy does not decrease during the time evolution. In numerical
illustrations, in which the one-dimensional Riemann problem is explored, we
require that the Euler structure is also preserved in the discretization.
| arxiv topic:cond-mat.soft physics.flu-dyn |
arxiv_dataset-43331305.6032 | The two-dimensional Contou-Carr\`{e}re symbol and reciprocity laws
math.AG math.CT math.NT
We define a two-dimensional Contou-Carr\`{e}re symbol, which is a deformation
of the two-dimensional tame symbol and is a natural generalization of the
(usual) one-dimensional Contou-Carr\`{e}re symbol. We give several
constructions of this symbol and investigate its properties. Using higher
categorical methods, we prove reciprocity laws on algebraic surfaces for this
symbol. We relate also the two-dimensional Contou-Carr\`{e}re symbol with the
two-dimensional class field theory.
| arxiv topic:math.AG math.CT math.NT |
arxiv_dataset-43341305.6132 | Fission process of low excited nuclei with Langevin approach
nucl-th
Fragment mass distributions from the fission of U and Pu isotopes at low
excitation energies are studied using a dynamical model based on the
fluctuation-dissipation theorem formulated as Langevin equations. The present
calculations reproduced the overall trend of the asymmetric mass distribution
without parameter adjustment for the first time using the Langevin approach.
The Langevin trajectories show a complicated time evolution on the potential
surface, which causes the time delay of fission, showing that dynamical
treatment is vital. It was found that the shell effect of the potential energy
landscape has a dominant role in determining the mass distribution, although it
is rather insensitive to the strength of dissipation. Nevertheless, it is
essential to include the effect of dissipation, since it has a crucial role in
giving "fluctuation" to Langevin trajectories as well as for explaining the
multiplicities of pre-scission neutrons as the excitation energy increases.
Therefore, the present approach can serve as a basis for more refined analysis.
| arxiv topic:nucl-th |
arxiv_dataset-43351305.6232 | Simultaneous XMM-Newton and HST-COS observation of 1H0419-577: the
absorbing and emitting ionized gas
astro-ph.HE astro-ph.CO
In this paper we analyze the X-ray, UV and optical data of the Seyfert 1.5
galaxy 1H0419-577, with the aim of detecting and studying an ionized-gas
outflow. The source was observed simultaneously in the X-rays with XMM and in
the UV with HST-COS. Optical data were also acquired with the XMM Optical
Monitor. We detected a thin, lowly ionized warm absorber (log xi ~ 0.03, log NH
~19.9 cm^-2) in the X-ray spectrum, consistent to be produced by the same
outflow already detected in the UV. Provided the gas density estimated in the
UV, the outflow is consistent to be located in the host galaxy, at ~ kpc scale.
Narrow emission lines were detected in the X-rays, in the UV and also in the
optical spectrum. A single photoionized-gas model cannot account for all the
narrow lines emission, indicating that the narrow line region is probably a
stratified environment, differing in density and ionization. X-ray lines are
unambiguously produced in a more highly ionized gas phase than the one emitting
the UV lines. The analysis suggests also that the X-ray emitter may be just a
deeper portion of the same gas layer producing the UV lines. Optical lines are
probably produced in another, disconnected gas system. The different ionization
condition, and the ~ pc scale location suggested by the line width for the
narrow lines emitters, argue against a connection between the warm absorber and
the narrow line region in this source.
| arxiv topic:astro-ph.HE astro-ph.CO |
arxiv_dataset-43361305.6332 | The Story of Telebrain: A multi-performer telematic platform for
performatization
cs.HC cs.ET cs.MM cs.PL
This paper presents Telebrain, a browser-based performatization platform
invented for organizing real-time telematic performances. Performatization is
the human performance of algorithms. When computers and humans performatize
cooperatively, the human-computer interaction (HCI) becomes the location of
computation. Novel modes of machine-human communication are necessary for
organizing performatizations. Telebrain is designed to facilitate machine-human
languages. Capitalizing on the ubiquity and cross-platform compatibility of the
Internet, Telebrain is an open-source web application supporting PerPL
(Performer Programming Language), a human-interpreted configurable language of
multi-media instructions used to program performers. Telebrain facilitates a
variety of performance disciplines such as music, theater, dance, computational
performance, networked scoring (image and audio), prompted improvisation,
real-space multi-player gaming, collaborative transdisciplinary karaoke and
quantum square-dancing. (http://telebrain.org)
| arxiv topic:cs.HC cs.ET cs.MM cs.PL |
arxiv_dataset-43371305.6432 | The Complexity of the Proper Orientation Number
cs.CC cs.DM cs.DS math.CO
Graph orientation is a well-studied area of graph theory. A proper
orientation of a graph $G = (V,E)$ is an orientation $D$ of $E(G)$ such that
for every two adjacent vertices $ v $ and $ u $, $ d^{-}_{D}(v) \neq
d^{-}_{D}(u)$ where $d_{D}^{-}(v)$ is the number of edges with head $v$ in $D$.
The proper orientation number of $G$ is defined as $ \overrightarrow{\chi} (G)
=\displaystyle \min_{D\in \Gamma} \displaystyle\max_{v\in V(G)} d^{-}_{D}(v) $
where $\Gamma$ is the set of proper orientations of $G$. We have $ \chi(G)-1
\leq \overrightarrow{\chi} (G)\leq \Delta(G) $. We show that, it is $
\mathbf{NP} $-complete to decide whether $\overrightarrow{\chi}(G)=2$, for a
given planar graph $G$. Also, we prove that there is a polynomial time
algorithm for determining the proper orientation number of 3-regular graphs. In
sharp contrast, we will prove that this problem is $ \mathbf{NP} $-hard for
4-regular graphs.
| arxiv topic:cs.CC cs.DM cs.DS math.CO |
arxiv_dataset-43381305.6532 | The nonlinear Dirac equation in Bose-Einstein condensates: I.
Relativistic solitons in armchair nanoribbon optical lattices
cond-mat.quant-gas
We present a thorough analysis of soliton solutions to the
quasi-one-dimensional nonlinear Dirac equation (NLDE) for a Bose-Einstein
condensate in a honeycomb lattice with armchair geometry. Our NLDE corresponds
to a quasi-one-dimensional reduction of the honeycomb lattice along the zigzag
direction, in direct analogy to graphene nanoribbons. Excitations in the
remaining large direction of the lattice correspond to the linear subbands in
the armchair nanoribbon spectrum. Analytical as well as numerical soliton Dirac
spinor solutions are obtained. We analyze the solution space of the
quasi-one-dimensional NLDE by finding fixed points, delineating the various
regions in solution space, and through an invariance relation which we obtain
as a first integral of the NLDE. We obtain spatially oscillating multi-soliton
solutions as well as asymptotically flat single soliton solutions using five
different methods: by direct integration; an invariance relation; parametric
transformation; a series expansion; and by numerical shooting. By tuning the
ratio of the chemical potential to the nonlinearity for a fixed value of the
energy-momentum tensor, we can obtain both bright and dark solitons over a
nonzero density background.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-43391305.6632 | Photon-atomic solitons in a Bose-Einstein condensate trapped in a soft
optical lattice
cond-mat.quant-gas nlin.PS physics.optics
We investigate the ground state (GS) of a collisionless Bose-Einstein
condensate (BEC) trapped in a soft one-dimensional optical lattice (OL), which
is formed by two counterpropagating optical beams perturbed by the BEC density
profile through the local-field effect (LFE). We show that LFE gives rise to an
envelope-deformation potential, a nonlocal potential resulting from the phase
deformation, and an effective self-interaction of the condensate. As a result,
stable photon-atomic lattice solitons, including an optical component, in the
form of the deformation of the soft OL, in a combination with a localized
matter-wave component, are generated in the blue-detuned setting, without any
direct interaction between atoms. These self-trapped modes, which realize the
system's GS, are essentially different from the gap solitons supported by the
interplay of the OL potential and collisional interactions between atoms. A
transition to tightly bound modes from loosely bound ones occurs with the
increase of the number of atoms in the BEC.
| arxiv topic:cond-mat.quant-gas nlin.PS physics.optics |
arxiv_dataset-43401305.6732 | Comparison of the atomic level structure of the plastic crystalline and
the liquid phases of CBr2Cl2: neutron diffraction and Reverse Monte Carlo
modeling
cond-mat.dis-nn cond-mat.mtrl-sci
Neutron diffraction results obtained for plastic crystalline
dichlorodibromomethane (CBr2Cl2) have been modelled by means of the Reverse
Monte Carlo method. Comparison with its liquid phase is provided at several
levels of the atomic structure (total scattering structure factors, partial
radial distribution functions, orientational and dipole-dipole correlations).
Results reveal that the relative orientation of neighbouring molecules largely
depends on the steric effect. The small dipole moment has not as strong
influence as the steric effect on the short range order. Our observations fit
well with earlier findings presented for the series CBrnCl4-n (n=0, 1, 2, 4).
| arxiv topic:cond-mat.dis-nn cond-mat.mtrl-sci |
arxiv_dataset-43411305.6832 | Discovery of the broad-lined Type Ic SN 2013cq associated with the very
energetic GRB 130427A
astro-ph.HE
Long-duration gamma-ray bursts (GRBs) at z < 1 are in most cases found to be
accompanied by bright, broad-lined Type Ic supernovae (SNe Ic-BL). The
highest-energy GRBs are mostly located at higher redshifts, where the
associated SNe are hard to detect observationally. Here we present early and
late observations of the optical counterpart of the very energetic GRB 130427A.
Despite its moderate redshift z = 0.3399+/-0.0002, GRB 130427A is at the high
end of the GRB energy distribution, with an isotropic-equivalent energy release
of Eiso ~ 9.6x10^53 erg, more than an order of magnitude more energetic than
other GRBs with spectroscopically confirmed SNe. In our dense photometric
monitoring, we detect excess flux in the host-subtracted r-band light curve,
consistent with what expected from an emerging SN, ~0.2 mag fainter than the
prototypical SN 1998bw. A spectrum obtained around the time of the SN peak
(16.7 days after the GRB) reveals broad undulations typical of SNe Ic-BL,
confirming the presence of a SN, designated SN 2013cq. The spectral shape and
early peak time are similar to those of the high expansion velocity SN 2010bh
associated with GRB 100316D. Our findings demonstrate that high-energy
long-duration GRBs, commonly detected at high redshift, can also be associated
with SNe Ic-BL, pointing to a common progenitor mechanism.
| arxiv topic:astro-ph.HE |
arxiv_dataset-43421305.6932 | A giant graviton genealogy
hep-th
In this article we extend the construction of giant gravitons from
holomorphic surfaces [arXiv:hep-th/0010206] to the ABJM correspondence. We
construct a new class of 1/6-BPS M5-branes wrapping 5-manifolds in S^7/Z_k and
supported by a large angular momentum in the orbifold space. These orbifold
giant gravitons undergo a supersymmetry enhancement to 1/3-BPS and 1/2-BPS
configurations in special cases. The compactification of M-theory on AdS_4 x
S^7/Z_k to type IIA superstring theory on AdS_4 x CP^3 then gives rise to
another new class of 1/6-BPS D4 and NS5-branes wrapping 4 and 5-manifolds in
CP^3. The D4-branes carry a combination of D0-brane charge and angular momentum
in the complex projective space, while the NS5-branes are supported only by
D0-brane charge. Finally, we present a detailed analysis of a one-parameter
family of 1/2-BPS M5-brane orbifold giant gravitons, and their D4 and NS5-brane
CP^3 descendants.
| arxiv topic:hep-th |
arxiv_dataset-43431305.7032 | Gravitational lensing in plasma: Relativistic images at homogeneous
plasma
astro-ph.CO gr-qc
We investigate the influence of plasma presence on relativistic images formed
by Schwarzschild black hole lensing. When a gravitating body is surrounded by a
plasma, the lensing angle depends on a frequency of the electromagnetic wave
due to refraction properties, and the dispersion properties of the light
propagation in gravitational field in plasma. The last effect leads to
difference, even in uniform plasma, of gravitational deflection angle in plasma
from vacuum case. This angle depends on the photon frequency, what resembles
the properties of the refractive prism spectrometer. Here we consider the case
of a strong deflection angle for the light, traveling near the Schwarzschild
black hole, surrounded by a uniform plasma. Asymptotic formulae are obtained
for the case of a very large deflection angle, exceeding $2\pi$. We apply these
formulae for calculation of position and magnification of relativistic images
in a homogeneous plasma, which are formed by the photons performing one or
several revolutions around the central object. We conclude that the presence of
the uniform plasma increases the angular size of relativistic rings or the
angular separation of point images from the gravitating center. The presence of
the uniform plasma increases also a magnification of relativistic images. The
angular separation and the magnification become significantly larger than in
the vacuum case, when the photon frequency goes to a plasma frequency.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-43441305.7132 | Analytical shock solutions at large and small Prandtl number
physics.flu-dyn astro-ph.HE
Exact one-dimensional solutions to the equations of fluid dynamics are
derived in the large-Pr and small-Pr limits (where Pr is the Prandtl number).
The solutions are analogous to the Pr = 3/4 solution discovered by Becker and
analytically capture the profile of shock fronts in ideal gases. The large-Pr
solution is very similar to Becker's solution, differing only by a scale
factor. The small-Pr solution is qualitatively different, with an embedded
isothermal shock occurring above a critical Mach number. Solutions are derived
for constant viscosity and conductivity as well as for the case in which
conduction is provided by a radiation field. For a completely general density-
and temperature-dependent viscosity and conductivity, the system of equations
in all three limits can be reduced to quadrature. The maximum error in the
analytical solutions when compared to a numerical integration of the finite-Pr
equations is O(1/Pr) for large Pr and O(Pr) for small Pr.
| arxiv topic:physics.flu-dyn astro-ph.HE |
arxiv_dataset-43451305.7232 | Wind-driven Accretion in Protoplanetary Disks --- II: Radial Dependence
and Global Picture
astro-ph.EP astro-ph.SR
Non-ideal magnetohydrodynamical effects play a crucial role in determining
the mechanism and efficiency of angular momentum transport as well as the level
of turbulence in protoplanetary disks (PPDs), which are key to understanding
PPD evolution and planet formation. It was shown in our previous work that at 1
AU, the magnetorotational instability (MRI) is completely suppressed when both
Ohmic resistivity and ambipolar diffusion (AD) are taken into account,
resulting in a laminar flow with accretion driven by magnetocentrifugal wind.
In this work, we study the radial dependence of the laminar wind solution using
local shearing-box simulations. Scaling relation on the angular momentum
transport for the laminar wind is obtained, and we find that the wind-driven
accretion rate can be approximated as
M_dot~0.91x10^(-8)R_AU^(1.21)(B_z/10mG)^(0.93)M_Sun/yr, where B_z is the
strength of the large-scale vertical magnetic field threading the disk. The
result is independent of disk surface density. Four criteria are outlined for
the existence of the laminar wind solution: 1). Ohmic resistivity dominated
midplane region; 2). AD dominated disk upper layer; 3). Presence of (not too
weak) net vertical magnetic flux. 4). Sufficiently well ionized gas beyond disk
surface. All these criteria are likely to be met in the inner region of the
disk from ~0.3 AU to about 5-10 AU for typical PPD accretion rates. Beyond this
radius, angular momentum transport is likely to proceed due to a combination of
the MRI and disk wind, and eventually dominated by the MRI (in the presence of
strong AD) in the outer disk. Our simulation results provide key ingredients
for a new paradigm on the accretion processes in PPDs.
| arxiv topic:astro-ph.EP astro-ph.SR |
arxiv_dataset-43461305.7332 | Compositional Verification and Optimization of Interactive Markov Chains
cs.LO cs.SY
Interactive Markov chains (IMC) are compositional behavioural models
extending labelled transition systems and continuous-time Markov chains. We
provide a framework and algorithms for compositional verification and
optimization of IMC with respect to time-bounded properties. Firstly, we give a
specification formalism for IMC. Secondly, given a time-bounded property, an
IMC component and the assumption that its unknown environment satisfies a given
specification, we synthesize a scheduler for the component optimizing the
probability that the property is satisfied in any such environment.
| arxiv topic:cs.LO cs.SY |
arxiv_dataset-43471305.7432 | Real-world Transfer of Evolved Artificial Immune System Behaviours
between Small and Large Scale Robotic Platforms
cs.NE cs.RO
In mobile robotics, a solid test for adaptation is the ability of a control
system to function not only in a diverse number of physical environments, but
also on a number of different robotic platforms. This paper demonstrates that a
set of behaviours evolved in simulation on a miniature robot (epuck) can be
transferred to a much larger-scale platform (Pioneer), both in simulation and
in the real world. The chosen architecture uses artificial evolution of epuck
behaviours to obtain a genetic sequence, which is then employed to seed an
idiotypic, artificial immune system (AIS) on the Pioneers. Despite numerous
hardware and software differences between the platforms, navigation and
target-finding experiments show that the evolved behaviours transfer very well
to the larger robot when the idiotypic AIS technique is used. In contrast,
transferability is poor when reinforcement learning alone is used, which
validates the adaptability of the chosen architecture.
| arxiv topic:cs.NE cs.RO |
arxiv_dataset-43481306.0016 | Angular momentum evolution in laser-plasma accelerators
physics.plasm-ph
The transverse properties of an electron beam are characterized by two
quantities, the emittance which indicates the electron beam extend in the phase
space and the angular momentum which allows for non-planar electron
trajectories. Whereas the emittance of electron beams produced in laser- plasma
accelerator has been measured in several experiments, their angular momentum
has been scarcely studied. It was demonstrated that electrons in laser-plasma
accelerator carry some angular momentum, but its origin was not established.
Here we identify one source of angular momentum growth and we present
experimental results showing that the angular momentum content evolves during
the acceleration.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-43491306.0116 | Harmonic oscillators in a Snyder geometry
physics.gen-ph
We find that, in presence of the Snyder geometry, the quantization of d
isotropic harmonic oscillators can be solved exactly.
| arxiv topic:physics.gen-ph |
arxiv_dataset-43501306.0216 | Circular unitary ensemble with highly oscillatory potential
math.PR math-ph math.MP
We study the effect of highly oscillatory potentials to the eigenvalues of a
random matrix. Consider the circular unitary ensembles with an external
potential which is periodic with the period comparable to the average spacing
of the eigenvalues. We show that in this case the density of states is periodic
and does not converge in the large matrix limit, but the local correlation
functions converge to some simple combinations of the sine kernel and the
potential. We evaluate the correlation functions exactly and also
asymptotically.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-43511306.0316 | Localization and Compactness in Bergman and Fock spaces
math.CV math.FA
In this paper we study the compactness of operators on the Bergman space of
the unit ball and on very generally weighted Bargmann-Fock spaces in terms of
the behavior of their Berezin transforms and the norms of the operators acting
on reproducing kernels. In particular, in the Bergman space setting we show how
a vanishing Berezin transform combined with certain (integral) growth
conditions on an operator $T$ are sufficient to imply that the operator is
compact. In the weighted Bargmann-Fock space setting we show that the
reproducing kernel thesis for compactness holds for operators satisfying
similar growth conditions. The main results extend the results of Xia and Zheng
to the case of the Bergman space when $1 < p < \infty$, and in the weighted
Bargmann-Fock space setting, our results provide new, more general conditions
that imply the work of Xia and Zheng via a more familiar approach that can also
handle the $1 < p < \infty$ case.
| arxiv topic:math.CV math.FA |
arxiv_dataset-43521306.0416 | Phase transition in a super superspin glass
cond-mat.dis-nn
We here confirm the occurrence of spin glass phase transition and extract
estimates of associated critical exponents of a highly monodisperse and densely
compacted system of bare maghemite nanoparticles. This system has earlier been
found to behave like an archetypal spin glass, with e.g. a sharp transition
from paramagnetic to non-equilibrium behavior, suggesting that this system
undergoes a spin-glass phase transition at a relatively high temperature, $T_g$
$\sim$ 140 K.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-43531306.0516 | Black Hole Information as Topological Qubits
hep-th
The principle of balanced holography, introduced in [1], posits that black
hole information is stored in non-local correlations between the interior and
exterior. Based on this concept, we propose that black hole information
decomposes into elementary units in the form of topological qubits, and is
protected from local sources of decoherence. The topological protection
mechanism ensures that the horizon of an evaporating black hole stays young and
smooth.
| arxiv topic:hep-th |
arxiv_dataset-43541306.0616 | Asymptotic enumeration of magic series
math.CO math.PR
A magic series is a set of natural numbers that, by virtue of its size, sum,
and maximum value, could fill a row of a normal magic square. In this paper, we
derive an exact two-dimensional integral representation for the number of magic
series of order N. By applying the stationary phase approximation, we develop
an expansion in powers of 1/N for the number of magic series and calculate the
first few terms. We find excellent agreement between our approximation and the
known exact values. Related results are presented for magic cube and hypercube
series, bimagic series, and trimagic series.
| arxiv topic:math.CO math.PR |
arxiv_dataset-43551306.0716 | Lieb-Robinson bounds and the simulation of time evolution of local
observables in lattice systems
quant-ph cond-mat.str-el math-ph math.MP
This is an introductory text reviewing Lieb-Robinson bounds for open and
closed quantum many-body systems. We introduce the Heisenberg picture for
time-dependent local Liouvillians and state a Lieb-Robinson bound that gives
rise to a maximum speed of propagation of correlations in many body systems of
locally interacting spins and fermions. Finally, we discuss a number of
important consequences concerning the simulation of time evolution and
properties of ground states and stationary states.
| arxiv topic:quant-ph cond-mat.str-el math-ph math.MP |
arxiv_dataset-43561306.0816 | A Critical Assessment of Cost-Based Nash Methods for Demand Scheduling
in Smart Grids
cs.GT cs.CE
Demand-side management (DSM) is becoming an increasingly important component
of the envisioned smart grid. The ability to improve the efficiency of energy
use in the power system by altering demand is widely viewed as being not merely
promising but in fact essential. However, while the advantages of DSM are
clear, arriving at an efficient implementation has so far proven to be less
straightforward. There have recently been many proposals put forth in the
literature to tackle the demand scheduling aspect of DSM. One particular
approach based on a game-theoretic treatment of the day-ahead load-scheduling
problem has recently gained tremendous popularity in the DSM literature. In
this letter, an assessment of this approach is conducted, and its main result
is challenged.
| arxiv topic:cs.GT cs.CE |
arxiv_dataset-43571306.0916 | GaN / VO2 heteroepitaxial p-n junctions: Band offset and minority
carrier dynamics
cond-mat.mtrl-sci cond-mat.str-el
We report on experimental realization of p-n heterojunctions based on p-type
GaN, and an n-type correlated oxide, VO2. The band offsets are evaluated by
current-voltage and capacitance voltage measurements at various temperatures. A
band diagram based on the conventional band bending picture is proposed to
explain the evolution of the apparent barier height from electrical
measurements and it suggests that the work function of VO2 decreases by ~0.2 eV
when it goes through the insulator to metal transtion, in qualitative agreement
with Kelvin force microscopy measurements reported in literature. The frequency
dependent capacitance measurements allows us to differentiate the miniority
carrier effect from the interface states and series resistance contributions,
and estimate the minority carrier lifetime in insulating phase of VO2 to be of
the order of few microseconds. The nitride-oxide based p-n heterojunctions
provide a new dimension
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-43581306.1016 | Displacement Waves of Oxygen Atoms in Bi,Pb-2223 Lattice of Composites
Annealed in Oxygen Reduced (O2+N2) Atmosphere
cond-mat.supr-con
Annealing of Bi,Pb-2223/Ag composites in (O2+N2) atmosphere at 820-780C is
believed to reduce the number of the accompanying phases, to make contacts
between crystallites closer and to increase the critical current. The goals of
this study were to reveal the changes in the 2223 lattice at annealing in the
reduced oxygen atmosphere, to elucidate the reasons of these changes and to
discuss their effect on the ceramics superconductivity. After the annealing the
transversely-polarized displacement waves of oxygen atoms in [010]2223
direction have been found in the 2223 phase by electron diffraction analysis.
These waves could appear due to the lack of oxygen in the 2223 lattice or to
the nitrogen penetration in it. As demonstrated by the X-ray photo-electron
spectroscopy and nuclear microanalysis, nitrogen does not interact with the
2223 lattice, and the oxygen index decreases to 9.67, which is lower than the
stoichiometric. Thus, the atomic displacement waves result from the lack of
oxygen in Bi-O bilayers.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-43591306.1116 | Instability and bifurcation in a trend depending price formation model
math.AP
A well-known model due to J.-M. Lasry and P.L. Lions that presents the
evolution of prices in a market as the evolution of a free boundary in a
diffusion equation is suggested to be modified in order to show instabilities
for some values of the parameters. This loss of stability is associated to the
appearance of new types of solutions, namely periodic solutions, due to a Hopf
bifurcation and representing price oscillations, and traveling waves, that
represent either inflationary or deflationary behavior.
| arxiv topic:math.AP |
arxiv_dataset-43601306.1216 | Luminous Satellites versus Dark Subhaloes: Clustering in the Milky Way
astro-ph.GA astro-ph.CO
The observed population of the Milky Way satellite galaxies offer a unique
testing ground for galaxy formation theory on small-scales. Our novel approach
was to investigate the clustering of the known Milky Way satellite galaxies and
to quantify the amount of substructure within their distribution using a
two-point correlation function statistic in each of three spaces: configuration
space, line-of-sight velocity space, and four-dimensional phase-space. These
results were compared to those for three sets of subhaloes in the Via Lactea II
Cold Dark Matter simulation defined to represent the luminous dwarfs. We found
no evidence at a significance level above 2-sigma of substructure within the
distribution of the Milky Way satellite galaxies in any of the three spaces.
The "luminous" subhalo sets are more strongly clustered than are the Milky Way
satellites in all three spaces and over a broader range of scales in
four-dimensional phase-space. Each of the "luminous" subhalo sets are clustered
as a result of substructure within their line-of-sight velocity space
distributions at greater than 3-sigma significance, whereas the Milky Way
satellite galaxies are randomly distributed in line-of-sight velocity space.
While our comparison is with only one Cold Dark Matter simulation, the
inconsistencies between the Milky Way satellite galaxies and the Via Lactea II
subhalo sets for all clustering methods suggest a potential new 'small-scale'
tension between Cold Dark Matter theory and the observed Milky Way satellites.
Future work will obtain a more robust comparison between the observed Milky Way
satellites and Cold Dark Matter theory by studying additional simulations.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-43611306.1316 | Partitioned scheduling of multimode multiprocessor real-time systems
with temporal isolation
cs.OS
We consider the partitioned scheduling problem of multimode real-time systems
upon identical multiprocessor platforms. During the execution of a multimode
system, the system can change from one mode to another such that the current
task set is replaced with a new one. In this paper, we consider a synchronous
transition protocol in order to take into account mode-independent tasks, i.e.,
tasks of which the execution pattern must not be jeopardized by the mode
changes. We propose two methods for handling mode changes in partitioned
scheduling. The first method is offline/optimal and computes a static
allocation of tasks schedulable and respecting both tasks and transition
deadlines (if any). The second approach is subject to a sufficient condition in
order to ensure online First Fit based allocation to satisfy the timing
constraints.
| arxiv topic:cs.OS |
arxiv_dataset-43621306.1416 | Measuring molecular electric dipoles using trapped atomic ions and
ultrafast laser pulses
cond-mat.quant-gas physics.atom-ph quant-ph
We study a hybrid quantum system composed of an ion and an electric dipole.
We show how a trapped ion can be used to measure the small electric field
generated by a classical dipole. We discuss the application of this scheme to
measure the electric dipole moment of cold polar molecules, whose internal
state can be controlled with ultrafast laser pulses, by trapping them in the
vicinity of a trapped ion.
| arxiv topic:cond-mat.quant-gas physics.atom-ph quant-ph |
arxiv_dataset-43631306.1516 | The Gopakumar-Vafa formula for symplectic manifolds
math.SG math.AG
The Gopakumar-Vafa conjecture predicts that the Gromov-Witten invariants of a
Calabi-Yau 3-fold can be canonically expressed in terms of integer invariants
called BPS numbers. Using the methods of symplectic Gromov-Witten theory, we
prove that the Gopakumar-Vafa formula holds for any symplectic Calabi-Yau
6-manifold, and hence for Calabi-Yau 3-folds. The results extend to all
symplectic 6-manifolds and to the genus zero GW invariants of semipositive
manifolds.
| arxiv topic:math.SG math.AG |
arxiv_dataset-43641306.1616 | Scale Invariant Gravitation and Unambiguous Interpretation of Physical
Theories
physics.gen-ph
Our conventional system of physical units is based on local or microscopic
{\it dimensional} quantities which are {\it defined}, for convenience or
otherwise aesthetic reasons, to be spacetime-independent. A more general choice
of units may entail variation of fundamental physical quantities (`constants')
in spacetime. The theory of gravitation generally does not satisfy conformal
symmetry, i.e. it is not invariant to local changes of the unit of length.
Consequently, the {\it dimensionless} action associated with the
Einstein-Hilbert action ($S_{EH}$) of gravitation, $\phi_{EH}=S_{EH}/\hbar$, is
not invariant to local changes of the length unit; clearly an unsatisfactory
feature for a dimensionless quantity. Here we amend the phase by adding extra
terms that account for spacetime variation of the physical `constants' in
arbitrary unit systems. In such a unit system, all dimensional quantities are
implicitly spacetime-dependent; this is achieved by a conformal transformation
of the metric augmented by appropriate metric-dependent rescalings of the
dimensional quantities. The resulting modified dimensionless action is
scale-invariant, i.e. independent of the unit system, as desired. The deep
connection between gravitation, dimensionless physical quantities, and quantum
mechanics, is elucidated and the implicit ambiguity in interpretations of
dimensional quantities is underlined.
| arxiv topic:physics.gen-ph |
arxiv_dataset-43651306.1716 | Fast greedy algorithm for subspace clustering from corrupted and
incomplete data
cs.LG cs.DS math.NA stat.ML
We describe the Fast Greedy Sparse Subspace Clustering (FGSSC) algorithm
providing an efficient method for clustering data belonging to a few
low-dimensional linear or affine subspaces. The main difference of our
algorithm from predecessors is its ability to work with noisy data having a
high rate of erasures (missed entries with the known coordinates) and errors
(corrupted entries with unknown coordinates). We discuss here how to implement
the fast version of the greedy algorithm with the maximum efficiency whose
greedy strategy is incorporated into iterations of the basic algorithm.
We provide numerical evidences that, in the subspace clustering capability,
the fast greedy algorithm outperforms not only the existing state-of-the art
SSC algorithm taken by the authors as a basic algorithm but also the recent
GSSC algorithm. At the same time, its computational cost is only slightly
higher than the cost of SSC.
The numerical evidence of the algorithm significant advantage is presented
for a few synthetic models as well as for the Extended Yale B dataset of facial
images. In particular, the face recognition misclassification rate turned out
to be 6-20 times lower than for the SSC algorithm. We provide also the
numerical evidence that the FGSSC algorithm is able to perform clustering of
corrupted data efficiently even when the sum of subspace dimensions
significantly exceeds the dimension of the ambient space.
| arxiv topic:cs.LG cs.DS math.NA stat.ML |
arxiv_dataset-43661306.1816 | Krein signatures of transfer operators for half-space topological
insulators
math-ph math.MP
We propose a complementary point of view on the topological invariants of
two-dimensional tight-binding models restricted to half-spaces. The transfer
operators for such systems are $J$-unitary on a infinite dimensional Krein
space $(\mathcal{K},J)$ and, for energies in the bulk gap, only have discrete
spectrum on the unit circle. These eigenvalues have Krein inertia which can be
used to define topological invariants determining the nature of the surface
modes and allowing to distinguish different topological phases. This is
illustrated by numerical results.
| arxiv topic:math-ph math.MP |
arxiv_dataset-43671306.1916 | Performance Evaluation of Low Power MIPS Crypto Processor based on
Cryptography Algorithms
cs.CR cs.AR
This paper presents the design and implementation of low power 32-bit
encrypted and decrypted MIPS processor for Data Encryption Standard (DES),
Triple DES, Advanced Encryption Standard (AES) based on MIPS pipeline
architecture. The organization of pipeline stages has been done in such a way
that pipeline can be clocked at high frequency. Encryption and Decryption
blocks of three standard cryptography algorithms on MIPS processor and
dependency among themselves are explained in detail with the help of a block
diagram. Clock gating technique is used to reduce the power consumption in MIPS
crypto processor. This approach results in processor that meets power
consumption and performance specification for security applications. Proposed
Implementation approach concludes higher system performance while reducing
operating power consumption. Testing results shows that the MIPS crypto
processor operates successfully at a working frequency of 218MHz and a
bandwidth of 664Mbits/s.
| arxiv topic:cs.CR cs.AR |
arxiv_dataset-43681306.2016 | Energy calibration and resolution of the CMS electromagnetic calorimeter
in pp collisions at sqrt(s) = 7 TeV
hep-ex physics.ins-det
The energy calibration and resolution of the electromagnetic calorimeter
(ECAL) of the CMS detector have been determined using proton-proton collision
data from LHC operation in 2010 and 2011 at a centre-of-mass energy of
sqrt(s)=7 TeV with integrated luminosities of about 5 inverse femtobarns.
Crucial aspects of detector operation, such as the environmental stability,
alignment, and synchronization, are presented. The in-situ calibration
procedures are discussed in detail and include the maintenance of the
calibration in the challenging radiation environment inside the CMS detector.
The energy resolution for electrons from Z-boson decays is better than 2% in
the central region of the ECAL barrel (for pseudorapidity abs(eta)<0.8) and is
2-5% elsewhere. The derived energy resolution for photons from 125 GeV Higgs
boson decays varies across the barrel from 1.1% to 2.6% and from 2.2% to 5% in
the endcaps. The calibration of the absolute energy is determined from Z to
e+e- decays to a precision of 0.4% in the barrel and 0.8% in the endcaps.
| arxiv topic:hep-ex physics.ins-det |
arxiv_dataset-43691306.2116 | Consistency of the maximum likelihood estimate for Non-homogeneous
Markov-switching models
stat.AP
Many nonlinear time series models have been proposed in the last decades.
Among them, the models with regime switchings provide a class of versatile and
interpretable models which have received a particular attention in the
literature. In this paper, we consider a large family of such models which
generalize the well known Markov-switching AutoRegressive (MS-AR) by allowing
non-homogeneous switching and encompass Threshold AutoRegressive (TAR) models.
We prove various theoretical results related to the stability of these models
and the asymptotic properties of the Maximum Likelihood Estimates (MLE). The
ability of the model to catch complex nonlinearities is then illustrated on
various time series.
| arxiv topic:stat.AP |
arxiv_dataset-43701306.2216 | Angular Preisach analysis of Hysteresis loops and FMR lineshapes of
ferromagnetic nanowire arrays
cond-mat.mtrl-sci
Preisach analysis is applied to the study of hysteresis loops measured for
different angles between the applied magnetic field and the common axis of
ferromagnetic Nickel nanowire arrays. When extended to Ferromagnetic Resonance
(FMR) lineshapes, with same set of parameters extracted from the corresponding
hysteresis loops, Preisach analysis shows that a different distribution of
interactions or coercivities ought to be used in order to explain experimental
results. Inspecting the behavior of hysteresis loops and FMR linewidth versus
field angle, we infer that angular dependence might be exploited in angle
sensing devices that could compete with Anisotropic (AMR) or Giant
Magnetoresistive (GMR) based devices.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-43711306.2316 | Dynamical Versus Stellar Masses in Compact Early-Type Galaxies: Further
Evidence for Systematic Variation in the Stellar Initial Mass Function
astro-ph.CO
Several independent lines of evidence suggest that the stellar initial mass
function (IMF) in early-type galaxies becomes increasingly `bottom-heavy' with
increasing galaxy mass and/or velocity dispersion, sigma. Here we consider
evidence for IMF variation in a sample of relatively compact early-type
galaxies drawn from the Sloan Digital Sky Survey. These galaxies are of
sufficiently high stellar density that a dark halo likely makes a minor
contribution to the total dynamical mass, Mdyn, within one effective radius. We
fit our detailed stellar population synthesis models to the stacked absorption
line spectra of these galaxies in bins of sigma and find evidence from
IMF-sensitive spectral features for a bottom-heavy IMF at high sigma. We also
apply simple `mass-follows-light' dynamical models to the same data and find
that Mdyn is significantly higher than what would be expected if these galaxies
were stellar dominated and had a universal Milky Way IMF. Adopting Mdyn M_*
therefore implies that the IMF is `heavier' at high sigma. Most importantly,
the quantitative amount of inferred IMF variation is very similar between the
two techniques, agreeing to within 0.1 dex in mass. The agreement between two
independent techniques, when applied to the same data, provides compelling
evidence for systematic variation in the IMF as a function of early-type galaxy
velocity dispersion. Any alternative explanations must reproduce both the
results from dynamical and stellar population-based techniques.
| arxiv topic:astro-ph.CO |
arxiv_dataset-43721306.2416 | Aspects of Gond Astronomy
physics.hist-ph
The Gond community is considered to be one of the most ancient tribes of
India with a continuing history of several thousand years. They are also known
for their largely isolated history which they have retained through the
millennia. Several of their intellectual traditions therefore are a record of
parallel aspects of human intellectual growth, and still preserve their
original flavour and have not been homogenised by the later traditions of
India. In view of this, the Gonds provide a special window to the different
currents that constitute contemporary India. In the present study, we summarise
their mythology, genetics and script. We then investigate their astronomical
traditions and try to understand this community through a survey of 15 Gond
villages spread over Maharashtra, Andhra Pradesh and Madhya Pradesh. We show
that they have a distinctly different view of the sky from the conventional
astronomical ideas encountered elsewhere in India, which is both interesting
and informative. We briefly comment on other aspects of their life as culled
from our encounters with different members of the Gond community.
| arxiv topic:physics.hist-ph |
arxiv_dataset-43731306.2516 | Projections Onto Convex Sets (POCS) Based Optimization by Lifting
math.OC
Two new optimization techniques based on projections onto convex space (POCS)
framework for solving convex and some non-convex optimization problems are
presented. The dimension of the minimization problem is lifted by one and sets
corresponding to the cost function are defined. If the cost function is a
convex function in R^N the corresponding set is a convex set in R^(N+1). The
iterative optimization approach starts with an arbitrary initial estimate in
R^(N+1) and an orthogonal projection is performed onto one of the sets in a
sequential manner at each step of the optimization problem. The method provides
globally optimal solutions in total-variation, filtered variation, l1, and
entropic cost functions. It is also experimentally observed that cost functions
based on lp, p<1 can be handled by using the supporting hyperplane concept.
| arxiv topic:math.OC |
arxiv_dataset-43741306.2616 | The Euler Characteristic of a Haken 4-Manifold
math.GT math.CO
Haken n-manifolds are aspherical manifolds, defined and studied by B.
Foozwell and H. Rubinstein, that can be successively cut open along essential
codimension-one submanifolds until a disjoint union of n-cells is obtained.
Such manifolds come equipped with a boundary pattern, a particular kind of
decomposition of the boundary into codimension-zero submanifolds. We prove that
there is a certain numerical function phi(X^4) depending only on the boundary
and boundary pattern of the compact Haken 4-manifold X^4 (and vanishing if X^4
has empty boundary), such that for any compact Haken 4-manifold X^4 the Euler
characteristic satisfies the inequality chi(X^4) >= phi(X^4). In particular, if
X^{4} is a closed Haken 4-manifold, then chi(X^4) >= 0.
| arxiv topic:math.GT math.CO |
arxiv_dataset-43751306.2716 | Constraining new fundamental physics with multiwavelength astrometry
astro-ph.CO gr-qc
While the deflection of light is achromatic in General Relativity, it is not
always so in several new-physics models (e.g. certain quantum-gravity and
string-inspired models, models with nonminimal photon-gravity coupling or with
massive photon etc.). We discuss how parameters of these models may be
constrained by precise astrometry at different wavelenghts. From published
observations of the gravitational lens MG J2016+112, we obtain world-best
limits on chromatic gravitational deflection of light (and the unique limit on
the photon mass relevant for distance scales >Mpc). We also outline prospects
for further improvement of these limits.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-43761306.2816 | Solvable limits of a 4D noncommutative QFT
math-ph hep-th math.MP
In previous work we have shown that the (\theta->\infty)-limit of
\phi^4_4-quantum field theory on noncommutative Moyal space is an exactly
solvable matrix model. In this paper we translate these results to position
space. We show that the Schwinger functions are symmetric and invariant under
the full Euclidean group. The Schwinger functions only depend on matrix
correlation functions at coinciding indices per topological sector, and
clustering is violated. We prove that Osterwalder-Schrader reflection
positivity of the Schwinger two-point function is equivalent to the question
whether the diagonal matrix two-point function is a Stieltjes function.
Numerical investigations suggest that this can at best be expected for the
wrong sign of the coupling constant. The corresponding Wightman functions would
describe particles which interact without momentum transfer. The theory differs
from a free theory by the presence of non-trivial topological sectors.
| arxiv topic:math-ph hep-th math.MP |
arxiv_dataset-43771306.2916 | The pion vector form factor from lattice QCD and NNLO chiral
perturbation theory
hep-lat hep-ph
We present a comprehensive study of the electromagnetic form factor, the
decay constant and the mass of the pion computed in lattice QCD with two
degenerate O(a)-improved Wilson quarks at three different lattice spacings in
the range 0.05-0.08fm and pion masses between 280 and 630MeV at m_pi L >~ 4.
Using partially twisted boundary conditions and stochastic estimators, we
obtain a dense set of precise data points for the form factor at very small
momentum transfers, allowing for a model-independent extraction of the charge
radius. Chiral Perturbation Theory (ChPT) augmented by terms which model
lattice artefacts is then compared to the data. At next-to-leading order the
effective theory fails to produce a consistent description of the full set of
pion observables but describes the data well when only the decay constant and
mass are considered. By contrast, using the next-to-next-to-leading order
expressions to perform global fits result in a consistent description of all
data. We obtain <r^2_pi>=0.481(33)(13)fm^2 as our final result for the charge
radius at the physical point. Our calculation also yields estimates for the
pion decay constant in the chiral limit, F_pi/F=1.080(16)(6), the quark
condensate, Sigma^{1/3}_MSbar(2GeV)=261(13)(1)MeV and several low-energy
constants of SU(2) ChPT.
| arxiv topic:hep-lat hep-ph |
arxiv_dataset-43781306.3016 | Analysis of the Time Reversible Born-Oppenheimer Molecular Dynamics
math.NA physics.chem-ph physics.comp-ph
We analyze the time reversible Born-Oppenheimer molecular dynamics (TRBOMD)
scheme, which preserves the time reversibility of the Born-Oppenheimer
molecular dynamics even with non-convergent self-consistent field iteration. In
the linear response regime, we derive the stability condition as well as the
accuracy of TRBOMD for computing physical properties such as the phonon
frequency obtained from the molecular dynamic simulation. We connect and
compare TRBOMD with the Car-Parrinello molecular dynamics in terms of accuracy
and stability. We further discuss the accuracy of TRBOMD beyond the linear
response regime for non-equilibrium dynamics of nuclei. Our results are
demonstrated through numerical experiments using a simplified one dimensional
model for Kohn-Sham density functional theory.
| arxiv topic:math.NA physics.chem-ph physics.comp-ph |
arxiv_dataset-43791306.3116 | A Peculiar Microwave Quasi-periodic Pulsation with Zigzag Pattern in a
CME-related Flare on 2005-01-15
astro-ph.SR
A peculiar microwave quasi-periodic pulsation with zigzag pattern (Z-QPP) is
observed first by the Chinese Solar Broadband Spectrometer in Huairou
(SBRS/Huairou) at 1.10-1.34 GHz in a solar flare on 2005-01-15. The Z-QPP
occurred just in the early rising phase of the flare with weakly right-handed
circular polarization. Its period is only several decades millisecond.
Particularly, before and after the pulsation, there are many spectral fine
structures, such as zebra patterns, fibers, and millisecond spikes. The
microwave Z-QPP can provide some kinematic information of the source region in
the early rising phase of the flare, and the source width changes from about
1000 km to 3300 km, even if we have no imaging observations. The abundant
spectral fine structures possibly reflect the dynamic features of non-thermal
particles.
| arxiv topic:astro-ph.SR |
arxiv_dataset-43801306.3216 | On the 'Reality' of Observable Properties
quant-ph
This note contains some initial work on attempting to bring recent
developments in the foundations of quantum mechanics concerning the nature of
the wavefunction within the scope of more logical and structural methods. A
first step involves generalising and reformulating a criterion for the reality
of the wavefunction proposed by Harrigan & Spekkens, which was central to the
PBR theorem. The resulting criterion has several advantages, including the
avoidance of certain technical difficulties relating to sets of measure zero.
By considering the 'reality' not of the wavefunction but of the observable
properties of any ontological physical theory a novel characterisation of
non-locality and contextuality is found.
Secondly, a careful analysis of preparation independence, one of the key
assumptions of the PBR theorem, leads to an analogy with Bell locality, and
thence to a proposal to weaken it to an assumption of
`no-preparation-signalling' in analogy with no-signalling. This amounts to
introducing non-local correlations in the joint ontic state, which is, at
least, consistent with the Bell and Kochen-Specker theorems. The question of
whether the PBR result can be strengthened to hold under this relaxed
assumption is therefore posed.
| arxiv topic:quant-ph |
arxiv_dataset-43811306.3316 | 12-fold Quasicrystallography from affine F4, B6, and E6
math-ph math.MP
One possible way to obtain the quasicrystallographic structures is the
projections of the higher dimensional lattices into 2D or 3D subspaces. In this
work we introduce a general technique applicable to any higher dimensional
lattice. We point out that the Coxeter number and the Coxeter exponents of a
Coxeter-Weyl group play a crucial role in determining the plane onto which the
lattice to be projected as well as the dihedral symmetry of the quasicrystal
structure. The eigenvectors and eigenvalues of the Cartan matrix are used to
determine the set of orthonormal vectors in nD Euclidean space which lead
suitable choices for the projection subspaces. The maximal dihedral subgroup of
the Coxeter-Weyl group is identified to determine the symmetry of the
quasicrystal structure. We give examples for 12-fold symmetric quasicrystal
structures obtained by projecting the higher dimensional lattices determined by
the affine Coxeter-Weyl groups Wa(F4), Wa(B6) and Wa(E6) . These groups share
the same Coxeter number h=12 with different Coxeter exponents. The dihedral
subgroup D12 of the Coxeter groups can be obtained by defining two generators
R1 and R2 as the products of generators of the Coxeter-Weyl groups. The
reflection generators R1 and R2 operate in the Coxeter planes where the Coxeter
element R1R2 of the Coxeter group represents the rotation of order 12. The
canonical projections (strip projections) of the lattices determine the nature
of the quasicrystallographic structures with 12-fold symmetry as well as the
crystallographic structures with 4-fold and 6-fold symmetry. We note that the
quasicrystal structures obtained from the lattices Wa(F4) and Wa(B6) and are
compatible with the experimental results.
| arxiv topic:math-ph math.MP |
arxiv_dataset-43821306.3416 | Percolation of a general network of networks
physics.soc-ph cond-mat.stat-mech physics.comp-ph
Percolation theory is an approach to study vulnerability of a system. We
develop analytical framework and analyze percolation properties of a network
composed of interdependent networks (NetONet). Typically, percolation of a
single network shows that the damage in the network due to a failure is a
continuous function of the fraction of failed nodes. In sharp contrast, in
NetONet, due to the cascading failures, the percolation transition may be
discontinuous and even a single node failure may lead to abrupt collapse of the
system. We demonstrate our general framework for a NetONet composed of $n$
classic Erd\H{o}s-R\'{e}nyi (ER) networks, where each network depends on the
same number $m$ of other networks, i.e., a random regular network of
interdependent ER networks. In contrast to a \emph{treelike} NetONet in which
the size of the largest connected cluster (mutual component) depends on $n$,
the loops in the RR NetONet cause the largest connected cluster to depend only
on $m$. We also analyzed the extremely vulnerable feedback condition of
coupling. In the case of ER networks, the NetONet only exhibits two phases, a
second order phase transition and collapse, and there is no first phase
transition regime unlike the no feedback condition. In the case of NetONet
composed of RR networks, there exists a first order phase transition when $q$
is large and second order phase transition when $q$ is small. Our results can
help in designing robust interdependent systems.
| arxiv topic:physics.soc-ph cond-mat.stat-mech physics.comp-ph |
arxiv_dataset-43831306.3516 | Time-Dependent Charge-Order and Spin-Order Recovery in Striped Systems
cond-mat.str-el
Using time-dependent Ginzburg-Landau theory, we study the role of amplitude
and phase fluctuations in the recovery of charge and spin stripe phases in
response to a pump pulse that melts the orders. For parameters relevant to the
case where charge order precedes spin order thermodynamically, amplitude
recovery governs the initial time scales, while phase recovery controls
behavior at longer times. In addition to these intrinsic effects, there is a
longer spin re-orientation time scale related to the scattering geometry that
dominates the recovery of the spin phase. Coupling between the charge and spin
orders locks the amplitude and similarly the phase recovery, reducing the
number of distinct time scales. Our results well reproduce the major
experimental features of pump-probe x-ray diffraction measurements on the
striped nickelate La$_{1.75}$Sr$_{0.25}$NiO$_4$. They highlight the main idea
of this work, which is the use of time-dependent Ginzburg-Landau theory to
study systems with multiple coexisting order parameters.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-43841306.3616 | Time-dependent density-functional theory of exciton-exciton correlations
in the nonlinear optical response
cond-mat.mtrl-sci cond-mat.mes-hall
We analyze possible nonlinear exciton-exciton correlation effects in the
optical response of semiconductors by using a time-dependent density-functional
theory (TDDFT) approach. For this purpose, we derive the nonlinear
(third-order) TDDFT equation for the excitonic polarization. In this equation,
the nonlinear time-dependent effects are described by the time-dependent
(non-adiabatic) part of the effective exciton-exciton interaction, which
depends on the exchange-correlation (XC) kernel. We apply the approach to study
the nonlinear optical response of a GaAs quantum well. In particular, we
calculate the 2D Fourier spectra of the system and compare it with experimental
data. We find that it is necessary to use a non-adiabatic XC kernel to describe
excitonic bound states - biexcitons, which are formed due to the retarded TDDFT
exciton-exciton interaction.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-43851306.3716 | Artin--Schreier and Cyclotomic Extensions
math.NT
In this paper we prove that any Artin--Schreier extension of a congruence
rational function field is contained in the composite of a cyclotomic function
field and a constant field extension that are explicitly prescribed.
| arxiv topic:math.NT |
arxiv_dataset-43861306.3816 | Probing holographic semi-local quantum liquids with D-branes
hep-th
We study dynamics of probe D-branes in $(d+2)$-dimensional background with
general semi-locality. The background is characterized by a parameter $\eta$
and is conformal to $AdS_{2}\times\mathbb{R}^{d}$. We discuss thermodynamics of
the probe D-branes and find that the entropy density is vanishing in the
extremal limit, which indicates that the background may correspond to the true
ground state of the system. We also clarify the conditions under which the
specific heat matches to the behavior of a Fermi liquid or a Bose liquid. We
calculate the current-current and density-density retarded Green's functions,
from which we can obtain the AC conductivity and the zero sound mode. The AC
conductivity scales as $\omega^{-1}$ when $d/\eta<2$ and $\omega^{-2\eta/d}$
when $d/\eta>2$, while it contains a logarithmic term in $\omega$ when
$d/\eta=2$. We also observe that there is no quasi-particle excitation when
$d/\eta\geq2$ and classify the conditions under which the quasi-particle
description is valid when $d/\eta<2$.
| arxiv topic:hep-th |
arxiv_dataset-43871306.3916 | Two notions of unit distance graphs
math.CO cs.DM math.MG
A {\em faithful (unit) distance graph} in $\mathbb{R}^d$ is a graph whose set
of vertices is a finite subset of the $d$-dimensional Euclidean space, where
two vertices are adjacent if and only if the Euclidean distance between them is
exactly $1$. A {\em (unit) distance graph} in $\mathbb{R}^d$ is any subgraph of
such a graph. In the first part of the paper we focus on the differences
between these two classes of graphs. In particular, we show that for any fixed
$d$ the number of faithful distance graphs in $\mathbb{R}^d$ on $n$ labelled
vertices is $2^{(1+o(1)) d n \log_2 n}$, and give a short proof of the known
fact that the number of distance graphs in $\mathbb{R}^d$ on $n$ labelled
vertices is $2^{(1-1/\lfloor d/2 \rfloor +o(1))n^2/2}$. We also study the
behavior of several Ramsey-type quantities involving these graphs. % and
high-girth graphs from these classes. In the second part of the paper we
discuss the problem of determining the minimum possible number of edges of a
graph which is not isomorphic to a faithful distance graph in $\mathbb R^d$.
| arxiv topic:math.CO cs.DM math.MG |
arxiv_dataset-43881306.4016 | A comparison of Landau-Ginzburg models for odd dimensional Quadrics
math.AG
In [Rie08], the second author defined a Landau-Ginzburg model for homogeneous
spaces G/P. In this paper, we reformulate this LG model in the case of the
odd-dimensional quadric X=Q_{2m-1}. Namely we introduce a regular function Wcan
on a variety Xcan x C*, where Xcan is the complement of a particular
anticanonical divisor in the the projective space CP^{2m-1}=P(H*(X,C)*).
Firstly we prove that the Jacobi ring associated to Wcan is isomorphic to the
quantum cohomology ring of the quadric, and that this isomorphism is compatible
with the identification of homogeneous coordinates on Xcan with elements of
H*(X,C). Secondly we find a very natural Laurent polynomial formula for Wcan by
restricting it to a `Lusztig torus' in Xcan. Thirdly we show that the Dubrovin
connection on H*(X,C[q]) embeds into the Gauss-Manin system associated to Wcan
and deduce a flat section formula in terms of oscillating integrals. Finally,
we compare (Xcan,Wcan) with previous Landau-Ginzburg models defined for odd
quadrics. Namely, we prove that it is a partial compactification of Givental's
original LG model [Giv96]. We show that our LG model is isomorphic to the
Lie-theoretic LG model from [Rie08]. Moreover it is birationally equivalent to
an LG model introduced by Gorbounov and Smirnov [GS13], and it is algebraically
isomorphic to Gorbounov and Smirnov's mirror for Q_3, implying a tameness
property in that case.
| arxiv topic:math.AG |
arxiv_dataset-43891306.4116 | Broadband absorption enhancement in ultra-thin crystalline Si solar
cells by incorporating metallic and dielectric nanostructures in the back
reflector
cond-mat.mes-hall physics.optics
We propose a back-reflecting scheme in order to enhance the maximum
achievable current in one micron thick crystalline silicon solar cells. We
perform 3-dimensional numerical investigations of the scattering properties of
metallic nanostructures located at the back side, and optimize them for
enhancing absorption in the silicon layer. We validate our numerical results
experimentally and also compare the absorption enhancement in the solar cell
structure, both with quasi-periodic and random metallic nanostructures. We have
looked at the interplay between the metallic nanostructures and an integrated
back-reflector. We show that the combination of metallic nanoparticles and a
metallic reflector results in significant parasitic absorption. We compared
this to another implementation based on titanium dioxide nanoparticles which
act as a lambertian reflector of light. Our simulation and experimental results
show that this proposed configuration results in reduced absorption losses and
in broadband enhancement of absorption for ultra-thin solar cells, paving the
way to an optimal back reflector for thin film photovoltaics.
| arxiv topic:cond-mat.mes-hall physics.optics |
arxiv_dataset-43901306.4216 | Spectrum of a magnetized strong-leg quantum spin ladder
cond-mat.str-el
Inelastic neutron scattering is used to measure the spin excitation spectrum
of the Heisenberg $S=1/2$ ladder material (C$_7$H$_10$N)$_2$CuBr$_4$ in its
entirety, both in the gapped spin-liquid and the magnetic field induced
Tomonaga-Luttinger spin liquid regimes. A fundamental change of the spin
dynamics is observed between these two regimes. DMRG calculations
quantitatively reproduce and help understand the observed commensurate and
incommensurate excitations. The results validate long-standing quantum field
theoretical predictions, but also test the limits of that approach.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-43911306.4316 | The Effect of Partial Obscuration on the Luminosity Dependence of the
Obscured Fraction in Active Galactic Nuclei
astro-ph.CO
Surveys of Active Galactic Nuclei (AGN) in different observational regimes
seem to give different answers for the behaviour of the obscured fraction with
luminosity. Based on the complex spectra seen in recent studies, we note that
partial covering could significantly change the apparent luminosities of many
AGN, even after apparent X-ray absorption correction. We explore whether this
effect could reproduce the observed dependence of the obscured fraction on the
apparent X-ray luminosities seen between 2--10 keV. We can reproduce the
observed trend in a model where 33 per cent of AGN are unobscured, 30 per cent
are heavily buried, and 37 per cent have a range of intermediate partial
coverings. Our model is also tentatively successful at reproducing observed
trends in the X-ray vs. infrared luminosity ratio for AGN.
| arxiv topic:astro-ph.CO |
arxiv_dataset-43921306.4416 | Conditions for the solvability of the Cauchy problem for linear
first-order functional differential equations
math.CA
Conditions for the unique solvability of the Cauchy problem for a family of
scalar functional differential equations are obtained. These conditions are
sufficient for the solvability of the Cauchy problem for every equation from
the family and are necessary for the solvability of the Cauchy problem for all
equations from the family. In contrast to many known articles, we consider
equations with functional operators acting into the space of essentially
bounded functions.
| arxiv topic:math.CA |
arxiv_dataset-43931306.4516 | Phase transition, critical behavior, and critical exponents of
Myers-Perry black holes
gr-qc hep-th
The critical behavior of Myers-Perry black holes with equal angular momenta
in even dimensions are studied. We include the corrections beyond the
semiclassical approximation on Hawking temperature in the grand canonical
ensemble. Having done so, we find that the critical behavior and critical
exponents of Myers-Perry black holes correspond to those of a Van der Waals
liquid-gas where this analogy holds in any dimension. Also, using Ehrenfest's
equations, we calculate the order of the phase transition in the semiclassical
approximation for the canonical ensemble and beyond the semiclassical
approximation for the grand canonical ensemble near the critical point.
Finally, the Ruppeiner curvature formula is used to investigate the
thermodynamic geometry of Myers-Perry black holes.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-43941306.4616 | Axially symmetric static scalar solitons and black holes with scalar
hair
gr-qc
We construct static, asymptotically flat black hole solutions with scalar
hair. They evade the no-hair theorems by having a scalar potential which is not
strictly positive. By including an azimuthal winding number in the scalar field
ansatz, we find hairy black hole solutions which are static but axially
symmetric only. These solutions possess a globally regular limit, describing
scalar solitons. A branch of axially symmetric black holes is found to possess
a positive specific heat.
| arxiv topic:gr-qc |
arxiv_dataset-43951306.4716 | How many-body effects modify the van der Waals interaction between
graphene sheets
cond-mat.str-el cond-mat.mes-hall
Undoped graphene (Gr) sheets at low temperatures are known, via Random Phase
Approximation (RPA) calculations, to exhibit unusual van der Waals (vdW)
forces. Here we show that graphene is the first known system where effects
beyond the RPA make qualitative changes to the vdW force. For large
separations, $D \gtrsim 10$nm where only the $\pi_z$ vdW forces remain, we find
the Gr-Gr vdW interaction is substantially reduced from the RPA prediction. Its
$D$ dependence is very sensitive to the form of the long-wavelength many-body
enhancement of the velocity of the massless Dirac fermions, and may provide
independent confirmation of the latter via direct force measurements.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall |
arxiv_dataset-43961306.4816 | On differentiability of stochastic flow for a multidimensional SDE with
discontinuous drift
math.PR
We consider a $d$-dimensional SDE with an identity diffusion matrix and a
drift vector being a vector function of bounded variation. We give a
representation for the derivative of the solution with respect to the initial
data.
| arxiv topic:math.PR |
arxiv_dataset-43971306.4916 | Determinantal and eigenvalue inequalities for matrices with numerical
ranges in a sector
math.NA
Let $A = \pmatrix A_{11} & A_{12} \cr A_{21} & A_{22}\cr\pmatrix \in M_n$,
where $A_{11} \in M_m$ with $m \le n/2$, be such that the numerical range of
$A$ lies in the set $\{e^{i\varphi} z \in \IC: |\Im z| \le (\Re z) \tan
\alpha\}$, for some $\varphi \in [0, 2\pi)$ and $\alpha \in [0, \pi/2)$. We
obtain the optimal containment region for the generalized eigenvalue $\lambda$
satisfying $$\lambda \pmatrix A_{11} & 0 \cr 0 & A_{22}\cr\pmatrix x = \pmatrix
0 & A_{12} \cr A_{21} & 0\cr\pmatrix x \quad \hbox{for some nonzero} x \in
\IC^n,$$ and the optimal eigenvalue containment region of the matrix $I_m -
A_{11}^{-1}A_{12} A_{22}^{-1}A_{21}$ in case $A_{11}$ and $A_{22}$ are
invertible. From this result, one can show $|\det(A)| \le \sec^{2m}(\alpha)
|\det(A_{11})\det(A_{22})|$. In particular, if $A$ is a accretive-dissipative
matrix, then $|\det(A)| \le 2^m |\det(A_{11})\det(A_{22})|$. These affirm some
conjectures of Drury and Lin.
| arxiv topic:math.NA |
arxiv_dataset-43981306.5016 | Nonlocal Hormander's hypoellipticity theorem
math.PR
Consider the following nonlocal integro-differential operator: for
$\alpha\in(0,2)$, $$ \cal L^{(\alpha)}_{\sigma,b} f(x):=\mbox{p.v.}
\int_{\mathbb{R}^d-\{0\}}\frac{f(x+\sigma(x)z)-f(x)}{|z|^{d+\alpha}}d
z+b(x)\cdot\nabla f(x), $$ where
$\sigma:\mathbb{R}^d\to\mathbb{R}^d\times\mathbb{R}^d$ and
$b:\mathbb{R}^d\to\mathbb{R}^d$ are two $C^\infty_b$-functions, and p.v. stands
for the Cauchy principal value. Let $B_1(x):=\sigma(x)$ and
$B_{j+1}(x):=b(x)\cdot\nabla B_j(x)-\nabla b(x)\cdot B_j(x)$ for
$j\in\mathbb{N}$. Under the following H\"ormander's type condition: for any
$x\in\mathbb{R}^d$ and some $n=n(x)\in\mathbb{N}$, $$ \mathrm{Rank}[B_1(x),
B_2(x),\cdots, B_n(x)]=d, $$ by using the Malliavin calculus, we prove the
existence of the heat kernel $\rho_t(x,y)$ to the operator $\cal
L^{(\alpha)}_{\sigma,b}$ as well as the continuity of $x\mapsto
\rho_t(x,\cdot)$ in $L^1(\mathbb{R}^d)$ for each $t>0$. Moreover, when
$\sigma(x)=\sigma$ is constant, under the following uniform H\"ormander's type
condition: for some $j_0\in\mathbb{N}$, $$
\inf_{x\in\mathbb{R}^d}\inf_{|u|=1}\sum_{j=1}^{j_0}|u B_j(x)|^2>0, $$ we also
prove the smoothness of $(t,x,y)\mapsto\rho_t(x,y)$ with
$\rho_t(\cdot,\cdot)\in C^\infty_b(\mathbb{R}^d\times\mathbb{R}^d)$ for each
$t>0$.
| arxiv topic:math.PR |
arxiv_dataset-43991306.5116 | On the positive eigenvalues and eigenvectors of a non-negative matrix
math.FA math.OA math.PR
The paper develops the general theory for the items in the title, assuming
that the matrix is countable and cofinal.
| arxiv topic:math.FA math.OA math.PR |
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