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arxiv_dataset-31001112.4445 | The projective space has maximal volume among all toric
K\"ahler-Einstein manifolds
math.DG
We prove a conjecture saying that complex projective space has maximal volume
(degree) among all toric Kaehler-Einstein manifolds of dimension n. The proof
is inspired by our recent work on sharp Moser-Trudinger and Brezis-Merle type
inequalities for the complex Monge-Ampere operator, but is essentially
self-contained.
| arxiv topic:math.DG |
arxiv_dataset-31011112.4545 | Synchronization of Huygens' clocks and the Poincare method
math-ph math.DS math.MP nlin.CD
We study two models of connected pendulum clocks synchronizing their
oscillations, a phenomenon originally observed by Huygens. The oscillation
angles are assumed to be small so that the pendulums are modeled by harmonic
oscillators, clock escapements are modeled by the van der Pol terms. The mass
ratio of the pendulum bobs to their casings is taken as a small parameter.
Analytic conditions for existence and stability of synchronization regimes, and
analytic expressions for their stable amplitudes and period corrections are
derived using the Poincare theorem on existence of periodic solutions in
autonomous quasi-linear systems. The anti-phase regime always exists and is
stable under variation of the system parameters. The in-phase regime may exist
and be stable, exist and be unstable, or not exist at all depending on
parameter values. As the damping in the frame connecting the clocks is
increased the in-phase stable amplitude and period are decreasing until the
regime first destabilizes and then disappears. The results are most complete
for the traditional three degrees of freedom model, where the clock casings and
the frame are consolidated into a single mass.
| arxiv topic:math-ph math.DS math.MP nlin.CD |
arxiv_dataset-31021112.4645 | Towards realistic modeling of IP-level routing topology dynamics
cs.NI
Many works have studied the Internet topology, but few have investigated the
question of how it evolves over time. This paper focuses on the Internet
routing IP-level topology and proposes a first step towards realistic modeling
of its dynamics. We study periodic measurements of routing trees from a single
monitor to a fixed destination set and identify invariant properties of its
dynamics. We then propose a simple model for the underlying mechanisms of the
topology dynamics. Simulations show that it effectively captures the observed
behaviors, thus providing key insights of relevant mechanisms governing the
Internet routing dynamics.
| arxiv topic:cs.NI |
arxiv_dataset-31031112.4745 | Fluctuation preserving coarse graining for biochemical systems
physics.bio-ph cond-mat.stat-mech q-bio.QM
Finite stochastic Markov models play a major role for modelling biochemical
pathways. Such models are a coarse-grained description of the underlying
microscopic dynamics and can be considered mesoscopic. The level of
coarse-graining is to a certain extend arbitrary since it depends on the
resolution of accomodating measurements. Here, we present a way to simplify
such stochastic descriptions, which preserves both the meso-micro and the
meso-macro connection. The former is achieved by demanding locality, the latter
by considering cycles on the network of states. Using single- and multicycle
examples we demonstrate how our new method preserves fluctuations of
observables much better than na\"ive approaches.
| arxiv topic:physics.bio-ph cond-mat.stat-mech q-bio.QM |
arxiv_dataset-31041112.4845 | Unitarity and the Holographic S-Matrix
hep-th hep-ph
The bulk S-Matrix can be given a non-perturbative definition in terms of the
flat space limit of AdS/CFT. We show that the unitarity of the S-Matrix, ie the
optical theorem, can be derived by studying the behavior of the OPE and the
conformal block decomposition in the flat space limit. When applied to
perturbation theory in AdS, this gives a holographic derivation of the cutting
rules for Feynman diagrams.
To demonstrate these facts we introduce some new techniques for the analysis
of conformal field theories. Chief among these is a method for conglomerating
local primary operators to extract the contribution of an individual primary in
their OPE. This provides a method for isolating the contribution of specific
conformal blocks which we use to prove an important relation between certain
conformal block coefficients and anomalous dimensions. These techniques make
essential use of the simplifications that occur when CFT correlators are
expressed in terms of a Mellin amplitude.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-31051112.4945 | Chebotarev Sets
math.NT
We consider the problem of determining whether a set of primes, or, more
generally, prime ideals in a number field, can be realized as a finite union of
residue classes, or of Frobenius conjugacy classes. We give criteria for a set
to be realized in this manner, and show that the subset of primes consisting of
every other prime cannot be expressed in this way, even if we allow a finite
number of exceptions.
| arxiv topic:math.NT |
arxiv_dataset-31061112.5045 | An Anomaly in the Angular Distribution of Quasar Spectra
astro-ph.CO gr-qc
Quasars provide our farthest-reaching view of the Universe. The Sloan Survey
now contains over 100,000 quasar candidates. A careful look at the angular
distribution of quasar spectra shows a surprising "bullseye" pattern on the sky
toward (RA, Dec) ~ (190{\deg}, 0{\deg}) for all wavelengths from UV through
infrared. The angular distribution of the shift in the UV suggests a large
peculiar velocity vp toward that direction. However, the size of the shift
would indicate a vp ~0.2 c, which is two orders of magnitude larger than
measures of our peculiar velocity from nearby galaxies and cosmic microwave
background (CMB) measurements. The angular pattern and size of the shift is
very similar for all wavelengths, which is inconsistent with a Doppler shift.
The shift is also too large to explain as a systematic error in the quasar
magnitudes. The anomaly appears to be a very large hotspot in the Universe. Its
direction is close to that of the reported anomalies in the CMB, the so-called
"axis of evil". The angular pattern of the shift and its redshift dependence
are consistent with the existence of an expanding bubble universe in that
direction, which could also explain the CMB anomalies.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-31071112.5145 | Thermal emission at 3.6-8 micron from WASP-19b: a hot Jupiter without a
stratosphere orbiting an active star
astro-ph.EP
We report detection of thermal emission from the exoplanet WASP-19b at 3.6,
4.5, 5.8 and 8.0 micron. We used the InfraRed Array Camera on the Spitzer Space
Telescope to observe two occultations of WASP-19b by its host star. We combine
our new detections with previous measurements of WASP-19b's emission at 1.6 and
2.09 micron to construct a spectral energy distribution of the planet's dayside
atmosphere. By comparing this with model-atmosphere spectra, we find that the
dayside atmosphere of WASP-19b lacks a strong temperature inversion. As WASP-19
is an active star (log RHK = -4.50 +/- 0.03), this finding supports the
hypothesis of Knutson, Howard & Isaacson (2010) that inversions are suppressed
in hot Jupiters orbiting active stars. The available data are unable to
differentiate between a carbon-rich and an oxygen-rich atmosphere.
| arxiv topic:astro-ph.EP |
arxiv_dataset-31081112.5245 | A Complexity Approach for Steganalysis
cs.CR cs.CC
In this proposal for the Journ\`ees Codes et St\'eganographie 2012, we define
a new rigorous approach for steganalysis based on the complexity theory. It is
similar to the definitions of security that can be found for hash functions,
PRNG, and so on. We propose here a notion of \emph{secure hiding} and we give a
first secure hiding scheme.
| arxiv topic:cs.CR cs.CC |
arxiv_dataset-31091112.5345 | Holographic hydrodynamics: models and methods
hep-th
We review recent developments in holographic hydrodynamics. We start from
very basic discussion on hydrodynamic systems and motivate why string theory is
an essential tool to deal with these systems when they are strongly coupled.
The main purpose of this review article is to understand different holographic
techniques to compute transport coefficients (first order and higher order) and
their corrections in presence of higher derivative terms in the bulk
Lagrangian. We also mention some open challenges in this subject.
| arxiv topic:hep-th |
arxiv_dataset-31101112.5445 | Explicit expressions for meromorphic solution of autonomous nonlinear
ordinary differential equations
nlin.PS
Meromorphic solutions of autonomous nonlinear ordinary differential equations
are studied. An algorithm for constructing meromorphic solutions in explicit
form is presented. General expressions for meromorphic solutions (including
rational, periodic, elliptic) are found for a wide class of autonomous
nonlinear ordinary differential equations.
| arxiv topic:nlin.PS |
arxiv_dataset-31111112.5545 | Disjointness properties for Cartesian products of weakly mixing systems
math.DS
For $n\geq 1$ we consider the class JP($n$) of dynamical systems whose every
ergodic joining with a Cartesian product of $k$ weakly mixing automorphisms
($k\geq n$) can be represented as the independent extension of a joining of the
system with only $n$ coordinate factors. For $n\geq 2$ we show that, whenever
the maximal spectral type of a weakly mixing automorphism $T$ is singular with
respect to the convolution of any $n$ continuous measures, i.e. $T$ has the
so-called convolution singularity property of order $n$, then $T$ belongs to
JP($n-1$). To provide examples of such automorphisms, we exploit spectral
simplicity on symmetric Fock spaces. This also allows us to show that for any
$n\geq 2$ the class JP($n$) is essentially larger than JP($n-1$). Moreover, we
show that all members of JP($n$) are disjoint from ergodic automorphisms
generated by infinitely divisible stationary processes.
| arxiv topic:math.DS |
arxiv_dataset-31121112.5645 | Quadratic modular symbols on Shimura curves
math.NT
We introduce the concept of quadratic modular symbol and study how these
symbols are related to quadratic p-adic L-functions. These objects were
introduced in [3] in the case of modular curves. In this paper, we discuss a
method to attach quadratic modular symbols and quadratic p-adic L-functions to
more general Shimura curves.
| arxiv topic:math.NT |
arxiv_dataset-31131112.5745 | Bayesian Active Learning for Classification and Preference Learning
stat.ML cs.LG
Information theoretic active learning has been widely studied for
probabilistic models. For simple regression an optimal myopic policy is easily
tractable. However, for other tasks and with more complex models, such as
classification with nonparametric models, the optimal solution is harder to
compute. Current approaches make approximations to achieve tractability. We
propose an approach that expresses information gain in terms of predictive
entropies, and apply this method to the Gaussian Process Classifier (GPC). Our
approach makes minimal approximations to the full information theoretic
objective. Our experimental performance compares favourably to many popular
active learning algorithms, and has equal or lower computational complexity. We
compare well to decision theoretic approaches also, which are privy to more
information and require much more computational time. Secondly, by developing
further a reformulation of binary preference learning to a classification
problem, we extend our algorithm to Gaussian Process preference learning.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-31141112.5845 | Influence of phonons on exciton-photon interaction and photon statistics
of a quantum dot
quant-ph
In this paper, we investigate, phonon effects on the optical properties of a
spherical quantum dot. For this purpose, we consider the interaction of a
spherical quantum dot with classical and quantum fields while the exciton of
quantum dot interacts with a solid state reservoir. We show that phonons
strongly affect the Rabi oscillations and optical coherence on first
picoseconds of dynamics. We consider the quantum statistics of emitted photons
by quantum dot and we show that these photons are anti-bunched and obey the
sub-Poissonian statistics. In addition, we examine the effects of detuning and
interaction of quantum dot with the cavity mode on optical coherence of energy
levels. The effects of detuning and interaction of quantum dot with cavity mode
on optical coherence of energy levels are compared to the effects of its
interaction with classical pulse.
| arxiv topic:quant-ph |
arxiv_dataset-31151112.5945 | Controlling edge dynamics in complex networks
physics.soc-ph cond-mat.stat-mech cs.SI
The interaction of distinct units in physical, social, biological and
technological systems naturally gives rise to complex network structures.
Networks have constantly been in the focus of research for the last decade,
with considerable advances in the description of their structural and dynamical
properties. However, much less effort has been devoted to studying the
controllability of the dynamics taking place on them. Here we introduce and
evaluate a dynamical process defined on the edges of a network, and demonstrate
that the controllability properties of this process significantly differ from
simple nodal dynamics. Evaluation of real-world networks indicates that most of
them are more controllable than their randomized counterparts. We also find
that transcriptional regulatory networks are particularly easy to control.
Analytic calculations show that networks with scale-free degree distributions
have better controllability properties than uncorrelated networks, and
positively correlated in- and out-degrees enhance the controllability of the
proposed dynamics.
| arxiv topic:physics.soc-ph cond-mat.stat-mech cs.SI |
arxiv_dataset-31161112.6045 | Comparing intermittency and network measurements of words and their
dependency on authorship
physics.soc-ph cs.CL cs.SI physics.data-an
Many features from texts and languages can now be inferred from statistical
analyses using concepts from complex networks and dynamical systems. In this
paper we quantify how topological properties of word co-occurrence networks and
intermittency (or burstiness) in word distribution depend on the style of
authors. Our database contains 40 books from 8 authors who lived in the 19th
and 20th centuries, for which the following network measurements were obtained:
clustering coefficient, average shortest path lengths, and betweenness. We
found that the two factors with stronger dependency on the authors were the
skewness in the distribution of word intermittency and the average shortest
paths. Other factors such as the betweeness and the Zipf's law exponent show
only weak dependency on authorship. Also assessed was the contribution from
each measurement to authorship recognition using three machine learning
methods. The best performance was a ca. 65 % accuracy upon combining complex
network and intermittency features with the nearest neighbor algorithm. From a
detailed analysis of the interdependence of the various metrics it is concluded
that the methods used here are complementary for providing short- and
long-scale perspectives of texts, which are useful for applications such as
identification of topical words and information retrieval.
| arxiv topic:physics.soc-ph cs.CL cs.SI physics.data-an |
arxiv_dataset-31171112.6145 | Bonding mechanism in the nitrides Ti2AlN and TiN: an experimental and
theoretical investigation
cond-mat.mtrl-sci physics.comp-ph
The electronic structure of nanolaminate Ti2AlN and TiN thin films has been
investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured
Ti L, N K, Al L1 and Al L2,3 emission spectra are compared with calculated
spectra using ab initio density-functional theory including dipole transition
matrix elements. Three different types of bond regions are identified; a
relatively weak Ti 3d - Al 3p bonding between -1 and -2 eV below the Fermi
level, and Ti 3d - N 2p and Ti 3d - N 2s bonding which are deeper in energy
observed at -4.8 eV and -15 eV below the Fermi level, respectively. A strongly
modified spectral shape of 3s states of Al L2,3 emission from Ti2AlN in
comparison to pure Al metal is found, which reflects the Ti 3d - Al 3p
hybridization observed in the Al L1 emission. The differences between the
electronic and crystal structures of Ti2AlN and TiN are discussed in relation
to the intercalated Al layers of the former compound and the change of the
materials properties in comparison to the isostructural carbides.
| arxiv topic:cond-mat.mtrl-sci physics.comp-ph |
arxiv_dataset-31181112.6245 | Graded polynomial identities, group actions, and exponential growth of
Lie algebras
math.RA
Consider a finite dimensional Lie algebra L with an action of a finite group
G over a field of characteristic 0. We prove the analog of Amitsur's conjecture
on asymptotic behavior for codimensions of polynomial G-identities of L. As a
consequence, we prove the analog of Amitsur's conjecture for graded
codimensions of any finite dimensional Lie algebra graded by a finite Abelian
group.
| arxiv topic:math.RA |
arxiv_dataset-31191112.6345 | Solution of the relativistic bound state problem for hadrons
physics.gen-ph
A second order extension of the QED Lagrangian (including boson-boson
coupling) has been used to describe q\bar q hadrons. Assuming massless
elementary fermions (quantons) this results in a finite theory without open
parameters, which may be regarded as a fundamental description of the strong
interaction. Two potentials are deduced, a boson-exchange potential and one,
which can be identified with the known confinement potential in hadrons. This
formalism has been applied the mesonic systems omega(782), Phi(1020),
J/psi(3097) and Upsilon(9460), for which a good description is obtained.
The most important results are: 1. The confinement of hadrons is not due to
colour, but is a general property of relativistic bound states. 2. Massive
quarks in the Standard Model (QCD) are understood as effective fermions with a
mass given by the binding energy in the boson-exchange potential.
| arxiv topic:physics.gen-ph |
arxiv_dataset-31201201.0013 | Towards non-AdS holography in 3-dimensional higher spin gravity
hep-th gr-qc
We take the first steps towards non-AdS holography in higher spin gravity.
Namely, we propose a variational principle for generic 3-dimensional higher
spin gravity that accommodates asymptotic backgrounds beyond AdS, like
asymptotically Schrodinger, Lifshitz or warped AdS spacetimes. As examples we
study in some detail the four sl(2) embeddings of spin-4 gravity and provide
associated geometries, including an asymptotic Lifshitz black hole.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-31211201.0113 | Unobservable Planar Bimodal Linear Systems: Miniversal Deformations,
Controllability and Stabilization
math.DS
We consider the set of bimodal linear systems consisting of two linear
dynamics acting on each side of a given hyperplane, assuming continuity along
the separating hyperplane. Focusing on the unobservable planar ones, we obtain
a simple explicit characterization of controllability. Moreover, we apply the
canonical forms of these systems depending on two state variables to obtain
explicitly miniversal deformations, to illustrate bifurcation diagrams and to
prove that the unobservable controllable systems are stabilizable.
Preprint of an article submitted for consideration in IJBC \copyright 2011
copyright World Scientific Publishing Company http://www.worldscinet.com/ijbc/
| arxiv topic:math.DS |
arxiv_dataset-31221201.0213 | A Secured Health Care Application Architecture for Cyber-Physical
Systems
cs.NI
Cyber-physical systems (CPS) can be viewed as a new generation of systems
with integrated control, communication and computational capabilities. Like the
internet transformed how humans interact with one another, cyber-physical
systems will transform how people interact with the physical world. Currently,
the study of CPS is still in its infancy and there exist many research issues
and challenges ranging from electricity power, health care, transportation and
smart building etc. In this paper, an introduction of CPeSC3 (cyber physical
enhanced secured wireless sensor networks (WSNs) integrated cloud computing for
u-life care) architecture and its application to the health care monitoring and
decision support systems is given. The proposed CPeSC3 architecture is composed
of three main components, namely 1) communication core, 2) computation core,
and 3) resource scheduling and management core. Detailed analysis and
explanation are given for relevant models such as cloud computing, real time
scheduling and security models. Finally, a medical health care application
scenario is presented based on our practical test-bed which has been built for
3 years.
| arxiv topic:cs.NI |
arxiv_dataset-31231201.0313 | Reduced magnetohydrodynamic theory of oblique plasmoid instabilities
physics.plasm-ph
The three-dimensional nature of plasmoid instabilities is studied using the
reduced magnetohydrodynamic equations. For a Harris equilibrium with guide
field, represented by $\vc{B}_o = B_{po} \tanh (x/\lambda) \hat{y} + B_{zo}
\hat{z}$, a spectrum of modes are unstable at multiple resonant surfaces in the
current sheet, rather than just the null surface of the polodial field $B_{yo}
(x) = B_{po} \tanh (x/\lambda)$, which is the only resonant surface in 2D or in
the absence of a guide field. Here $B_{po}$ is the asymptotic value of the
equilibrium poloidal field, $B_{zo}$ is the constant equilibrium guide field,
and $\lambda$ is the current sheet width. Plasmoids on each resonant surface
have a unique angle of obliquity $\theta \equiv \arctan(k_z/k_y)$. The resonant
surface location for angle $\theta$ is $x_s = - \lambda \arctanh (\tan \theta
B_{zo}/B_{po})$, and the existence of a resonant surface requires $|\theta| <
\arctan (B_{po} / B_{zo})$. The most unstable angle is oblique, i.e. $\theta
\neq 0$ and $x_s \neq 0$, in the constant-$\psi$ regime, but parallel, i.e.
$\theta = 0$ and $x_s = 0$, in the nonconstant-$\psi$ regime. For a fixed angle
of obliquity, the most unstable wavenumber lies at the intersection of the
constant-$\psi$ and nonconstant-$\psi$ regimes. The growth rate of this mode is
$\gamma_{\textrm{max}}/\Gamma_o \simeq S_L^{1/4} (1-\mu^4)^{1/2}$, in which
$\Gamma_o = V_A/L$, $V_A$ is the Alfv\'{e}n speed, $L$ is the current sheet
length, and $S_L$ is the Lundquist number. The number of plasmoids scales as $N
\sim S_L^{3/8} (1-\mu^2)^{-1/4} (1 + \mu^2)^{3/4}$.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-31241201.0413 | Notions of M\"obius inversion
math.CT math.CO
M\"obius inversion, originally a tool in number theory, was generalized to
posets for use in group theory and combinatorics. It was later generalized to
categories in two different ways, both of which are useful. We provide a
unifying abstract framework. This allows us to compare and contrast the two
theories of M\"obius inversion for categories, and advance each of them. Among
several side benefits is an improved understanding of the following fact: the
Euler characteristic of the classifying space of a (suitably finite) category
depends only on its underlying graph.
| arxiv topic:math.CT math.CO |
arxiv_dataset-31251201.0513 | Group Colorings and Bernoulli Subflows
math.DS math.GR math.LO
In this paper we study the dynamics of Bernoulli flows and their subflows
over general countable groups from the symbolic and topological perspectives.
We study free subflows (subflows in which every point has trivial stabilizer),
minimal subflows, disjointness of subflows, the problem of classifying subflows
up to topological conjugacy, and the differences in dynamical behavior between
pairs of points which disagree on finitely many coordinates. We call a point
hyper aperiodic if the closure of its orbit is a free subflow and we call it
minimal if the closure of its orbit is a minimal subflow.
We prove that the set of all (minimal) hyper aperiodic points is always dense
but also meager and null. By employing notions and ideas from descriptive set
theory, we study the complexity of the sets of hyper aperiodic points and of
minimal points and completely determine their descriptive complexity. In doing
this we introduce a new notion of countable flecc groups and study their
properties. We obtain a dichotomy for the complexity of classifying free
subflows up to topological conjugacy. For locally finite groups the topological
conjugacy relation for all (free) subflows is hyperfinite and nonsmooth. For
nonlocally finite groups the relation is Borel bireducible with the universal
countable Borel equivalence relation.
A primary focus of the paper is to develop constructive methods for the
notions studied. To construct hyper aperiodic points, a fundamental method of
construction of multi-layer marker structures is developed with great
generality. Variations of the fundamental method are used in many proofs in the
paper, and we expect them to be useful more broadly in geometric group theory.
As a special case of such marker structures, we study the notion of ccc groups
and prove the ccc-ness for countable nilpotent, polycyclic, residually finite,
locally finite groups and for free products.
| arxiv topic:math.DS math.GR math.LO |
arxiv_dataset-31261201.0613 | Exploiting non-quantum entanglement to widen applicability of
limited-entanglement classical simulations of quantum systems
quant-ph
It is known that if the quantum gates in a proposed quantum computer are so
noisy that they are incapable of generating entanglement, then the device can
be efficiently simulated classically. If the measurements and single particle
operations are restricted, then the same statement can be true for generalised
non-quantum notions of entanglement. Here we show that this can improve the
applicability of limited-entanglement simulation algorithms. In particular, we
show that by using a non-quantum notion of separability a classical simulation
algorithm of Harrow & Nielsen can efficiently simulate magic state quantum
computers with noisy CNOTs (but otherwise ideal) for joint depolarising
strengths of 272/489 ~ 56%, in comparison to noise levels of 2/3 ~ 66% required
if the algorithm uses quantum notions of separability. This suggests that
quantum entanglement may not be the most appropriate notion of entanglement to
use when discussing the power of stabilizer based quantum computers.
| arxiv topic:quant-ph |
arxiv_dataset-31271201.0713 | Elementary Deuring-Heilbronn Phenomenon
math.NT
Adapting a technique of Pintz, we give an elementary demonstration of the
Deuring phenomenon: a zero of \zeta(s) off the critical line gives a lower
bound on L(1,\chi). The necessary tools are Dirichlet's 'method of the
hyperbola', Euler summation, summation by parts, and the Polya-Vinogradov
inequality.
| arxiv topic:math.NT |
arxiv_dataset-31281201.0813 | Landau-Ginzburg/Calabi-Yau correspondence, global mirror symmetry and
Orlov equivalence
math.AG math.SG
We show that the Gromov-Witten theory of Calabi-Yau hypersurfaces matches, in
genus zero and after an analytic continuation, the quantum singularity theory
(FJRW theory) recently introduced by Fan, Jarvis and Ruan following ideas of
Witten. Moreover, on both sides, we highlight two remarkable integral local
systems arising from the common formalism of Gamma-integral structures applied
to the derived category of the hypersurface {W=0} and to the category of graded
matrix factorizations of W. In this setup, we prove that the analytic
continuation matches Orlov equivalence between the two above categories.
| arxiv topic:math.AG math.SG |
arxiv_dataset-31291201.0913 | Novel Modulation Techniques using Isomers as Messenger Molecules for
Molecular Communication via Diffusion
q-bio.QM cs.CE cs.IT math.IT
In this paper, we propose novel modulation techniques using isomers as
messenger molecules for nano communication via diffusion. To evaluate
achievable rate performance, we compare the proposed techniques with
concentration-based and molecular-type-based methods. Analytical and numerical
results confirm that the proposed modulation techniques achieve higher data
transmission rate performance than conventional insulin based concepts.
| arxiv topic:q-bio.QM cs.CE cs.IT math.IT |
arxiv_dataset-31301201.1013 | The WiggleZ Dark Energy Survey: Galaxy Evolution at 0.25 < z < 0.75
Using The Second Red-Sequence Cluster Survey (RCS-2)
astro-ph.CO
We study the evolution of galaxy populations around the spectroscopic WiggleZ
sample of starforming galaxies at 0.25 < z < 0.75 using the photometric catalog
from the Second Red-Sequence Cluster Survey (RCS2). We probe the optical
photometric properties of the net excess neighbor galaxies. The key concept is
that the marker galaxies and their neighbors are located at the same redshift,
providing a sample of galaxies representing a complete census of galaxies in
the neighborhood of star-forming galaxies. The results are compared with those
using the RCS WiggleZ Spare-Fibre (RCS-WSF) sample as markers, representing
galaxies in cluster environments at 0.25 < z < 0.45. By analyzing the stacked
color-color properties of the WiggleZ neighbor galaxies, we find that their
optical colors are not a strong function of indicators of star-forming
activities such as EW([OII]) or GALEX NUV luminoisty of the markers. The
galaxies around the WiggleZ markers exhibit a bimodal distribution on the
color-magnitude diagram, with most of them located in the blue cloud. The
optical galaxy luminosity functions (GLF) of the blue neighbor galaxies have a
faint-end slope \alpha of \sim -1.3, similar to that for galaxies in cluster
environments drawn from the RCS-WSF sample. The faint-end slope of the GLF for
the red neighbors, however, is \sim -0.4, significantly shallower than the \sim
-0.7 found for those in cluster environments. This suggests that the build-up
of the faint-end of the red sequence in cluster environments is in a
significantly more advanced stage than that in the star-forming and lower
galaxy density WiggleZ neighborhoods. We find that the red galaxy fraction
(fred) around the star-forming WiggleZ galaxies has similar values from z \sim
0.3 to z \sim 0.6 with fred \sim 0.28, but drops to fred \sim 0.20 at z >
\sim0.7. This change of fred with redshift suggests that (and more...)
| arxiv topic:astro-ph.CO |
arxiv_dataset-31311201.1113 | Tailoring of the luminescent ions local environment in optical fibers,
and applications
physics.optics
The chapter is situated in the fields of fiber materials sciences and
technologies (particularly dealing with the fiber glass compositions and
luminescent ion doping, and transparent glass ceramic optical fibers), and
applications such as fiber lasers and amplifiers. We propose to present a
review of research activities on rare-earth (RE) and transition metals (TM)
doped silica-based optical fibers, aiming at understanding theier spectral
properties, and particularly some of their optical transitions that will allow
interesting and alternative applications. Silica, as opposed to alternative,
low temperature materials, is chosen for practical and economical reasons.
Selected RE and TM ions are studied both as probes of their local environment
and for their application potentials. In this chapter, we will focus on erbium
(Er) ions for the potential spectral 'tailoring' of its gain curve at 1.55
$\mu$m, thulium (Tm) as local environment probe along both near infrared
transitions around 0.8 and 1.47 $\mu$m, and chromium (Cr) for the sensitivity
of valency and spectroscopy to the glass composition and its potential as
saturable absorber in lasers. We will present some extensive studies on the
influence of the local environment on dopants: such as (but not limited to)
energy transfer mechanisms between rare-earth ions of same nature (Tm-Tm) or
different nature (Yb-Tm), effect of the local phonon energy on Tm ions emission
efficiency, broadening of Er ions emission induced by oxide nanoparticles grown
in situ during the fabrication process, etc. Knowledge of these effects is
essential for photonics applications, and many studies are under progress or
are still needed in this field. The potential of some applications which could
benefit from the basic studies on materials are also numerically studied :
0.8-$\mu$m thulium-doped fiber laser, so-called S-band (1.47 $\mu$m)
thulium-doped amplifier for telecommunications and laser applications,
sensitisation of Tm-based devices using ytterbium sensitized ions.
| arxiv topic:physics.optics |
arxiv_dataset-31321201.1213 | Direct measurement of the three dimensional magnetization vector
trajectory in GaMnAs by a magneto-optical pump-and-probe method
cond-mat.mtrl-sci
We report on a quantitative experimental determination of the
three-dimensional magnetization vector trajectory in GaMnAs by means of the
static and time-resolved pump-and-probe magneto-optical measurements. The
experiments are performed in a normal incidence geometry and the time evolution
of the magnetization vector is obtained without any numerical modeling of
magnetization dynamics. Our experimental method utilizes different polarization
dependences of the polar Kerr effect and magnetic linear dichroism to
disentangle the pump-induced out-of-plane and in-plane motions of
magnetization, respectively. We demonstrate that the method is sensitive enough
to allow for the determination of small angle excitations of the magnetization
in GaMnAs. The method is readily applicable to other magnetic materials with
sufficiently strong circular and linear magneto-optical effects.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-31331201.1313 | Integral points in two-parameter orbits
math.NT
Let K be a number field, let f: P_1 --> P_1 be a nonconstant rational map of
degree greater than 1, let S be a finite set of places of K, and suppose that
u, w in P_1(K) are not preperiodic under f. We prove that the set of (m,n) in
N^2 such that f^m(u) is S-integral relative to f^n(w) is finite and effectively
computable. This may be thought of as a two-parameter analog of a result of
Silverman on integral points in orbits of rational maps.
This issue can be translated in terms of integral points on an open subset of
P_1^2; then one can apply a modern version of the method of Runge, after
increasing the number of components at infinity by iterating the rational map.
Alternatively, an ineffective result comes from a well-known theorem of Vojta.
| arxiv topic:math.NT |
arxiv_dataset-31341201.1413 | Phenomenology of a Light Cold Dark Matter Two-Singlet Model
hep-ph
We study the implications of phenomenological processes on a two-singlet
extension of the Standard Model we introduced in a previous work to describe
light cold dark matter. We look into the rare decays of $\Upsilon $ and $B$
mesons, most particularly the invisible channels, and study the decay channels
of the Higgs particle. Preferred regions of the parameter space are indicated,
together with others that are excluded. Comments in relation to recent Higgs
searches and finds at the LHC are made.
| arxiv topic:hep-ph |
arxiv_dataset-31351201.1513 | A uniform inf--sup condition with applications to preconditioning
math.NA
A uniform inf-sup condition related to a parameter dependent Stokes problem
is established. Such conditions are intimately connected to the construction of
uniform preconditioners for the problem, i.e., preconditioners which behave
uniformly well with respect to variations in the model parameter as well as the
discretization parameter. For the present model, similar results have been
derived before, but only by utilizing extra regularity ensured by convexity of
the domain. The purpose of this paper is to remove this artificial assumption.
As a byproduct of our analysis, in the two dimensional case we also construct a
new projection operator for the Taylor-Hood element which is uniformly bounded
in $L^2$ and commutes with the divergence operator. This construction is based
on a tight connection between a subspace of the Taylor-Hood velocity space and
the lowest order Nedelec edge element.
| arxiv topic:math.NA |
arxiv_dataset-31361201.1613 | Numerical Weather Prediction (NWP) and hybrid ARMA/ANN model to predict
global radiation
cs.NE physics.data-an
We propose in this paper an original technique to predict global radiation
using a hybrid ARMA/ANN model and data issued from a numerical weather
prediction model (ALADIN). We particularly look at the Multi-Layer Perceptron.
After optimizing our architecture with ALADIN and endogenous data previously
made stationary and using an innovative pre-input layer selection method, we
combined it to an ARMA model from a rule based on the analysis of hourly data
series. This model has been used to forecast the hourly global radiation for
five places in Mediterranean area. Our technique outperforms classical models
for all the places. The nRMSE for our hybrid model ANN/ARMA is 14.9% compared
to 26.2% for the na\"ive persistence predictor. Note that in the stand alone
ANN case the nRMSE is 18.4%. Finally, in order to discuss the reliability of
the forecaster outputs, a complementary study concerning the confidence
interval of each prediction is proposed
| arxiv topic:cs.NE physics.data-an |
arxiv_dataset-31371201.1713 | The ultrafilter number for singular cardinals
math.LO
We prove the consistency of a singular cardinal $\lambda$ with small value of
the ultrafilter number $u_\lambda$, and arbitrarily large value of $2^\lambda$.
| arxiv topic:math.LO |
arxiv_dataset-31381201.1813 | Towards a quantum universe
physics.gen-ph
In this short review we study the state of the art of the great problems in
cosmology and their interrelationships. The reconciliation of these problems
passes undoubtedly through the idea of a quantum universe.
| arxiv topic:physics.gen-ph |
arxiv_dataset-31391201.1913 | Which galaxy property is the best indicator of its host dark matter halo
properties?
astro-ph.CO
In this work we investigate the link between galaxy velocity dispersion, mass
and other properties (color, morphology) with the properties of dark matter
halos by comparing the clustering of galaxies at both fixed mass and velocity
dispersion. We use the Sloan Digital Sky Survey to define a volume limited
sample of massive galaxies complete in both stellar mass (>6e10 Msun) and
velocity dispersion (>75 km/s). Using this sample we show that at fixed
velocity dispersion there is no dependence of the clustering amplitude on
stellar or dynamical mass. Conversely when stellar or dynamical mass are fixed
there is a clear dependence of the clustering amplitude on velocity dispersion
with higher dispersion galaxies showing a higher clustering amplitude. We also
show that whilst when stellar or dynamical mass are fixed there remains a
dependence of clustering amplitude on morphology, there is no such dependency
when dispersion is fixed. However, we do see a dependence of the clustering
amplitude on color when both mass and dispersion are fixed. Despite this, even
when we restrict our samples to only elliptical or red galaxies the
relationship between dispersion and clustering amplitude at fixed mass remains.
It seems likely that the residual correlation with color is driven by satellite
galaxies in massive halos being redder at fixed dispersion. The lack of a
similar morphology dependence implies that the mechanism turning satellites red
is not changing their morphology. Our central result is that velocity
dispersion is more closely related to the clustering amplitude of galaxies than
either stellar or dynamical mass. This implies that velocity dispersion is more
tightly correlated with the halo properties that determine clustering, either
halo mass or age, and supports the notion that the star formation history of a
galaxy is more closely related to its halo properties than its overall mass.
| arxiv topic:astro-ph.CO |
arxiv_dataset-31401201.2013 | Signatures of an intermediate-age metal-rich bulge population
astro-ph.GA
We have determined detailed elemental abundances and stellar ages for a
sample of now 38 microlensed dwarf and subgiant stars in the Galactic bulge.
Stars with sub-solar metallicities are all old and have enhanced alpha-element
abundances -- very similar to what is seen for local thick disk stars. The
metal-rich stars on the other hand show a wide variety of stellar ages, ranging
from 3-4 Gyr to 12 Gyr, and an average around 7-8 Gyr. The existence of young
and metal-rich stars are in conflict with recent photometric studies of the
bulge which claim that the bulge only contains old stars.
| arxiv topic:astro-ph.GA |
arxiv_dataset-31411201.2113 | Is J enough? Comparison of gravitational waves emitted along the total
angular momentum direction with other preferred orientations
gr-qc astro-ph.CO
The gravitational wave signature emitted from a merging binary depends on the
orientation of an observer relative to the binary. Previous studies suggest
that emission along the total initial or total final angular momenta leads to
both the strongest and simplest signal from a precessing compact binary. In
this paper we describe a concrete counterexample: a binary with $m_1/m_2=4$,
$a_1=0.6 \hat{x} = -a_2$, placed in orbit in the x,y plane. We extract the
gravitational wave emission along several proposed emission directions,
including the initial (Newtonian) orbital angular momentum; the final (~
initial) total angular momentum; and the dominant principal axis of $<L_a
L_b>_M$. Using several diagnostics, we show that the suggested preferred
directions are not representative. For example, only for a handful of other
directions (< 15%) will the gravitational wave signal have comparable shape to
the one extracted along each of these fiducial directions, as measured by a
generalized overlap (>0.95). We conclude that the information available in just
one direction (or mode) does not adequately encode the complexity of
orientation-dependent emission for even short signals from merging black hole
binaries. Future investigations of precessing, unequal-mass binaries should
carefully explore and model their orientation-dependent emission.
| arxiv topic:gr-qc astro-ph.CO |
arxiv_dataset-31421201.2213 | Is N-doped SrO magnetic? A first-principles view
cond-mat.mtrl-sci
N-doped SrO seems to be one of the model systems for d^0 magnetism, in which
magnetism (or ideally, ferromagnetism) was ascribed to the localized N 2p spins
mediated by delocalized O 2p holes. Here we offer a different view, using
density functional calculations. We find that N-doped SrO with solely
substitutional N impurities as widely assumed in the literature is unstable,
and instead that a pairing state of substitutional and interstitial N
impurities is significantly more stable and has a much lower formation energy
than the former by 6.7 eV. The stable (N_{sub}-N_{int})^{2-} dimers behave like
a charged (N_2)^{2-} molecule and have each a molecular spin=1. However, their
spin-polarized molecular levels lie well inside the wide band gap of SrO and
thus the exchange interaction is negligibly weak. As a consequence, N-doped SrO
could not be ferromagnetic but paramagnetic.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-31431201.2313 | The Stability of the Suggested Planet in the nu Octantis System: A
Numerical and Statistical Study
astro-ph.EP
We provide a detailed theoretical study aimed at the observational finding
about the nu Octantis binary system that indicates the possible existence of a
Jupiter-type planet in this system. If a prograde planetary orbit is assumed,
it has earlier been argued that the planet, if existing, should be located
outside the zone of orbital stability. However, a previous study by Eberle &
Cuntz (2010) [ApJ 721, L168] concludes that the planet is most likely stable if
assumed to be in a retrograde orbit with respect to the secondary system
component. In the present work, we significantly augment this study by taking
into account the observationally deduced uncertainty ranges of the orbital
parameters for the stellar components and the suggested planet. Furthermore,
our study employs additional mathematical methods, which include monitoring the
Jacobi constant, the zero velocity function, and the maximum Lyapunov exponent.
We again find that the suggested planet is indeed possible if assumed to be in
a retrograde orbit, but it is virtually impossible if assumed in a prograde
orbit. Its existence is found to be consistent with the deduced system
parameters of the binary components and of the suggested planet, including the
associated uncertainty bars given by observations.
| arxiv topic:astro-ph.EP |
arxiv_dataset-31441201.2413 | Integrated Optical Polarization of Nearby Galaxies
astro-ph.CO
We performed an integrated optical polarization survey of 70 nearby galaxies
to study the relationship between linear polarization and galaxy properties. To
date this is the largest survey of its kind. The data were collected at
McDonald Observatory using the Imaging Grism Polarimeter on the Otto Struve
2.1m telescope. Most of the galaxies did not have significant level of linear
polarization, where the bulk is <1%. A fraction of the galaxies showed a loose
correlation between the polarization and position angle of the galaxy,
indicating that dust scattering is the main source of optical polarization. The
unbarred spiral galaxies are consistent with the predicted relationship with
inclination from scattering models of ~sin^2i.
| arxiv topic:astro-ph.CO |
arxiv_dataset-31451201.2513 | On Geometric Upper Bounds for Positioning Algorithms in Wireless Sensor
Networks
cs.IT math.IT
This paper studies the possibility of upper bounding the position error of an
estimate for range based positioning algorithms in wireless sensor networks. In
this study, we argue that in certain situations when the measured distances
between sensor nodes are positively biased, e.g., in non-line-of-sight
conditions, the target node is confined to a closed bounded convex set (a
feasible set) which can be derived from the measurements. Then, we formulate
two classes of geometric upper bounds with respect to the feasible set. If an
estimate is available, either feasible or infeasible, the worst-case position
error can be defined as the maximum distance between the estimate and any point
in the feasible set (the first bound). Alternatively, if an estimate given by a
positioning algorithm is always feasible, we propose to get the maximum length
of the feasible set as the worst-case position error (the second bound). These
bounds are formulated as nonconvex optimization problems. To progress, we relax
the nonconvex problems and obtain convex problems, which can be efficiently
solved. Simulation results indicate that the proposed bounds are reasonably
tight in many situations.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-31461201.2613 | Chemical Processes in Protoplanetary Disks II. On the importance of
photochemistry and X-ray ionization
astro-ph.GA astro-ph.EP
We investigate the impact of photochemistry and X-ray ionization on the
molecular composition of, and ionization fraction in, a protoplanetary disk
surrounding a typical T Tauri star. We use a sophisticated physical model,
which includes a robust treatment of the radiative transfer of UV and X-ray
radiation, and calculate the time-dependent chemical structure using a
comprehensive chemical network. In previous work, we approximated the
photochemistry and X-ray ionization, here, we recalculate the photoreaction
rates using the explicit UV wavelength spectrum and wavelength-dependent
reaction cross sections. We recalculate the X-ray ionization rate using our
explicit elemental composition and X-ray energy spectrum. We find
photochemistry has a larger influence on the molecular composition than X-ray
ionization. Observable molecules sensitive to the photorates include OH, HCO+,
N2H+, H2O, CO2 and CH3OH. The only molecule significantly affected by the X-ray
ionization is N2H+ indicating it is safe to adopt existing approximations of
the X-ray ionization rate in typical T Tauri star-disk systems. The
recalculation of the photorates increases the abundances of neutral molecules
in the outer disk, highlighting the importance of taking into account the shape
of the UV spectrum in protoplanetary disks. A recalculation of the
photoreaction rates also affects the gas-phase chemistry due to the adjustment
of the H/H2 and C+/C ratios. The disk ionization fraction is not significantly
affected by the methods adopted to calculate the photochemistry and X-ray
ionization. We determine there is a probable 'dead zone' where accretion is
suppressed, present in a layer, Z/R <~ 0.1 - 0.2, in the disk midplane, within
R \approx 200 AU.
| arxiv topic:astro-ph.GA astro-ph.EP |
arxiv_dataset-31471201.2713 | Charge and orbital order in frustrated Pb3Mn7O15
cond-mat.str-el
The candidate magnetoelectric Pb3Mn7O15 has a structure consisting of 1/3
filled Kagome layers linked by ribbons of edge-sharing octahedra in the
stacking direction. Previous reports have indicated a complex
hexagonal-orthorhombic structural transition upon cooling to room temperature,
although its origins are uncertain. Here both structures are revisited using a
combination of neutron and synchrotron X-ray diffraction data. Large shifts of
oxygen positions are detected which show that the interlayer sites and those
which occupy voids in the kagome lattice are trivially charge ordered in both
phases. The symmetry breaking is found to occur due to Mn3+ orbital ordering on
the ribbon sites and charge ordering of the sub-set of layer sites which make
up a Kagome network.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-31481201.2813 | Higher-dimensional Kundt waves and gyratons
gr-qc hep-th
We present and analyze exact solutions of the Einstein-Maxwell equations in
higher dimensions which form a large subclass of the Kundt family of
spacetimes. We assume that the cosmological constant may be nonvanishing, and
the matter consists of a background aligned electromagnetic field and an
additional pure radiation (gyratonic) field with a spin. We show that the field
equations reduce to a set of linear equations on the transverse space which can
be solved exactly and expressed in terms of the Green functions. We thus find
explicit exact gyratonic gravitational and electromagnetic fields created by a
radiation beam of null matter with arbitrary profiles of energy density and
angular momenta. In the absence of the gyratonic matter we obtain pure
nonexpanding higher-dimensional gravitational waves.
In particular, we investigate gyratons and waves propagating on backgrounds
which are a direct-product of 2-spaces of constant curvature. Such type D or 0
background spacetimes generalize 4-dimensional Nariai, anti-Nariai and
Plebanski-Hacyan universes, and conformally flat Bertotti-Robinson and
Minkowski spaces. These spacetimes belong to a wider class of spaces which
admit the Kahler structure related to the background magnetic field. The
obtained wave and gyraton solutions are also members of the recently discussed
class of spacetimes with constant scalar invariants (CSI) of the curvature
tensor.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-31491201.2913 | The Standardizability of Type Ia Supernovae in the Near-Infrared:
Evidence for a Peak Luminosity-Decline Rate Relation in the Near-Infrared
astro-ph.CO
We analyze the standardizability of Type Ia supernovae (SNe Ia) in the
near-infrared (NIR) by investigating the correlation between observed peak NIR
absolute magnitude and post-maximum B-band decline rate. A sample of 27
low-redshift SNe Ia observed by the Carnegie Supernova Project between 2004 to
2007 is used. All 27 objects have pre-maximum coverage in optical bands, with a
subset of 13 having pre-maximum NIR observations as well. We describe the
methods used to derive absolute peak magnitudes and decline rates from both
spline- and template-fitting procedures, and confirm prior findings that
fitting templates to SNe Ia light curves in the NIR is problematic due to the
diversity of post-maximum behaviour of objects that are characterized by
similar decline rate values, especially at high decline rates. Nevertheless, we
show that NIR light curves can be reasonably fit with a template, especially if
the observations begin within 5 days after NIR maximum. For the subset of 13
objects in our dataset that excludes the highly reddened and fast declining SNe
Ia, and includes only those objects for which NIR observations began prior to
five days after maximum light, we find modest evidence for a peak
luminosity-decline rate relation in Y, and stronger evidence in J and H. Using
Rv values differing from the canonical value of 3.1 is shown to have little
effect on the results. A Hubble diagram is presented for the NIR bands and the
B band. The resulting scatter for the combined NIR bands is 0.13 mag, while the
B band produces a scatter of 0.22 mag. The data suggest that applying a
correction to SNe Ia peak luminosities for decline rate is likely to be
beneficial in the J and H bands to make SNe Ia more precise distance
indicators, but of only marginal importance in the Y band.
| arxiv topic:astro-ph.CO |
arxiv_dataset-31501201.3013 | Universal rigidity of bar frameworks in general position: a Euclidean
distance matrix approach
math.MG
A configuration p in r-dimensional Euclidean space is a finite collection of
labeled points p^1,p^2,...,p^n in R^r that affinely span R^r. Each
configuration p defines a Euclidean distance matrix D_p = (d_ij) =
(||p^i-p^j||^2), where ||.|| denotes the Euclidean norm. A fundamental problem
in distance geometry is to find out whether or not, a given proper subset of
the entries of D_p suffices to uniquely determine the entire matrix D_p. This
problem is known as the universal rigidity problem of bar frameworks. In this
chapter, we present a unified approach for the universal rigidity of bar
frameworks, based on Euclidean distance matrices (EDMs), or equivalently, on
projected Gram matrices. This approach makes the universal rigidity problem
amenable to semi-definite programming methodology. Using this approach, we
survey some recently obtained results and their proofs, emphasizing the case
where the points p^1,...,p^n are in general position.
| arxiv topic:math.MG |
arxiv_dataset-31511201.3113 | Magnetocaloric materials: the search for new systems
cond-mat.mtrl-sci cond-mat.str-el
The prospect of efficient solid state refrigeration at room temperature is
driving research into magnetic cooling engine design and magnetic phase
transition-based refrigerants. In this Viewpoint an Ashby-style map of magnetic
refrigerant properties is constructed, comparing popular materials with limits
derived from an idealised first order transition model. This comparison
demonstrates the potential for new magnetocaloric material systems to be
established through structural control and optimisation at the atomic-, nano-
and micro-scale.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-31521201.3213 | Dynamical brane with angles : Collision of the universes
hep-th gr-qc
We present the time-dependent solutions corresponding to the dynamical
D-brane with angles in ten-dimensional type II supergravity theories. Our
solutions with angles are different from the known dynamical intersecting brane
solutions in supergravity theories. Because of our ansatz for fields, all warp
factors in the solutions can depend on time. Applying these solutions, we
construct cosmological models from those solutions by smearing some dimensions
and compactifying the internal space. We find the
Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological solutions with
power-law expansion. We also discuss the dynamics of branes based on these
solutions. When the spacetime is contracting in ten dimensions, each brane
approaches the others as the time evolves. However, for Dp-brane ($p\le 7$)
without smearing branes, a singularity appears before branes collide. In
contrast, the D6-D8 brane system or the smeared D(p-2)-Dp brane system with one
uncompactified extra dimension can provide an example of colliding branes (and
collision of the universes), if they have the same charges.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-31531201.3313 | A New Integral Equation for the Spheroidal equations in case of m equal
1
physics.gen-ph
The spheroidal wave functions are investigated in the case m=1. The integral
equation is obtained for them. For the two kinds of eigenvalues in the
differential and corresponding integral equations, the relation between them
are given explicitly. Though there are already some integral equations for the
spheroidal equations, the relation between their two kinds of eigenvalues is
not known till now. This is the great advantage of our integral equation, which
will provide useful information through the study of the integral equation.
Also an example is given for the special case, which shows another way to study
the eigenvalue problem.
| arxiv topic:physics.gen-ph |
arxiv_dataset-31541201.3413 | A unified constraint on the Lorentz invariance violation from both short
and long GRBs
astro-ph.HE
Possible Lorentz invariance violation (LIV) has been investigated for a long
time based on observations of GRBs . These arguments relied on the assumption
that photons with different energy are emitted at the same place and time. In
this work, we try to take account of the intrinsic time delay $\Delta t_{\rm
int}$ between emissions of low and high energy photons by using the magnetic
jet model. The possible LIV effects are discussed in a unified scenario both
for long and short {\it Fermi}-detected GRBs. This leads to a unique quantum
gravity energy scale $M_1c^2 \sim 1.0 \times 10^{20}$ GeV respecting the linear
dispersion relation.
| arxiv topic:astro-ph.HE |
arxiv_dataset-31551201.3513 | A note on dyadic coverings and nondoubling Calder\'on-Zygmund theory
math.CA
We construct a family of n+1 dyadic filtrations in R^n, so that every
Euclidean ball B is contained in some cube Q of our family satisfying diam(Q)
\le c_n diam(B) for some dimensional constant c_n. Our dyadic covering is
optimal on the number of filtrations and improves previous results of Christ
and Garnett/Jones by extending a construction of Mei for the n-torus. Based on
this covering and motivated by applications to matrix-valued functions, we
provide a dyadic nondoubling Calder\'on-Zygmund decomposition which avoids
Besicovitch type coverings in Tolsa's decomposition. We also use a recent
result of Hyt\"onen and Kairema to extend our dyadic nondoubling decomposition
to the more general setting of upper doubling metric spaces.
| arxiv topic:math.CA |
arxiv_dataset-31561201.3613 | On the exact evaluation of spin networks
gr-qc hep-th math-ph math.GT math.MP
We introduce a fully coherent spin network amplitude whose expansion
generates all SU(2) spin networks associated with a given graph. We then give
an explicit evaluation of this amplitude for an arbitrary graph. We show how
this coherent amplitude can be obtained from the specialization of a generating
functional obtained by the contraction of parametrized intertwiners a la
Schwinger. We finally give the explicit evaluation of this generating
functional for arbitrary graphs.
| arxiv topic:gr-qc hep-th math-ph math.GT math.MP |
arxiv_dataset-31571201.3713 | Magnetization and Magneto-resistance in Y(Ba1-xSrx)2Cu3O7-{\delta} (x =
0.00 - 0.50) superconductor
cond-mat.supr-con
Here we present the magnetic properties and upper critical field (BC2) of
polycrystalline Y(Ba1-xSrx)2Cu3O7-{\delta} superconductors, which are being
determined through detailed ac/dc susceptibility and resistivity under magnetic
field (RTH) study. All the samples are synthesized through solid state reaction
route. Reduction in Meissner fraction (the ratio of field cooled to zero field
cooled magnetization) is observed with increasing Sr content, suggesting
occurrence of flux pining in the doped samples. The ac susceptibility and
resistivity measurements reveal improved grain couplings in Sr substituted
samples. Consequently the inter-grain critical current density (Jc), upturn
curvature near the Tc in temperature dependence of upper critical field
[BC2(T)], and BC2 are enhanced. Both Jc and BC2 increase in lower Sr
substitution (up to x = 0.10) samples followed by decrease in higher doping due
to degradation in effective pining and grain coupling.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-31581201.3813 | Spatial ordering due to hydrodynamic interactions between a pair of
colliding drops in a confined shear
physics.flu-dyn
Pair-collision between viscous drops in a confined shear is numerically
simulated to show that the confinement drastically alters the trajectories of
the drops. In contrast to free shear, drops here move towards the centerline
giving rise to a zero cross-stream separation and a net stream-wise separation.
The latter varies as inverse of capillary number and the cube of the
confinement (distance between the walls). The stream-wise separation does not
depend on the initial positions of the drops. An analytical theory for the
phenomenon is offered.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-31591201.3913 | Exchange-correlation potentials for inhomogeneous electron systems in
two dimensions from exact diagonalization: comparison with the
local-spin-density approximation
cond-mat.mes-hall
We consider electronic exchange and correlation effects in density-functional
calculations of two-dimensional systems. Starting from wave function
calculations of total energies and electron densities of inhomogeneous model
systems, we derive corresponding exchange-correlation potentials and energies.
We compare these with predictions of the local-spin-density approximation and
discuss its accuracy. Our data will be useful as reference data in testing,
comparing and parametrizing exchange and correlation functionals for
two-dimensional electronic systems.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-31601201.4013 | Connectivity of Confined Dense Networks: Boundary Effects and Scaling
Laws
cs.NI cs.IT math.IT
In this paper, we study the probability that a dense network confined within
a given geometry is fully connected. We employ a cluster expansion approach
often used in statistical physics to analyze the effects that the boundaries of
the geometry have on connectivity. To maximize practicality and applicability,
we adopt four important point-to-point link models based on outage probability
in our analysis: single-input single-output (SISO), single-input
multiple-output (SIMO), multiple-input single-output (MISO), and multiple-input
multiple-output (MIMO). Furthermore, we derive diversity and power scaling laws
that dictate how boundary effects can be mitigated (to leading order) in
confined dense networks for each of these models. Finally, in order to
demonstrate the versatility of our theory, we analyze boundary effects for
dense networks comprising MIMO point-to-point links confined within a right
prism, a polyhedron that accurately models many geometries that can be found in
practice. We provide numerical results for this example, which verify our
analytical results.
| arxiv topic:cs.NI cs.IT math.IT |
arxiv_dataset-31611201.4113 | Neutral kaon interferometry at KLOE and KLOE-2
nucl-ex
Neutral kaons produced in correlated pairs at a phi-factory offer unique
possibilities to perform fundamental tests of CPT invariance, as well as of the
basic principles of quantum mechanics. The analysis of the data collected by
the KLOE experiment at DAFNE is still ongoing with the aim of improving
previous results and limits on several parameters describing CPT violation and
decoherence. Ancillary measurements like the regeneration cross section on the
beam pipe materials are also in progress and will be very useful to reduce the
systematic uncertainties. Prospects on improvements at the KLOE-2 experiment,
aiming at an increase of the integrated luminosity of about a factor of ten
with an upgraded detector, will be also discussed.
| arxiv topic:nucl-ex |
arxiv_dataset-31621201.4213 | The Relation between Ion Temperature Anisotropy and Formation of Slow
Shocks in Collisionless Magnetic Reconnection
astro-ph.EP
We perform a two-dimensional simulation by using an electromagnetic hybrid
code to study the formation of slow-mode shocks in collisionless magnetic
reconnection in low beta plasmas, and we focus on the relation between the
formation of slow shocks and the ion temperature anisotropy enhanced at the
shock downstream region. It is known that as magnetic reconnection develops,
the parallel temperature along the magnetic field becomes large in association
with the anisotropic PSBL (plasma sheet boundary layer) ion beams, and this
temperature anisotropy has a tendency to suppress the formation of slow shocks.
Based on our simulation result, we found that the slow shock formation is
suppressed due to the large temperature anisotropy near the X-type region, but
the ion temperature anisotropy relaxes with increasing the distance from the
magnetic neutral point. As a result, two pairs of current structures, which are
the strong evidence of dissipation of magnetic field in slow shocks, are formed
at the distance x > 115 ion inertial lengths from the neutral point.
| arxiv topic:astro-ph.EP |
arxiv_dataset-31631201.4313 | Quantifying the Significance of the Magnetic Field from Large-Scale
Cloud to Collapsing Core: Self-Similarity, Mass-to-Flux Ratio and Star
Formation Efficiency
astro-ph.GA
Dust polarization observational results are analyzed for the high-mass star
formation region W51 from the largest parent cloud ($\sim$ 2~pc, JCMT) to the
large-scale envelope ($\sim$ 0.5~pc, BIMA) down to the collapsing core e2
($\sim$ 60~mpc, SMA). Magnetic field and dust emission gradient orientations
reveal a correlation which becomes increasingly more tight with higher
resolution. The previously developed polarization - intensity gradient method
(Koch et al. 2012) is applied in order to quantify the magnetic field
significance. This technique provides a way to estimate the local magnetic
field force compared to gravity without the need of any mass or field strength
measurements, solely making use of measured angles which reflect the
geometrical imprint of the various forces. All three data sets clearly show
regions with distinct features in the field-to-gravity force ratio. Azimuthally
averaged radial profiles of this force ratio reveal a transition from a field
dominance at larger distances to a gravity dominance closer to the emission
peaks. Normalizing these profiles to a characteristic core scale points toward
self-similarity. Furthermore, the polarization intensity-gradient method is
linked to the mass-to-flux ratio, providing a new approach to estimate the
latter one without mass and field strength inputs. A transition from a
magnetically supercritical to a subcritical state as a function of distance
from the emission peak is found for the e2 core. Finally, based on the measured
radius-dependent field-to-gravity force ratio we derive a modified star
formation efficiency with a diluted gravity force. Compared to a standard
(free-fall) efficiency, the observed field is capable of reducing the
efficiency down to 10\% or less.
| arxiv topic:astro-ph.GA |
arxiv_dataset-31641201.4413 | Implications For The Origin Of GRB 051103 From LIGO Observations
astro-ph.HE gr-qc
We present the results of a LIGO search for gravitational waves (GWs)
associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst
(GRB) whose electromagnetically determined sky position is coincident with the
spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for
short-hard GRBs include compact object mergers and soft gamma repeater (SGR)
giant flares. A merger progenitor would produce a characteristic GW signal that
should be detectable at the distance of M81, while GW emission from an SGR is
not expected to be detectable at that distance. We found no evidence of a GW
signal associated with GRB 051103. Assuming weakly beamed gamma-ray emission
with a jet semi-angle of 30 deg we exclude a binary neutron star merger in M81
as the progenitor with a confidence of 98%. Neutron star-black hole mergers are
excluded with > 99% confidence. If the event occurred in M81 our findings
support the the hypothesis that GRB 051103 was due to an SGR giant flare,
making it the most distant extragalactic magnetar observed to date.
| arxiv topic:astro-ph.HE gr-qc |
arxiv_dataset-31651201.4513 | Comment on "Turbulence-free ghost imaging" [Appl. Phys. Lett. 98, 111115
(2011)]
quant-ph physics.optics
It is shown that lensless pseudothermal ghost imaging is not immune to
spatial resolution loss from the presence of atmospheric turbulence along the
propagation paths.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-31661201.4613 | Gravitational-wave emission from compact Galactic binaries
astro-ph.GA astro-ph.SR gr-qc
Compact Galactic binaries where at least one member is a white dwarf or
neutron star constitute the majority of individually detectable sources for
future low-frequency space-based gravitational-wave (GW) observatories; they
also form an unresolved continuum, the dominant Galactic foreground at
frequencies below a few mHz. Due to the paucity of electromagnetic
observations, the majority of studies of Galactic-binary populations so far
have been based on population-synthesis simulations. However, recent surveys
have reported several new detections of white-dwarf binaries, providing new
constraints for population estimates. In this article, we evaluate the impact
of revised local densities of interacting white-dwarf binaries on future GW
observations. Specifically: we consider five scenarios that explain these
densities with different assumptions on the formation of interacting systems;
we simulate corresponding populations of detached and interacting white-dwarf
binaries; we estimate the number of individually detectable GW sources and the
magnitude of the confusion-noise foreground, as observed by space-based
detectors with 5- and 1-Mkm arms. We confirm earlier estimates of thousands of
detached-binary detections, but project only few ten to few hundred detections
of interacting systems. This reduction is partly due to our assessment of
detection prospects, based on the iterative identification and subtraction of
bright sources with respect to both instrument and confusion noise. We also
confirm earlier estimates for the confusion-noise foreground, except in one
scenario that explains smaller local densities of interacting systems with
smaller numbers of progenitor detached systems.
| arxiv topic:astro-ph.GA astro-ph.SR gr-qc |
arxiv_dataset-31671201.4713 | The Kepler Problem: Orbit Cones and Cylinders
physics.class-ph
Planetary orbits, being conic sections, may be obtained as the locus of
intersection of planes and cones. The planes involved are familiar to anyone
who has studied the classical Kepler problem. We focus here on the cones.
| arxiv topic:physics.class-ph |
arxiv_dataset-31681201.4813 | Noncommutative Common Cause Principles in Algebraic Quantum Field Theory
math-ph math.MP
States in algebraic quantum field theory "typically" establish correlation
between spacelike separated events. Reichenbach's Common Cause Principle,
generalized to the quantum field theoretical setting, offers an apt tool to
causally account for these superluminal correlations. In the paper we motivate
first why commutativity between the common cause and the correlating events
should be abandoned in the definition of the common cause. Then we show that
the Noncommutative Weak Common Cause Principle holds in algebraic quantum field
theory with locally finite degrees of freedom. Namely, for any pair of
projections A, B supported in spacelike separated regions V_A and V_B,
respectively, there is a local projection C not necessarily commuting with A
and B such that C is supported within the union of the backward light cones of
V_A and V_B and the set {C, non-C} screens off the correlation between A and B.
| arxiv topic:math-ph math.MP |
arxiv_dataset-31691201.4913 | A variational method in the problem of screening an external charge in
strongly correlated metals
cond-mat.str-el
We describe a variational calculation for the problem of screening of a point
charge in a layered correlated metal for dopings close to the Mott transition
where the screening is non-linear due to the proximity to the incompressible
insulating state. We find that external charge can induce locally
incompressible regions and that the non-linear dependence of the screening on
density can induce overscreening in the nearest nearby layers while preserving
overall charge neutrality.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-31701201.5013 | On the Eddington limit and WR Stars
astro-ph.SR
We examine some properties of stars evolving close to the classical Eddington
limit for electron-scattering opacity, when these stars maintain a chemically
homogeneous structure as a result of mixing and/or mass loss.
We consider analytical relations and models computed with the Geneva code.
Homologous, chemically homogeneous stars evolving with a constant Eddington
factor obey a relation of the form mu^2 M = const. This applies, for example,
to Wolf-Rayet (WR) stars in stages without hydrogen. The value of the constant
may depend on the metallicity, initial mass, evolutionary stage, and physical
processes included in the considered homologous evolutionary sequence. An
average value of the constant between 20 and 40 in solar units is consistent
with the masses of Galactic WR stars.
| arxiv topic:astro-ph.SR |
arxiv_dataset-31711201.5113 | Transverse conductivity in the sliding CDW state of NbSe_3
cond-mat.str-el
The dynamical properties of longitudinal and transverse conduction of
NbSe$_3$ single-crystals have been simultaneously studied when the current is
applied along the b axis (chain direction). In the vicinity of the threshold
electric field for CDW sliding, the transverse conduction sharply decreases.
When a rf field is applied, voltage Shapiro steps for longitudinal transport
are observed as usual, but also current Shapiro steps in the transverse
direction. The possible mechanisms of this effect are discussed.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-31721201.5213 | Nonequilibrium representative ensembles for isolated quantum systems
cond-mat.stat-mech hep-ph quant-ph
An isolated quantum system is considered, prepared in a nonequilibrium
initial state. In order to uniquely define the system dynamics, one has to
construct a representative statistical ensemble. From the principle of least
action it follows that the role of the evolution generator is played by a grand
Hamiltonian, but not merely by its energy part. A theorem is proved expressing
the commutators of field operators with operator products through variational
derivatives of these products. A consequence of this theorem is the equivalence
of the variational equations for field operators with the Heisenberg equations
for the latter. A finite quantum system cannot equilibrate in the strict sense.
But it can tend to a quasi-stationary state characterized by ergodic averages
and the appropriate representative ensemble depending on initial conditions.
Microcanonical ensemble, arising in the eigenstate thermalization, is just a
particular case of representative ensembles. Quasi-stationary representative
ensembles are defined by the principle of minimal information. The latter also
implies the minimization of an effective thermodynamic potential.
| arxiv topic:cond-mat.stat-mech hep-ph quant-ph |
arxiv_dataset-31731201.5313 | Propagation Speed of the Maximum of the Fundamental Solution to the
Fractional Diffusion-Wave Equation
math-ph cond-mat.stat-mech math.MP
In this paper, the one-dimensional time-fractional diffusion-wave equation
with the fractional derivative of order $1 \le \alpha \le 2$ is revisited. This
equation interpolates between the diffusion and the wave equations that behave
quite differently regarding their response to a localized disturbance: whereas
the diffusion equation describes a process, where a disturbance spreads
infinitely fast, the propagation speed of the disturbance is a constant for the
wave equation. For the time fractional diffusion-wave equation, the propagation
speed of a disturbance is infinite, but its fundamental solution possesses a
maximum that disperses with a finite speed. In this paper, the fundamental
solution of the Cauchy problem for the time-fractional diffusion-wave equation,
its maximum location, maximum value, and other important characteristics are
investigated in detail. To illustrate analytical formulas, results of numerical
calculations and plots are presented. Numerical algorithms and programs used to
produce plots are discussed.
| arxiv topic:math-ph cond-mat.stat-mech math.MP |
arxiv_dataset-31741201.5413 | The Allen Telescope Array Commensal Observing System
astro-ph.IM
This memo describes the system used to conduct commensal correlator and
beamformer observations at the Allen Telescope Array (ATA). This system was
deployed for ~2 years until the ATA hibernation in 2011 and was responsible for
collecting >5 TB of data during thousands of hours of observations. The general
system design is presented and the implementation is discussed in detail. I
emphasize the rationale for various design decisions and attempt to document a
few aspects of ATA operations that might not be obvious to non-insiders. I
close with some recommendations from my experience developing the software
infrastructure and managing the correlator observations. These include: reuse
existing systems; solve, don't avoid, tensions between projects, and share
infrastructure; plan to make standalone observations to complement the
commensal ones; and be considerate of observatory staff when deploying new and
unusual observing modes. The structure of the software codebase is documented.
| arxiv topic:astro-ph.IM |
arxiv_dataset-31751201.5513 | Faster and Simpler Minimal Conflicting Set Identification
cs.DS
Let C be a finite set of N elements and R = r_1,r_2,..., r_m a family of M
subsets of C. A subset X of R verifies the Consecutive Ones Property (C1P) if
there exists a permutation P of C such that each r_i in X is an interval of P.
A Minimal Conflicting Set (MCS) S is a subset of R that does not verify the
C1P, but such that any of its proper subsets does. In this paper, we present a
new simpler and faster algorithm to decide if a given element r in R belongs to
at least one MCS. Our algorithm runs in O(N^2M^2 + NM^7), largely improving the
current O(M^6N^5 (M+N)^2 log(M+N)) fastest algorithm of [Blin {\em et al}, CSR
2011]. The new algorithm is based on an alternative approach considering
minimal forbidden induced subgraphs of interval graphs instead of Tucker
matrices.
| arxiv topic:cs.DS |
arxiv_dataset-31761201.5613 | Entropy production and Kullback-Leibler divergence between stationary
trajectories of discrete systems
cond-mat.stat-mech
The irreversibility of a stationary time series can be quantified using the
Kullback-Leibler divergence (KLD) between the probability to observe the series
and the probability to observe the time-reversed series. Moreover, this KLD is
a tool to estimate entropy production from stationary trajectories since it
gives a lower bound to the entropy production of the physical process
generating the series. In this paper we introduce analytical and numerical
techniques to estimate the KLD between time series generated by several
stochastic dynamics with a finite number of states. We examine the accuracy of
our estimators for a specific example, a discrete flashing ratchet, and
investigate how close is the KLD to the entropy production depending on the
number of degrees of freedom of the system that are sampled in the
trajectories.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-31771201.5713 | Opposite power series
math.CA math.GR
Let $\gamma_n$ ($n\in \mathbb{Z}_{\ge0}$) be a sequence of complex numbers,
which is tame: $0<\exists u\le \gamma_{n-1}/\gamma_n \le \exists v<\infty$ for
all $n>0$. We show a resonance between the singularities of the function of the
power series $P(t):=\sum_{n=0}^\infty \gamma_n t^n$ on its boundary of the disc
of convergence and the oscillation behavior of the sequences
$\gamma_{n-k}/\gamma_n$ ($n\in \mathbb{Z}_{>>0}$) for $k>0$. The resonance is
proven by introducing the space of opposite power series, which is the compact
subspace of the space of all formal power series in the opposite variable
$s=1/t$ and is defined as the accumulating set of the sequence
$X_n(s):=\sum_{k=0}^n\frac{\gamma_{n-k}}{\gamma_n}t^k$ ($n\in
\mathbb{Z}_{\ge0}$). We analyze in details an example of the growth series
$P(t)$ for the modular group $PSL(2,Z)$ due to Machi.
| arxiv topic:math.CA math.GR |
arxiv_dataset-31781201.5813 | Field theory and the physics of disordered systems
cond-mat.dis-nn
In this talk I will present some of the main difficulties we encounter in
studying the large scale behavior of disordered systems. This presentation will
be done using a field theory language. The difficulties in applying the
standard renormalization group approach are due to the presence of strong
non-perturbative effects that we do not know how to master. These difficulties
are particular acute in the case of ferromagnets in random field, localized
electrons, growth models and spin glasses. I will review the situation
presenting at the end a promising approach based on fat diagrams.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-31791201.5913 | A Component-wise EM Algorithm for Mixtures
stat.CO
In some situations, EM algorithm shows slow convergence problems. One
possible reason is that standard procedures update the parameters
simultaneously. In this paper we focus on finite mixture estimation. In this
framework, we propose a component-wise EM, which updates the parameters
sequentially. We give an interpretation of this procedure as a proximal point
algorithm and use it to prove the convergence. Illustrative numerical
experiments show how our algorithm compares to EM and a version of the SAGE
algorithm.
| arxiv topic:stat.CO |
arxiv_dataset-31801201.6013 | Electronic states and magnetic structure at the Co3O4 (110) surface: a
first principles study
cond-mat.mtrl-sci
Tricobalt tetraoxide (Co3O4) is an important catalyst and Co3O4(110) is a
frequently exposed surface in Co3O4 nanomaterials. We employed
Density-functional theory with on-site Coulomb repulsion U term to study the
atomic structures, energetics, magnetic and electronic properties of the two
possible terminations, A and B, of this surface. These calculations predict A
as the stable termination in a wide range of oxygen chemical potentials,
consistent with recent experimental observations. The Co3+ ions do not have a
magnetic moment in the bulk, but become magnetic at the surface, which leads to
surface magnetic orderings different from the one in the bulk. Surface
electronic states are present in the lower half of the bulk band gap and cause
partial metallization of both surface terminations. These states are
responsible for the charge compensation mechanism stabilizing both polar
terminations. The computed critical thickness for polarity compensation is 4
layers.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-31811201.6113 | Fractional calculus, completely monotonic functions, a generalized
Mittag-Leffler function and phase-space consistency of separable augmented
densities
math-ph math.MP
Under the separability assumption on the augmented density, a distribution
function can be always constructed for a spherical population with the
specified density and anisotropy profile. Then, a question arises, under what
conditions the distribution constructed as such is non-negative everywhere in
the entire accessible subvolume of the phase-space. We rediscover necessary
conditions on the augmented density expressed with fractional calculus. The
condition on the radius part R(r^2) -- whose logarithmic derivative is the
anisotropy parameter -- is equivalent to R(1/w)/w being a completely monotonic
function whereas the condition on the potential part is stated as its
derivative up to the order not greater than 3/2-b being non-negative (where b
is the central limiting value for the anisotropy parameter). We also derive the
set of sufficient conditions on the separable augmented density for the
non-negativity of the distribution, which generalizes the condition derived for
the generalized Cuddeford system by Ciotti & Morganti to arbitrary separable
systems. This is applied for the case when the anisotropy is parameterized by a
monotonic function of the radius of Baes & Van Hese. The resulting criteria are
found based on the complete monotonicity of generalized Mittag-Leffler
functions.
| arxiv topic:math-ph math.MP |
arxiv_dataset-31821201.6213 | Extra Dimensional Curvature Supression of the Effective Four Dimensional
Vacuum Energy Density
gr-qc hep-th
Considering a very large number of extra dimensions, $N\rightarrow \infty$,
we show that in the effective four dimensional picture, to leading order in
$N$, both the cosmological constant in $N+4$ dimensions and the curvature of
the extra dimensions (curved as spheres) give the same type of contributions.
Furthermore in this limit, the extra dimensional curvature naturally supress
the effect of a positive Cosmological Constant, so that the resulting effective
potential governing the vacuum energy in the effective $4-D$ picture has a
leading 1/N dependence (i.e. vanishing in the large $N$ limit). We can
understand qualitatively this effect in a heuristic picture, by thinking that
all dimensions, both visible and extra have an equal sharing of the curvature
caused by $\Lambda$, in this case when increasing the overall number of
dimensions by adding $N$ extra dimensions, then if $N$ is large, the visible
dimensions do not have to curve too much, hence a small four dimensional vacuum
energy follows. In the large $N$ picture the potential can be also stabilized
by a small (i.e. vanishing at large $N$) expectaction value of a four index
field strength.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-31831201.6313 | On X-Channels with Feedback and Delayed CSI
cs.IT math.IT
The sum degrees of freedom (DoF) of the two-user MIMO X-channel is
characterized in the presence of output feedback and delayed channel state
information (CSI). The number of antennas at each transmitters is assumed to be
M and the number of antennas at each of the receivers is assumed to be N. It is
shown that the sum DoF of the two-user MIMO X-channel is the same as the sum
DoF of a two-user MIMO broadcast channel with 2M transmit antennas, and N
antennas at each receiver. Hence, for this symmetric antenna configuration,
there is no performance loss in the sum degrees of freedom due to the
distributed nature of the transmitters. This result highlights the usefulness
of feedback and delayed CSI for the MIMO X-channel.
The K-user X-channel with single antenna at each transmitter and each
receiver is also studied. In this network, each transmitter has a message
intended for each receiver. For this network, it is shown that the sum DoF with
partial output feedback alone is at least 2K/(K+1). This lower bound is
strictly better than the best lower bound known for the case of delayed CSI
assumption for all values of K.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-31841201.6413 | Limit Theorems for Decoherent Two Dimensional Quantum Walks
quant-ph math-ph math.MP
In this paper we consider the model with decoherence operators introduced by
[Brun,T.A, et.al, Phys.Rev.A 67 (2003) 032304] which has recently been
considered in the two-dimensional setting by [Ampadu,C., Brun-Type Formalism
for Decoherence in Two Dimensional Quantum Walks, Communication in Theoretical
Physics To Appear, arXiv:1104.2061 (2011)] to obtain the limit of the
decoherent quantum walk.
| arxiv topic:quant-ph math-ph math.MP |
arxiv_dataset-31851201.6513 | On the Width of Verbal Subgroups of the Groups of Triangular Matrices
over a Field of Arbitrary Characteristic
math.GR
The width $\wid(G,W)$ of the verbal subgroup $v(G,W)$ of a group $G$ defined
by a collection of group words $W$ is the smallest number $m$ in $\mathbb N
\cup {+\infty}$ such that every element of $v(G,W)$ is can be represented as
the product of at most $m$ words in $W$ evaluated on the group $G$ and their
inverses. Recall that every verbal subgroup of the group $T_{n} (K)$ of
triangular matrices over an arbitrary field $K$ can be defined by just one
word: an outer commutator word or a power word. We prove that for every outer
commutator word $w$ the equality $\wid(T_{n} (K),w)=1$ holds on the group
$T_{n} (K)$ and that if $w=x^{s}$ then $\wid(T_{n}(K),w)=1$ except in two
cases:
(1) the field $K$ is finite and $s$ is divisible by the characteristic $p$ of
$K$ but not by $|K|-1$;
(2) the field $K$ is finite and $s=p^{t} (|K|-1)^{u} r$ for $r,t,u\in \mathbb
N$ with $n\ge p^{t} +3$, while $r$ not divisible by $p$.
In these cases the width equals 2. For finitary triangular groups the
situation is similar, but in the second case the restriction $n\ge p^{t} +3$ is
superfluous.
| arxiv topic:math.GR |
arxiv_dataset-31861201.6613 | Geometrical engineering of a two-bands Chern insulator in two dimensions
with arbitrary topological index
cond-mat.mes-hall
Two-dimensional 2-bands insulators breaking time reversal symmetry can
present topological phases indexed by a topological invariant called the Chern
number. Here we first propose an efficient procedure to determine this
topological index. This tool allows in principle to conceive 2-bands
Hamiltonians with arbitrary Chern numbers. We apply our methodology to
gradually construct a quantum anomalous Hall insulator (Chern insulator) which
can be tuned through five topological phases indexed by the Chern numbers
{0,+/-1,+/-2}. On a cylindrical finite geometry, such insulator can therefore
sustain up to two edge states which we characterize analytically. From this
non-trivial Chern insulator and its time reversed copy, we build a quantum spin
Hall insulator and show how the phases with a +/-2 Chern index yield trivial Z2
insulating phases.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-31871202.0026 | Ohmic Heating Suspends, not Reverses, the Cooling Contraction of Hot
Jupiters
astro-ph.EP
We study the radius evolution of close-in extra-solar jupiters under Ohmic
heating, a mechanism that was recently proposed to explain the large observed
sizes of many of these planets. Planets are born with high entropy and they
subsequently cool and contract. We focus on two cases: first, that ohmic
heating commences when the planet is hot (high entropy); and second, that it
commences after the planet has cooled. In the former case, we use analytical
scalings and numerical experiments to confirm that Ohmic heating is capable of
suspending the cooling as long as a few percent of the stellar irradiation is
converted into Ohmic heating, and the planet has a surface wind that extends to
pressures of ~10 bar or deeper. For these parameters, the radii at which
cooling is stalled are consistent with (or larger than) the observed radii of
most planets. The only two exceptions are WASP-17b and HAT-P-32b. In contrast
to the high entropy case, we show that Ohmic heating cannot significantly
re-inflate planets after they have already cooled. This leads us to suggest
that the diversity of radii observed in hot jupiters may be partially explained
by the different epochs at which they are migrated to their current locations.
| arxiv topic:astro-ph.EP |
arxiv_dataset-31881202.0126 | Nonlinear self-duality in N = 2 supergravity
hep-th
For nonlinear models of an Abelian vector supermultiplet coupled to N = 2
supergravity in four dimensions, we formulate the self-duality equation which
expresses invariance under U(1) duality rotations. In the flat space limit,
this equation reduces to the N = 2 self-duality equation proposed in
hep-th/0001068. We also give an example of a self-dual locally supersymmetric
model containing a higher-derivative extension of the Born-Infeld action at the
component level.
| arxiv topic:hep-th |
arxiv_dataset-31891202.0226 | Amplitude death in systems of coupled oscillators with distributed-delay
coupling
nlin.CD math.DS
This paper studies the effects of coupling with distributed delay on the
suppression of oscillations in a system of coupled Stuart-Landau oscillators.
Conditions for amplitude death are obtained in terms of strength and phase of
the coupling, as well as the mean time delay and the width of the delay
distribution for uniform and gamma distributions. Analytical results are
confirmed by numerical computation of the eigenvalues of the corresponding
characteristic equations. These results indicate that larger widths of delay
distribution increase the regions of amplitude death in the parameter space. In
the case of a uniformly distributed delay kernel, for sufficiently large width
of the delay distribution it is possible to achieve amplitude death for an
arbitrary value of the average time delay, provided that the coupling strength
has a value in the appropriate range. For a gamma distribution of delay,
amplitude death is also possible for an arbitrary value of the average time
delay, provided that it exceeds a certain value as determined by the coupling
phase and the power law of the distribution. The coupling phase has a
destabilizing effect and reduces the regions of amplitude death.
| arxiv topic:nlin.CD math.DS |
arxiv_dataset-31901202.0326 | Tilting modules in category O and sheaves on moment graphs
math.RT
We describe tilting modules of the deformed category O over a semisimple Lie
algebra as certain sheaves on a moment graph associated to the corresponding
block of category O. We prove that they map to Braden-MacPherson sheaves
constructed along the reversed Bruhat order under Fiebig's localization
functor. By this means, we get character formulas for tilting modules and
explain how Soergel's result about the Andersen filtration gives a Koszul dual
proof of the semisimplicity of subquotients of the Jantzen filtration.
| arxiv topic:math.RT |
arxiv_dataset-31911202.0426 | Abelian categories and definable additive categories
math.CT math.LO math.RA math.RT
We consider three (2-)categories and their (anti-)equivalence. They are the
category of small abelian categories and exact functors, the category of
definable additive categories and interpretation functors, the category of
locally coherent abelian categories and coherent morphisms. These categories
link algebra, model theory and "geometry".
| arxiv topic:math.CT math.LO math.RA math.RT |
arxiv_dataset-31921202.0526 | Coherent states for quantum gravity: towards collective variables
gr-qc
We investigate the construction of coherent states for quantum theories of
connections based on graphs embedded in a spatial manifold, as in loop quantum
gravity. We discuss the many subtleties of the construction, mainly related to
the diffeomorphism invariance of the theory. Aiming at approximating a
continuum geometry in terms of discrete, graph-based data, we focus on coherent
states for collective observables characterizing both the intrinsic and
extrinsic geometry of the hypersurface, and we argue that one needs to revise
accordingly the more local definitions of coherent states considered in the
literature so far. In order to clarify the concepts introduced, we work through
a concrete example that we hope will be useful to applying coherent state
techniques to cosmology.
| arxiv topic:gr-qc |
arxiv_dataset-31931202.0626 | Mesoscopic Anderson Box: Connecting Weak to Strong Coupling
cond-mat.mes-hall cond-mat.str-el
Both the weakly coupled and strong coupling Anderson impurity problems are
characterized by a Fermi-liquid theory with weakly interacting quasiparticles.
In an Anderson box, mesoscopic fluctuations of the effective single particle
properties will be large. We study how the statistical fluctuations at low
temperature in these two problems are connected, using random matrix theory and
the slave boson mean field approximation (SBMFA). First, for a resonant level
model such as results from the SBMFA, we find the joint distribution of energy
levels with and without the resonant level present. Second, if only energy
levels within the Kondo resonance are considered, the distributions of
perturbed levels collapse to universal forms for both orthogonal and unitary
ensembles for all values of the coupling. These universal curves are described
well by a simple Wigner-surmise type toy model. Third, we study the
fluctuations of the mean field parameters in the SBMFA, finding that they are
small. Finally, the change in the intensity of an eigenfunction at an arbitrary
point is studied, such as is relevant in conductance measurements: we find that
the introduction of the strongly-coupled impurity considerably changes the wave
function but that a substantial correlation remains.
| arxiv topic:cond-mat.mes-hall cond-mat.str-el |
arxiv_dataset-31941202.0726 | The complementarity of SuperB with the LHC
hep-ph hep-ex
The complementarity between results anticipated from SuperB with those from
the LHC experiments is discussed here. SuperB can contribute to searches for
new physics using indirect constraints via precision tests of the standard
model. In addition to the indirect constraints, there are a number of direct
searches that can be performed at low energy. There is a well motivated
programme of measurements to make at SuperB, the results of which will add to
our understanding of possible scenarios of physics beyond the standard model.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-31951202.0826 | Boosting equal time bound states
hep-ph hep-th nucl-th
We present an explicit and exact boost of a relativistic bound state defined
at equal time of the constituents in the Born approximation (lowest order in
hbar). To this end, we construct the Poincar\'e generators of QED and QCD in
D=1+1 dimensions, using Gauss' law to express A^0 in terms of the fermion
fields in A^1=0 gauge. We determine the fermion-antifermion bound states in the
Born approximation as eigenstates of the time and space translation generators
P^0 and P^1. The boost operator is combined with a gauge transformation so as
to maintain the gauge condition A^1=0 in the new frame. We verify that the
boosted state remains an eigenstate of P^0 and P^1 with appropriately
transformed eigenvalues and determine the transformation law of the equal-time,
relativistic wave function. The shape of the wave function is independent of
the CM momentum when expressed in terms of a variable, which is quadratically
related to the distance x between the fermions. As a consequence, the Lorentz
contraction of the wave function is proportional to 1/(E-V(x)) and thus depends
on x via the linear potential V(x).
| arxiv topic:hep-ph hep-th nucl-th |
arxiv_dataset-31961202.0926 | Kinetic simulation of the electron-cyclotron maser instability: effect
of a finite source size
astro-ph.SR astro-ph.EP
The electron-cyclotron maser instability is widespread in the Universe,
producing, e.g., radio emission of the magnetized planets and cool substellar
objects. Diagnosing the parameters of astrophysical radio sources requires
comprehensive nonlinear simulations of the radiation process. We simulate the
electron-cyclotron maser instability in a very low-beta plasma. The model used
takes into account the radiation escape from the source region and the particle
flow through this region. We developed a kinetic code to simulate the time
evolution of an electron distribution in a radio emission source. The model
includes the terms describing the particle injection to and escape from the
emission source region. The spatial escape of the emission from the source is
taken into account by using a finite amplification time. The unstable electron
distribution of the horseshoe type is considered. A number of simulations were
performed for different parameter sets typical of the magnetospheres of planets
and ultracool dwarfs. The generated emission (corresponding to the fundamental
extraordinary mode) has a frequency close to the electron cyclotron frequency
and propagates across the magnetic field. Shortly after the onset of a
simulation, the electron distribution reaches a quasi-stationary state. If the
emission source region is relatively small, the resulting electron distribution
is similar to that of the injected electrons; the emission intensity is low. In
larger sources, the electron distribution may become nearly flat due to the
wave-particle interaction, while the conversion efficiency of the particle
energy flux into waves reaches 10-20%. We found good agreement of our model
with the in situ observations in the source regions of auroral radio emissions
of the Earth and Saturn. The expected characteristics of the electron
distributions in the magnetospheres of ultracool dwarfs were obtained.
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-31971202.1026 | Practices in Code Discoverability
astro-ph.IM
Much of scientific progress now hinges on the reliability, falsifiability and
reproducibility of computer source codes. Astrophysics in particular is a
discipline that today leads other sciences in making useful scientific
components freely available online, including data, abstracts, preprints, and
fully published papers, yet even today many astrophysics source codes remain
hidden from public view. We review the importance and history of source codes
in astrophysics and previous efforts to develop ways in which information about
astrophysics codes can be shared. We also discuss why some scientist coders
resist sharing or publishing their codes, the reasons for and importance of
overcoming this resistance, and alert the community to a reworking of one of
the first attempts for sharing codes, the Astrophysics Source Code Library
(ASCL). We discuss the implementation of the ASCL in an accompanying poster
paper. We suggest that code could be given a similar level of referencing as
data gets in repositories such as ADS.
| arxiv topic:astro-ph.IM |
arxiv_dataset-31981202.1126 | Private-Capacity Bounds for Bosonic Wiretap Channels
quant-ph
We prove an upper bound on the private capacity of the single-mode noiseless
bosonic wiretap channel. Combined with a previous lower bound, we obtain the
low photon-number asymptotic expression for the private capacity. We then show
that the multiple-mode noiseless bosonic wiretap channel is equivalent to
parallel single-mode channels, hence the single-mode bounds can be applied.
Finally, we consider multiple-spatial-mode propagation through atmospheric
turbulence, and derive a private-capacity lower bound that only requires second
moments of the channel matrix.
| arxiv topic:quant-ph |
arxiv_dataset-31991202.1226 | Effects of the Modified Uncertainty Principle on the Inflation
Parameters
hep-ph astro-ph.CO gr-qc
In this Letter we study the effects of the Modified Uncertainty Principle as
proposed in [8] on the inflationary dynamics of the early universe in both
standard and Randall-Sundrum type II scenarios. We find that the quantum
gravitational effect increase the amplitude of density fluctuation, which is
oscillatory in nature, with an increase in the tensor-to-scalar ratio.
| arxiv topic:hep-ph astro-ph.CO gr-qc |
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