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arxiv_dataset-18001003.4193 | Commuting Conformal and Dual Conformal Symmetries in the Regge limit
hep-th hep-ph
In this paper we continue our study of the dual SL(2,C) symmetry of the BFKL
equation, analogous to the dual conformal symmetry of N=4 Super Yang Mills. We
find that the ordinary and dual SL(2,C) symmetries do not generate a Yangian,
in contrast to the ordinary and dual conformal symmetries in the
four-dimensional gauge theory. The algebraic structure is still reminiscent of
that of N=4 SYM, however, and one can extract a generator from the dual SL(2,C)
close to the bi-local form associated with Yangian algebras. We also discuss
the issue of whether the dual SL(2,C) symmetry, which in its original form is
broken by IR effects, is broken in a controlled way, similar to the way the
dual conformal symmetry of N=4 satisfies an anomalous Ward identity. At least
for the lowest orders it seems possible to recover the dual SL(2,C) by
deforming its representation, keeping open the possibility that it is an exact
symmetry of BFKL.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-18011003.4293 | Flaring Behavior of the Quasar 3C~454.3 across the Electromagnetic
Spectrum
astro-ph.HE astro-ph.CO
We analyze the behavior of the parsec-scale jet of the quasar 3C~454.3 during
pronounced flaring activity in 2005-2008. Three major disturbances propagated
down the jet along different trajectories with Lorentz factors $\Gamma>$10. The
disturbances show a clear connection with millimeter-wave outbursts, in 2005
May/June, 2007 July, and 2007 December. High-amplitude optical events in the
$R$-band light curve precede peaks of the millimeter-wave outbursts by 15-50
days. Each optical outburst is accompanied by an increase in X-ray activity. We
associate the optical outbursts with propagation of the superluminal knots and
derive the location of sites of energy dissipation in the form of radiation.
The most prominent and long-lasting of these, in 2005 May, occurred closer to
the black hole, while the outbursts with a shorter duration in 2005 Autumn and
in 2007 might be connected with the passage of a disturbance through the
millimeter-wave core of the jet. The optical outbursts, which coincide with the
passage of superluminal radio knots through the core, are accompanied by
systematic rotation of the position angle of optical linear polarization. Such
rotation appears to be a common feature during the early stages of flares in
blazars. We find correlations between optical variations and those at X-ray and
$\gamma$-ray energies. We conclude that the emergence of a superluminal knot
from the core yields a series of optical and high-energy outbursts, and that
the mm-wave core lies at the end of the jet's acceleration and collimation
zone.
| arxiv topic:astro-ph.HE astro-ph.CO |
arxiv_dataset-18021003.4393 | On quadratic twists of elliptic curves and some applications of a
refined version of Yu's formula
math.NT math.AG
In this paper, we study some cohomology groups and quadratic twists of
elliptic curves, and apply Tate local duality and the results of Kramer-Tunnell
on local norm cokernel to give a refined version of Yu's formula in the case of
elliptic curves. Then, by using this refinement formula, we obtain explicit
orders of Shafarevich-Tate groups of some elliptic curves in quadratic number
fields, including a few unconditional cases.
| arxiv topic:math.NT math.AG |
arxiv_dataset-18031003.4493 | Geometric composition in quilted Floer theory
math.SG
We prove that Floer cohomology of cyclic Lagrangian correspondences is
invariant under transverse and embedded composition of Lagrangians under a
general set of assumptions.
In the Corrigendum, we introduce an additional assumption of monotonicity for
cylinders which is needed to avoid bubbling at the Y-end.
| arxiv topic:math.SG |
arxiv_dataset-18041003.4593 | Atmospheric image blur with finite outer scale or partial adaptive
correction
astro-ph.IM
Seeing-limited resolution in large telescopes working over wide wavelength
range depends substantially on the turbulence outer scale and cannot be
adequately described by one "seeing" value. We attempt to clarify frequent
confusions on this matter. We study the effects of finite turbulence outer
scale and partial adaptive corrections by means of analytical calculations and
numerical simulations. If a von Karman turbulence model is adopted, a simple
approximate formula captures the dependence of atmospheric long-exposure
resolution on the outer scale over the entire practically interesting range of
telescope diameters and wavelengths. In the infrared (IR), the difference with
the standard Kolmogorov seeing formula can exceed a factor of two. We find that
low-order adaptive turbulence correction produces residual wave-fronts with
effectively small outer scale, so even very low compensation order leads to a
substantial improvement in resolution over seeing, compared to the standard
theory. Seeing-limited resolution of large telescopes, especially in the IR, is
currently under-estimated by not accounting for the outer scale. On the other
hand, adaptive-optics systems designed for diffraction-limited imaging in the
IR can improve the resolution in the visible by as much as two times.
| arxiv topic:astro-ph.IM |
arxiv_dataset-18051003.4693 | Photon-pion transition form factor: BABAR puzzle is cracked
hep-ph hep-ex
Recently, the BABAR collaboration published (arXiv:0905.4778) data for the
photon-pion transition form factor $F_{\pi\gamma\gamma^{\ast}}(Q^{2})$, which
are in strong contradiction to the predictions of the standard factorization
approach to perturbative QCD. Immediately afterwards, two mechanisms were
suggested (A.E. Dorokhov, arXiv:0905.4577; A.V. Radyushkin, arXiv:0906.0323),
that logarithmically enhance the form factor asymptotics and therefore provide
a qualitatively satisfactory description of the BABAR data. However, the
physics of the BABAR effect was not fully clarified. In the present work, based
on a nonperturbative approach to the QCD vacuum and on rather universal
assumptions, we show that there exists two asymptotic regimes for the pion
transition form factor. One regime with asymptotics
$F_{\pi\gamma^{\ast}\gamma}(Q^{2})\sim1/Q^{2}$ corresponds to the result of the
standard QCD factorization approach, while other violates the standard
factorization and leads to asymptotic behavior as
$F_{\pi\gamma^{\ast}\gamma}(Q^{2})\sim\ln(Q^{2})Q^{2}$. Furthermore,
considering specific nonlocal chiral quark models, we find the region of
parameters, where the existing CELLO, CLEO and BABAR data for the pion
transition form factor are successfully described.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-18061003.4793 | Compositions and Averages of Two Resolvents: Relative Geometry of Fixed
Points Sets and a Partial Answer to a Question by C. Byrne
math.FA math.OC
We show that the set of fixed points of the average of two resolvents can be
found from the set of fixed points for compositions of two resolvents
associated with scaled monotone operators. Recently, the proximal average has
attracted considerable attention in convex analysis. Our results imply that the
minimizers of proximal-average functions can be found from the set of fixed
points for compositions of two proximal mappings associated with scaled convex
functions. When both convex functions in the proximal average are indicator
functions of convex sets, least squares solutions can be completely recovered
from the limiting cycles given by compositions of two projection mappings. This
provides a partial answer to a question posed by C. Byrne. A novelty of our
approach is to use the notion of resolvent average and proximal average.
| arxiv topic:math.FA math.OC |
arxiv_dataset-18071003.4893 | Asymptotic Stability of the Relativistic Boltzmann Equation for the Soft
Potentials
math.AP math-ph math.MP
In this paper it is shown that unique solutions to the relativistic Boltzmann
equation exist for all time and decay with any polynomial rate towards their
steady state relativistic Maxwellian provided that the initial data starts out
sufficiently close in $L^\infty_\ell$. If the initial data are continuous then
so is the corresponding solution. We work in the case of a spatially periodic
box. Conditions on the collision kernel are generic in the sense of
(Dudy{\'n}ski and Ekiel-Je{\.z}ewska, Comm. Math. Phys., 1988); this resolves
the open question of global existence for the soft potentials.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-18081003.4993 | Relativistic Suppression of Black Hole Recoils
astro-ph.CO gr-qc
Numerical-relativity simulations indicate that the black hole produced in a
binary merger can recoil with a velocity up to v_max ~ 4,000 km/s with respect
to the center of mass of the initial binary. This challenges the paradigm that
most galaxies form through hierarchical mergers, yet retain supermassive black
holes at their centers despite having escape velocities much less than v_max.
Interaction with a circumbinary disk can align the binary black hole spins with
their orbital angular momentum, reducing the recoil velocity of the final black
hole produced in the subsequent merger. However, the effectiveness of this
alignment depends on highly uncertain accretion flows near the binary black
holes. In this Letter, we show that if the spin S_1 of the more massive binary
black hole is even partially aligned with the orbital angular momentum L,
relativistic spin precession on sub-parsec scales can align the binary black
hole spins with each other. This alignment significantly reduces the recoil
velocity even in the absence of gas. For example, if the angle between S_1 and
L at large separations is 10 degrees while the second spin S_2 is isotropically
distributed, the spin alignment discussed in this paper reduces the median
recoil from 864 km/s to 273 km/s for maximally spinning black holes with a mass
ratio of 9/11. This reduction will greatly increase the fraction of galaxies
retaining their supermassive black holes.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-18091003.5093 | Tunnel effect in ferromagnetic half-metal Co$_2$CrAl-superconductor
heterostructures
cond-mat.supr-con
Ferromagnetic half-metal Co$_2$CrAl films and tunnel contacts Co$_2$CrAl -
insulator (I) - Pb are fabricated and investigated. It is found that the
normalized differential conductivity $\sigma ^{\rm FS} $ of such tunnel
junctions with low resistance is larger than the normalized differential
conductivity $\sigma ^{\rm NS} $ of known normal metal - I - superconductor
type tunnel junctions. It is shown that the observed increase in $\sigma ^{\rm
FS} $ is caused by the accumulation of spin polarized electrons in a
superconductor and can be used for estimating the spin polarization degree $P$
in ferromagnets. This method shows that $P$ of L2$_1$-type ordered Co$_2$CrAl
Heusler alloy films at $T = 4.2{\rm K}$ is close to 1.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-18101003.5193 | Structurally driven metamagnetism in MnP and related Pnma compounds
cond-mat.mtrl-sci cond-mat.str-el
We investigate the structural conditions for metamagnetism in MnP and related
materials using Density Functional Theory. A magnetic stability plot is
constructed taking into account the two shortest Mn-Mn distances. We find that
a particular Mn-Mn separation plays the dominant role in determining the change
from antiferromagnetic to ferromagnetic order in such systems. We establish a
good correlation between our calculations and structural and magnetic data from
the literature. Based on our approach it should be possible to find new
Mn-containing alloys that possess field-induced metamagnetism and associated
magnetocaloric effects.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-18111003.5293 | The Importance of Fundamental Taxonomic Principles for Sensible
Underpinning of Epoch Photometry Datasets
astro-ph.SR
The dangers inherent in the utilisation of easily available and readily
analysed datasets in tandem with "blackbox" software applications without
supporting taxonomic understanding and data nature familiarity is exemplified
via examination of a misrepresentation of the results from a DEBIL analysis of
OGLE II Galactic Bulge candidate variables.
| arxiv topic:astro-ph.SR |
arxiv_dataset-18121003.5393 | Selected aspects of the condensed matter physics. Work and life of
Professor B.Ya. Sukharevsky
cond-mat.mtrl-sci cond-mat.soft
The paper contains a short description of the scientific papers of Professor
Boris Ya. Sukharevsky on condensed matter physics. His basic scientific
activity was related to following directions: structural vacancies concept;
influence of point defects on statics and kinetics of phase transitions; DNA
crystallization and low-dimensional systems properties; phase transitions in
Jahn-Teller crystals; Thermophysics of superconductors e.a. The list of most
essential papers of Prof. B.Ya. Sukharevsky is included.
| arxiv topic:cond-mat.mtrl-sci cond-mat.soft |
arxiv_dataset-18131003.5493 | Derivation of a transfer function model for a high pressure pipeline
math.DS math.OC
In this report a lumped transfer function model for High Pressure Natural Gas
Pipelines is derived. Starting with a partial nonlinear differential equation
(PDE) model a high order continuous state space (SS) linear model is obtained
using a finite difference method. Next, from the SS representation an infinite
order transfer function (TF) model is calculated. In the end, this TF is
approximated by a compact non-rational function.
| arxiv topic:math.DS math.OC |
arxiv_dataset-18141003.5593 | The noncommutative standard model, post- and predictions
hep-th hep-ph
I try to assess the weak and strong points of the standard model of
electro-magnetic, weak and strong forces, how it can be derived from general
relativity by generalizing Riemannian to noncommutative geometry and what post-
and predictions this unification of all four forces entails in particle
physics.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-18151003.5693 | An Iteratively Decodable Tensor Product Code with Application to Data
Storage
cs.IT math.IT
The error pattern correcting code (EPCC) can be constructed to provide a
syndrome decoding table targeting the dominant error events of an inter-symbol
interference channel at the output of the Viterbi detector. For the size of the
syndrome table to be manageable and the list of possible error events to be
reasonable in size, the codeword length of EPCC needs to be short enough.
However, the rate of such a short length code will be too low for hard drive
applications. To accommodate the required large redundancy, it is possible to
record only a highly compressed function of the parity bits of EPCC's tensor
product with a symbol correcting code. In this paper, we show that the proposed
tensor error-pattern correcting code (T-EPCC) is linear time encodable and also
devise a low-complexity soft iterative decoding algorithm for EPCC's tensor
product with q-ary LDPC (T-EPCC-qLDPC). Simulation results show that
T-EPCC-qLDPC achieves almost similar performance to single-level qLDPC with a
1/2 KB sector at 50% reduction in decoding complexity. Moreover, 1 KB
T-EPCC-qLDPC surpasses the performance of 1/2 KB single-level qLDPC at the same
decoder complexity.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-18161003.5793 | Chemistry in Disks. III. -- Photochemistry and X-ray driven chemistry
probed by the ethynyl radical (CCH) in DM Tau, LkCa 15, and MWC 480
astro-ph.GA astro-ph.HE
We studied several representative circumstellar disks surrounding the Herbig
Ae star MWC 480 and the T Tauri stars LkCa 15 and DM Tau at (sub-)millimeter
wavelengths in lines of CCH. Our aim is to characterize photochemistry in the
heavily UV-irradiated MWC 480 disk and compare the results to the disks around
cooler T Tauri stars. We detected and mapped CCH in these disks with the IRAM
Plateau de Bure Interferome- ter in the C- and D-configurations in the (1-0)
and (2-1) transitions. Using an iterative minimization technique, the CCH
column densities and excitation conditions are con- strained. Very low
excitation temperatures are derived for the T Tauri stars. These values are
compared with the results of advanced chemical modeling, which is based on a
steady-state flared disk structure with a vertical temperature gradient, and a
gas- grain chemical network with surface reactions. Both model and observations
suggest that CCH is a sensitive tracer of the X-ray and UV irradiation. The
predicted radial dependency and source to source variations of CCH column
densities qualitatively agree with the observed values, but the predicted
column densities are too low by a factor of several. The chemical model fails
to reproduce high concentrations of CCH in very cold disk midplane as derived
from the observed low excitation condition for both the (1-0) and (2-1)
transitions.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-18171003.5893 | Recognition of Handwritten Textual Annotations using Tesseract Open
Source OCR Engine for information Just In Time (iJIT)
cs.CV
Objective of the current work is to develop an Optical Character Recognition
(OCR) engine for information Just In Time (iJIT) system that can be used for
recognition of handwritten textual annotations of lower case Roman script.
Tesseract open source OCR engine under Apache License 2.0 is used to develop
user-specific handwriting recognition models, viz., the language sets, for the
said system, where each user is identified by a unique identification tag
associated with the digital pen. To generate the language set for any user,
Tesseract is trained with labeled handwritten data samples of isolated and
free-flow texts of Roman script, collected exclusively from that user. The
designed system is tested on five different language sets with free- flow
handwritten annotations as test samples. The system could successfully segment
and subsequently recognize 87.92%, 81.53%, 92.88%, 86.75% and 90.80%
handwritten characters in the test samples of five different users.
| arxiv topic:cs.CV |
arxiv_dataset-18181003.5993 | A Triple-Error-Correcting Cyclic Code from the Gold and Kasami-Welch APN
Power Functions
cs.DM cs.IT math.IT
Based on a sufficient condition proposed by Hollmann and Xiang for
constructing triple-error-correcting codes, the minimum distance of a binary
cyclic code $\mathcal{C}_{1,3,13}$ with three zeros $\alpha$, $\alpha^3$, and
$\alpha^{13}$ of length $2^m-1$ and the weight divisibility of its dual code
are studied, where $m\geq 5$ is odd and $\alpha$ is a primitive element of the
finite field $\mathbb{F}_{2^m}$. The code $\mathcal{C}_{1,3,13}$ is proven to
have the same weight distribution as the binary triple-error-correcting
primitive BCH code $\mathcal{C}_{1,3,5}$ of the same length.
| arxiv topic:cs.DM cs.IT math.IT |
arxiv_dataset-18191003.6093 | Ground-based follow-up in relation to Kepler Asteroseismic Investigation
astro-ph.SR
The Kepler space mission, successfully launched in March 2009, is providing
continuous, high-precision photometry of thousands of stars simultaneously. The
uninterrupted time-series of stars of all known pulsation types are a precious
source for asteroseismic studies. The Kepler data do not provide information on
the physical parameters, such as effective temperature, surface gravity,
metallicity, and vsini, which are crucial for successful asteroseismic
modelling. Additional ground-based time-series data are needed to characterize
mode parameters in several types of pulsating stars. Therefore, ground-based
multi-colour photometry and mid/high-resolution spectroscopy are needed to
complement the space data. We present ground-based activities within KASC on
selected asteroseismic Kepler targets of several pulsation types.
(Based on observations made with the Isaac Newton Telescope, William Herschel
Telescope, Nordic Optical Telescope, Telescopio Nazionale Galileo, Mercator
Telescope (La Palma, Spain), and IAC-80 (Tenerife, Spain). Also based on
observations taken at the observatories of Sierra Nevada, San Pedro Martir,
Vienna, Xinglong, Apache Point, Lulin, Tautenburg, Loiano, Serra la Nave,
Asiago, McDonald, Skinakas, Pic du Midi, Mauna Kea, Steward Observatory, Mt
Wilson, Bialkow Observatory of the Wroclaw University, Piszkesteto Mountain
Station, Observatoire de Haute Provence, and Centro Astronomico Hispano Aleman
at Calar Alto. Based on data from the AAVSO International Database.)
| arxiv topic:astro-ph.SR |
arxiv_dataset-18201004.006 | Got the Flu (or Mumps)? Check the Eigenvalue!
physics.soc-ph cond-mat.stat-mech q-bio.PE
For a given, arbitrary graph, what is the epidemic threshold? That is, under
what conditions will a virus result in an epidemic? We provide the super-model
theorem, which generalizes older results in two important, orthogonal
dimensions. The theorem shows that (a) for a wide range of virus propagation
models (VPM) that include all virus propagation models in standard literature
(say, [8][5]), and (b) for any contact graph, the answer always depends on the
first eigenvalue of the connectivity matrix. We give the proof of the theorem,
arithmetic examples for popular VPMs, like flu (SIS), mumps (SIR), SIRS and
more. We also show the implications of our discovery: easy (although sometimes
counter-intuitive) answers to `what-if' questions; easier design and evaluation
of immunization policies, and significantly faster agent-based simulations.
| arxiv topic:physics.soc-ph cond-mat.stat-mech q-bio.PE |
arxiv_dataset-18211004.016 | Stone duality for topological theories
math.CT math.GN
In the context of categorical topology, more precisely that of T-categories
[Hofmann, 2007], we define the notion of T-colimit as a particular colimit in a
V-category. A complete and cocomplete V-category in which limits distribute
over T-colimits, is to be thought of as the generalisation of a (co-)frame to
this categorical level. We explain some ideas on a T-categorical version of
"Stone duality", and show that Cauchy completeness of a T-category is precisely
its sobriety.
| arxiv topic:math.CT math.GN |
arxiv_dataset-18221004.026 | Angle-dependence of quantum oscillations in YBa2Cu3O6.59 shows free spin
behaviour of quasiparticles
cond-mat.supr-con
Measurements of quantum oscillations in the cuprate superconductors afford a
new opportunity to assess the extent to which the electronic properties of
these materials yield to a description rooted in Fermi liquid theory. However,
such an analysis is hampered by the small number of oscillatory periods
observed. Here we employ a genetic algorithm to globally model the field,
angular, and temperature dependence of the quantum oscillations observed in the
resistivity of YBa2Cu3O6.59. This approach successfully fits an entire data set
to a Fermi surface comprised of two small, quasi-2-dimensional cylinders. A key
feature of the data is the first identification of the effect of Zeeman
splitting, which separates spin-up and spin-down contributions, indicating that
the quasiparticles in the cuprates behave as nearly free spins, constraining
the source of the Fermi surface reconstruction to something other than a
conventional spin density wave with moments parallel to the CuO2 planes.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-18231004.036 | On the domain of meromorphy of a multivariate Euler product of Igusa
type
math.NT math.CV
This work is an answer to a problem posed by N. Kurokawa and H. Ochiai
concerning the natural boundary of meromorphy of a multivariate Euler product
of Igusa type. More generally, we introduce and determine the maximal domain of
meromorphy of a class of multivariate pseudo-uniform Euler products.
| arxiv topic:math.NT math.CV |
arxiv_dataset-18241004.046 | Invariants of singular sets of smooth maps
math.GT
A singular point of a smooth map F: M -> N of manifolds is a point in M at
which the rank of the differential dF is less than the minimum of dimensions of
M and N. The classical invariant of the set S of singular points of F of a
given type is defined by taking the fundamental class [\bar{S}]\in H_*(M) of
the closure of S. We introduce and study new invariants of singular sets for
which the classical invariants may not be defined, i.e., for which \bar{S} may
not possess the fundamental class. The simplest new invariant is defined by
carefully choosing the fundamental class of the intersection of \bar{S} and its
slight perturbation in M. Surprisingly, for certain singularity types such an
invariant is well-define (and not trivial) despite the fact that \bar{S} does
not possess the fundamental class.
We determine new invariants for maps with Morin singularities---i.e.,
singularities of types A_k for k>0 in the ADE-classification of simple
singularities by Dynkin diagrams---and, as an application, show that these
invariants together with generalized Miller-Morita-Mumford classes form a
commutative graded algebra of characteristic classes that completely determine
the cobordism groups of maps with at most A_k-singularities for each k>0.
| arxiv topic:math.GT |
arxiv_dataset-18251004.056 | Enstatite-rich Warm Debris Dust around HD165014
astro-ph.EP
We present the Spitzer/Infrared Spectrograph spectrum of the main-sequence
star HD165014, which is a warm (>~ 200 K) debris disk candidate discovered by
the AKARI All-Sky Survey. The star possesses extremely large excess emission at
wavelengths longer than 5 \mum. The detected flux densities at 10 and 20 \mum
are ~ 10 and ~ 30 times larger than the predicted photospheric emission,
respectively. The excess emission is attributable to the presence of
circumstellar warm dust. The dust temperature is estimated as 300-750 K,
corresponding to the distance of 0.7-4.4 AU from the central star. Significant
fine-structured features are seen in the spectrum and the peak positions are in
good agreement with those of crystalline enstatite. Features of crystalline
forsterite are not significantly seen. HD165014 is the first debris disk sample
that has enstatite as a dominant form of crystalline silicate rather than
forsterite. Possible formation of enstatite dust from differentiated parent
bodies is suggested according to the solar system analog. The detection of an
enstatite-rich debris disk in the current study suggests the presence of large
bodies and a variety of silicate dust processing in warm debris disks.
| arxiv topic:astro-ph.EP |
arxiv_dataset-18261004.066 | Nonlinear Hall effect and multichannel conduction in LaTiO3/SrTiO3
superlattices
cond-mat.str-el cond-mat.mtrl-sci
We report magneto-transport properties of heterointerfaces between the Mott
insulator LaTiO3 and the band insulator SrTiO3 in a delta-doping geometry. At
low temperatures, we have found a strong nonlinearity in the magnetic field
dependence of the Hall resistivity, which can be effectively controlled by
varying the temperature and the electric field. We attribute this effect to
multichannel conduction of interfacial charges generated by an electronic
reconstruction. In particular, the formation of a highly mobile conduction
channel revealed by our data is explained by the greatly increased dielectric
permeability of SrTiO3 at low temperatures, and its electric-field dependence
reflects the spatial distribution of the quasi-two-dimensional electron gas.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-18271004.076 | Hyperboloidal evolution of test fields in three spatial dimensions
gr-qc
We present the numerical implementation of a clean solution to the outer
boundary and radiation extraction problems within the 3+1 formalism for
hyperbolic partial differential equations on a given background. Our approach
is based on compactification at null infinity in hyperboloidal scri fixing
coordinates. We report numerical tests for the particular example of a scalar
wave equation on Minkowski and Schwarzschild backgrounds. We address issues
related to the implementation of the hyperboloidal approach for the Einstein
equations, such as nonlinear source functions, matching, and evaluation of
formally singular terms at null infinity.
| arxiv topic:gr-qc |
arxiv_dataset-18281004.086 | Toeplitz operators on generalized harmonic Bergman spaces
math.FA math.OA
We study Toeplitz operators with uniformly continuous symbols on generalized
harmonic Bergman spaces of the unit ball in $\mathbb{R}^n$. We describe their
essential spectra and establish a short exact sequence associated with the
$C^{*}$-algebra generated by these operators.
| arxiv topic:math.FA math.OA |
arxiv_dataset-18291004.096 | A model independent null test on the cosmological constant
astro-ph.CO gr-qc hep-ph hep-th
We use the Om statistic and the Genetic Algorithms (GA) in order to derive a
null test on the spatially flat cosmological constant model $\Lambda$CDM. This
is done in two steps: first, we apply the GA to the Constitution SNIa data in
order to acquire a model independent reconstruction of the expansion history of
the Universe $H(z)$ and second, we use the reconstructed $H(z)$ in conjunction
with the Om statistic, which is constant only for the $\Lambda$CDM model, to
derive our constraints. We find that while $\Lambda$CDM is consistent with the
data at the $2\sigma$ level, some deviations from $\Lambda$CDM model at low
redshifts can be accommodated.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
arxiv_dataset-18301004.106 | Water masers accompanying OH and methanol masers in star formation
regions
astro-ph.GA
The ATCA has been used to measure positions with arcsecond accuracy for 379
masers at the 22-GHz transition of water. The principal observation targets
were 202 OH masers of the variety associated with star formation regions (SFR)s
in the Southern Galactic plane. At a second epoch, most of these targets were
observed again, and new targets of methanol masers were added. Many of the
water masers reported here are new discoveries. Variability in the masers is
often acute, with very few features directly corresponding to those discovered
two decades ago. Within our current observations, less than a year apart,
spectra are often dissimilar, but positions at the later epoch, even when
measured for slightly different features, mostly correspond to the detected
maser site measured earlier, to within the typical extent of the whole site, of
a few arcseconds. The precise water positions show that approximately 79% (160
of 202) of the OH maser sites show coincident water maser emission, the best
estimate yet obtained for this statistic; however, there are many instances
where additional water sites are present offset from the OH target, and
consequently less than half of the water masers coincide with a 1665-MHz
ground-state OH maser counterpart. We explore the differences between the
velocities of peak emission from the three species (OH, methanol and water),
and quantify the typically larger deviations shown by water maser peaks from
systemic velocities. Clusters of two or three distinct but nearby sites, each
showing one or several of the principal molecular masing transitions, are found
to be common. In combination with an investigation of correlations with IR
sources from the GLIMPSE catalogue, these comparative studies allow further
progress in the use of the maser properties to assign relative evolutionary
stages in star formation to individual sites.
| arxiv topic:astro-ph.GA |
arxiv_dataset-18311004.116 | The Number of Inversions and the Major Index of Permutations are
Asymptotically Joint-Independently Normal
math.CO
We use recurrences (alias difference equations) to prove the longstanding
conjecture that the two most important permutation statistics, namely the
number of inversions and the major index, are asymptotically
joint-independently-normal. We even derive more-precise-than needed asymptotic
formulas for the (normalized) mixed moments. This is the fully revised second
edition, incorportating the many insightful comments of nine conscientious
NON-anonymous referees listed under the authors' names. This article is
exclusively published in the on-line journal "Personal Journal of Shalosh B.
Ekhad and Doron Zeilberger" and this arxiv.
| arxiv topic:math.CO |
arxiv_dataset-18321004.126 | Design of Easily Synchronizable Oscillator Networks Using the Monte
Carlo Optimization Method
nlin.AO
Starting with an initial random network of oscillators with a heterogeneous
frequency distribution, its autonomous synchronization ability can be largely
improved by appropriately rewiring the links between the elements. Ensembles of
synchronization-optimized networks with different connectivities are generated
and their statistical properties are studied.
| arxiv topic:nlin.AO |
arxiv_dataset-18331004.136 | Isospectral metrics on weighted projective spaces
math.DG math.SP
We construct the first examples of families of bad Riemannian orbifolds which
are isospectral with respect to the Laplacian but not isometric. In our case
these are particular fixed weighted projective spaces equipped with isospectral
metrics obtained by a generalization of Sch\"uth's version of the torus method.
| arxiv topic:math.DG math.SP |
arxiv_dataset-18341004.146 | Security Policy Enforcement Through Refinement Process
cs.CR cs.LO
In the area of networks, a common method to enforce a security policy
expressed in a high-level language is based on an ad-hoc and manual rewriting
process. We argue that it is possible to build a formal link between concrete
and abstract terms, which can be dynamically computed from the environment
data. In order to progressively introduce configuration data and then simplify
the proof obligations, we use the B refinement process. We present a case study
modeling a network monitor. This program, described by refinement following the
layers of the TCP/IP suite protocol, has to warn for all observed events which
do not respect the security policy. To design this model, we use the event-B
method because it is suitable for modeling network concepts. This work has been
done within the framework of the POTESTAT project, based on the research of
network testing methods from a high-level security policy.
| arxiv topic:cs.CR cs.LO |
arxiv_dataset-18351004.156 | Strong Coupling of a Quantum Oscillator to a Flux Qubit at its Symmetry
Point
cond-mat.mes-hall cond-mat.supr-con quant-ph
A flux qubit biased at its symmetry point shows a minimum in the energy
splitting (the gap), providing protection against flux noise. We have
fabricated a qubit whose gap can be tuned fast and have coupled this qubit
strongly to an LC oscillator. We show full spectroscopy of the qubit-resonator
system and generate vacuum Rabi oscillations. When the gap is made equal to the
oscillator frequency $\nu_{osc}$ we find the strongest qubit-resonator coupling
($g/h\sim0.1\nu_{\rm osc}$). Here being at resonance coincides with the optimal
coherence of the symmetry point. Significant further increase of the coupling
is possible.
| arxiv topic:cond-mat.mes-hall cond-mat.supr-con quant-ph |
arxiv_dataset-18361004.166 | Representation Theory of Finite Semigroups over Semirings
math.RA math.RT
We develop the representation theory of a finite semigroup over an arbitrary
commutative semiring with unit, in particular classifying the irreducible and
minimal representations. The results for an arbitrary semiring are as good as
the results for a field. Special attention is paid to the boolean semiring,
where we also characterize the simple representations and introduce the
beginnings of a character theory.
| arxiv topic:math.RA math.RT |
arxiv_dataset-18371004.176 | Trapping Horizons in the Sultana-Dyer Space-Time
gr-qc
The Sultana-Dyer space-time is suggested as a model describing a black hole
embedded in an expanding universe. Recently, in \cite{0705.4012}, its global
structure is analyzed and the trapping horizons are shown. In the paper, by
directly calculating the expansions of the radial null vector fields normal to
the space-like two-spheres foliating the trapping horizons, we find that the
trapping horizon outside the event horizon in the Sultana-Dyer space-time is a
past trapping horizon. Further, we find that the past trapping horizon is an
outer, instantaneously degenerate or inner trapping horizon accordingly when
the radial coordinate is less than, equal to or greater than some value.
| arxiv topic:gr-qc |
arxiv_dataset-18381004.186 | Signature Pairs for Group-Invariant Hermitian Polynomials
math.CV
We study the signature pair for certain group-invariant Hermitian polynomials
arising in CR geometry. In particular, we determine the signature pair for the
finite subgroups of $SU(2)$. We introduce the asymptotic positivity ratio and
compute it for cyclic subgroups of $U(2)$. We calculate the signature pair for
dihedral subgroups of $U(2)$.
| arxiv topic:math.CV |
arxiv_dataset-18391004.196 | On the simplest quartic fields and related Thue equations
math.NT
Let $K$ be a field of char $K\neq 2$. For $a\in K$, we give an explicit
answer to the field isomorphism problem of the simplest quartic polynomial
$X^4-aX^3-6X^2+aX+1$ over $K$ as the special case of the field intersection
problem via multi-resolvent polynomials. From this result, over an infinite
field $K$, we see that the polynomial gives the same splitting field over $K$
for infinitely many values $a$ of $K$. We also see by Siegel's theorem for
curves of genus zero that only finitely many algebraic integers
$a\in\mathcal{O}_K$ in a number field $K$ may give the same splitting field. By
applying the result over the field $\mathbb{Q}$ of rational numbers, we
establish a correspondence between primitive solutions to the parametric family
of quartic Thue equations \[ X^4-mX^3Y-6X^2Y^2+mXY^3+Y^4=c, \] where
$m\in\mathbb{Z}$ is a rational integer and $c$ is a divisor of $4(m^2+16)$, and
isomorphism classes of the simplest quartic fields.
| arxiv topic:math.NT |
arxiv_dataset-18401004.206 | On free discrete subgroups of Diff(I)
math.GR math.DS math.GT
We prove that a free group F_2 admits a faithful discrete representation into
Diff_{+}(I). We also prove that F_2 admits a faithful discrete representation
into Homeo_{+}(I). Some properties of these representations have been studied.
In the last section we raise several questions.
| arxiv topic:math.GR math.DS math.GT |
arxiv_dataset-18411004.216 | Effect of doping and pressure on magnetism and lattice structure of
Fe-based superconductors
cond-mat.supr-con cond-mat.mtrl-sci
Using first principles calculations, we analyze structural and magnetic
trends as a function of charge doping and pressure in BaFe$_2$As$_2$, and
compare to experimentally established facts. We find that density functional
theory, while accurately reproducing the structural and magnetic ordering at
ambient pressure, fails to reproduce some structural trends as pressure is
increased. Most notably, the Fe-As bondlength which is a gauge of the magnitude
of the magnetic moment, $\mu$, is rigid in experiment, but soft in calculation,
indicating residual local Coulomb interactions. By calculating the magnitude of
the magnetic ordering energy, we show that the disruption of magnetic order as
a function of pressure or doping can be qualitatively reproduced, but that in
calculation, it is achieved through diminishment of $|\mu|$, and therefore
likely does not reflect the same physics as detected in experiment. We also
find that the strength of the stripe order as a function of doping is strongly
site-dependent: magnetism decreases monotonically with the number of electrons
doped at the Fe site, but increases monotonically with the number of electrons
doped at the Ba site. Intra-planar magnetic ordering energy (the difference
between checkerboard and stripe orderings) and interplanar coupling both follow
a similar trend. We also investigate the evolution of the orthorhombic
distortion, $e=(a-b)/(a+b),$ as a function of $\mu$, and find that in the
regime where experiment finds a linear relationship, our calculations are
impossible to converge, indicating that in density functional theory, the
transition is first order, signalling anomalously large higher order terms in
the Landau functional.
| arxiv topic:cond-mat.supr-con cond-mat.mtrl-sci |
arxiv_dataset-18421004.226 | The new vertices and canonical quantization
gr-qc
We present two results on the recently proposed new spin foam models. First,
we show how a (slightly modified) restriction on representations in the EPRL
model leads to the appearance of the Ashtekar-Barbero connection, thus bringing
this model even closer to LQG. Second, we however argue that the quantization
procedure used to derive the new models is inconsistent since it relies on the
symplectic structure of the unconstraint BF theory.
| arxiv topic:gr-qc |
arxiv_dataset-18431004.236 | Limits on the parameters of the equation of state for interacting dark
energy
astro-ph.CO gr-qc hep-th
Under the assumption that cold dark matter and dark energy interact with each
other through a small coupling term, $Q$, we constrain the parameter space of
the equation of state $w$ of those dark energy fields whose variation of the
field since last scattering do not exceed Planck's mass. We use three
parameterizations of $w$ and two different expressions for $Q$. Our work
extends previous ones.
| arxiv topic:astro-ph.CO gr-qc hep-th |
arxiv_dataset-18441004.246 | The Chooser-Picker 7-in-a-row-game
math.CO
One of the main objective of this paper is to relate Beck's conjecture for
k-in-a-row games. The conjecture states that playing on the same board Picker
is better off in a Chooser-Picker game than the second player in the
Maker-Breaker version. It was shown that the 8-in-a-row game is a blocking draw
that is a Breaker win. To give the outcome of 7-, or 6-in-a-row-games is
hopeless, but these games are widely believed to be Breaker's win. If both
conjectures hold, Picker must win the Chooser-Picker version of the 7-in-a-row
game, and that is what we prove.
| arxiv topic:math.CO |
arxiv_dataset-18451004.256 | Enhancing Curriculum Acceptance among Students with E-learning 2.0
cs.CY
E-learning; enhanced by communicating and interacting is becoming
increasingly accepted and this puts Web 2.0 at the center of the new
educational technologies. E-Learning 2.0 emerges as an innovative method of
online learning for its incorporation of Web 2.0 tools. For any academic study,
the curriculum provides overview of intact learning area. The Curriculum
provides overview to content of the Subject. Many institutions place student
interaction as a priority of their online curriculum design. It is proved that
interaction has a great effect on the students' involvement in learning and
acceptance of Curriculum. Students are accepting curriculum that is designed by
teacher; whereas E-learning 2.0 enabled Curriculum management system allows
student to involve in learning activities. It works as a stimulus and increases
their dedication to the Curriculum. While Institute adapts E-Learning 2.0 as
Learning Management System, it also provides Social Networking services and
provides direct and transparent interaction between students and teachers. This
view of the e-Learning 2.0 shifts its focus from LMS to the students, equipping
them, with the means to become ever more autonomous, accepting them to make use
of these means in solving problems on their own initiative. Curriculum usage
will empower student involvement and enhancing E-learning 2.0 spreading. This
paper, analyzing implementation E-learning 2.0 for Curriculum management and
discusses Opportunities & Challenges for Curriculum over Web 2.0.
| arxiv topic:cs.CY |
arxiv_dataset-18461004.266 | The topological K-theory of certain crystallographic groups
math.KT math.AT math.GT
Let Gamma be a semidirect product of the form Z^n rtimes Z/p where p is prime
and the Z/p-action on Z^n is free away from the origin. We will compute the
topological K-theory of the real and complex group C*-algebra of Gamma and show
that Gamma satisfies the unstable Gromov-Lawson-Rosenberg Conjecture. On the
way we will analyze the (co-)homology and the topological K-theory of the
classifying spaces BGamma and underbar{B}Gamma. The latter is the quotient of
the induced Z/p-action on the torus T^n.
| arxiv topic:math.KT math.AT math.GT |
arxiv_dataset-18471004.276 | Harmonic coordinates in the string and membrane equations
math-ph math.MP
In this note, we first show that the solutions to Cauchy problems for two
versions of relativistic string and membrane equations are diffeomorphic. Then
we investigate the coordinates transformation presented in Ref. [9] (see (2.20)
in Ref. [9]) which plays an important role in the study on the dynamics of the
motion of string in Minkowski space. This kind of transformed coordinates are
harmonic coordinates, and the nonlinear relativistic string equations can be
straightforwardly simplified into linear wave equations under this
transformation.
| arxiv topic:math-ph math.MP |
arxiv_dataset-18481004.286 | Behavioural Correlation for Detecting P2P Bots
cs.AI cs.CR cs.NE
In the past few years, IRC bots, malicious programs which are remotely
controlled by the attacker through IRC servers, have become a major threat to
the Internet and users. These bots can be used in different malicious ways such
as issuing distributed denial of services attacks to shutdown other networks
and services, keystrokes logging, spamming, traffic sniffing cause serious
disruption on networks and users. New bots use peer to peer (P2P) protocols
start to appear as the upcoming threat to Internet security due to the fact
that P2P bots do not have a centralized point to shutdown or traceback, thus
making the detection of P2P bots is a real challenge. In response to these
threats, we present an algorithm to detect an individual P2P bot running on a
system by correlating its activities. Our evaluation shows that correlating
different activities generated by P2P bots within a specified time period can
detect these kind of bots.
| arxiv topic:cs.AI cs.CR cs.NE |
arxiv_dataset-18491004.296 | The Abundance Pattern of O, Ne, Mg, and Fe in the Interstellar Medium of
S0 Galaxy NGC 4382 Observed with Suzaku
astro-ph.CO
We derived O, Ne, and Mg abundances in the interstellar medium (ISM) of a
relatively isolated S0 galaxy, NGC 4382, observed with the Suzaku XIS
instruments and compared the O/Ne/Mg/Fe abundance pattern to those of the ISM
in elliptical galaxies. The derived temperature and Fe abundance in the ISM are
about 0.3 keV and 0.6--2.9 solar, respectively. The abundance ratios are
derived with a better accuracy than the abundances themselves: O/Fe, Ne/Fe, and
Mg/Fe ratios are 0.3, 0.7, and 0.6, respectively, in solar units. The O/Fe
ratio is smaller than that of the ISM in elliptical galaxies, NGC 720, NGC
1399, NGC 1404, and NGC 4636, observed with Suzaku. Since O, Ne, and Mg are
predominantly synthesized by supernovae (SNe) of type II, the observed
abundance pattern indicates that the contribution of SN Ia products is higher
in the S0 galaxy than in the elliptical galaxies Since the hot ISM in
early-type galaxies is an accumulation of stellar mass and SN Ia products, the
low O/Fe ratio in the ISM of NGC 4382 reflects a higher rate of present SNe Ia,
or stars containing more SN Ia products than those in elliptical galaxies.
| arxiv topic:astro-ph.CO |
arxiv_dataset-18501004.306 | Controlling the transverse instability of dark solitons and nucleation
of vortices by a potential barrier
cond-mat.quant-gas nlin.PS
We study possibilities to suppress the transverse modulational instability
(MI) of dark-soliton stripes in two-dimensional (2D) Bose-Einstein condensates
(BECs) and self-defocusing bulk optical waveguides by means of quasi-1D
structures. Adding an external repulsive barrier potential (which can be
induced in BEC by a laser sheet, or by an embedded plate in optics), we
demonstrate that it is possible to reduce the MI wavenumber band, and even
render the dark-soliton stripe completely stable. Using this method, we
demonstrate the control of the number of vortex pairs nucleated by each spatial
period of the modulational perturbation. By means of the perturbation theory,
we predict the number of the nucleated vortices per unit length. The analytical
results are corroborated by the numerical computation of eigenmodes of small
perturbations, as well as by direct simulations of the underlying
Gross-Pitaevskii/nonlinear Schr\"{o}dinger equation.
| arxiv topic:cond-mat.quant-gas nlin.PS |
arxiv_dataset-18511004.316 | Synchronization time in a hyperbolic dynamical system with long-range
interactions
nlin.CD
We show that the threshold of complete synchronization in a lattice of
coupled non-smooth chaotic maps is determined by linear stability along the
directions transversal to the synchronization subspace. We examine carefully
the sychronization time and show that a inadequate observation of the system
evolution leads to wrong results. We present both careful numerical experiments
and a rigorous mathematical explanation confirming this fact, allowing for a
generalization involving hyperbolic coupled map lattices.
| arxiv topic:nlin.CD |
arxiv_dataset-18521004.326 | Decision Support Systems (DSS) in Construction Tendering Processes
cs.AI
The successful execution of a construction project is heavily impacted by
making the right decision during tendering processes. Managing tender
procedures is very complex and uncertain involving coordination of many tasks
and individuals with different priorities and objectives. Bias and inconsistent
decision are inevitable if the decision-making process is totally depends on
intuition, subjective judgement or emotion. In making transparent decision and
healthy competition tendering, there exists a need for flexible guidance tool
for decision support. Aim of this paper is to give a review on current
practices of Decision Support Systems (DSS) technology in construction
tendering processes. Current practices of general tendering processes as
applied to the most countries in different regions such as United States,
Europe, Middle East and Asia are comprehensively discussed. Applications of
Web-based tendering processes is also summarised in terms of its properties.
Besides that, a summary of Decision Support System (DSS) components is included
in the next section. Furthermore, prior researches on implementation of DSS
approaches in tendering processes are discussed in details. Current issues
arise from both of paper-based and Web-based tendering processes are outlined.
Finally, conclusion is included at the end of this paper.
| arxiv topic:cs.AI |
arxiv_dataset-18531004.336 | Structure formation in $f(R)$ gravity: A distinguishing probe between
the dark energy and modified gravity
astro-ph.CO gr-qc
In this work, we study the large scale structure formation in the modified
gravity in the framework of Palatini formalism and compare the results with the
equivalent smooth dark energy models as a tool to distinguish between these
models. Through the inverse method, we reconstruct the dynamics of universe,
modified gravity action and the structure formation indicators like the
screened mass function and gravitational slip parameter. Consequently, we
extract the matter density power spectrum for these two models in the linear
regime and show that the modified gravity and dark energy models predictions
are slightly different from each other at large scales. It is also shown that
the growth index in the modified gravity unlike to the dark energy models is a
scale dependent parameter. We also compare the results with those from the
modified gravity in the metric formalism. The modification on the structure
formation can also change the CMB spectrum at large scales however due to the
cosmic variance it is hard to detect this signature. We show that a large
number of SNIa data in the order of 2000 will enable us to reconstruct the
modified gravity action with a suitable confidence level and test the cosmic
acceleration models by the structure formation.
| arxiv topic:astro-ph.CO gr-qc |
arxiv_dataset-18541004.346 | PCA 4 DCA: The Application Of Principal Component Analysis To The
Dendritic Cell Algorithm
cs.AI cs.NE
As one of the newest members in the field of artificial immune systems (AIS),
the Dendritic Cell Algorithm (DCA) is based on behavioural models of natural
dendritic cells (DCs). Unlike other AIS, the DCA does not rely on training
data, instead domain or expert knowledge is required to predetermine the
mapping between input signals from a particular instance to the three
categories used by the DCA. This data preprocessing phase has received the
criticism of having manually over-?tted the data to the algorithm, which is
undesirable. Therefore, in this paper we have attempted to ascertain if it is
possible to use principal component analysis (PCA) techniques to automatically
categorise input data while still generating useful and accurate classication
results. The integrated system is tested with a biometrics dataset for the
stress recognition of automobile drivers. The experimental results have shown
the application of PCA to the DCA for the purpose of automated data
preprocessing is successful.
| arxiv topic:cs.AI cs.NE |
arxiv_dataset-18551004.356 | Comparison of the Performance of Two Service Disciplines for a Shared
Bus Multiprocessor with Private Caches
cs.PF
In this paper, we compare two analytical models for evaluation of cache
coherence overhead of a shared bus multiprocessor with private caches. The
models are based on a closed queuing network with different service
disciplines. We find that the priority discipline can be used as a lower-level
bound. Some numerical results are shown graphically.
| arxiv topic:cs.PF |
arxiv_dataset-18561004.366 | About flavor, spin and color
hep-ph hep-th
Chiral symmetry breaking (restoration) for SU(N) gauge theories is a topic of
great interest and not yet fully explained. We consider the phenomenon as a
collective spin effect and determine its behavior in terms of the number of
flavors, N_f.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-18571004.376 | Dynamically-Driven Star Formation In Models Of NGC 7252
astro-ph.CO
We present new dynamical models of the merger remnant NGC 7252 which include
star formation simulated according to various phenomenological rules. By using
interactive software to match our model with the observed morphology and gas
velocity field, we obtain a consistent dynamical model for NGC 7252. In our
models, this proto-elliptical galaxy formed by the merger of two similar
gas-rich disk galaxies which fell together with an initial pericentric
separation of ~2 disk scale lengths approximately 620 Myr ago. Results from two
different star formation rules--- density-dependent and shock-induced--- show
significant differences in star formation during and after the first passage.
Shock-induced star formation yields a prompt and wide-spread starburst at the
time of first passage, while density-dependent star formation predicts a more
slowly rising and centrally concentrated starburst. A comparison of the
distributions and ages of observed clusters with results of our simulations
favors shock-induced mechanism of star formation in NGC 7252. We also present
simulated color images of our model of NGC 7252, constructed by incorporating
population synthesis with radiative transfer and dust attenuation. Overall the
predicted magnitudes and colors of the models are consistent with observations,
although the simulated tails are fainter and redder than observed. We suggest
that a lack of star formation in the tails, reflected by the redder colors, is
due to an incomplete description of star formation in our models rather than
insufficient gas in the tails.
| arxiv topic:astro-ph.CO |
arxiv_dataset-18581004.386 | Algebraic renormalization of supersymmetric gauge theories with
dimensionful parameters
hep-th hep-lat hep-ph
It is usually believed that there are no perturbative anomalies in
supersymmetric gauge theories beyond the well-known chiral anomaly. In this
paper we revisit this issue, because previously given arguments are incomplete.
Specifically, we rule out the existence of soft anomalies, i.e., quantum
violations of supersymmetric Ward identities proportional to a mass parameter
in a classically supersymmetric theory. We do this by combining a previously
proven theorem on the absence of hard anomalies with a spurion analysis, using
the methods of Algebraic Renormalization. We work in the on-shell component
formalism throughout. In order to deal with the nonlinearity of on-shell
supersymmetry transformations, we take the spurions to be dynamical, and show
how they nevertheless can be decoupled.
| arxiv topic:hep-th hep-lat hep-ph |
arxiv_dataset-18591004.396 | Spin current in topologically trivial and nontrivial noncentrosymmetric
superconductors
cond-mat.supr-con
We study theoretically the surface of time-reversal-symmetric,
noncentrosymmetric superconductor with mixed singlet and triplet order
parameters. A pair of counterpropagating subgap quasiparticle surface bound
states with opposite spin projections are obtained in the nontrivial Z$_2$ case
where the triplet component is larger than the singlet one, contributing to a
spin current. In contrast to the pure p-wave cases, these subgap states do not
have a fixed spin projections but depend on the momenta along the surface. In
the trivial Z$_2$ case where the singlet order parameter is larger, no subgap
surface bound states show up. In both cases, there is also a finite
contribution to the spin current from the continuum states with energies
between the two gaps. The method for obtaining the quasiclassical Green's
functions associated with the noncentrosymmetric superconductors is also
presented.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-18601004.406 | The axiom of {\theta}-holomorphic 2-planes in the almost Hermitian
geometry
math.DG
The axiom of {\theta}-holomorphic 2-planes is introduced. It is proved, that
if an almost Hermitian manifold satisfies this axiom for a fixed {\theta}, 0<
{\theta}< {\pi}/2, then it is a real space form.
| arxiv topic:math.DG |
arxiv_dataset-18611004.416 | Lectures on neutrino phenomenology
hep-ph hep-ex
The fundamental properties of the lepton sector include the neutrino masses
and flavor mixings. Both are difficult to observe because of the extremely
small neutrino masses and neutrino-matter cross sections. In these lectures, we
focus on the basic concepts for the determination of neutrino properties. We
introduce neutrino oscillations as standard mechanism for neutrino flavor
changes, and we discuss methods to measure the neutrino mass. Furthermore, we
illustrate how precision measurements in neutrino oscillations will be
performed in the future, and may even open a window to new physics properties,
such as motivated by LHC physics. Finally, we discuss some applications of
neutrinos in astrophysics, such as neutrino oscillations in the Sun. We also
illustrate how neutrinos from extragalactic cosmic accelerators may be used for
the determination of neutrino properties.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-18621004.426 | The yoga of schemic Grothendieck rings, a topos-theoretical approach
math.AG math.KT math.LO
We propose a suitable substitute for the classical Grothendieck ring of an
algebraically closed field, in which any quasi-projective scheme is
represented, while maintaining its non-reduced structure. This yields a more
subtle invariant, called the schemic Grothendieck ring, in which we can
formulate a form of integration resembling Kontsevich's motivic integration via
arc schemes. Whereas the original construction was via definability, we have
translated in this paper everything into a topos-theoretic framework.
| arxiv topic:math.AG math.KT math.LO |
arxiv_dataset-18631004.436 | Tree cumulants and the geometry of binary tree models
math.ST stat.TH
In this paper we investigate undirected discrete graphical tree models when
all the variables in the system are binary, where leaves represent the
observable variables and where all the inner nodes are unobserved. A novel
approach based on the theory of partially ordered sets allows us to obtain a
convenient parametrization of this model class. The construction of the
proposed coordinate system mirrors the combinatorial definition of cumulants. A
simple product-like form of the resulting parametrization gives insight into
identifiability issues associated with this model class. In particular, we
provide necessary and sufficient conditions for such a model to be identified
up to the switching of labels of the inner nodes. When these conditions hold,
we give explicit formulas for the parameters of the model. Whenever the model
fails to be identified, we use the new parametrization to describe the geometry
of the unidentified parameter space. We illustrate these results using a simple
example.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-18641004.446 | Handling Overload Conditions In High Performance Trustworthy Information
Retrieval Systems
cs.IR
Web search engines retrieve a vast amount of information for a given search
query. But the user needs only trustworthy and high-quality information from
this vast retrieved data. The response time of the search engine must be a
minimum value in order to satisfy the user. An optimum level of response time
should be maintained even when the system is overloaded. This paper proposes an
optimal Load Shedding algorithm which is used to handle overload conditions in
real-time data stream applications and is adapted to the Information Retrieval
System of a web search engine. Experiment results show that the proposed
algorithm enables a web search engine to provide trustworthy search results to
the user within an optimum response time, even during overload conditions.
| arxiv topic:cs.IR |
arxiv_dataset-18651004.456 | A Simple Polynomial Algorithm for the Longest Path Problem on
Cocomparability Graphs
cs.DM
Given a graph $G$, the longest path problem asks to compute a simple path of
$G$ with the largest number of vertices. This problem is the most natural
optimization version of the well known and well studied Hamiltonian path
problem, and thus it is NP-hard on general graphs. However, in contrast to the
Hamiltonian path problem, there are only few restricted graph families such as
trees and some small graph classes where polynomial algorithms for the longest
path problem have been found. Recently it has been shown that this problem can
be solved in polynomial time on interval graphs by applying dynamic programming
to a characterizing ordering of the vertices of the given graph
\cite{longest-int-algo}, thus answering an open question. In the present paper,
we provide the first polynomial algorithm for the longest path problem on a
much greater class, namely on cocomparability graphs. Our algorithm uses a
similar - but essentially simpler - dynamic programming approach, which is
applied to a Lexicographic Depth First Search (LDFS) characterizing ordering of
the vertices of a cocomparability graph. Therefore, our results provide
evidence that this general dynamic programming approach can be used in a more
general setting, leading to efficient algorithms for the longest path problem
on greater classes of graphs. LDFS has recently been introduced in
\cite{Corneil-LDFS08}. Since then, a similar phenomenon of extending an
existing interval graph algorithm to cocomparability graphs by using an LDFS
preprocessing step has also been observed for the minimum path cover problem
\cite{Corneil-MPC}. Therefore, more interestingly, our results also provide
evidence that cocomparability graphs present an interval graph structure when
they are considered using an LDFS ordering of their vertices, which may lead to
other new and more efficient combinatorial algorithms.
| arxiv topic:cs.DM |
arxiv_dataset-18661004.466 | Full Lensing Analysis of Abell 1703: Comparison of Independent
Lens-Modelling Techniques
astro-ph.CO
The inner mass-profile of the relaxed cluster Abell 1703 is analysed by two
very different strong-lensing techniques applied to deep ACS and WFC3 imaging.
Our parametric method has the accuracy required to reproduce the many sets of
multiple images, based on the assumption that mass approximately traces light.
We test this assumption with a fully non-parametric, adaptive grid method, with
no knowledge of the galaxy distribution. Differences between the methods are
seen on fine scales due to member galaxies which must be included in models
designed to search for lensed images, but on the larger scale the general
distribution of dark matter is in good agreement, with very similar radial mass
profiles. We add undiluted weak-lensing measurements from deep multi-colour
Subaru imaging to obtain a fully model-independent mass profile out to the
virial radius and beyond. Consistency is found in the region of overlap between
the weak and strong lensing, and the full mass profile is well-described by an
NFW model of a concentration parameter, $c_{\rm vir}\simeq 7.15\pm0.5$ (and
$M_{vir}\simeq 1.22\pm0.15 \times 10^{15}M_{\odot}/h$). Abell 1703 lies above
the standard $c$--$M$ relation predicted for the standard $\Lambda$CDM model,
similar to other massive relaxed clusters with accurately determined
lensing-based profiles.
| arxiv topic:astro-ph.CO |
arxiv_dataset-18671004.476 | Effects of misalignments in the optical vortex transformation performed
by holograms with embedded phase singularity
physics.optics
Spatial characteristics of diffracted beams produced by a "fork" hologram
from an incident circular Laguerre-Gaussian beam whose axis differ from the
hologram optical axis are studied theoretically. General analytical
representations for the complex amplitude distribution of a diffracted beam are
derived in terms of superposition of Kummer beams or hypergeometric-Gaussian
beams. The diffracted beam structure is determined by combination of the
"proper" topological charge m of the incident vortex beam and the topological
charge l of the singularity "imparted" by the hologram. Evolution of the
diffracted beam structure is studied in detail for several combinations of m
and l and for various incident beam displacements with respect to the optical
axis of the hologram. Variations of the intensity and phase distribution due to
the incident beam misalignment are investigated and possible applications for
the purposeful optical-vortex beam generation and optical measurements are
discussed.
| arxiv topic:physics.optics |
arxiv_dataset-18681004.486 | Coexistence and competition of magnetism and superconductivity on the
nanometer scale in underdoped BaFe1.89Co0.11As2
cond-mat.supr-con
We report muon spin rotation (muSR) and infrared (IR) spectroscopy
experiments on underdoped BaFe1.89Co0.11As2 which show that bulk magnetism and
superconductivity (SC) coexist and compete on the nanometer length scale. Our
combined data reveal a bulk magnetic order, likely due to an incommensurate
spin density wave (SDW), which develops below Tmag \approx 32 K and becomes
reduced in magnitude (but not in volume) below Tc = 21.7 K. A slowly
fluctuating precursor of the SDW seems to develop alrady below the structural
transition at Ts \approx 50 K. The bulk nature of SC is established by the muSR
data which show a bulk SC vortex lattice and the IR data which reveal that the
majority of low-energy states is gapped and participates in the condensate at T
<< Tc.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-18691004.496 | Shallow Circuits with High-Powered Inputs
cs.CC
A polynomial identity testing algorithm must determine whether an input
polynomial (given for instance by an arithmetic circuit) is identically equal
to 0. In this paper, we show that a deterministic black-box identity testing
algorithm for (high-degree) univariate polynomials would imply a lower bound on
the arithmetic complexity of the permanent. The lower bounds that are known to
follow from derandomization of (low-degree) multivariate identity testing are
weaker. To obtain our lower bound it would be sufficient to derandomize
identity testing for polynomials of a very specific norm: sums of products of
sparse polynomials with sparse coefficients. This observation leads to new
versions of the Shub-Smale tau-conjecture on integer roots of univariate
polynomials. In particular, we show that a lower bound for the permanent would
follow if one could give a good enough bound on the number of real roots of
sums of products of sparse polynomials (Descartes' rule of signs gives such a
bound for sparse polynomials and products thereof). In this third version of
our paper we show that the same lower bound would follow even if one could only
prove a slightly superpolynomial upper bound on the number of real roots. This
is a consequence of a new result on reduction to depth 4 for arithmetic
circuits which we establish in a companion paper. We also show that an even
weaker bound on the number of real roots would suffice to obtain a lower bound
on the size of depth 4 circuits computing the permanent.
| arxiv topic:cs.CC |
arxiv_dataset-18701004.506 | STDP-driven networks and the \emph{C. elegans} neuronal network
q-bio.NC nlin.CD
We study the dynamics of the structure of a formal neural network wherein the
strengths of the synapses are governed by spike-timing-dependent plasticity
(STDP). For properly chosen input signals, there exists a steady state with a
residual network. We compare the motif profile of such a network with that of a
real neural network of \emph{C. elegans} and identify robust qualitative
similarities. In particular, our extensive numerical simulations show that this
STDP-driven resulting network is robust under variations of the model
parameters.
| arxiv topic:q-bio.NC nlin.CD |
arxiv_dataset-18711004.516 | A Search for Scalar Chameleons with ADMX
astro-ph.CO
Scalar fields with a "chameleon" property, in which the effective particle
mass is a function of its local environment, are common to many theories beyond
the standard model and could be responsible for dark energy. If these fields
couple weakly to the photon, they could be detectable through the "afterglow"
effect of photon-chameleon-photon transitions. The ADMX experiment was used in
the first chameleon search with a microwave cavity to set a new limit on scalar
chameleon-photon coupling excluding values between 2*10^9 and 5*10^14 for
effective chameleon masses between 1.9510 and 1.9525 micro-eV.
| arxiv topic:astro-ph.CO |
arxiv_dataset-18721004.526 | Ground state at high density
cond-mat.other math-ph math.MP
Weak limits as the density tends to infinity of classical ground states of
integrable pair potentials are shown to minimize the mean-field energy
functional. By studying the latter we derive global properties of high-density
ground state configurations in bounded domains and in infinite space. Our main
result is a theorem stating that for interactions having a strictly positive
Fourier transform the distribution of particles tends to be uniform as the
density increases, while high-density ground states show some pattern if the
Fourier transform is partially negative. The latter confirms the conclusion of
earlier studies by Vlasov (1945), Kirzhnits and Nepomnyashchii (1971), and
Likos et al. (2007). Other results include the proof that there is no Bravais
lattice among high-density ground states of interactions whose Fourier
transform has a negative part and the potential diverges or has a cusp at zero.
We also show that in the ground state configurations of the penetrable sphere
model particles are superposed on the sites of a close-packed lattice.
| arxiv topic:cond-mat.other math-ph math.MP |
arxiv_dataset-18731004.536 | Acoustic Black Holes from Abelian Higgs Model with Lorentz Symmetry
Breaking
hep-th gr-qc hep-ph
In this paper we derive acoustic black hole metrics in the (3+1) and
(2+1)-dimensional Abelian Higgs model with Lorentz symmetry breaking. In this
set up the sound waves lose the Lorentz boost invariance and suffer a
'birefringence' effect. We have found acoustic black holes and respective
Hawking temperatures depending on the Lorentz violating parameter. Furthermore,
we obtain an acoustic Kerr-like black hole metric with the Lorentz violating
term affecting its rate of loss of mass. We also have shown that for suitable
values of the Lorentz violating parameter a wider spectrum of particle wave
function can be scattered with increased amplitude by the acoustic black hole.
| arxiv topic:hep-th gr-qc hep-ph |
arxiv_dataset-18741004.546 | Quasiparticle interference in the spin-density wave phase of iron-based
superconductors
cond-mat.supr-con cond-mat.str-el
We propose an explanation for the electronic nematic state observed recently
in parent iron-based superconductors [T.-M. Chuang et al., Science 327, 181
(2010)]. We argue that the quasi-one-dimensional nanostructure identified in
the quasiparticle interference (QPI) is a consequence of the interplay of the
magnetic ($\pi$, 0) spin-density wave (SDW) order with the underlying
electronic structure. We show that the evolution of the QPI peaks largely
reflects quasiparticle scattering between electronic bands involved in the SDW
formation. Because of the ellipticity of the electron pocket and the fact that
only one of the electron pockets is involved in the SDW, the resulting QPI has
a pronounced one-dimensional structure. We further predict that the QPI crosses
over to two-dimensionality on an energy scale, set by the SDW gap, which we
estimate from neutron scattering data to be around 90 meV.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-18751004.556 | Scalability of Atomic-Thin-Body (ATB) Transistors Based on Graphene
Nanoribbons
cond-mat.mes-hall
A general solution for the electrostatic potential in an atomic-thin-body
(ATB) field-effect transistor geometry is presented. The effective
electrostatic scaling length, {\lambda}eff, is extracted from the analytical
model, which cannot be approximated by the lowest order eigenmode as
traditionally done in SOI-MOSFETs. An empirical equation for the scaling length
that depends on the geometry parameters is proposed. It is shown that even for
a thick SiO2 back oxide {\lambda}eff can be improved efficiently by thinner top
oxide thickness, and to some extent, with high-k dielectrics. The model is then
applied to self-consistent simulation of graphene nanoribbon (GNR)
Schottky-barrier field-effect transistors (SB-FETs) at the ballistic limit. In
the case of GNR SB-FETs, for large {\lambda}eff, the scaling is limited by the
conventional electrostatic short channel effects (SCEs). On the other hand, for
small {\lambda}eff, the scaling is limited by direct source-to-drain tunneling.
A subthreshold swing below 100mV/dec is still possible with a sub-10nm gate
length in GNR SB-FETs.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-18761005.0058 | Linear solutions for cryptographic nonlinear sequence generators
cs.CR
This letter shows that linear Cellular Automata based on rules 90/150
generate all the solutions of linear difference equations with binary constant
coefficients. Some of these solutions are pseudo-random noise sequences with
application in cryptography: the sequences generated by the class of shrinking
generators. Consequently, this contribution show that shrinking generators do
not provide enough guarantees to be used for encryption purposes. Furthermore,
the linearization is achieved through a simple algorithm about which a full
description is provided.
| arxiv topic:cs.CR |
arxiv_dataset-18771005.0158 | Elastic Time Reversal Mirror Experiment in a Mesoscopic Natural Medium
at the Low Noise Underground Laboratory of Rustrel, France
physics.geo-ph
A seismic time reversal experiment based on Time Reversal Mirror (TRM)
technique was conducted in the mesoscopically scaled medium at the LSBB
Laboratory, France. Two sets of 50 Hz geophones were distributed at one meter
intervals in two horizontal and parallel galleries 100 m apart, buried 250 m
below the surface. The shot source used was a 4 kg sledgehammer. Analysis shows
that elastic seismic energy is refocused in space and time to the shot
locations with good accuracy. The refocusing ability of seismic energy to the
shot locations is roughly achieved for the direct field, and with excellent
quality, for the early and later coda. Hyper-focussing is achieved at the shot
points as a consequence of the fine scale randomly heterogeneous medium between
the galleries. TRM experiment is sensitive to the roughness of the mirror used.
Roughness induces a slight experimental discrepancy between recording and
re-emitting directions degrading the quality of the reversal process.
| arxiv topic:physics.geo-ph |
arxiv_dataset-18781005.0258 | CMF models of hot star winds I. Test of the Sobolev approximation in the
case of pure line transitions
astro-ph.SR
We provide hot star wind models with radiative force calculated using the
solution of comoving frame (CMF) radiative transfer equation. The wind models
are calculated for the first stars, O stars, and the central stars of planetary
nebulae. We show that without line overlaps and with solely thermal line
broadening the pure Sobolev approximation provides a reliable estimate of the
radiative force even close to the wind sonic point. Consequently, models with
the Sobolev line force provide good approximations to solutions obtained with
non-Sobolev transfer. Taking line overlaps into account, the radiative force
becomes slightly lower, leading to a decrease in the wind mass-loss rate by
roughly 40%. Below the sonic point, the CMF line force is significantly lower
than the Sobolev one. In the case of pure thermal broadening, this does not
influence the mass-loss rate, as the wind mass-loss rate is set in the
supersonic part of the wind. However, when additional line broadening is
present (e.g., the turbulent one) the region of low CMF line force may extend
outwards to the regions where the mass-loss rate is set. This results in a
decrease in the wind mass-loss rate. This effect can at least partly explain
the low wind mass-loss rates derived from some observational analyses of
luminous O stars.
| arxiv topic:astro-ph.SR |
arxiv_dataset-18791005.0358 | Nearby Lagrangians with vanishing Maslov class are homotopy equivalent
math.SG math.GT
We prove that the inclusion of every closed exact Lagrangian with vanishing
Maslov class in a cotangent bundle is a homotopy equivalence. We start by
adapting an idea of Fukaya-Seidel-Smith to prove that such a Lagrangian is
equivalent to the zero section in the Fukaya category with integral
coefficients. We then study an extension of the Fukaya category in which
Lagrangians equipped with local systems of arbitrary dimension are admitted as
objects, and prove that this extension is generated, in the appropriate sense,
by local systems over a cotangent fibre. Whenever the cotangent bundle is
simply connected, this generation statement implies that the universal covering
of every closed exact Lagrangian of vanishing Maslov index is trivial. Finally,
we borrow ideas from coarse geometry to develop a Fukaya category associated to
the universal cover, allowing us to prove the result in the general case.
| arxiv topic:math.SG math.GT |
arxiv_dataset-18801005.0458 | Interacting multi-component exciton gases in a potential trap: phase
separation and Bose-Einstein condensation
cond-mat.quant-gas
The system under consideration is a multi-component gas of interacting para-
and orthoexcitons confined in a three dimensional potential trap. We calculate
the spatially resolved optical emission spectrum due to interband transitions
involving weak direct and phonon mediated exciton-photon interactions. For each
component, the occurrence of a Bose-Einstein condensate changes the spectrum in
a characteristic way so that it directly reflects the constant chemical
potential of the excitons and the renormalization of the quasiparticle
excitation spectrum. Moreover, the interaction between the components leads, in
dependence on temperature and particle number, to modifications of the spectra
indicating phase separation of the subsystems. Typical examples of density
profiles and luminescence spectra of ground-state para- and orthoexcitons in
cuprous oxide are given.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-18811005.0558 | Torsion of elliptic curves over quadratic cyclotomic fields
math.NT
In this paper we study the possible torsions of elliptic curves over $\mathbb
Q(i)$ and $\mathbb Q(\sqrt {-3})$.
| arxiv topic:math.NT |
arxiv_dataset-18821005.0658 | On the sum of two integral squares in certain quadratic fields
math.NT
In this note, we give a necessary and sufficient condition for determining
which integers can be written as a sum of two integral squares for certain
quadratic fields by using the integral Brauer-manin obstruction (see
\cite{CTX}). The condition is computable and originally from the reciprocity
law.
| arxiv topic:math.NT |
arxiv_dataset-18831005.0758 | Canonical and microcanonical ensemble descriptions of thermal pairing
within BCS and quasiparticle RPA
nucl-th
We propose a description of pairing properties in finite systems within the
canonical and microcanonical ensembles. The approach is derived by solving the
BCS and self-consistent quasiparticle random-phase approximation with the
Lipkin-Nogami particle-number projection at zero temperature. The obtained
eigenvalues are embedded into the canonical and microcanonical ensembles. The
results obtained are found in quite good agreement with the exact solutions of
the doubly-folded equidistant multilevel pairing model as well as the
experimental data for $^{56}$Fe nucleus. The merit of the present approach
resides in its simplicity and its application to a wider range of particle
number, where the exact solution is impracticable.
| arxiv topic:nucl-th |
arxiv_dataset-18841005.086 | Phase Fluctuations near the Chiral Critical Point
nucl-th
The Helmholtz free energy density is parametrized as a function of
temperature and baryon density near the chiral critical point of QCD. The
parametrization incorporates the expected critical exponents and amplitudes. An
expansion away from equilibrium states is achieved with Landau theory. This is
used to calculate the probability that the system is found at a density other
than the equilibrium one. Such fluctuations are predicted to be very large in
heavy ion collisions.
| arxiv topic:nucl-th |
arxiv_dataset-18851005.096 | A logic road from special relativity to general relativity
gr-qc math-ph math.LO math.MP
We present a streamlined axiom system of special relativity in first-order
logic. From this axiom system we "derive" an axiom system of general relativity
in two natural steps. We will also see how the axioms of special relativity
transform into those of general relativity. This way we hope to make general
relativity more accessible for the non-specialist.
| arxiv topic:gr-qc math-ph math.LO math.MP |
arxiv_dataset-18861005.106 | The Pulsar Search Collaboratory
astro-ph.SR astro-ph.IM
The Pulsar Search Collaboratory [PSC, NSF #0737641] is a joint project
between the National Radio Astronomy Observatory (NRAO) and West Virginia
University (WVU) designed to interest high school students in science,
technology, engineering, and mathematics [STEM] related career paths by helping
them to conduct authentic scientific research. The 3- year PSC program, which
began in summer 2008, teaches students to analyze astronomical radio data
acquired with the 100-m Robert C. Byrd Green Bank Telescope for the purpose of
discovering new pulsars. We present the results of the first complete year of
the PSC, which includes two astronomical discoveries.
| arxiv topic:astro-ph.SR astro-ph.IM |
arxiv_dataset-18871005.116 | Algebraic hulls of solvable groups and exponential iterated integrals on
solvmanifolds
math.GT math.GR
We represent the coordinate ring of algebraic hulls (which are
generalizations of the Malcev completions of nilpotent groups for solvable
groups) of solvmanifolds $G/\Gamma$ by using Miller's exponential iterated
integrals (which are extensions of Chen's iterated integrals) of invariant
differential forms.
| arxiv topic:math.GT math.GR |
arxiv_dataset-18881005.126 | M-ideals of homogeneous polynomials
math.FA
We study the problem of whether $\mathcal{P}_w(^nE)$, the space of
$n$-homogeneous polynomials which are weakly continuous on bounded sets, is an
$M$-ideal in the space of continuous $n$-homogeneous polynomials
$\mathcal{P}(^nE)$. We obtain conditions that assure this fact and present some
examples. We prove that if $\mathcal{P}_w(^nE)$ is an $M$-ideal in
$\mathcal{P}(^nE)$, then $\mathcal{P}_w(^nE)$ coincides with
$\mathcal{P}_{w0}(^nE)$ ($n$-homogeneous polynomials that are weakly continuous
on bounded sets at 0). We introduce a polynomial version of property $(M)$ and
derive that if $\mathcal{P}_w(^nE)=\mathcal{P}_{w0}(^nE)$ and $\mathcal{K}(E)$
is an $M$-ideal in $\mathcal{L}(E)$, then $\mathcal{P}_w(^nE)$ is an $M$-ideal
in $\mathcal{P}(^nE)$. We also show that if $\mathcal{P}_w(^nE)$ is an
$M$-ideal in $\mathcal{P}(^nE)$, then the set of $n$-homogeneous polynomials
whose Aron-Berner extension do not attain the norm is nowhere dense in
$\mathcal{P}(^nE)$. Finally, we face an analogous $M$-ideal problem for block
diagonal polynomials.
| arxiv topic:math.FA |
arxiv_dataset-18891005.136 | Optimal dividend and investing control of a insurance company with
higher solvency constraints
q-fin.RM math.OC math.PR
This paper considers optimal control problem of a large insurance company
under a fixed insolvency probability. The company controls proportional
reinsurance rate, dividend pay-outs and investing process to maximize the
expected present value of the dividend pay-outs until the time of bankruptcy.
This paper aims at describing the optimal return function as well as the
optimal policy. As a by-product, the paper theoretically sets a risk-based
capital standard to ensure the capital requirement of can cover the total risk.
| arxiv topic:q-fin.RM math.OC math.PR |
arxiv_dataset-18901005.146 | New Gauge Symmetry in Gravity and the Evanescent Role of Torsion
gr-qc
If the Einstein-Hilbert action ${\cal L}_{\rm EH}\propto R$ is re-expressed
in Riemann-Cartan spacetime using the gauge fields of translations, the
vierbein field $h^\alpha{}_\mu$, and the gauge field of local Lorentz
transformations, the spin connection $A_{\mu \alpha}{}^ \beta $, there exists a
new gauge symmetry which permits reshuffling the torsion, partially or totally,
into the Cartan curvature term of the Einstein tensor, and back, via a {\em new
multivalued gauge transformation\/}. Torsion can be chosen at will by an
arbitrary gauge fixing functional. There exist many equivalent ways of
specifing the theory, for instance Einstein's traditional way where ${\cal
L}_{\rm EH}$ is expressed completely in terms of the metric $g_{\mu \nu}=h^
\alpha {}_\mu h_ \alpha {}_ \nu $, and the torsion is zero, or Einstein's
teleparallel formulation, where ${\cal L}_{\rm EH}$ is expressed in terms of
the torsion tensor, or an infinity of intermediate ways. As far as the
gravitational field in the far-zone of a celestial object is concerned, matter
composed of spinning particles can be replaced by matter with only orbital
angular momentum, without changing the long-distance forces, no matter which of
the various new gauge representations is used.
| arxiv topic:gr-qc |
arxiv_dataset-18911005.156 | Computation using Noise-based Logic: Efficient String Verification over
a Slow Communication Channel
cs.IT math.IT physics.gen-ph
Utilizing the hyperspace of noise-based logic, we show two string
verification methods with low communication complexity. One of them is based on
continuum noise-based logic. The other one utilizes noise-based logic with
random telegraph signals where a mathematical analysis of the error probability
is also given. The last operation can also be interpreted as computing
universal hash functions with noise-based logic and using them for string
comparison. To find out with 10^-25 error probability that two strings with
arbitrary length are different (this value is similar to the error probability
of an idealistic gate in today's computer) Alice and Bob need to compare only
83 bits of the noise-based hyperspace.
| arxiv topic:cs.IT math.IT physics.gen-ph |
arxiv_dataset-18921005.166 | Vortices as nurseries for planetesimal formation in protoplanetary discs
astro-ph.EP astro-ph.GA
Turbulent, two-dimensional, hydrodynamic flows are characterized by the
emergence of coherent, long-lived vortices without a need to invoke special
initial conditions. Vortices have the ability to sequester particles, with
typical radii from about 1 mm to 10 cm, that are slightly decoupled from the
gas. A generic feature of discs with surface density and effective temperature
profiles that are decreasing, power-law functions of radial distance is that
four vortex zones exist for a fixed particle size. In particular, two of the
zones form an annulus at intermediate radial distances within which small
particles reside. Particle capture by vortices occurs on a dynamical time scale
near and at the boundaries of this annulus. As the disc ages and the particles
grow via coagulation, the size of the annulus shrinks. Older discs prefer to
capture smaller particles because the gas surface density decreases with time,
a phenomenon we term "vortex aging". More viscous, more dust-opaque and/or less
massive discs can have vortices that age faster and trap a broader range of
particle sizes throughout the lifetime of the disc. Thus, how efficiently a
disc retains its mass in solids depends on the relative time scales between
coagulation and vortex aging. If vortices form in protoplanetary discs, they
are important in discs with typical masses and for particles that are likely to
condense out of the protostellar nebula. Particle capture also occurs at
distances relevant to planet formation. Future infrared, submillimetre and
centimetre observations of grain opacity as a function of radial distance will
test the hypothesis that vortices serve as nurseries for particle growth in
protoplanetary discs.
| arxiv topic:astro-ph.EP astro-ph.GA |
arxiv_dataset-18931005.176 | Two stock options at the races: Black-Scholes forecasts
q-fin.ST math.PR q-fin.GN q-fin.PR
Suppose one buys two very similar stocks and is curious about how much, after
some time T, one of them will contribute to the overall asset, expecting, of
course, that it should be around 1/2 of the sum. Here we examine this question
within the classical Black and Scholes (BS) model, focusing on the evolution of
the probability density function P(w) of a random variable w =
a_T^{(1)}/(a_T^{(1)} + a_T^{(2)}) where a_T^{(1)} and a_T^{(2)} are the values
of two (either European- or the Asian-style) options produced by two absolutely
identical BS stochastic equations. We show that within the realm of the BS
model the behavior of P(w) is surprisingly different from common-sense-based
expectations. For the European-style options P(w) always undergoes a
transition, (when T approaches a certain threshold value), from a unimodal to a
bimodal form with the most probable values being close to 0 and 1, and,
strikingly, w =1/2 being the least probable value. This signifies that the
symmetry between two options spontaneously breaks and just one of them
completely dominates the sum. For path-dependent Asian-style options we observe
the same anomalous behavior, but only for a certain range of parameters.
Outside of this range, P(w) is always a bell-shaped function with a maximum at
w = 1/2.
| arxiv topic:q-fin.ST math.PR q-fin.GN q-fin.PR |
arxiv_dataset-18941005.186 | Feature Selection Using Regularization in Approximate Linear Programs
for Markov Decision Processes
cs.AI
Approximate dynamic programming has been used successfully in a large variety
of domains, but it relies on a small set of provided approximation features to
calculate solutions reliably. Large and rich sets of features can cause
existing algorithms to overfit because of a limited number of samples. We
address this shortcoming using $L_1$ regularization in approximate linear
programming. Because the proposed method can automatically select the
appropriate richness of features, its performance does not degrade with an
increasing number of features. These results rely on new and stronger sampling
bounds for regularized approximate linear programs. We also propose a
computationally efficient homotopy method. The empirical evaluation of the
approach shows that the proposed method performs well on simple MDPs and
standard benchmark problems.
| arxiv topic:cs.AI |
arxiv_dataset-18951005.196 | From high-mass starless cores to high-mass protostellar objects
astro-ph.SR
Aims: Our aim is to understand the evolutionary sequence of high-mass star
formation from the earliest evolutionary stage of high-mass starless cores, via
high-mass cores with embedded low- to intermediate-mass objects, to finally
high-mass protostellar objects. Methods: Herschel far-infrared PACS and SPIRE
observations are combined with existing data at longer and shorter wavelengths
to characterize the spectral and physical evolution of massive star-forming
regions. Results: The new Herschel images spectacularly show the evolution of
the youngest and cold high-mass star-forming regions from mid-infrared shadows
on the Wien-side of the spectral energy distribution (SED), via structures
almost lost in the background emission around 100mum, to strong emission
sources at the Rayleigh-Jeans tail. Fits of the SEDs for four exemplary regions
covering evolutionary stages from high-mass starless cores to high-mass
protostellar objects reveal that the youngest regions can be fitted by
single-component black-bodies with temperatures on the order of 17K. More
evolved regions show mid-infrared excess emission from an additional warmer
component, which however barely contributes to the total luminosities for the
youngest regions. Exceptionally low values of the ratio between bolometric and
submm luminosity additionally support the youth of the infrared-dark sources.
Conclusions: The Herschel observations reveal the spectral and physical
properties of young high-mass star-forming regions in detail. The data clearly
outline the evolutionary sequence in the images and SEDs. Future work on larger
samples as well as incorporating full radiative transfer calculations will
characterize the physical nature at the onset of massive star formation in even
more depth.
| arxiv topic:astro-ph.SR |
arxiv_dataset-18961005.206 | First observations of a dome-shaped large-scale coronal EUV wave
astro-ph.SR
We present first observations of a dome-shaped large-scale EUV coronal wave,
recorded by the EUVI instrument onboard STEREO-B on January 17, 2010. The main
arguments that the observed structure is the wave dome (and not the CME) are:
a) the spherical form and sharpness of the dome's outer edge and the erupting
CME loops observed inside the dome; b) the low-coronal wave signatures above
the limb perfectly connecting to the on-disk signatures of the wave; c) the
lateral extent of the expanding dome which is much larger than that of the
coronal dimming; d) the associated high-frequency type II burst indicating
shock formation low in the corona. The velocity of the upward expansion of the
wave dome ($v \sim 650$ km s$^{-1}$) is larger than that of the lateral
expansion of the wave ($v \sim 280$ km s$^{-1}$), indicating that the upward
dome expansion is driven all the time, and thus depends on the CME speed,
whereas in the lateral direction it is freely propagating after the CME lateral
expansion stops. We also examine the evolution of the perturbation
characteristics: First the perturbation profile steepens and the amplitude
increases. Thereafter, the amplitude decreases with r$^{-2.5 \pm 0.3}$, the
width broadens, and the integral below the perturbation remains constant. Our
findings are consistent with the spherical expansion and decay of a weakly
shocked fast-mode MHD wave.
| arxiv topic:astro-ph.SR |
arxiv_dataset-18971005.216 | On complete integrability of the Mikhailov-Novikov-Wang system
nlin.SI math-ph math.MP
We obtain compatible Hamiltonian and symplectic structure for a new
two-component fifth-order integrable system recently found by Mikhailov,
Novikov and Wang (arXiv:0712.1972), and show that this system possesses a
hereditary recursion operator and infinitely many commuting symmetries and
conservation laws, as well as infinitely many compatible Hamiltonian and
symplectic structures, and is therefore completely integrable. The system in
question admits a reduction to the Kaup--Kupershmidt equation.
| arxiv topic:nlin.SI math-ph math.MP |
arxiv_dataset-18981005.226 | Quantitative embedded contact homology
math.SG
Define a "Liouville domain" to be a compact exact symplectic manifold with
contact-type boundary. We use embedded contact homology to assign to each
four-dimensional Liouville domain (or subset thereof) a sequence of real
numbers, which we call "ECH capacities". The ECH capacities of a Liouville
domain are defined in terms of the "ECH spectrum" of its boundary, which
measures the amount of symplectic action needed to represent certain classes in
embedded contact homology. Using cobordism maps on embedded contact homology
(defined in joint work with Taubes), we show that the ECH capacities are
monotone with respect to symplectic embeddings. We compute the ECH capacities
of ellipsoids, polydisks, certain subsets of the cotangent bundle of T2, and
disjoint unions of examples for which the ECH capacities are known. The
resulting symplectic embedding obstructions are sharp in some interesting
cases, for example for the problem of embedding an ellipsoid into a ball (as
shown by work of McDuff-Schlenk) or embedding a disjoint union of balls into a
ball. We also state and present evidence for a conjecture under which the
asymptotics of the ECH capacities of a Liouville domain recover its symplectic
volume.
| arxiv topic:math.SG |
arxiv_dataset-18991005.236 | Are Superfluid Vortices in Pulsars Violating the Weak Equivalence
Principle?
gr-qc astro-ph.SR cond-mat.other
In the present paper we argue that timing irregularities in pulsars, like
glitches and timing noise, could be associated with the violation of the weak
equivalence principle for vortices in the superfluid core of rotating neutron
stars.
| arxiv topic:gr-qc astro-ph.SR cond-mat.other |
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