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arxiv_dataset-21001008.5243 | Light Dark Matter from the U(1)_X Sector in the NMSSM with Gauge
Mediation
hep-ph astro-ph.HE
Cosmic ray anomalies observed by PAMELA and Fermi-LAT experiments may be
interpreted by heavy (TeV-scale) dark matter annihilation enhanced by
Sommerfeld effects mediated by a very light (sub-GeV) U(1)_X gauge boson, while
the recent direct searches from CoGeNT and DAMA/LIBRA experiments may indicate
a rather light (\sim 7 GeV) dark matter with weak interaction. Motivated by
these apparently different scales, we consider a gauge mediated next-to-the
minimal supersymmetric standard model (NMSSM) entended with a light U(1)_X
sector plus a heavy sector (\bar H_h,H_h), which can provide both a light (\sim
7 GeV) and a heavy (TeV-scale) dark matter without introducing any ad hoc new
scale. Through the Yukawa coupling between H_h and the messager fields, the
U(1)_X gauge symmetry is broken around the GeV scale radiatively and a large
negative m_S^2 is generated for the NMSSM singlet S. Furthermore, the small
kinetic mixing parameter between U(1)_X and U(1)_Y is predicted to be
\theta\sim 10^{-5}-10^{-6} after integrating out the messengers. Such a light
dark matter, which can have a normal relic density from the late decay of the
right-handed sneutrino (assumed to be the ordinary next-to-the lightest
supersymmetric particle and thermally produced in the early universe), can
serve a good candidate to explain the recent CoGeNT and DAMA/LIBRA results.
| arxiv topic:hep-ph astro-ph.HE |
arxiv_dataset-21011008.5343 | Strain Analysis of a Chiral Smectic A Elastomer
cond-mat.soft
We present a detailed analysis of the molecular packing of a strained liquid
crystal elastomer composed of chiral mesogens in the smectic A phase. X-ray
diffraction patterns of the elastomer collected over a range of orientations
with respect to the X-ray beam were used to reconstruct the three-dimensional
scattering intensity as a function of tensile strain. For the first time, we
show that the smectic domain order is preserved in these strained elastomers.
Changes in the intensity within a given scattering plane are due to
reorientation, and not loss, of the molecular order in directions orthogonal to
the applied strain. Incorporating the physical parameters of the elastomer, a
nonlinear elastic model is presented to describe the rotation of the
smectic-layered domains under strain, thus providing a fundamental analysis to
the mechanical response of these unique materials.
| arxiv topic:cond-mat.soft |
arxiv_dataset-21021009.0044 | Improved Loss-Tolerant Quantum Coin Flipping
quant-ph
In this paper, we present a loss-tolerant quantum strong coin flipping
protocol with bias 0.359. This is an improvement over Berlin etal's protocol
[BBBG08] which achieves a bias of 0.4. To achieve this, we extend Berlin et
al.'s protocol by adding an encryption step that hides some information to Bob
until he confirms that he successfully measured. We also show using numerical
analysis that a we cannot improve this bias by considering a k-fold repetition
of Berlin etal's protocol for k > 2.
| arxiv topic:quant-ph |
arxiv_dataset-21031009.0144 | On complete functions in Jucys-Murphy elements
math.CO
The problem of computing the class expansion of some symmetric functions
evaluated in Jucys-Murphy elements appears in different contexts, for instance
in the computation of matrix integrals. Recently, M. Lassalle gave a unified
algebraic method to obtain some induction relations on the coefficients in this
kind of expansion. In this paper, we give a simple purely combinatorial proof
of his result. Besides, using the same type of argument, we obtain new simpler
formulas. We also prove an analogous formula in the Hecke algebra of
$(S_{2n},H_n)$ and use it to solve a conjecture of S. Matsumoto on the
subleading term of orthogonal Weingarten function. Finally, we propose a
conjecture for a continuous interpolation between both problems.
| arxiv topic:math.CO |
arxiv_dataset-21041009.0244 | Solution of the Bosonic and Algebraic Hamiltonians by using AIM
math-ph math.MP quant-ph
We apply the notion of asymptotic iteration method (AIM) to determine
eigenvalues of the bosonic Hamiltonians that include a wide class of quantum
optical models. We consider solutions of the Hamiltonians, which are even
polynomials of the fourth order with the respect to Boson operators. We also
demonstrate applicability of the method for obtaining eigenvalues of the simple
Lie algebraic structures. Eigenvalues of the multi-boson Hamiltonians have been
obtained by transforming in the form of the single boson Hamiltonian in the
framework of AIM.
| arxiv topic:math-ph math.MP quant-ph |
arxiv_dataset-21051009.0344 | OGLE-2005-BLG-153: Microlensing Discovery and Characterization of A Very
Low Mass Binary
astro-ph.SR
The mass function and statistics of binaries provide important diagnostics of
the star formation process. Despite this importance, the mass function at low
masses remains poorly known due to observational difficulties caused by the
faintness of the objects. Here we report the microlensing discovery and
characterization of a binary lens composed of very low-mass stars just above
the hydrogen-burning limit. From the combined measurements of the Einstein
radius and microlens parallax, we measure the masses of the binary components
of $0.10\pm 0.01\ M_\odot$ and $0.09\pm 0.01\ M_\odot$. This discovery
demonstrates that microlensing will provide a method to measure the mass
function of all Galactic populations of very low mass binaries that is
independent of the biases caused by the luminosity of the population.
| arxiv topic:astro-ph.SR |
arxiv_dataset-21061009.0444 | Quantization and Semiclassics
math-ph math.MP quant-ph
This course is aimed at graduate students in physics in mathematics and
designed to give a comprehensive introduction to Weyl quantization and
semiclassics via Egorov's theorem.
Chapter 2 gives a quick overview of classical and quantum mechanics on R^d.
Some mathematical preliminaries concerning Hilbert space theory, operator
theory and tempered distributions are detailed in Chapters 3-5. Weyl
quantization and semiclassics are the content of Chapters 6 and 7. Finally, an
application of Weyl calculus to Born-Oppenheimer systems is discussed in
Chapter 8.
| arxiv topic:math-ph math.MP quant-ph |
arxiv_dataset-21071009.0544 | Discussion on Lechicki and Spakowski's counterexample
math.GT
It is well-known that intersection of continuous correspondences can lost the
continuity property. Lechicki and Spakowski's theorem says that intersection of
H-lsc functions remains H-lsc if the intersection is a bounded subset of a
normed space and its interior is nonempty. Lechicki and Spakowski pointed to
the importance of the boundedness assumption in the case of infinite
dimensional range giving a counterexample. Even though the counterexample works
properly and is one of the most cited patterns of discontinuity, it has no
detailed discussion in the literature of economics and optimization theory.
What is more, some misleading interpretation of this very important
counterexample can be observed. Our technical note clarifies the exact role of
Lechicki and Spakowski's counterexample, computing each of the important
properties of the correspondences rigorously.
| arxiv topic:math.GT |
arxiv_dataset-21081009.0644 | Nature of the low temperature ordering of Pr in PrBa_2Cu_3O_(6+x)
cond-mat.str-el
Theoretical model is presented to describe the anomalous ordered phase of Pr
ions in PrBa_2Cu_3O_(6+x) below T_Pr = 12-17 K. The model considers the Pr
multipole degrees of freedom and coupling between the Cu and Pr subsystems. We
identify the symmetry allowed coupling of Cu and Pr ions and conclude that only
an ab-plane Pr dipole ordering can explain the Cu spin rotation observed at
T_Pr by neutron diffraction by Boothroyd et al. [A. T. Boothroyd et al., Phys.
Rev. Lett. 78, 130 (1997)]. A substantial enhancement of the Pr ordering
temperature is shown to arise from the Cu-Pr coupling which is the key for the
anomalous magnetic behavior in PrBa_2Cu_3O_(6+x).
| arxiv topic:cond-mat.str-el |
arxiv_dataset-21091009.0744 | New and improved Johnson-Lindenstrauss embeddings via the Restricted
Isometry Property
cs.IT math.IT math.NA math.PR
Consider an m by N matrix Phi with the Restricted Isometry Property of order
k and level delta, that is, the norm of any k-sparse vector in R^N is preserved
to within a multiplicative factor of 1 +- delta under application of Phi. We
show that by randomizing the column signs of such a matrix Phi, the resulting
map with high probability embeds any fixed set of p = O(e^k) points in R^N into
R^m without distorting the norm of any point in the set by more than a factor
of 1 +- delta. Consequently, matrices with the Restricted Isometry Property and
with randomized column signs provide optimal Johnson-Lindenstrauss embeddings
up to logarithmic factors in N. In particular, our results improve the best
known bounds on the necessary embedding dimension m for a wide class of
structured random matrices; for partial Fourier and partial Hadamard matrices,
we improve the recent bound m = O(delta^(-4) log(p) log^4(N)) appearing in
Ailon and Liberty to m = O(delta^(-2) log(p) log^4(N)), which is optimal up to
the logarithmic factors in N. Our results also have a direct application in the
area of compressed sensing for redundant dictionaries.
| arxiv topic:cs.IT math.IT math.NA math.PR |
arxiv_dataset-21101009.0844 | Going Green: A Holistic Approach to Transform Business
cs.CY cs.GL
In recent years environmental and energy conservation issues have taken the
central theme in the global business arena. The reality of rising energy cost
and their impact on international affairs coupled with the different kinds of
environmental issues has shifted the social and economic consciousness of the
business community. Hence, the business community is now in search of an
eco-friendly business model. This paper highlights the concept of green
business and their needs in the current global scenario.
| arxiv topic:cs.CY cs.GL |
arxiv_dataset-21111009.0944 | Well-posedness and stability in the periodic case for the Benney system
math.AP
We establish local well-posedness results in weak periodic function spaces
for the Cauchy problem of the Benney system. The Sobolev space $H^{1/2}\times
L^2$ is the lowest regularity attained and also we cover the energy space
$H^{1}\times L^2$, where global well-posedness follows from the conservation
laws of the system. Moreover, we show the existence of smooth explicit family
of periodic travelling waves of \emph{dnoidal} type and we prove, under certain
conditions, that this family is orbitally stable in the energy space.
| arxiv topic:math.AP |
arxiv_dataset-21121009.1044 | Conformal carpet and grating cloaks
physics.optics
We introduce a class of conformal versions of the previously introduced
quasi-conformal carpet cloak, and show how to construct such conformal cloaks
for different cloak shapes. Our method provides exact refractive-index profiles
in closed mathematical form for the usual carpet cloak as well as for other
shapes. By analyzing their asymptotic behavior, we find that the performance of
finite-size cloaks becomes much better for metal shapes with zero average
value, e.g., for gratings.
| arxiv topic:physics.optics |
arxiv_dataset-21131009.1144 | An Atlas of z=5.7 and z=6.5 Ly alpha Emitters
astro-ph.CO
We present an atlas of 88 z~5.7 and 30 z~6.5 Ly alpha emitters obtained from
a wide-field narrowband survey. We combined deep narrowband imaging in 120A
bandpass filters centered at 8150A and 9140A with deep BVRIz broadband imaging
to select high-redshift galaxy candidates over an area of 4180 square arcmin.
The goal was to obtain a uniform selection of comparable depth over the 7
targeted fields in the two filters. For the GOODS-N region of the HDF-N field,
we also selected candidates using a 120A filter centered at 9210A. We made
spectroscopic observations with Keck DEIMOS of nearly all the candidates to
obtain the final sample of Ly alpha emitters. At the 3.3A resolution of the
DEIMOS observations the asymmetric profile for Ly alpha emission with its steep
blue fall-off can be clearly seen in the spectra of nearly all the galaxies. We
show that the spectral profiles are surprisingly similar for many of the
galaxies and that the composite spectral profiles are nearly identical at z=5.7
and z=6.5. We analyze the distributions of line widths and Ly alpha equivalent
widths and find that the lines are marginally narrower at the higher redshift,
with median values of 0.77A at z=6.5 and 0.92A at z=5.7. The line widths have a
dependence on the Ly alpha luminosity of the form L(L alpha)^(0.3). We compare
the surface densities and the luminosity functions at the two redshifts and
find that there is a multiplicative factor of 2 decrease in the number density
of bright Ly alpha emitters from z=5.7 to z=6.5, while the characteristic
luminosity is unchanged.
| arxiv topic:astro-ph.CO |
arxiv_dataset-21141009.1244 | An adaptive algorithm for the cornea modeling from keratometric data
physics.med-ph math.NA physics.optics
In this paper we describe an adaptive and multi-scale algorithm for the
parsimonious fit of the corneal surface data that allows to adapt the number of
functions used in the reconstruction to the conditions of each cornea. The
method implements also a dynamical selection of the parameters and the
management of noise. It can be used for the real-time reconstruction of both
altimetric data and corneal power maps from the data collected by keratoscopes,
such as the Placido rings based topographers, decisive for an early detection
of corneal diseases such as keratoconus.
Numerical experiments show that the algorithm exhibits a steady exponential
error decay, independently of the level of aberration of the cornea. The
complexity of each anisotropic gaussian basis functions in the functional
representation is the same, but their parameters vary to fit the current scale.
This scale is determined only by the residual errors and not by the number of
the iteration. Finally, the position and clustering of their centers, as well
as the size of the shape parameters, provides an additional spatial information
about the regions of higher irregularity. These results are compared with the
standard approximation procedures based on the Zernike polynomials expansions.
| arxiv topic:physics.med-ph math.NA physics.optics |
arxiv_dataset-21151009.1344 | On Scheduling and Redundancy for P2P Backup
cs.NI cs.DC
An online backup system should be quick and reliable in both saving and
restoring users' data. To do so in a peer-to-peer implementation, data transfer
scheduling and the amount of redundancy must be chosen wisely. We formalize the
problem of exchanging multiple pieces of data with intermittently available
peers, and we show that random scheduling completes transfers nearly optimally
in terms of duration as long as the system is sufficiently large. Moreover, we
propose an adaptive redundancy scheme that improves performance and decreases
resource usage while keeping the risks of data loss low. Extensive simulations
show that our techniques are effective in a realistic trace-driven scenario
with heterogeneous bandwidth.
| arxiv topic:cs.NI cs.DC |
arxiv_dataset-21161009.1444 | Optimal designs for rational function regression
stat.CO stat.ME
We consider optimal non-sequential designs for a large class of (linear and
nonlinear) regression models involving polynomials and rational functions with
heteroscedastic noise also given by a polynomial or rational weight function.
The proposed method treats D-, E-, A-, and $\Phi_p$-optimal designs in a
unified manner, and generates a polynomial whose zeros are the support points
of the optimal approximate design, generalizing a number of previously known
results of the same flavor. The method is based on a mathematical optimization
model that can incorporate various criteria of optimality and can be solved
efficiently by well established numerical optimization methods. In contrast to
previous optimization-based methods proposed for similar design problems, it
also has theoretical guarantee of its algorithmic efficiency; in fact, the
running times of all numerical examples considered in the paper are negligible.
The stability of the method is demonstrated in an example involving high degree
polynomials. After discussing linear models, applications for finding locally
optimal designs for nonlinear regression models involving rational functions
are presented, then extensions to robust regression designs, and trigonometric
regression are shown. As a corollary, an upper bound on the size of the support
set of the minimally-supported optimal designs is also found. The method is of
considerable practical importance, with the potential for instance to impact
design software development. Further study of the optimality conditions of the
main optimization model might also yield new theoretical insights.
| arxiv topic:stat.CO stat.ME |
arxiv_dataset-21171009.1544 | Pan-private Algorithms: When Memory Does Not Help
cs.CR cs.DS
Consider updates arriving online in which the $t$th input is $(i_t,d_t)$,
where $i_t$'s are thought of as IDs of users. Informally, a randomized function
$f$ is {\em differentially private} with respect to the IDs if the probability
distribution induced by $f$ is not much different from that induced by it on an
input in which occurrences of an ID $j$ are replaced with some other ID $k$
Recently, this notion was extended to {\em pan-privacy} where the computation
of $f$ retains differential privacy, even if the internal memory of the
algorithm is exposed to the adversary (say by a malicious break-in or by fiat
by the government). This is a strong notion of privacy, and surprisingly, for
basic counting tasks such as distinct counts, heavy hitters and others, Dwork
et al~\cite{dwork-pan} present pan-private algorithms with reasonable accuracy.
The pan-private algorithms are nontrivial, and rely on sampling. We reexamine
these basic counting tasks and show improved bounds. In particular, we estimate
the distinct count $\Dt$ to within $(1\pm \eps)\Dt \pm O(\polylog m)$, where
$m$ is the number of elements in the universe. This uses suitably noisy
statistics on sketches known in the streaming literature. We also present the
first known lower bounds for pan-privacy with respect to a single intrusion.
Our lower bounds show that, even if allowed to work with unbounded memory,
pan-private algorithms for distinct counts can not be significantly more
accurate than our algorithms. Our lower bound uses noisy decoding. For heavy
hitter counts, we present a pan private streaming algorithm that is accurate to
within $O(k)$ in worst case; previously known bound for this problem is
arbitrarily worse. An interesting aspect of our pan-private algorithms is that,
they deliberately use very small (polylogarithmic) space and tend to be
streaming algorithms, even though using more space is not forbidden.
| arxiv topic:cs.CR cs.DS |
arxiv_dataset-21181009.1644 | X-ray monitoring of classical novae in the central region of M 31. I.
June 2006 - March 2007
astro-ph.HE
(Abridged) Classical novae (CNe) have recently been reported to represent the
major class of supersoft X-ray sources (SSSs) in the central region of our
neighbour galaxy M 31. We carried out a dedicated monitoring of the M 31
central region with XMM-Newton and Chandra in order to find SSS counterparts of
CNe, determine the duration of their SSS phase and derive physical outburst
parameters. We systematically searched our data for X-ray counterparts of CNe
and determined their X-ray light curves and spectral properties. Additionally,
we determined luminosity upper limits for all novae from previous studies which
are not detected anymore and for all CNe in our field of view with optical
outbursts between May 2005 and March 2007. We detected eight X-ray counterparts
of CNe in M 31, four of which were not previously known. Seven sources can be
classified as SSSs, one is a candidate SSS. Two SSSs are still visible more
than nine years after the nova outburst, whereas two other nova counterparts
show a short SSS phase of less than 150 days. Of the latter sources, M31N
2006-04a exhibits a short-time variable X-ray light curve with an apparent
period of (1.6+-0.3) h. This periodicity could indicate the binary period of
the system. From the 14 SSS nova counterparts known from previous studies, ten
are not detected anymore. Additionally, we found four SSSs in our XMM-Newton
data without a nova counterpart, one of which is a new source. Out of eleven
SSSs detected in our monitoring, seven are counterparts of CNe. We therefore
confirm the earlier finding that CNe are the major class of SSSs in the central
region of M 31. We use the measured SSS turn-on and turn-off times to estimate
the mass ejected in the nova outburst and the mass burned on the white dwarf.
Classical novae with short SSS phases seem to be an important contributor to
the overall population.
| arxiv topic:astro-ph.HE |
arxiv_dataset-21191009.1744 | On the consistency of the quantum-like representation algorithm for
hyperbolic interference
quant-ph math.PR
Recently quantum-like representation algorithm (QLRA) was introduced by A.
Khrennikov [20]--[28] to solve the so-called "inverse Born's rule problem": to
construct a representation of probabilistic data by a complex or more general
(in particular, hyperbolic) probability amplitude which matches Born's rule or
its generalizations. The outcome from QLRA is coupled to the formula of total
probability with an additional term corresponding to trigonometric, hyperbolic
or hyper-trigonometric interference. The consistency of QLRA for probabilistic
data corresponding to trigonometric interference was recently proved [29]. We
now complete the proof of the consistency of QLRA to cover hyperbolic
interference as well. We will also discuss hyper trigonometric interference.
The problem of consistency of QLRA arises, because formally the output of QLRA
depends on the order of conditioning. For two observables (e.g., physical or
biological) a and b, b|a- and a|b- conditional probabilities produce two
representations, say in Hilbert spaces H^{b| a} and H^{a|b} (in this paper over
the hyperbolic algebra). We prove that under "natural assumptions" these two
representations are unitary equivalent (in the sense of hyperbolic Hilbert
space).
| arxiv topic:quant-ph math.PR |
arxiv_dataset-21201009.1844 | Quantum Interference between a Single-Photon Fock State and a Coherent
State
quant-ph
We derive analytical expressions for the single mode quantum field state at
the individual output ports of a beam splitter when a single-photon Fock state
and a coherent state are incident on the input ports. The output states turn
out to be a statistical mixture between a displaced Fock state and a coherent
state. Consequently we are able to find an analytical expression for the
corresponding Wigner function. Because of the generality of our calculations
the obtained results are valid for all passive and lossless optical four port
devices. We show further how the results can be adapted to the case of the
Mach-Zehnder interferometer. In addition we consider the case for which the
single-photon Fock state is replaced with a general input state: a coherent
input state displaces each general quantum state at the output port of a beam
splitter with the displacement parameter being the amplitude of the coherent
state.
| arxiv topic:quant-ph |
arxiv_dataset-21211009.1944 | Exceptional orthogonal polynomials, QHJ formalism and SWKB quantization
condition
math-ph math.MP quant-ph
We study the quantum Hamilton-Jacobi (QHJ) equation of the recently obtained
exactly solvable models, related to the newly discovered exceptional
polynomials and show that the QHJ formalism reproduces the exact eigenvalues
and the eigenfunctions. The fact that the eigenfunctions have zeros and poles
in complex locations leads to an unconventional singularity structure of the
quantum momentum function $p(x)$, the logarithmic derivative of the wave
function, which forms the crux of the QHJ approach to quantization. A
comparison of the singularity structure for these systems with the known
exactly solvable and quasi-exactly solvable models reveals interesting
differences. We find that the singularities of the momentum function for these
new potentials lie between the above two distinct models, sharing similarities
with both of them. This prompted us to examine the exactness of the
supersymmetric WKB (SWKB) quantization condition. The interesting singularity
structure of $p(x)$ and of the superpotential for these models has important
consequences for the SWKB rule and in our proof of its exactness for these
quantal systems.
| arxiv topic:math-ph math.MP quant-ph |
arxiv_dataset-21221009.2044 | Computational Modalities of Belousov-Zhabotinsky Encapsulated Vesicles
nlin.CG physics.bio-ph
We present both simulated and partial empirical evidence for the
computational utility of many connected vesicle analogs of an encapsulated
non-linear chemical processing medium. By connecting small vesicles containing
a solution of sub-excitable Belousov-Zhabotinsky (BZ) reaction, sustained and
propagating wave fragments are modulated by both spatial geometry, network
connectivity and their interaction with other waves. The processing ability is
demonstrated through the creation of simple Boolean logic gates and then by the
combination of those gates to create more complex circuits.
| arxiv topic:nlin.CG physics.bio-ph |
arxiv_dataset-21231009.2144 | Chromomagnetic Dipole-Operator Corrections in Bbar -> X_sgamma at
O(beta_0 alpha_s^2)
hep-ph hep-ex
We calculate the fermionic corrections to the photon-energy spectrum of Bbar
-> X_sgamma which arise from the self-interference of the chromomagnetic dipole
operator Q_8 at next-to-next-to-leading order by applying naive
non-abelianization. The resulting O(beta_0 alpha_s^2) correction to the Bbar ->
X_sgamma branching ratio amounts to a relative shift of +0.12% (+0.27%) for a
photon-energy cut of 1.6 GeV (1.0 GeV). We also comment on the potential size
of resummation and non-perturbative effects related to Q_8.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-21241009.2244 | Remote Dipolar Interactions for Objective Density Calibration and Flow
Control of Excitonic Fluids
cond-mat.mes-hall cond-mat.quant-gas
In this paper we suggest a method to observe remote interactions of spatially
separated dipolar quantum fluids, and in particular of dipolar excitons in GaAs
bilayer based devices. The method utilizes the static electric dipole moment of
trapped dipolar fluids to induce a local potential change on spatially
separated test dipoles. We show that such an interaction can be used for a
model- independent, objective fluid density measurements, an outstanding
problem in this field of research, as well as for inter-fluid exciton flow
control and trapping. For a demonstration of the effects on realistic devices,
we use a full two-dimensional hydrodynamical model.
| arxiv topic:cond-mat.mes-hall cond-mat.quant-gas |
arxiv_dataset-21251009.2344 | QED with a spherical mirror
quant-ph
We investigate the Quantum-Electro-Dynamic properties of an atomic electron
close to the focus of a spherical mirror. We first show that the spontaneous
emission and excited state level shift of the atom can be fully suppressed with
mirror-atom distances of many wavelengths. A three-dimensional theory predicts
that the spectral density of vacuum fluctuations can indeed vanish within a
volume $\lambda^3$ around the atom, with the use of a far distant mirror
covering only half of the atomic emission solid angle. The modification of
these QED atomic properties is also computed as a function of the mirror size
and large effects are found for only moderate numerical apertures. We also
evaluate the long distance ground state energy shift (Casimir-Polder shift) and
find that it scales as $(\lambda/R)^2$ at the focus of a hemi-spherical mirror
of radius $R$, as opposed to the well known $(\lambda/R)^4$ scaling law for an
atom at a distance $R$ from an infinite plane mirror. Our results are relevant
for investigations of QED effects, and also free space coupling to single atoms
using high-numerical aperture lenses.
| arxiv topic:quant-ph |
arxiv_dataset-21261009.2444 | High mass exclusive diffractive dijet production in $\mathbf{p\bar{p}}$
collisions at $\mathbf{\sqrt{s}}$ = 1.96 TeV
hep-ex
We present evidence for diffractive exclusive dijet production with an
invariant dijet mass greater than 100 GeV in data collected with the D0
experiment at the Fermilab Tevatron Collider. A discriminant based on
calorimeter information is used to measure a significant number of events with
little energy (typically less than 10 GeV) outside the dijet system, consistent
with the diffractive exclusive dijet production topology. The probability for
these events to be explained by other dijet production processes is $2 \times
10^{-5}$, corresponding to a 4.1 standard deviation significance.
| arxiv topic:hep-ex |
arxiv_dataset-21271009.2544 | Loading characteristics of a microscopic optical dipole trap
physics.atom-ph
We report on an investigation of loading characteristics of deep microscopic
dipole traps. The dipole trap is loaded from a low density magneto optical trap
(MOT) containing $\approx 5\times 10^{6}$ atoms. We determine the loading
parameters that maximize the trapped atom number for a trap of waist 5 {\mu}m
with trap depths ranging from 3.5 mK to 10 mK. We determine the optimal trap
loading conditions and the loading rates, loss coefficients and temperature of
the trapped atoms under these conditions. We show that it is possible to load a
few hundred to thousand atoms in dipole traps of depth 3.5 mK to 8.5 mK under
the optimal loading conditions.
| arxiv topic:physics.atom-ph |
arxiv_dataset-21281009.2644 | A complete locally convex space of countable dimension admitting an
operator with no invariant subspaces
math.FA
We construct a complete locally convex topological vector space $X$ of
countable algebraic dimension and a continuous linear operator $T:X\to X$ such
that $T$ has no non-trivial closed invariant subspaces.
| arxiv topic:math.FA |
arxiv_dataset-21291009.2744 | Entanglement of qutrits and ququarts
quant-ph
We investigate in a general form entanglement of biphoton qutrits and
ququarts, i.e. states formed in the processes of collinear and,
correspondingly, degenerate and non-degenerate Spontaneous Parametric
Down-Conversion. Indistinguishability of photons and, for ququarts, joint
presence of the frequency and and polarization entanglement are fully taken
into account. In the case of qutrits the most general 3-parametric families of
maximally entangled and non-entangled states are found, and anti-correlation of
the degree of entanglement and polarization is shown to occur and to be
characterized by a rather simple formula. Biphoton ququarts are shown to be
two-qudits with the single-photon Hilbert space dimensionality $d=4$, which
differs them significantly from the often used two-qubit model ($d=2$). New
expressions for entanglement quantifiers of biphoton ququarts are derived and
discussed. Rather simple procedures for a direct measurement of the degree of
entanglement are described for both qutrits and ququarts.
| arxiv topic:quant-ph |
arxiv_dataset-21301009.2844 | Thin discs, thick dwarfs, and the importance of feedback effects
astro-ph.CO
We investigate the role of stellar mass in shaping the intrinsic thickness of
faint systems by determining the probability distribution of apparent axis
ratios for two different samples that probe the faint end of the galaxy
luminosity function (M_B < -8). We find that the (b/a) distribution is a strong
function of M*, and identify a limiting stellar mass M* ~ 2x10^9 Msun below
which galaxies start to be systematically thicker. We argue that this is the
result of the complex interplay between galaxy mass, specific angular momentum
and stellar feedback effects: the increasing importance of turbulent motions in
lower mass galaxies leads to the formation of thicker systems. We find a good
agreement between our results and the latest numerical simulations of dwarf
galaxy formation, and discuss several further implications of this finding
--including the formation of bars and spirals in faint galaxies, the
deprojection of HI line profiles and simulations of environmental effects on
dwarf galaxies.
| arxiv topic:astro-ph.CO |
arxiv_dataset-21311009.2944 | Le plus grand facteur premier de la fonction de Landau
math.NT
After Landau, we define g(n) as the maximal order of a permutation of the
symmetric group S(n) on n letters. We give several estimates of the largest
prime divisor of g(n).
| arxiv topic:math.NT |
arxiv_dataset-21321009.3044 | Integral Excision for K-Theory
math.AT math.AG math.CT math.KT math.RA
If A is a homotopy cartesian square of ring spectra satisfying connectivity
hypotheses, then the cube induced by Goodwillie's integral cyclotomic trace
from K(A) to TC(A) is homotopy cartesian. In other words, the homotopy fiber of
the cyclotomic trace satisfies excision. The method of proof gives as a
spin-off new proofs of some old results, as well as some new results, about
periodic cyclic homology, and - more relevantly for our current application -
the T-Tate spectrum of topological Hochschild homology, where T is the circle
group
| arxiv topic:math.AT math.AG math.CT math.KT math.RA |
arxiv_dataset-21331009.3144 | An elementary proof of Hilbert's theorem on ternary quartics
math.AG
In 1888, Hilbert proved that every non-negative quartic form f=f(x,y,z) with
real coefficients is a sum of three squares of quadratic forms. His proof was
ahead of its time and used advanced methods from topology and algebraic
geometry. Up to now, no elementary proof is known. Here we present a completely
new approach. Although our proof is not easy, it uses only elementary
techniques. As a by-product, it gives information on the number of
representations f=p_1^2+p_2^2+p_3^2 of f up to orthogonal equivalence. We show
that this number is 8 for generically chosen f, and that it is 4 when f is
chosen generically with a real zero. Although these facts were known, there was
no elementary approach to them so far.
| arxiv topic:math.AG |
arxiv_dataset-21341009.3244 | Elliptic and triangular flow in event-by-event (3+1)D viscous
hydrodynamics
hep-ph nucl-th
We present results for the elliptic and triangular flow coefficients in Au+Au
collisions at root-s=200 AGeV using event-by-event (3+1)D viscous hydrodynamic
simulations. We study the effect of initial state fluctuations and finite
viscosities on the flow coefficients v_2 and v_3 as functions of transverse
momentum and pseudo-rapidity. Fluctuations are essential to reproduce the
measured centrality dependence of elliptic flow. We argue that simultaneous
measurements of v_2 and v_3 can determine eta/s more precisely.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-21351009.3344 | A realistic technique for selection of angular momenta from hot nuclei:
A case study with 4He + 115In \to 119Sb at E_Lab = 35 MeV
nucl-ex
A rather new approach employing Monte Carlo GEANT simulation for converting
the experimentally measured fold distribution to angular momentum distribution
has been described. The technique has been successfully utilized to measure the
angular momentum of the compound nucleus formed in the reaction 4He + 115In -->
119Sb at E_Lab = 35 MeV. A 50 element gamma multiplicity filter, fabricated
in-house, was used to measure experimentally the required fold distribution.
The present method has been compared with the other ones exiting in the
literature and relative merits have been discussed.
| arxiv topic:nucl-ex |
arxiv_dataset-21361009.3444 | On noise treatment in radio measurements of cosmic ray air showers
astro-ph.IM astro-ph.HE
Precise measurements of the radio emission by cosmic ray air showers require
an adequate treatment of noise. Unlike to usual experiments in particle
physics, where noise always adds to the signal, radio noise can in principle
decrease or increase the signal if it interferes by chance destructively or
constructively. Consequently, noise cannot simply be subtracted from the
signal, and its influence on amplitude and time measurement of radio pulses
must be studied with care. First, noise has to be determined consistently with
the definition of the radio signal which typically is the maximum field
strength of the radio pulse. Second, the average impact of noise on radio pulse
measurements at individual antennas is studied for LOPES. It is shown that a
correct treatment of noise is especially important at low signal-to-noise
ratios: noise can be the dominant source of uncertainty for pulse height and
time measurements, and it can systematically flatten the slope of lateral
distributions. The presented method can also be transfered to other experiments
in radio and acoustic detection of cosmic rays and neutrinos.
| arxiv topic:astro-ph.IM astro-ph.HE |
arxiv_dataset-21371009.3544 | Generalized L/'evy Stochastic Areas and Selfdecomposability
math.PR
We show that a conditional characteristic function of generalized L\'evy
stochastic areas can be viewed as a product a selfdecomposable distribution
(i.e., L\'evy class L distribution) and its background driving characteristic
function. This provides a stochastic interpretation for a ratio of some Bessel
functions as well as examples of characteristic functions from van Dantzig
class.
| arxiv topic:math.PR |
arxiv_dataset-21381009.3644 | GYES, a multifibre spectrograph for the CFHT
astro-ph.IM astro-ph.GA
We have chosen the name of GYES, one of the mythological giants with one
hundred arms, offspring of Gaia and Uranus, for our instrument study of a
multifibre spectrograph for the prime focus of the Canada-France-Hawaii
Telescope. Such an instrument could provide an excellent ground-based
complement for the Gaia mission and a northern complement to the HERMES project
on the AAT. The CFHT is well known for providing a stable prime focus
environment, with a large field of view, which has hosted several imaging
instruments, but has never hosted a multifibre spectrograph. Building upon the
experience gained at GEPI with FLAMES-Giraffe and X-Shooter, we are
investigating the feasibility of a high multiplex spectrograph (about 500
fibres) over a field of view 1 degree in diameter. We are investigating an
instrument with resolution in the range 15000 to 30000, which should provide
accurate chemical abundances for stars down to 16th magnitude and radial
velocities, accurate to 1 km/s for fainter stars. The study is led by
GEPI-Observatoire de Paris with a contribution from Oxford for the study of the
positioner. The financing for the study comes from INSU CSAA and Observatoire
de Paris. The conceptual study will be delivered to CFHT for review by October
1st 2010.
| arxiv topic:astro-ph.IM astro-ph.GA |
arxiv_dataset-21391009.3744 | Truncation errors in self-similar continuous unitary transformations
cond-mat.str-el quant-ph
Effects of truncation in self-similar continuous unitary transformations
(S-CUT) are estimated rigorously. We find a formal description via an
inhomogeneous flow equation. In this way, we are able to quantify truncation
errors within the framework of the S-CUT and obtain rigorous error bounds for
the ground state energy and the highest excited level. These bounds can be
lowered exploiting symmetries of the Hamiltonian. We illustrate our approach
with results for a toy model of two interacting hard-core bosons and the
dimerized S=1/2 Heisenberg chain.
| arxiv topic:cond-mat.str-el quant-ph |
arxiv_dataset-21401009.3844 | New Precise Measurements of the $\xilamgam$ and $\xisiggam$ Decay
Asymmetries
hep-ex
The decay asymmetries of the weak radiative Hyperon decays Xi0 \to Lambda
gamma and Xi0 \to Sigma0 gamma have been measured with high precision using
data of the NA48/1 experiment at CERN. From about 52000 Xi0 \to Lambda gamma
and 15000 Xi0 \to Sigma0 gamma decays, we obtain for the decay asymmetries
alpha(Xi0 \to Lambda gamma) = -0.704 +/- 0.019(stat) +/- 0.064(syst) and
alpha(Xi0 \to Sigma0 gamma) = -0.729 +/- 0.030(stat) +/- 0.076(syst),
respectively. These results are in good agreement with previous experiments,
but more precise.
| arxiv topic:hep-ex |
arxiv_dataset-21411009.3944 | Oscillatory Spin Polarization and Magneto-Optic Kerr Effect in Fe3O4
Thin Films on GaAs(001)
cond-mat.mes-hall cond-mat.mtrl-sci
The spin dependent properties of epitaxial Fe3O4 thin films on GaAs(001) are
studied by the ferromagnetic proximity polarization (FPP) effect and
magneto-optic Kerr effect (MOKE). Both FPP and MOKE show oscillations with
respect to Fe3O4 film thickness, and the oscillations are large enough to
induce repeated sign reversals. We attribute the oscillatory behavior to
spin-polarized quantum well states forming in the Fe3O4 film. Quantum
confinement of the t2g states near the Fermi level provides an explanation for
the similar thickness dependences of the FPP and MOKE oscillations.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-21421009.4044 | Algorithms for Del Pezzo Surfaces of Degree 5 (Construction,
Parametrization)
math.AG
It is well known that every Del Pezzo surface of degree 5 defined over k is
parametrizable over k. In this paper we give an efficient construction for
parametrizing, as well as algorithms for constructing examples in every
isomorphism class and for deciding equivalence.
| arxiv topic:math.AG |
arxiv_dataset-21431009.4144 | Nevanlinna-Pick interpolation on distinguished varieties in the bidisk
math.FA
This article treats Nevanlinna-Pick interpolation in the setting of a special
class of algebraic curves called distinguished varieties. An interpolation
theorem, along with additional operator theoretic results, is given using a
family of reproducing kernels naturally associated to the variety. The examples
of the Neil parabola and doubly connected domains are discussed.
| arxiv topic:math.FA |
arxiv_dataset-21441009.4244 | Equivalence problem for the orthogonal webs on the sphere
math-ph math.DG math.MP
We solve the equivalence problem for the orthogonally separable webs on the
three-sphere under the action of the isometry group. This continues a classical
project initiated by Olevsky in which he solved the corresponding canonical
forms problem. The solution to the equivalence problem together with the
results by Olevsky forms a complete solution to the problem of orthogonal
separation of variables to the Hamilton-Jacobi equation defined on the
three-sphere via orthogonal separation of variables. It is based on invariant
properties of the characteristic Killing two-tensors in addition to properties
of the corresponding algebraic curvature tensor and the associated Ricci
tensor. The result is illustrated by a non-trivial application to a natural
Hamiltonian defined on the three-sphere.
| arxiv topic:math-ph math.DG math.MP |
arxiv_dataset-21451009.4344 | Troubles of describing multiple pion production in chiral dynamics
hep-ph hep-ex nucl-th
Generalized Hidden Local Symmetry (GHLS) model as the chiral model of
pseudoscalar, vector, and axial vector mesons and their interactions containing
also the couplings of strongly interacting particles with electroweak gauge
bosons, is confronted with the ALEPH data on the decay
$\tau^-\to\pi^-\pi^-\pi^+\nu_\tau$ and BABAR and CMD data on the reaction
$e^+e^-\to\pi^+\pi^-\pi^+\pi^-$. It is shown that both the invariant mass
spectrum of final pions in $\tau$ decay calculated in the GHLS framework with
the single $a_1(1260)$ resonance and the cross section
$e^+e^-\to\pi^+\pi^-\pi^+\pi^-$ calculated in the above framework with the
single $\rho(770)$ resonance, disagree with the experimental data. The
modifications of GHLS model based on inclusion of two additional heavier axial
vector mesons $a_1^\prime$, $a_1^{\prime\prime}$ in the $\tau$ decay and the
vector mesons $\rho^\prime$, $\rho^{\prime\prime}$ in
$e^+e^-\to\pi^+\pi^-\pi^+\pi^-$ are shown to be necessary for the good
description of the above data.
| arxiv topic:hep-ph hep-ex nucl-th |
arxiv_dataset-21461009.4444 | Universal Robotic Gripper based on the Jamming of Granular Material
cond-mat.soft
Gripping and holding of objects are key tasks for robotic manipulators. The
development of universal grippers able to pick up unfamiliar objects of widely
varying shape and surface properties remains, however, challenging. Most
current designs are based on the multi-fingered hand, but this approach
introduces hardware and software complexities. These include large numbers of
controllable joints, the need for force sensing if objects are to be handled
securely without crushing them, and the computational overhead to decide how
much stress each finger should apply and where. Here we demonstrate a
completely different approach to a universal gripper. Individual fingers are
replaced by a single mass of granular material that, when pressed onto a target
object, flows around it and conforms to its shape. Upon application of a vacuum
the granular material contracts and hardens quickly to pinch and hold the
object without requiring sensory feedback. We find that volume changes of less
than 0.5% suffice to grip objects reliably and hold them with forces exceeding
many times their weight. We show that the operating principle is the ability of
granular materials to transition between an unjammed, deformable state and a
jammed state with solid-like rigidity. We delineate three separate mechanisms,
friction, suction and interlocking, that contribute to the gripping force.
Using a simple model we relate each of them to the mechanical strength of the
jammed state. This opens up new possibilities for the design of simple, yet
highly adaptive systems that excel at fast gripping of complex objects.
| arxiv topic:cond-mat.soft |
arxiv_dataset-21471009.4544 | Composite spherically symmetric configurations in Jordan-Brans-Dicke
theory
gr-qc
In this article, a study of the scalar field shells in relativistic
spherically symmetric configurations has been performed. We construct the
composite solution of Jordan-Brans-Dicke field equation by matching the
conformal Brans solutions at each junction surfaces. This approach allows us to
associate rigorously with all solutions as a single glued "space", which is a
unique differentiable manifold M^4.
| arxiv topic:gr-qc |
arxiv_dataset-21481009.4644 | NNLO hard-thermal-loop thermodynamics for QCD
hep-ph hep-lat nucl-th
We calculate the thermodynamic functions of a quark-gluon plasma for general
N_c and N_f to three-loop order using hard-thermal-loop perturbation theory. At
this order, all the ultraviolet divergences can be absorbed into
renormalizations of the vacuum, the HTL mass parameters, and the strong
coupling constant.We show that at three loops, the results for the pressure and
trace anomaly are in very good agreement with recent lattice data down to
temperatures T~2T_c.
| arxiv topic:hep-ph hep-lat nucl-th |
arxiv_dataset-21491009.4744 | Continuous Quantum Error Correction Through Local Operations
quant-ph
We propose local strategies to protect global quantum information. The
protocols, which are quantum error correcting codes for dissipative systems,
are based on environment measurements, direct feedback control and simple
encoding of the logical qubits into physical qutrits whose decaying transitions
are indistinguishable and equally probable. The simple addition of one extra
level in the description of the subsystems allows for local actions to fully
and deterministically protect global resources, such as entanglement. We
present codes for both quantum jump and quantum state diffusion measurement
strategies and test them against several sources of inefficiency. The use of
qutrits in information protocols suggests further characterization of
qutrit-qutrit disentanglement dynamics, which we also give together with simple
local environment measurement schemes able to prevent distillability sudden
death and even enhance entanglement in situations in which our feedback error
correction is not possible.
| arxiv topic:quant-ph |
arxiv_dataset-21501009.4844 | Full counting statistics of the interference contrast from independent
Bose-Einstein condensates
cond-mat.quant-gas
We show that the visibility in interference experiments with Bose-Einstein
condensates is directly related to the condensate fraction. The probability
distribution of the contrast over many runs of an interference experiment thus
gives the full counting statistics of the condensed atom number. For
two-dimensional Bose gases, we discuss the universal behavior of the
probability distribution in the superfluid regime and provide analytical
expressions for the distributions for both homogeneous and harmonically trapped
samples. They are non-Gaussian and unimodal with a variance that is directly
related to the superfluid density. In general, the visibility is a
self-averaging observable only in the presence of long range phase coherence.
Close to the transition temperature, the visibility distribution reflects the
universal order parameter distribution in the vicinity of the critical point.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-21511009.4944 | Nonhomogeneous Cooling, Entropic Gravity and MOND Theory
hep-th
In this paper, by using the holographic principle, a modified equipartition
theorem where we assume that below a critical temperature the energy is not
equally divided on all bits, and the Unruh temperature, we derive MOND theory
and a modified Friedmann equation compatible with MOND theory. Furthermore, we
rederive a modified Newton's law of gravitation by employing an adequate
redefinition of the numbers of bits.
| arxiv topic:hep-th |
arxiv_dataset-21521009.5044 | Effective super Tonks-Girardeau gases as ground states of strongly
attractive multi-component fermions
cond-mat.quant-gas
In the strong interaction limit, attractive fermions with $N$-component
hyperfine states in a one-dimensional waveguide form unbreakable bound cluster
states. We demonstrate that the ground state of strongly attractive SU($N$)
Fermi gases can be effectively described by a super Tonks-Girardeau gas-like
state composed of bosonic cluster states with strongly attractive
cluster-cluster interaction for even $N$, and a Fermi duality of a super
Tonks-Girardeau gas-like state composed of fermionic cluster states with weakly
interacting cluster-cluster p-wave interaction for odd $N$.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-21531009.5144 | Monte Carlo simulations of a diffusive shock with multiple scattering
angular distributions
astro-ph.EP astro-ph.HE astro-ph.SR
We independently develop a simulation code following the previous dynamical
Monte Carlo simulation of the diffusive shock acceleration under the isotropic
scattering law during the scattering process, and the same results are
obtained. Since the same results test the validity of the dynamical Monte Carlo
method for simulating a collisionless shock, we extend the simulation toward
including an anisotropic scattering law for further developing this dynamical
Monte Carlo simulation. Under this extended anisotropic scattering law, a
Gaussian distribution function is used to describe the variation of scattering
angles in the particle's local frame. As a result, we obtain a series of
different shock structures and evolutions in terms of the standard deviation
values of the given Gaussian scattering angular distributions. We find that the
total energy spectral index increases as the standard deviation value of the
scattering angular distribution increases, but the subshock's energy spectral
index decreases as the standard deviation value of the scattering angular
distribution increases.
| arxiv topic:astro-ph.EP astro-ph.HE astro-ph.SR |
arxiv_dataset-21541009.5244 | Lovely pairs for independence relations
math.LO
In the literature there are two different notions of lovely pairs of a theory
T, according to whether T is simple or geometric. We introduce a notion of
lovely pairs for an independence relation, which generalizes both the simple
and the geometric case, and show how the main theorems for those two cases
extend to our general notion.
| arxiv topic:math.LO |
arxiv_dataset-21551009.5344 | Multitriangulations, pseudotriangulations and primitive sorting networks
math.CO cs.CG
We study the set of all pseudoline arrangements with contact points which
cover a given support. We define a natural notion of flip between these
arrangements and study the graph of these flips. In particular, we provide an
enumeration algorithm for arrangements with a given support, based on the
properties of certain greedy pseudoline arrangements and on their connection
with sorting networks. Both the running time per arrangement and the working
space of our algorithm are polynomial.
As the motivation for this work, we provide in this paper a new
interpretation of both pseudotriangulations and multitriangulations in terms of
pseudoline arrangements on specific supports. This interpretation explains
their common properties and leads to a natural definition of
multipseudotriangulations, which generalizes both. We study elementary
properties of multipseudotriangulations and compare them to iterations of
pseudotriangulations.
| arxiv topic:math.CO cs.CG |
arxiv_dataset-21561009.5444 | Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae.
II: The Second Year (2009-2010)
astro-ph.SR
As an extension of the project in Kato et al. (2009, arXiv:0905.1757), we
collected times of superhump maxima for 61 SU UMa-type dwarf novae mainly
observed during the 2009-2010 season. The newly obtained data confirmed the
basic findings reported in Kato et al. (2009): the presence of stages A-C, as
well as the predominance of positive period derivatives during stage B in
systems with superhump periods shorter than 0.07 d. There was a systematic
difference in period derivatives for systems with superhump periods longer than
0.075 d between this study and Kato et al. (2009). We suggest that this
difference is possibly caused by the relative lack of frequently outbursting SU
UMa-type dwarf novae in this period regime in the present study. We recorded a
strong beat phenomenon during the 2009 superoutburst of IY UMa. The close
correlation between the beat period and superhump period suggests that the
changing angular velocity of the apsidal motion of the elliptical disk is
responsible for the variation of superhump periods. We also described three new
WZ Sge-type objects with established early superhumps and one with likely early
superhumps. We also suggest that two systems, VX For and EL UMa, are WZ
Sge-type dwarf novae with multiple rebrightenings. The O-C variation in OT
J213806.6+261957 suggests that the frequent absence of rebrightenings in very
short-Porb objects can be a result of sustained superoutburst plateau at the
epoch when usual SU UMa-type dwarf novae return to quiescence preceding a
rebrightening. We also present a formulation for a variety of Bayesian
extension to traditional period analyses.
| arxiv topic:astro-ph.SR |
arxiv_dataset-21571009.5544 | Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes
physics.ao-ph astro-ph.EP
Terrestrial Gamma-Ray Flashes (TGFs) are very short bursts of high energy
photons and electrons originating in Earth's atmosphere. We present here a
localization study of TGFs carried out at gamma-ray energies above 20 MeV based
on an innovative event selection method. We use the AGILE satellite Silicon
Tracker data that for the first time have been correlated with TGFs detected by
the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies
above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of 5-10
degrees at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible
with a terrestrial production site closer to the sub-satellite point than 400
km. Considering that our gamma rays reach the AGILE satellite at 540 km
altitude with limited scattering or attenuation, our measurements provide the
first precise direct localization of TGFs from space.
| arxiv topic:physics.ao-ph astro-ph.EP |
arxiv_dataset-21581009.5644 | Modeling High-Velocity QSO Absorbers with Photoionized MHD Disk-Winds
astro-ph.HE
We extend our modeling of the ionization structure of magnetohydrodynamic
(MHD) accretion-disk winds, previously applied to Seyfert galaxies, to a
population of quasi-stellar-objects (QSOs) of much lower X-ray-to-UV flux
ratios, i.e. smaller $\alpha_{\rm ox}$ index, motivated by UV/X-ray ionized
absorbers with extremely high outflow velocities in UV-luminous QSOs. We
demonstrate that magnetically-driven winds ionized by a spectrum with
$\alpha_{\rm ox} \simeq -2$ can produce the charge states responsible for \civ
~and \fexxv/\fexxvi ~absorption in wind regions with corresponding maximum
velocities of $v$(\civ) $\lsim 0.1c$ and $v({\rm \fexxv}) \lsim 0.6 c$ (where
$c$ is the speed of light) and column densities $N_H \sim 10^{23}-10^{24}$
cm$^{-2}$, in general agreement with observations. In contrast to the
conventional radiation-driven wind models, {\it high-velocity flows are always
present in our MHD-driven winds} but manifest in the absorption spectra only
for $\alpha_{\rm ox} \lsim -2$, as larger $\alpha_{\rm ox}$ values ionize the
wind completely out to radii too large to demonstrate the presence of these
high velocities. We thus predict increasing velocities of these ionized
absorbers with decreasing (steeper) $\alpha_{\rm ox}$, a quantity that emerges
as the defining parameter in the kinematics of the AGN UV/X-ray absorbers.
| arxiv topic:astro-ph.HE |
arxiv_dataset-21591009.5744 | Discovering influential variables: A method of partitions
stat.AP
A trend in all scientific disciplines, based on advances in technology, is
the increasing availability of high dimensional data in which are buried
important information. A current urgent challenge to statisticians is to
develop effective methods of finding the useful information from the vast
amounts of messy and noisy data available, most of which are noninformative.
This paper presents a general computer intensive approach, based on a method
pioneered by Lo and Zheng for detecting which, of many potential explanatory
variables, have an influence on a dependent variable $Y$. This approach is
suited to detect influential variables, where causal effects depend on the
confluence of values of several variables. It has the advantage of avoiding a
difficult direct analysis, involving possibly thousands of variables, by
dealing with many randomly selected small subsets from which smaller subsets
are selected, guided by a measure of influence $I$. The main objective is to
discover the influential variables, rather than to measure their effects. Once
they are detected, the problem of dealing with a much smaller group of
influential variables should be vulnerable to appropriate analysis. In a sense,
we are confining our attention to locating a few needles in a haystack.
| arxiv topic:stat.AP |
arxiv_dataset-21601009.5844 | Engineering chromium related single photon emitters in single crystal
diamond
cond-mat.mtrl-sci quant-ph
Color centers in diamond as single photon emitters, are leading candidates
for future quantum devices due to their room temperature operation and
photostability. The recently discovered chromium related centers are
particularly attractive since they possess narrow bandwidth emission and a very
short lifetime. In this paper we investigate the fabrication methodologies to
engineer these centers in monolithic diamond. We show that the emitters can be
successfully fabricated by ion implantation of chromium in conjunction with
oxygen or sulfur. Furthermore, our results indicate that the background
nitrogen concentration is an important parameter, which governs the probability
of success to generate these centers.
| arxiv topic:cond-mat.mtrl-sci quant-ph |
arxiv_dataset-21611009.5944 | Throughput-Optimal Random Access with Order-Optimal Delay
cs.IT math.IT
In this paper, we consider CSMA policies for scheduling of multihop wireless
networks with one-hop traffic. The main contribution of this paper is to
propose Unlocking CSMA (U-CSMA) policy that enables to obtain high throughput
with low (average) packet delay for large wireless networks. In particular, the
delay under U-CSMA policy becomes order-optimal. For one-hop traffic, delay is
defined to be order-optimal if it is O(1), i.e., it stays bounded, as the
network-size increases to infinity. Using mean field theory techniques, we
analytically show that for torus (grid-like) interference topologies with
one-hop traffic, to achieve a network load of $\rho$, the delay under U-CSMA
policy becomes $O(1/(1-\rho)^{3})$ as the network-size increases, and hence,
delay becomes order optimal. We conduct simulations for general random
geometric interference topologies under U-CSMA policy combined with congestion
control to maximize a network-wide utility. These simulations confirm that
order optimality holds, and that we can use U-CSMA policy jointly with
congestion control to operate close to the optimal utility with a low packet
delay in arbitrarily large random geometric topologies. To the best of our
knowledge, it is for the first time that a simple distributed scheduling policy
is proposed that in addition to throughput/utility-optimality exhibits delay
order-optimality.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-21621009.6044 | Self-energy effects in the Polchinski and Wick-ordered
renormalization-group approaches
cond-mat.str-el hep-th math-ph math.MP
I discuss functional renormalization group (fRG) schemes, which allow for
non-perturbative treatment of the self-energy effects and do not rely on the
one-particle irreducible functional. In particular, I consider Polchinski or
Wick-ordered schemes with amputation of full (instead of bare) Green functions,
as well as more general schemes, and eastablish their relation to the
`dynamical adjustment propagator' scheme by M. Salmhofer [Ann. der Phys. 16,
171 (2007)]. While in the Polchinski scheme the amputation of full (instead of
bare) Green functions improves treatment of the self-energy effects, the
structure of the corresponding equations is not suitable to treat
strong-coupling problems; it is not also evident, how the mean-field (MF)
solution of these problems is recovered in this scheme. For Wick ordered
scheme, excluding fully or partly tadpole diagrams one can obtain forms of fRG
hierarchy, which are suitable to treat strong-coupling problems. In particular,
I emphasize usefullness of the schemes, which are local in cutoff parameter,
and compare them to the one-particle irreducible approach.
| arxiv topic:cond-mat.str-el hep-th math-ph math.MP |
arxiv_dataset-21631009.6144 | Cover-Decomposition and Polychromatic Numbers
math.CO cs.DM
A colouring of a hypergraph's vertices is polychromatic if every hyperedge
contains at least one vertex of each colour; the polychromatic number is the
maximum number of colours in such a colouring. Its dual, the
cover-decomposition number, is the maximum number of disjoint hyperedge-covers.
In geometric hypergraphs, there is extensive work on lower-bounding these
numbers in terms of their trivial upper bounds (minimum hyperedge size and
degree); our goal here is to broaden the study beyond geometric settings. We
obtain algorithms yielding near-tight bounds for three families of hypergraphs:
bounded hyperedge size, paths in trees, and bounded VC-dimension. This reveals
that discrepancy theory and iterated linear program relaxation are useful for
cover-decomposition. Finally, we discuss the generalization of
cover-decomposition to sensor cover.
| arxiv topic:math.CO cs.DM |
arxiv_dataset-21641010.0012 | An Embarrassingly Simple Speed-Up of Belief Propagation with Robust
Potentials
cs.CV cs.AI
We present an exact method of greatly speeding up belief propagation (BP) for
a wide variety of potential functions in pairwise MRFs and other graphical
models. Specifically, our technique applies whenever the pairwise potentials
have been {\em truncated} to a constant value for most pairs of states, as is
commonly done in MRF models with robust potentials (such as stereo) that impose
an upper bound on the penalty assigned to discontinuities; for each of the $M$
possible states in one node, only a smaller number $m$ of compatible states in
a neighboring node are assigned milder penalties. The computational complexity
of our method is $O(mM)$, compared with $O(M^2)$ for standard BP, and we
emphasize that the method is {\em exact}, in contrast with related techniques
such as pruning; moreover, the method is very simple and easy to implement.
Unlike some previous work on speeding up BP, our method applies both to
sum-product and max-product BP, which makes it useful in any applications where
marginal probabilities are required, such as maximum likelihood estimation. We
demonstrate the technique on a stereo MRF example, confirming that the
technique speeds up BP without altering the solution.
| arxiv topic:cs.CV cs.AI |
arxiv_dataset-21651010.0112 | Surface morphology and magnetic anisotropy in (Ga,Mn)As
cond-mat.mtrl-sci cond-mat.mes-hall quant-ph
Atomic Force Microscopy and Grazing incidence X-ray diffraction measurements
have revealed the presence of ripples aligned along the $[1\bar{1}0]$ direction
on the surface of (Ga,Mn)As layers grown on GaAs(001) substrates and buffer
layers, with periodicity of about 50 nm in all samples that have been studied.
These samples show the strong symmetry breaking uniaxial magnetic anisotropy
normally observed in such materials. We observe a clear correlation between the
amplitude of the surface ripples and the strength of the uniaxial magnetic
anisotropy component suggesting that these ripples might be the source of such
anisotropy.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall quant-ph |
arxiv_dataset-21661010.0212 | On effects of stochastic regularization for the pressureless gas
dynamics
math.AP math-ph math.MP
We extend our result of [1] and show that one can associate with the
stochastically perturbed non-viscid Burgers equation a system of viscous
balance laws. The Cauchy data for the Burgers equation generates the data for
this system. Till the moment of the shock formation in the solution to the
Burgers equation the above system of viscous balance laws can be reduced to the
pressureless gas dynamics system (in a limit as the parameters of perturbation
tend to zero). If the solution to the Burgers equation contains shocks, the
limit system is equivalent to the system with a specific pressure, in some
sense analogous to the pressure of barotropic monoatomic gas.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-21671010.0312 | Asymptotic distribution of conical-hull estimators of directional edges
math.ST stat.TH
Nonparametric data envelopment analysis (DEA) estimators have been widely
applied in analysis of productive efficiency. Typically they are defined in
terms of convex-hulls of the observed combinations of
$\mathrm{inputs}\times\mathrm{outputs}$ in a sample of enterprises. The shape
of the convex-hull relies on a hypothesis on the shape of the technology,
defined as the boundary of the set of technically attainable points in the
$\mathrm{inputs}\times\mathrm{outputs}$ space. So far, only the statistical
properties of the smallest convex polyhedron enveloping the data points has
been considered which corresponds to a situation where the technology presents
variable returns-to-scale (VRS). This paper analyzes the case where the most
common constant returns-to-scale (CRS) hypothesis is assumed. Here the DEA is
defined as the smallest conical-hull with vertex at the origin enveloping the
cloud of observed points. In this paper we determine the asymptotic properties
of this estimator, showing that the rate of convergence is better than for the
VRS estimator. We derive also its asymptotic sampling distribution with a
practical way to simulate it. This allows to define a bias-corrected estimator
and to build confidence intervals for the frontier. We compare in a simulated
example the bias-corrected estimator with the original conical-hull estimator
and show its superiority in terms of median squared error.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-21681010.0412 | Sequences of Inequalities Among New Divergence Measures
cs.IT math.IT
There are three classical divergence measures exist in the literature on
information theory and statistics. These are namely, Jeffryes-Kullback-Leiber
J-divergence. Sibson-Burbea-Rao Jensen-Shannon divegernce and Taneja
arithemtic-geometric mean divergence. These three measures bear an interesting
relationship among each other and are based on logarithmic expressions. The
divergence measures like Hellinger discrimination, symmetric chi-square
divergence, and triangular discrimination are also known in the literature and
are not based on logarithmic expressions. Past years Dragomir et al., Kumar and
Johnson and Jain and Srivastava studied different kind of divergence measures.
In this paper, we have presented some more new divergence measures and obtained
inequalities relating these new measures and also made connections with
previous ones. The idea of exponential divergence is also introduced.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-21691010.0512 | Consistent Energy-Based Atomistic/Continuum Coupling for Two-Body
Potentials in One and Two Dimensions
math.NA
This paper addresses the problem of consistent energy-based coupling of
atomistic and continuum models of materials, limited to zero-temperature
statics of simple crystals. It has been widely recognized that the most
practical coupled methods exhibit large errors on the atomistic/continuum
interface (which are often attributed to spurious forces called "ghost
forces"). There are only few existing works that propose a coupling which is
sufficiently accurate near the interface under certain limitations. In this
paper a novel coupling that is free from "ghost forces" is proposed for a
two-body interaction potential under the assumptions of either (i) one spatial
dimension, or (ii) two spatial dimensions and piecewise affine finite elements
for describing the continuum deformation. The performance of the proposed
coupling is demonstrated with numerical experiments. The coupling strategy is
based on judiciously defining the contributions of the atomistic bonds to the
discrete and the continuum potential energy. The same method in one dimension
has been independently developed and analyzed in Li and Luskin
(arXiv:1007.2336).
| arxiv topic:math.NA |
arxiv_dataset-21701010.0612 | Discrete Source Survey of 6 GHz OH emission from PNe & pPNe and first 6
GHz images of K 3-35
astro-ph.SR
The aim of this study is to investigate the physical properties of molecular
envelopes of planetary nebulae in their earliest stages of evolution. Using the
100m telescope at Effelsberg, we have undertaken a high sensitivity discrete
source survey for the first excited state of OH maser emission (J=5/2, 2PI3/2
at 6GHz) in the direction of planetary and proto-planetary nebulae exhibiting
18cm OH emission (main and/or satellite lines), and we further validate our
detections using the Nan\c{c}ay radio telescope at 1.6-1.7GHz and MERLIN
interferometer at 1.6-1.7 and 6GHz. Two sources have been detected at 6035MHz
(5cm), both of them are young (or very young) planetary nebulae. The first one
is a confirmation of the detection of a weak 6035MHz line in Vy 2-2. The second
one is a new detection, in K 3-35, which was already known to be an exceptional
late type star because it exhibits 1720MHz OH emission. The detection of
6035MHz OH maser emission is confirmed by subsequent observations made with the
MERLIN interferometer. These lines are very rarely found in evolved stars. The
1612MHz masers surround but are offset from the 1720 and 6035MHz masers which
in turn lie close to a compact 22GHz continuum source embedded in the optical
nebula.
| arxiv topic:astro-ph.SR |
arxiv_dataset-21711010.0712 | Transition nucleon resonance electrocouplings from CLAS data on
$\pi^{+}\pi^{-}p$ electroproduction off protons
nucl-ex hep-ex hep-ph
Electrocouplings of excited proton states with masses less than 1.8 GeV were
determined for the first time from the CLAS data on $\pi^+\pi^-p$
electroproduction at photon virtualities $Q^2$ $<$ 1.5 GeV$^2$.
Electrocouplings were obtained from a combined fit of all available observables
within the framework of a phenomenological reaction model.
| arxiv topic:nucl-ex hep-ex hep-ph |
arxiv_dataset-21721010.0812 | Tambarization of a Mackey functor and its application to the
Witt-Burnside construction
math.CT
For an arbitrary group $G$, a (semi-)Mackey functor is a pair of covariant
and contravariant functors from the category of $G$-sets, and is regarded as a
$G$-bivariant analog of a commutative (semi-)group. In this view, a
$G$-bivariant analog of a (semi-)ring should be a (semi-)Tambara functor. A
Tambara functor is firstly defined by Tambara, which he called a TNR-functor,
when $G$ is finite. As shown by Brun, a Tambara functor plays a natural role in
the Witt-Burnside construction.
It will be a natural question if there exist sufficiently many examples of
Tambara functors, compared to the wide range of Mackey functors. In the first
part of this article, we give a general construction of a Tambara functor from
any Mackey functor, on an arbitrary group $G$. In fact, we construct a functor
from the category of semi-Mackey functors to the category of Tambara functors.
This functor gives a left adjoint to the forgetful functor, and can be regarded
as a $G$-bivariant analog of the monoid-ring functor.
In the latter part, when $G$ is finite, we invsetigate relations with other
Mackey-functorial constructions ---crossed Burnside ring, Elliott's ring of
$G$-strings, Jacobson's $F$-Burnside ring--- all these lead to the study of the
Witt-Burnside construction.
| arxiv topic:math.CT |
arxiv_dataset-21731010.0912 | Asymptotic safety and the gauged SU(N) nonlinear sigma-model
hep-ph hep-th
We study the beta functions of the leading, two-derivative terms of the
left-gauged SU(N) nonlinear sigma-model in d dimensions. In d>2, we find the
usual Gaussian ultraviolet fixed point for the gauge coupling and an attractive
non-Gaussian fixed point for the Goldstone boson coupling. The position of the
latter fixed point controls the chiral expansion, unitarity and the strength of
the tree-level Goldstone boson scattering amplitudes. Attention is paid to the
gauge- and scheme-dependence of the results.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-21741010.1012 | On the irreducible representation algebra of the alternating group of
degree four
math.GR math.RA math.RT
We obtain a description of the irreducible representation algebra of the
alternating group of degree four over the ring of 2-adic integers.
| arxiv topic:math.GR math.RA math.RT |
arxiv_dataset-21751010.1112 | Deterministic and Energy-Optimal Wireless Synchronization
cs.DC
We consider the problem of clock synchronization in a wireless setting where
processors must power-down their radios in order to save energy. Energy
efficiency is a central goal in wireless networks, especially if energy
resources are severely limited. In the current setting, the problem is to
synchronize clocks of $m$ processors that wake up in arbitrary time points,
such that the maximum difference between wake up times is bounded by a positive
integer $n$, where time intervals are appropriately discretized. Currently, the
best-known results for synchronization for single-hop networks of $m$
processors is a randomized algorithm due to \cite{BKO09} of O(\sqrt {n /m}
\cdot poly-log(n)) awake times per processor and a lower bound of
Omega(\sqrt{n/m}) of the number of awake times needed per processor
\cite{BKO09}. The main open question left in their work is to close the
poly-log gap between the upper and the lower bound and to de-randomize their
probabilistic construction and eliminate error probability. This is exactly
what we do in this paper.
That is, we show a {deterministic} algorithm with radio use of Theta(\sqrt {n
/m}) that never fails. We stress that our upper bound exactly matches the lower
bound proven in \cite{BKO09}, up to a small multiplicative constant. Therefore,
our algorithm is {optimal} in terms of energy efficiency and completely
resolves a long sequence of works in this area. In order to achieve these
results we devise a novel {adaptive} technique that determines the times when
devices power their radios on and off. In addition, we prove several lower
bounds on the energy efficiency of algorithms for {multi-hop networks}.
Specifically, we show that any algorithm for multi-hop networks must have radio
use of Omega(\sqrt n) per processor.
| arxiv topic:cs.DC |
arxiv_dataset-21761010.1212 | On Calibrating Stochastic Volatility Models with time-dependent
Parameters
q-fin.PR
We consider stochastic volatility models using piecewise constant parameters.
We suggest a hybrid optimization algorithm for fitting the models to a
volatility surface and provide some numerical results. Finally, we provide an
outlook on how to further improve the calibration procedure.
| arxiv topic:q-fin.PR |
arxiv_dataset-21771010.1312 | A past capture event at Sagittarius A* inferred from the fluorescent
X-ray emission of Sagittarius B clouds
astro-ph.HE astro-ph.GA
The fluorescent X-ray emission from neutral iron in the molecular clouds (Sgr
B) indicates that the clouds are being irradiated by an external X-ray source.
The source is probably associated with the Galactic central black hole (Sgr
A*), which triggered a bright outburst one hundred years ago. We suggest that
such an outburst could be due to a partial capture of a star by Sgr A*, during
which a jet was generated. By constraining the observed flux and the time
variability ($\sim$ 10 years) of the Sgr B's fluorescent emission, we find that
the shock produced by the interaction of the jet with the dense interstellar
medium represents a plausible candidate for the X-ray source emission.
| arxiv topic:astro-ph.HE astro-ph.GA |
arxiv_dataset-21781010.1412 | Tightness of Fluctuations of First Passage Percolation on Some Large
Graphs
math.PR math.MG
The theorem of Dekking and Host regarding tightness around the mean of first
passage percolation on the binary tree, from the root to a boundary of a ball,
is generalized to a class of graphs which includes all lattices in hyperbolic
spaces and the lamplighter graph over N. This class of graphs is closed under
product with any bounded degree graph. Few open problems and conjectures are
gathered at the end.
| arxiv topic:math.PR math.MG |
arxiv_dataset-21791010.1512 | Precise asymptotics for the parabolic Anderson model with a moving
catalyst or trap
math.PR
We consider the solution $u\colon [0,\infty) \times\mathbb{Z}^d\rightarrow
[0,\infty) $ to the parabolic Anderson model, where the potential is given by
$(t,x)\mapsto\gamma\delta_{Y_t}(x)$ with $Y$ a simple symmetric random walk on
$\mathbb{Z}^d$. Depending on the parameter $\gamma\in[-\infty,\infty)$, the
potential is interpreted as a randomly moving catalyst or trap. In the trap
case, i.e., $\gamma<0$, we look at the annealed time asymptotics in terms of
the first moment of $u$. Given a localized initial condition, we derive the
asymptotic rate of decay to zero in dimensions 1 and 2 up to equivalence and
characterize the limit in dimensions 3 and higher in terms of the Green's
function of a random walk. For a homogeneous initial condition we give a
characterisation of the limit in dimension 1 and show that the moments remain
constant for all time in dimensions 2 and higher. In the case of a moving
catalyst ($\gamma>0$), we consider the solution $u$ from the perspective of the
catalyst, i.e., the expression $u(t,Y_t+x)$. Focusing on the cases where
moments grow exponentially fast (that is, $\gamma$ sufficiently large), we
describe the moment asymptotics of the expression above up to equivalence.
Here, it is crucial to prove the existence of a principal eigenfunction of the
corresponding Hamilton operator. While this is well-established for the first
moment, we have found an extension to higher moments.
| arxiv topic:math.PR |
arxiv_dataset-21801010.1612 | Anisotropic model of dark energy dominated universe with hybrid
expansion law
physics.gen-ph
The paper deals with the study of the dynamics of Universe within the
framework of a spatially homogeneous Bianchi-V space-time filled with a perfect
fluid composed of non-interacting matter and dynamical dark energy components.
We determine the Bianchi-V space-time by considering hybrid expansion law (HEL)
for the average scale factor that yields power-law and exponential-law
cosmologies in its special cases. In the HEL cosmology, the Universe exhibits
transition from deceleration to acceleration. We find that the HEL Universe
within the framework of Bianchi-V space-time is anisotropic at the early stages
of evolution and becomes isotropic at late times. The dynamical dark energy in
the HEL Bianchi-V Universe does not show departure from the usual cosmological
constant at later times.
| arxiv topic:physics.gen-ph |
arxiv_dataset-21811010.1712 | Regularity for eigenfunctions of Schr\"odinger operators
math-ph math.AP math.FA math.MP math.NA
We prove a regularity result in weighted Sobolev spaces (or
Babuska--Kondratiev spaces) for the eigenfunctions of a Schr\"odinger operator.
More precisely, let K_{a}^{m}(\mathbb{R}^{3N}) be the weighted Sobolev space
obtained by blowing up the set of singular points of the Coulomb type potential
V(x) = \sum_{1 \le j \le N} \frac{b_j}{|x_j|} + \sum_{1 \le i < j \le N}
\frac{c_{ij}}{|x_i-x_j|}, x in \mathbb{R}^{3N}, b_j, c_{ij} in \mathbb{R}. If u
in L^2(\mathbb{R}^{3N}) satisfies (-\Delta + V) u = \lambda u in distribution
sense, then u belongs to K_{a}^{m} for all m \in \mathbb{Z}_+ and all a \le 0.
Our result extends to the case when b_j and c_{ij} are suitable bounded
functions on the blown-up space. In the single-electron, multi-nuclei case, we
obtain the same result for all a<3/2.
| arxiv topic:math-ph math.AP math.FA math.MP math.NA |
arxiv_dataset-21821010.1812 | Modified Bully Algorithm using Election Commission
cs.DC
Electing leader is a vital issue not only in distributed computing but also
in communication network [1, 2, 3, 4, 5], centralized mutual exclusion
algorithm [6, 7], centralized control IPC, etc. A leader is required to make
synchronization between different processes. And different election algorithms
are used to elect a coordinator among the available processes in the system
such a way that there will be only one coordinator at any time. Bully election
algorithm is one of the classical and well-known approaches in coordinator
election process. This paper will present a modified version of bully election
algorithm using a new concept called election commission. This approach will
not only reduce redundant elections but also minimize total number of elections
and hence it will minimize message passing, network traffic, and complexity of
the existing system.
| arxiv topic:cs.DC |
arxiv_dataset-21831010.1912 | B -> Xs\gamma constraints on the top quark anomalous t-> c\gamma
coupling
hep-ph hep-ex
Observation of top quark flavor changing neutral process $t\to c +\gamma$ at
the LHC would be the signal of physics beyond the Standard Model. If anomalous
$t\to c\gamma$ coupling exists, it will affect the precisely measured
$\mathcal{B}(\bar{B} \to X_s \gamma)$. In this paper, we study the effects of a
dimension 5 anomalous $ tc \gamma$ operator in $\bar{B} \to X_s \gamma$ decay
to derive constraints on its possible strength. It is found that, for real
anomalous $t\to c\gamma$ coupling $\kappa_{\rm{tcR}}^\gamma$, the constraints
correspond to the upper bounds $\mathcal B (t \to c + \gamma)<6.54 \times
10^{-5}$ (for $\kappa_{\rm{tcR}}^\gamma>0$) and $\mathcal B (t \to c +
\gamma)<8.52 \times 10^{-5}$ (for $\kappa_{\rm{tcR}}^\gamma<0$), respectively,
which are about the same order as the $5\sigma$ discovery potential of ATLAS
($9.4\times 10^{-5}$) and slightly lower than that of CMS ($4.1\times 10^{-4}$)
with $10 \ \rm{fb}^{-1}$ integrated luminosity operating at $\sqrt{s} =14$ TeV.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-21841010.2012 | Correlation complementarity yields Bell monogamy relations
quant-ph
We present a method to derive Bell monogamy relations by connecting the
complementarity principle with quantum non-locality. The resulting monogamy
relations are stronger than those obtained from the no-signaling principle
alone. In many cases, they yield tight quantum bounds on violation of single
and multiple qubit correlation Bell inequalities. In contrast with the
two-qubit case, a rich structure of possible violation patterns is shown to
exist in the multipartite scenario.
| arxiv topic:quant-ph |
arxiv_dataset-21851010.2112 | Theory of real space imaging of Fermi surfaces
cond-mat.mes-hall
A scanning tunneling microscope can be used to visualize in real space Fermi
surfaces with buried impurities far below substrates acting as local probes. A
theory describing this feature is developed based on the stationary phase
approximation. It is demonstrated how a Fermi surface of a material acts as a
mirror focusing electrons that scatter at hidden impurities.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-21861010.2212 | Modular realizations of hyperbolic Weyl groups
math.NT hep-th math.RA
We study the recently discovered isomorphisms between hyperbolic Weyl groups
and unfamiliar modular groups. These modular groups are defined over integer
domains in normed division algebras, and we focus on the cases involving
quaternions and octonions. We outline how to construct and analyse automorphic
forms for these groups; their structure depends on the underlying arithmetic
properties of the integer domains. We also give a new realization of the Weyl
group W(E8) in terms of unit octavians and their automorphism group.
| arxiv topic:math.NT hep-th math.RA |
arxiv_dataset-21871010.2312 | A Cost-Minimizing Algorithm for School Choice
math.OC cs.GT math.CO
The school choice problem concerns the design and implementation of matching
mechanisms that produce school assignments for students within a given public
school district. In this note we define a simple student-optimal criterion that
is not met by any previously employed mechanism in the school choice
literature. We then use this criterion to adapt a well-known combinatorial
optimization technique (Hungarian algorithm) to the school choice problem.
| arxiv topic:math.OC cs.GT math.CO |
arxiv_dataset-21881010.2412 | Splitting schemes for hyperbolic heat conduction equation
cs.NA
Rapid processes of heat transfer are not described by the standard heat
conduction equation. To take into account a finite velocity of heat transfer,
we use the hyperbolic model of heat conduction, which is connected with the
relaxation of heat fluxes. In this case, the mathematical model is based on a
hyperbolic equation of second order or a system of equations for the
temperature and heat fluxes. In this paper we construct for the hyperbolic heat
conduction equation the additive schemes of splitting with respect to
directions. Unconditional stability of locally one-dimensional splitting
schemes is established. New splitting schemes are proposed and studied for a
system of equations written in terms of the temperature and heat fluxes.
| arxiv topic:cs.NA |
arxiv_dataset-21891010.2512 | The propagation of Elastic Waves in Granular Solid Hydrodynamics
physics.geo-ph cond-mat.soft
The anisotropic, stress-dependent velocity of elastic waves in glass beads --
as observed by Y. Khidas and X. Jia, see [Phys. Rev. E, 81:021303, Feb. 2010]
-- is shown to be well accounted for by ``granular solid hydrodynamics,'' a
broad-range macroscopic theory of granular behavior. As the theory makes no
reference to fabric anisotropy, the influence of which on sound is in doubt.
| arxiv topic:physics.geo-ph cond-mat.soft |
arxiv_dataset-21901010.2612 | Observable Divergence Theorem: Evolution Equations for Inviscid
Regularization of Shocks and Turbulence
physics.flu-dyn
The divergence theorem of Gauss plays a central role in the derivation of the
governing differential equations in fluid dynamics, electrodynamics,
gravitational fields, and optics. One is often interested in an evolution
equation for the large scale quantities without resolving the details of the
small scales. As a result, there has been a significant effort in developing
time-averaged and spatially-filtered equations for large scale dynamics from
the fully resolved governing differential equations. One should realize that by
starting from these fully-resolved equations (e.g. the Euler or Navier-Stokes
equations) to derive an averaged evolution equation one has already taken the
limit of the wave-numbers approaching infinity with no regards to our
observational abilities at such a limit. As a result, obtaining the evolution
equations for large scale quantities (low wave-numbers) by an averaging or
filtering process is done after the fact. This could explain many of the
theoretical and computational difficulties with the Euler or Navier-Stokes
equations. Here, a rather different approach is proposed. The averaging process
in implemented before the derivation of the differential form of the transport
equations. A new observable divergence concept is defined based on fluxes
calculated from observable quantities at a desired averaging scale, $\alpha$.
An observable divergence theorem is then proved and applied in the derivation
of the observable and regularized transport equations. We further show that the
application of the observable divergence theorem to incompressible flows
results in a formal derivation of the inviscid Leray turbulence model first
proposed in 1934. It is argued that such a methodology in deriving fluid
evolution equations removes many of the theoretical and computational
difficulties in multi-scale problems such as turbulence and shocks.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-21911010.2712 | Residues of functions of Cayley-Dickson variables and Fermat's last
theorem
math.GM
Function theory of Cayley-Dickson variables is applied to Fermat's last
theorem. For this the homotopy theorem, Rouch\'e's theorem and residues of
meromorphic functions over Cayley-Dickson algebras are used. A special
meromorphic function of Cayley-Dickson variables is constructed and its
properties are investigated.
| arxiv topic:math.GM |
arxiv_dataset-21921010.2812 | ILU Preconditioning Based on the FAPINV Algorithm
math.NA
A technique for computing an ILU preconditioner based on the FAPINV algorithm
is presented. We show that this algorithm is well-defined for H-matrices.
Moreover, when used in conjunction with Krylov-subspace-based iterative solvers
such as the GMRES algorithm, results in reliable solvers. Numerical experiments
on some test matrices are given to show the efficiency of the new ILU
preconditioner.
| arxiv topic:math.NA |
arxiv_dataset-21931010.2912 | Splash control using geometric targets
physics.flu-dyn
Experiments of water droplets impacting small geometric posts of equal
dimension to the drop diameter are shown in this fluid dynamics video. High
speed photography shows that the dynamics of drop splashing are significantly
affected by the geometrical boundary of the target and that finger formation
and drop break up are accurately controlled.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-21941010.3012 | Miniaturization of photonic waveguides by the use of left-handed
materials
physics.optics
We propose the use of a left-handed material in an optical waveguide
structure to reduce its thickness well below the wavelength of light. We
demonstrate that a layer of left-handed material, added to the cladding of a
planar waveguide rather than to its core, allows for good light confinement in
a subwavelength thin waveguide. We attribute the observed behavior to the
change in phase evolution of electromagnetic waves in the guide. This technique
can be used for the miniaturization of photonic integrated circuits.
| arxiv topic:physics.optics |
arxiv_dataset-21951010.3112 | An asymptotic sampling formula for the coalescent with Recombination
math.PR
Ewens sampling formula (ESF) is a one-parameter family of probability
distributions with a number of intriguing combinatorial connections. This
elegant closed-form formula first arose in biology as the stationary
probability distribution of a sample configuration at one locus under the
infinite-alleles model of mutation. Since its discovery in the early 1970s, the
ESF has been used in various biological applications, and has sparked several
interesting mathematical generalizations. In the population genetics community,
extending the underlying random-mating model to include recombination has
received much attention in the past, but no general closed-form sampling
formula is currently known even for the simplest extension, that is, a model
with two loci. In this paper, we show that it is possible to obtain useful
closed-form results in the case the population-scaled recombination rate $\rho$
is large but not necessarily infinite. Specifically, we consider an asymptotic
expansion of the two-locus sampling formula in inverse powers of $\rho$ and
obtain closed-form expressions for the first few terms in the expansion. Our
asymptotic sampling formula applies to arbitrary sample sizes and
configurations.
| arxiv topic:math.PR |
arxiv_dataset-21961010.3212 | Stability of dynamic coherent states in intrinsic Josephson-junction
stacks near internal cavity resonance
cond-mat.supr-con
Stacks of intrinsic Josephson junctions in the resistive state can by
efficiently synchronized by the internal cavity mode resonantly excited by the
Josephson oscillations. We study the stability of dynamic coherent states near
the resonance with respect to small perturbations. Three states are considered:
the homogeneous and alternating-kink states in zero magnetic field and the
homogeneous state in the magnetic field near the value corresponding to half
flux quantum per junction. We found two possible instabilities related to the
short-scale and long-scale perturbations. The homogeneous state in modulated
junction is typically unstable with respect to the short-scale alternating
phase deformations unless the Josephson current is completely suppressed in one
half of the stack. The kink state is stable with respect to such deformations
and homogeneous state in the magnetic field is only stable within a certain
range of frequencies and fields. Stability with respect to the long-range
deformations is controlled by resonance excitations of fast modes at finite
wave vectors and typically leads to unstable range of the wave-vectors. This
range shrinks with approaching the resonance and increasing the in-plane
dissipation. As a consequence, in finite-height stacks the stability frequency
range near the resonance increases with decreasing the height.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-21971010.3312 | List Decodability at Small Radii
cs.IT cs.DM math.CO math.IT
$A'(n,d,e)$, the smallest $\ell$ for which every binary error-correcting code
of length $n$ and minimum distance $d$ is decodable with a list of size $\ell$
up to radius $e$, is determined for all $d\geq 2e-3$. As a result, $A'(n,d,e)$
is determined for all $e\leq 4$, except for 42 values of $n$.
| arxiv topic:cs.IT cs.DM math.CO math.IT |
arxiv_dataset-21981010.3412 | Good gradings of basic Lie superalgebras
math.RT
We classify good Z-gradings of basic Lie superalgebras over an algebraically
closed field of characteristic zero. Good Z-gradings are used in quantum
Hamiltonian reduction for affine Lie superalgebras, where they play a role in
the construction of super W-algebras. We also describe the centralizer of a
nilpotent even element and of an sl(2)-triple in gl(m|n) and osp(m|2n).
| arxiv topic:math.RT |
arxiv_dataset-21991010.3512 | Growth factor in f(T) gravity
gr-qc astro-ph.CO
We derive the evolution equation of growth factor for the matter over-dense
perturbation in $f(T)$ gravity. For instance, we investigate its behavior in
power law model at small redshift and compare it to the prediction of
$\Lambda$CDM and dark energy with the same equation of state in the framework
of Einstein general relativity. We find that the perturbation in $f(T)$ gravity
grows slower than that in Einstein general relativity if $\p f/\p T>0$ due to
the effectively weakened gravity.
| arxiv topic:gr-qc astro-ph.CO |
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