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arxiv_dataset-1400908.2229 | The topology of systems of hyperspaces determined by dimension functions
math.GN math.AT
Given a non-degenerate Peano continuum $X$, a dimension function
$D:2^X_*\to[0,\infty]$ defined on the family $2^X_*$ of compact subsets of $X$,
and a subset $\Gamma\subset[0,\infty)$, we recognize the topological structure
of the system $(2^X,\D_{\le\gamma}(X))_{\alpha\in\Gamma}$, where $2^X$ is the
hyperspace of non-empty compact subsets of $X$ and $D_{\le\gamma}(X)$ is the
subspace of $2^X$, consisting of non-empty compact subsets $K\subset X$ with
$D(K)\le\gamma$.
| arxiv topic:math.GN math.AT |
arxiv_dataset-1401908.2329 | A Stellar Flare during the Transit of the Extrasolar Planet OGLE-TR-10b
astro-ph.EP astro-ph.SR
We report a stellar flare occurring during a transit of the exoplanet
OGLE-TR-10b, an event not previously reported in the literature. This reduces
the observed transit depth, particularly in the u'-band, but flaring could also
be significant in other bands and could lead to incorrect planetary parameters.
We suggest that OGLE-TR-10a is an active planet-hosting star and has an
unusually high X-ray luminosity.
| arxiv topic:astro-ph.EP astro-ph.SR |
arxiv_dataset-1402908.2429 | A New Approach to Searching for Dark Matter Signals in Fermi-LAT Gamma
Rays
astro-ph.HE
Several cosmic ray experiments have measured excesses in electrons and
positrons, relative to standard backgrounds, for energies from ~ 10 GeV - 1
TeV. These excesses could be due to new astrophysical sources, but an
explanation in which the electrons and positrons are dark matter annihilation
or decay products is also consistent. Fortunately, the Fermi-LAT diffuse gamma
ray measurements can further test these models, since the electrons and
positrons produce gamma rays in their interactions in the interstellar medium.
Although the dark matter gamma ray signal consistent with the local electron
and positron measurements should be quite large, as we review, there are
substantial uncertainties in the modeling of diffuse backgrounds and,
additionally, experimental uncertainties that make it difficult to claim a dark
matter discovery. In this paper, we introduce an alternative method for
understanding the diffuse gamma ray spectrum in which we take the intensity
ratio in each energy bin of two different regions of the sky, thereby canceling
common systematic uncertainties. For many spectra, this ratio fits well to a
power law with a single break in energy. The two measured exponent indices are
a robust discriminant between candidate models, and we demonstrate that dark
matter annihilation scenarios can predict index values that require "extreme"
parameters for background-only explanations.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1403908.2529 | A Low-Overhead Energy Detection Based Cooperative Sensing Protocol for
Cognitive Radio Systems
cs.IT math.IT
Cognitive radio and dynamic spectrum access represent a new paradigm shift in
more effective use of limited radio spectrum. One core component behind dynamic
spectrum access is the sensing of primary user activity in the shared spectrum.
Conventional distributed sensing and centralized decision framework involving
multiple sensor nodes is proposed to enhance the sensing performance. However,
it is difficult to apply the conventional schemes in reality since the overhead
in sensing measurement and sensing reporting as well as in sensing report
combining limit the number of sensor nodes that can participate in distributive
sensing. In this paper, we shall propose a novel, low overhead and low
complexity energy detection based cooperative sensing framework for the
cognitive radio systems which addresses the above two issues. The energy
detection based cooperative sensing scheme greatly reduces the quiet period
overhead (for sensing measurement) as well as sensing reporting overhead of the
secondary systems and the power scheduling algorithm dynamically allocate the
transmission power of the cooperative sensor nodes based on the channel
statistics of the links to the BS as well as the quality of the sensing
measurement. In order to obtain design insights, we also derive the asymptotic
sensing performance of the proposed cooperative sensing framework based on the
mobility model. We show that the false alarm and mis-detection performance of
the proposed cooperative sensing framework improve as we increase the number of
cooperative sensor nodes.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-1404908.2629 | All quiet in the outer halo: chemical abundances in the globular cluster
Pal 3
astro-ph.GA
Context: Globular clusters (GCs) in the outer halo are important probes of
the composition and origin of the Galactic stellar halo.
Aims: We derive chemical element abundance ratios in red giants belonging to
the remote (R~90 kpc) GC Pal 3 and compare our measurements to those for red
giant stars in both inner and outer halo GCs.
Methods: From high-resolution spectroscopy of four red giants, obtained with
the Magellan/MIKE spectrograph at moderately high S/N, we derive chemical
abundances for 25 alpha-, iron peak-, and neutron-capture elements. These
abundance ratios are confirmed by co-adding low S/N HIRES spectra of 19 stars
along the red giant branch.
Results: Pal 3 shows alpha-enhanced abundance patterns, and also its Fe-peak
and neutron-capture element ratios, are fully compatible with those found in
halo field stars and representative inner halo GCs of the same metallicity
(such as M 13). The heavy elements in Pal 3 appear to be governed by r-process
nucleosyn-thesis. Our limited sample does not show any significant star-to-star
abundance variations in this cluster, although a weak Na-O anti-correlation
cannot be ruled out by the present data.
Conclusions: Pal 3 thus appears as an archetypical GC with abundance ratios
dissimilar to dwarf spheroidal stars, ruling out a direct connection to such
external systems. This conclusion is underscored by the lack of significant
abundance spreads in this GC, in contrast to the broad abundance distributions
seen in the dwarf galaxies. Pal 3 appears to have evolved chemically coeval
with the majority of GCs belonging to Galactic inner and outer halo,
experiencing a similar enrichment history.
| arxiv topic:astro-ph.GA |
arxiv_dataset-1405908.2729 | Indefinite almost paracontact metric manifolds
math.DG math-ph math.MP
In this paper we introduce the concept of $(\varepsilon)$-almost paracontact
manifolds, and in particular, of $(\varepsilon)$-para Sasakian manifolds.
Several examples are presented. Some typical identities for curvature tensor
and Ricci tensor of $(\varepsilon)$-para Sasakian manifolds are obtained. We
prove that if a semi-Riemannian manifold is one of flat, proper recurrent or
proper Ricci-recurrent, then it can not admit an $(\varepsilon)$-para Sasakian
structure. We show that, for an $(\varepsilon)$-para Sasakian manifold, the
conditions of being symmetric, semi-symmetric or of constant sectional
curvature are all identical. It is shown that a symmetric spacelike (resp.
timelike) $(\varepsilon)$-para Sasakian manifold $M^{n}$ is locally isometric
to a pseudohyperbolic space $H_{\nu}^{n}(1)$ (resp. pseudosphere
$S_{\nu}^{n}(1)$). In last, it is proved that for an $(\varepsilon)$-para
Sasakian manifold, the conditions of being Ricci-semisymmetric, Ricci-symmetric
and Einstein are all identical.
| arxiv topic:math.DG math-ph math.MP |
arxiv_dataset-1406908.2829 | The quantum N-body problem and the auxiliary field method
math-ph hep-ph math.MP
Approximate analytical energy formulas for N-body relativistic Hamiltonians
with one- and two-body interactions are obtained within the framework of the
auxiliary field method. This method has already been proved to be a powerful
technique in the case of two-body problems. A general procedure is given and
applied to various Hamiltonians of interest, in atomic and hadronic physics in
particular. A test of formulas is performed for baryons described as a
three-quark system.
| arxiv topic:math-ph hep-ph math.MP |
arxiv_dataset-1407908.2929 | Repeating head-on collisions in an optical trap and the evaluation of
spin-dependent interactions among neutral particles
cond-mat.other
A dynamic process of repeating collisions of a pair of trapped neutral
particles with weak spin-dependent interaction is designed and studied. Related
theoretical derivation and numerical calculation have been performed to study
the inherent coordinate-spin and momentum-spin correlation. Due to the
repeating collisions the effect of the weak interaction can be accumulated and
enlarged, and therefore can be eventually detected. Numerical results suggest
that the Cr-Cr interaction, which has not yet been completely clear, could be
thereby determined. The design can be in general used to determine various
interactions among neutral atoms and molecules, in particular for the
determination of very weak forces.
| arxiv topic:cond-mat.other |
arxiv_dataset-1408908.3029 | T-duality and the weakly coupled heterotic string
hep-th
T-duality is a symmetry of the heterotic string to all orders in string
perturbation theory. This results in an effective four dimensional supergravity
theory with desirable features for phenomenology. T-duality, as well as,
generically, an anomalous U(1), is broken by quantum anomalies of the effective
field theory. The structure of the full anomaly is presented, and the
mechanisms for anomaly cancellation are described.
| arxiv topic:hep-th |
arxiv_dataset-1409908.3129 | Magnetooptic enhancement and magnetic properties in Fe antidot films
with hexagonal symmetry
cond-mat.mes-hall
The magnetooptic and magnetic properties of hexagonal arrays of holes in
optically thin iron films are presented. We analyze their dependence on the
hole radius and compare the results to a continuous iron film of same
thickness. We observe a large enhancement of the magnetooptic Kerr rotation
with respect to that of the continuous film, at frequecies where surface
plasmons excitations are expected. Additional simulations are in very good
agreement with the experiment and thus confirm the effect of the surface
plasmons on the Kerr rotation. The altering of the magnetic properties by the
hole array is also visible in the hysteretic behavior of the sample where a
dramatic change is observed.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-1410908.3229 | Perelman's collapsing theorem for 3-manifolds
math.DG math.GT
We will simplify the earlier proofs of Perelman's collapsing theorem of
3-manifolds given by Shioya-Yamaguchi and Morgan-Tian.
Among other things, we use Perelman's semi-convex analysis of distance
functions to construct the desired local Seifert fibration structure on
collapsed 3-manifolds. The verification of Perelman's collapsing theorem is the
last step of Perelman's proof of Thurston's Geometrization Conjecture on the
classification of 3-manifolds.
Our proof of Perelman's collapsing theorem is almost self-contained. We
believe that our proof of this collapsing theorem is accessible to non-experts
and advanced graduate students.
| arxiv topic:math.DG math.GT |
arxiv_dataset-1411908.3329 | Symmetries in Linear and Integer Programs
math.CO math.OC
The notion of symmetry is defined in the context of Linear and Integer
Programming. Symmetric linear and integer programs are studied from a group
theoretical viewpoint. We show that for any linear program there exists an
optimal solution in the fixed point set of its symmetry group. Using this
result, we develop an algorithm that allows for reducing the dimension of any
linear program having a non-trivial group of symmetries.
| arxiv topic:math.CO math.OC |
arxiv_dataset-1412908.3429 | A Sharp Bilinear Estimate for the Bourgain-type Space with Application
to the Benjamin Equation
math.AP
This note shows the existence of a sharp bilinear estimate for the
Bourgain-type space and gives its application to the optimal local
well/ill-posedness of the Cauchy problem for the Benjamin equation.
| arxiv topic:math.AP |
arxiv_dataset-1413908.3529 | Variable Metric Stochastic Approximation Theory
physics.data-an
We provide a variable metric stochastic approximation theory. In doing so, we
provide a convergence theory for a large class of online variable metric
methods including the recently introduced online versions of the BFGS algorithm
and its limited-memory LBFGS variant. We also discuss the implications of our
results for learning from expert advice.
| arxiv topic:physics.data-an |
arxiv_dataset-1414908.3629 | Critical random graphs: limiting constructions and distributional
properties
math.PR math.CO
We consider the Erdos-Renyi random graph G(n,p) inside the critical window,
where p = 1/n + lambda * n^{-4/3} for some lambda in R. We proved in a previous
paper (arXiv:0903.4730) that considering the connected components of G(n,p) as
a sequence of metric spaces with the graph distance rescaled by n^{-1/3} and
letting n go to infinity yields a non-trivial sequence of limit metric spaces C
= (C_1, C_2, ...). These limit metric spaces can be constructed from certain
random real trees with vertex-identifications. For a single such metric space,
we give here two equivalent constructions, both of which are in terms of more
standard probabilistic objects. The first is a global construction using
Dirichlet random variables and Aldous' Brownian continuum random tree. The
second is a recursive construction from an inhomogeneous Poisson point process
on R_+. These constructions allow us to characterize the distributions of the
masses and lengths in the constituent parts of a limit component when it is
decomposed according to its cycle structure. In particular, this strengthens
results of Luczak, Pittel and Wierman by providing precise distributional
convergence for the lengths of paths between kernel vertices and the length of
a shortest cycle, within any fixed limit component.
| arxiv topic:math.PR math.CO |
arxiv_dataset-1415908.3729 | A minimal model linking two great mysteries: neutrino mass and dark
matter
hep-ph
We present an economic model that establishes a link between neutrino masses
and properties of the dark matter candidate. The particle content of the model
can be divided into two groups: light particles with masses lighter than the
electroweak scale and heavy particles. The light particles, which also include
the dark matter candidate, are predicted to show up in the low energy
experiments such as $(K\to \ell +{\rm missing energy})$, making the model
testable. The heavy sector can show up at the LHC and may give rise to
Br($\ell_i \to \ell_j \gamma$) close to the present bounds. In principle, the
new couplings of the model can independently be derived from the data from the
LHC and from the information on neutrino masses and Lepton Flavor Violating
(LFV) rare decays, providing the possibility of an intensive cross-check of the
model.
| arxiv topic:hep-ph |
arxiv_dataset-1416908.3829 | A lower bound for eigenvalues of a clamped plate problem
math.DG math.AP
In this paper, we study eigenvalues of a clamped plate problem. We obtain a
lower bound for eigenvalues, which gives an important improvement of results
due to Levine and Protter.
| arxiv topic:math.DG math.AP |
arxiv_dataset-1417908.3929 | A Dynamic Boundary Guarding Problem with Translating Targets
cs.RO
We introduce a problem in which a service vehicle seeks to guard a deadline
(boundary) from dynamically arriving mobile targets. The environment is a
rectangle and the deadline is one of its edges. Targets arrive continuously
over time on the edge opposite the deadline, and move towards the deadline at a
fixed speed. The goal for the vehicle is to maximize the fraction of targets
that are captured before reaching the deadline. We consider two cases; when the
service vehicle is faster than the targets, and; when the service vehicle is
slower than the targets. In the first case we develop a novel vehicle policy
based on computing longest paths in a directed acyclic graph. We give a lower
bound on the capture fraction of the policy and show that the policy is optimal
when the distance between the target arrival edge and deadline becomes very
large. We present numerical results which suggest near optimal performance away
from this limiting regime. In the second case, when the targets are slower than
the vehicle, we propose a policy based on servicing fractions of the
translational minimum Hamiltonian path. In the limit of low target speed and
high arrival rate, the capture fraction of this policy is within a small
constant factor of the optimal.
| arxiv topic:cs.RO |
arxiv_dataset-1418908.4029 | Turning big bang into big bounce: II. Quantum dynamics
gr-qc astro-ph.CO hep-th quant-ph
We analyze the big bounce transition of the quantum FRW model in the setting
of the nonstandard loop quantum cosmology (LQC). Elementary observables are
used to quantize composite observables. The spectrum of the energy density
operator is bounded and continuous. The spectrum of the volume operator is
bounded from below and discrete. It has equally distant levels defining a
quantum of the volume. The discreteness may imply a foamy structure of
spacetime at semiclassical level which may be detected in astro-cosmo
observations. The nonstandard LQC method has a free parameter that should be
fixed in some way to specify the big bounce transition.
| arxiv topic:gr-qc astro-ph.CO hep-th quant-ph |
arxiv_dataset-1419908.4129 | Outflow Feedback Regulated Massive Star Formation in Parsec-Scale
Cluster Forming Clumps
astro-ph.SR
(Abridged) We investigate massive star formation in turbulent, magnetized,
parsec-scale clumps of molecular clouds including protostellar outflow feedback
using Enzo-based MHD simulations with accreting sink particles and effective
resolution $2048^3$. We find that, in the absence of regulation by magnetic
fields and outflow feedback, massive stars form readily in a turbulent,
moderately condensed clump of $\sim 1,600$ solar masses, along with a cluster
of hundreds of lower mass stars. The massive stars are fed at high rates by (1)
transient dense filaments produced by large-scale turbulent compression at
early times, and (2) by the clump-wide global collapse resulting from
turbulence decay at late times. In both cases, the bulk of the massive star's
mass is supplied from outside a 0.1 pc-sized "core" that surrounds the star. In
our simulation, the massive star is clump-fed rather than core-fed. The need
for large-scale feeding makes the massive star formation prone to regulation by
outflow feedback, which directly opposes the feeding processes. The outflows
reduce the mass accretion rates onto the massive stars by breaking up the dense
filaments that feed the massive star formation at early times, and by
collectively slowing down the global collapse that fuel the massive star
formation at late times. The latter is aided by a moderate magnetic field of
strength in the observed range. We conclude that the massive star formation in
our simulated turbulent, magnetized, parsec-scale clump is outflow-regulated
and clump-fed (ORCF for short). An important implication is that the formation
of low-mass stars in a dense clump can affect the formation of massive stars in
the same clump, through their outflow feedback on the clump dynamics.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1420908.4229 | Will NIF Work
cond-mat.mtrl-sci physics.plasm-ph
It is vital that new clean and abundant sources of energy be developed for
the sustainability of modern society. Nuclear fusion of the hydrogen isotopes
deuterium and tritium, if successful, might make a major contribution toward
satisfying this need. The U.S. has an important effort aimed at achieving
practical inertial confinement fusion, ICF, which has been under development
for decades at the Lawrence Livermore National Laboratory. The National
Ignition Facility (NIF) is a giant laser to multiply-shock and thus
quasi-isentropically compress a capsule of deuterium-tritium (DT) to high
density and temperature, where the fusion rate is proportional to density
squared times temperature to the fourth power. The principal problem that must
be solved for NIF to work successfully is elimination of the Rayleigh-Tailor
(R-T) instability that originates from the interface between the solid shell
and the DT fuel within it. The R-T instability poisons the fusion reaction by
reducing the temperature of the DT achieved by dynamic compression driven by
the NIF laser. The primary technological problem today is one of Condensed
Matter and Materials Physics (CMMP), rather than laser technology and plasma
physics. The CMMP of the fuel capsule that must be done to minimize growth of
the R-T instability is yet to be done. Based on what is known today, it is
unlikely that NIF will produce practical amounts of fusion energy.
| arxiv topic:cond-mat.mtrl-sci physics.plasm-ph |
arxiv_dataset-1421908.4329 | The Observational Implications of Loop Quantum Cosmology
gr-qc astro-ph.CO hep-th
In this paper we consider realistic model of inflation embedded in the
framework of loop quantum cosmology. Phase of inflation is preceded here by the
phase of a quantum bounce. We show how parameters of inflation depend on the
initial conditions established in the contracting, pre-bounce phase. Our
investigations indicate that phase of the bounce easily sets proper initial
conditions for the inflation. Subsequently we study observational effects that
might arise due to the quantum gravitational modifications. We perform
preliminary observational constraints for the Barbero-Immirzi parameter
$\gamma$, critical density $\rho_{\text{c}}$ and parameter $\lambda$. In the
next step we study effects on power spectrum of perturbations. We calculate
spectrum of perturbations from the bounce and from the joined bounce+inflation
phase. Based on these studies we indicate possible way to relate quantum
cosmological models with the astronomical observations. Using the Sachs-Wolfe
approximation we calculate spectrum of the super-horizontal CMB anisotropies.
We show that quantum cosmological effects can, in the natural way, explain
suppression of the low CMB multipoles. We show that fine-tuning is not required
here and model is consistent with observations. We also analyse other possible
probes of the quantum cosmologies and discuss perspectives of their
implementation.
| arxiv topic:gr-qc astro-ph.CO hep-th |
arxiv_dataset-1422908.4429 | On the Perturbative Expansion around a Lifshitz Point
hep-th cond-mat.str-el
The quantum Lifshitz model provides an effective description of a quantum
critical point. It has been shown that even though non--Lorentz invariant, the
action admits a natural supersymmetrization. In this note we introduce a
perturbative framework and show how the supersymmetric structure can be used to
greatly simplify the Feynman rules and thus the study of the model.
| arxiv topic:hep-th cond-mat.str-el |
arxiv_dataset-1423908.4529 | Effect of the reverse shock on the parameters of the observed X-Ray
emission during the 1998 outburst of CI Cam
astro-ph.HE
Based on the model of interaction between spherically symmetrical expanding
matter and the external medium, we have estimated the parameters of the matter
heated by the shock that was produced in the envelope ejected by the explosion
of a classical nova during its interaction with the stellar wind from the
optical companion. Using this model, we have shown that the matter ejected
during the outburst in the system CI Cam had no steep velocity gradients and
that the reverse shock could heat the ejected matter only to a temperature of
~0.1 keV. Therefore, this matter did not contribute to the mean temperature and
luminosity of the system observed in the energy range 3-20 keV.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1424909.0032 | A New Distance to M33 Using Blue Supergiants and the FGLR Method
astro-ph.CO astro-ph.GA
The quantitative spectral analysis of medium resolution optical spectra of A
and B supergiants obtained with DEIMOS and ESI at the Keck Telescopes is used
to determine a distance modulus of 24.93 +/- 0.11 mag for the Triangulum Galaxy
M33. The analysis yields stellar effective temperatures, gravities,
interstellar reddening, and extinction, the combination of which provides a
distance estimate via the Flux-weighted Gravity--Luminosity Relationship
(FGLR). This result is based on an FGLR calibration that is continually being
polished. An average reddening of <E(B-V)> ~ 0.08 mag is found, with a large
variation ranging from 0.01 to 0.16 mag however, demonstrating the importance
of accurate individual reddening measurements for stellar distance indicators
in galaxies with evident signatures of interstellar absorption. The large
distance modulus found is in good agreement with recent work on eclipsing
binaries, planetary nebulae, long period variables, RR Lyrae stars, and also
with HST observations of Cepheids, if reasonable reddening assumptions are made
for the Cepheids. Since distances based on the tip of the red giant branch
(TRGB) method found in the literature give conflicting results, we have used
HST ACS V- and I-band images of outer regions of M 33 to determine a TRGB
distance of 24.84 +/- 0.10 mag, in basic agreement with the FGLR result. We
have also determined stellar metallicities and discussed the metallicity
gradient in the disk of M33. We find metallicity of $Z_\odot$ at the center and
0.3 $Z_\odot$ in the outskirts at a distance of one isophotal radius. The
average logarithmic metallicity gradient is -0.07 +/- 0.01 dex kpc^-1. However,
there is a large scatter around this average value, very similar to what has
been found for the HII regions in M33.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-1425909.0132 | Breaking the self-averaging properties of spatial galaxy fluctuations in
the Sloan Digital Sky Survey - Data Release Six
astro-ph.CO
Statistical analyses of finite sample distributions usually assume that
fluctuations are self-averaging, i.e. that they are statistically similar in
different regions of the given sample volume. By using the scale-length method,
we test whether this assumption is satisfied in several samples of the Sloan
Digital Sky Survey Data Release Six. We find that the probability density
function (PDF) of conditional fluctuations, filtered on large enough spatial
scales (i.e., r>30 Mpc/h), shows relevant systematic variations in different
sub-volumes of the survey. Instead for scales r<30 Mpc/h the PDF is
statistically stable, and its first moment presents scaling behavior with a
negative exponent around one. Thus while up to 30 Mpc/h galaxy structures have
well-defined power-law correlations, on larger scales it is not possible to
consider whole sample average quantities as meaningful and useful statistical
descriptors. This situation is due to the fact that galaxy structures
correspond to density fluctuations which are too large in amplitude and too
extended in space to be self-averaging on such large scales inside the sample
volumes: galaxy distribution is inhomogeneous up to the largest scales, i.e. r
~ 100 Mpc/h, probed by the SDSS samples. We show that cosmological corrections,
as K-corrections and standard evolutionary corrections, do not qualitatively
change the relevant behaviors. Finally we show that the large amplitude galaxy
fluctuations observed in the SDSS samples are at odds with the predictions of
the standard LCDM model of structure formation.(Abridged version).
| arxiv topic:astro-ph.CO |
arxiv_dataset-1426909.0232 | Megaparsec-Scale Triggers for Star Formation: Clusters and Filaments of
Galaxies in the Horologium-Reticulum Supercluster
astro-ph.CO
Specific indications of star-formation are presented within cluster and
filament galaxies that are members of the Horologium-Reticulum supercluster
(HRS, z ~0.06). These indicators arise from multi-wavelength observations,
primarily emission lines from optical spectroscopy and faint excess from radio
continuum (1.4 GHz) photometry. HRS galaxies exhibiting current star formation
are consistent with previous studies in that the star-forming populations
organize around megaparsec-scale filament axes as well as near the cluster
core. Therefore with support from optical photometry, mechanisms for triggering
star formation in these galaxies are most likely due to merger interactions in
lower density (and lower velocity) environments and possible bursts prior to
stripping within the higher density (and higher velocity) environments.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1427909.0332 | Speed limit on Neptune migration imposed by Saturn tilting
astro-ph.EP
In this Letter, we give new constraints on planet migration. They were
obtained under the assumption that Saturn's current obliquity is due to a
capture in resonance with Neptune's ascending node. If planet migration is too
fast, then Saturn crosses the resonance without being captured and it keeps a
small obliquity. This scenario thus gives a lower limit on the migration time
scale tau. We found that this boundary depends strongly on Neptune's initial
inclination. For two different migration types, we found that tau should be at
least greater than 7 Myr. This limit increases rapidly as Neptune's initial
inclination decreases from 10 to 1 degree. We also give an algorithm to know if
Saturn can be tilted for any migration law.
| arxiv topic:astro-ph.EP |
arxiv_dataset-1428909.0432 | Statistics of Galactic Supernova Remnants (continued)
astro-ph.HE
Our statistics on Galactic supernova remnants (SNRs) shows that the electrons
temperature ($T$) of hard X-ray and the shock waves traveling velocity
($\upsilon$) decreases with ages ($t$) for all-sort remnants. However, the
shock waves swept-up mass ($M_{su}$) of ISM increases with the age. Second, the
remnant radio fluxes ($S$) at 1 GHz increase slightly with ISM electrons
density ($n_0$). At last, the number distributions illustrate that the
supernovae (SNe) initial kinetic energy ($E_0$), hydrogen column density
($N_H$), electrons temperature (kT) of hard X-ray, magnetic field ($B$) and the
shock waves swept-up mass ($M_{su}$) of ISM mainly peaked at $(1 \sim 10)
\times 10^{50}$ ergs, $(1 \sim 10)\times 10^{21}$ cm$^{-2}$, a few KeV, 100
$\mu$G and 10$\sim$100 $M_{\odot}$, respectively.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1429909.0532 | The Effects of Gravitational Slip on the Higher-Order Moments of the
Matter Distribution
astro-ph.CO
Cosmological departures from general relativity offer a possible explanation
for the cosmic acceleration. To linear order, these departures (quantified by
the model-independent parameter $\varpi$, referred to as a `gravitational
slip') amplify or suppress the growth of structure in the universe relative to
what we would expect to see from a general relativistic universe lately
dominated by a cosmological constant. As structures collapse and become more
dense, linear perturbation theory is an inadequate descriptor of their
behavior, and one must extend calculations to non-linear order. If the effects
of gravitational slip extend to these higher orders, we might expect to see a
signature of $\varpi$ in the bispectrum of galaxies distributed on the sky. We
solve the equations of motion for non-linear perturbations in the presence of
gravitational slip and find that, while there is an effect on the bispectrum,
it is too weak to be detected with present galaxy surveys. We also develop a
formalism for incorporating scale dependence into our description of
gravitational slip.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1430909.0632 | Correlations between sneutrino-antisneutrino oscillations and signatures
at the LHC in anomaly-mediated supersymmetry breaking
hep-ph
Sneutrino-antisneutrino oscillation can be observed at the LHC by studying a
charge asymmetry of the leptons in the final states. In this talk, we
demonstrate this in the context of an anomaly-mediated supersymmetry breaking
model which can give rise to a large oscillation probability. The preferred
region of the parameter space is characterized by the presence of a sneutrino
next-to-lightest supersymmetric particle and a stau lightest supersymmetric
particle. We show that the signals studied here have certain correlations with
the pattern of the sneutrino oscillation.
| arxiv topic:hep-ph |
arxiv_dataset-1431909.0732 | A Step towards Software Corrective Maintenance Using RCM model
cs.SE
From the preliminary stage of software engineering, selection of appropriate
enforcement of standards remained a challenge for stakeholders during entire
cycle of software development, but it can lead to reduce the efforts desired
for software maintenance phase. Corrective maintenance is the reactive
modification of a software product performed after delivery to correct
discovered faults. Studies conducted by different researchers reveal that
approximately 50 to 75 percent of the effort is spent on maintenance, out of
which about 17 to 21 percent is exercised on corrective maintenance. In this
paper, authors proposed a RCM (Reduce Corrective Maintenance) model which
represents the implementation process of number of checklists to guide the
stakeholders of all phases of software development. These check lists will be
filled by corresponding stake holder of all phases before its start. More
precise usage of the check list in relevant phase ensures successful
enforcement of analysis, design, coding and testing standards for reducing
errors in operation stage. Moreover authors represent the step by step
integration of checklists in software development life cycle through RCM model.
| arxiv topic:cs.SE |
arxiv_dataset-1432909.0832 | Reducing quantum control for spin-spin entanglement distribution
quant-ph cond-mat.mes-hall
We present a protocol that sets maximum stationary entanglement between
remote spins through scattering of mobile mediators without initialization,
post-selection or feedback of the mediators' state. No time-resolved tuning is
needed and, counterintuitively, the protocol generates two-qubit singlet states
even when classical mediators are used. The mechanism responsible for such
effect is resilient against non-optimal coupling strengths and dephasing
affecting the spins. The scheme uses itinerant particles and scattering centres
and can be implemented in various settings. When quantum dots and photons are
used a striking result is found: injection of classical mediators, rather than
quantum ones, improves the scheme efficiency.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-1433909.0932 | General physical properties of bright Fermi blazars
astro-ph.CO astro-ph.HE
We studied all blazars of known redshift detected by the Fermi satellite
during its first three months survey. For the majority of them, pointed Swift
observations ensures a good multiwavelength coverage, enabling us to to
reliably construct their spectral energy distributions (SED). We model the SEDs
using a one-zone leptonic model and study the distributions of the derived
interesting physical parameters as a function of the observed gamma-ray
luminosity. We confirm previous findings concerning the relation of the
physical parameters with source luminosity which are at the origin of the
blazar sequence. The SEDs allow to estimate the luminosity of the accretion
disk for the majority of broad emitting line blazars, while for the line-less
BL Lac objects in the sample upper limits can be derived. We find a positive
correlation between the jet power and the luminosity of the accretion disk in
broad line blazars. In these objects we argue that the jet must be
proton-dominated, and that the total jet power is of the same order of (or
slightly larger than) the disk luminosity. We discuss two alternative scenarios
to explain this result.
| arxiv topic:astro-ph.CO astro-ph.HE |
arxiv_dataset-1434909.1032 | On generalized Born--Infeld electrodynamics
hep-th gr-qc hep-ph
The generalized Born--Infeld electrodynamics with two parameters is
investigated. In this model the propagation of a linearly polarized laser beam
in the external transverse magnetic field is considered. It was shown that
there is the effect of vacuum birefringence, and we evaluate induced
ellipticity. The upper bounds on the combination of parameters introduced from
the experimental data of BRST and PVLAS Collaborations were obtained. When two
parameters are equal to each other, we arrive at Born--Infeld electrodynamics
and the effect of vacuum birefringence vanishes. We find the canonical and
symmetrical Belinfante energy-momentum tensors. The trace of the
energy-momentum tensor is not zero and the dilatation symmetry is broken. The
four-divergence of the dilatation current is equal to the trace of the
Belinfante energy-momentum tensor and is proportional to the parameter (with
the dimension of the field strength) of the model. The dual symmetry is also
broken in the model considered.
| arxiv topic:hep-th gr-qc hep-ph |
arxiv_dataset-1435909.1132 | A Mapping Survey of Dense Clumps Associated with Embedded Clusters :
Evolutionary Stages of Cluster-Forming Clumps
astro-ph.GA astro-ph.SR
We have carried out a survey of the dense clumps associated with 14 embedded
clusters in the C^18O (J=1-0) line emission with the Nobeyama 45m telescope in
order to understand the formation and evolution of stellar clusters in dense
clumps of molecular clouds. We have selected these clusters at distances from
0.3 to 2.1kpc and have mapped about 6' X 6' to 10' X 10'regions (corresponding
to 3.8pc X 3.8pc at 2.1kpc) for all the clumps with 22" resolution
(corresponding to Jeans length at 2.1kpc). We have obtained dense clumps with
radii of 0.40-1.6pc, masses of 150-4600M_sun, and velocity widths in FWHM of
1.4-3.3kms^-1. Most of the clumps are found to be approximately in virial
equilibrium, which implies that C^18O gas represents parental dense clumps for
cluster formation. From the spatial relation between the distributions of
clumps and clusters, we classified C^18O clumps into three types (Type A, B,
and C). The C^18O clumps as classified into Type A have emission distributions
with a single peak at the stellar clusters and higher brightness contrast than
that of other target sources. Type B clumps have double or triple peaks which
are associated with the cluster and moderately high brightness contrast
structure. Type C clumps have also multiple peaks although they are not
associated with the cluster and low brightness contrast structure. We suggest
that our classification represents an evolutionary trend of cluster-forming
dense clumps because dense gas in molecular clouds is expected to be converted
into stellar constituents, or to be dispersed by stellar activities. Moreover,
although there is a scatter, we found a tendency that the SFEs of the dense
clumps increase from Type A to Type C, which also supports our scenario.
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-1436909.1232 | Real eigenvalues in non-Hermitian Hamilton quantum physics
quant-ph
The dynamics of open quantum systems is determined by avoided and true
crossings of eigenvalue trajectories of a non-Hermitian Hamiltonian. The phases
of the eigenfunctions are not rigid so that environmentally induced
spectroscopic redistribution processes may take place and a dynamical phase
transition may occur. Due to the formal equivalence between the quantum
mechanical Schr\"odinger equation and the optical wave equation in PT symmetric
lattices, the dynamics of the system is determined also in this case by avoided
and true crossings of eigenvalue trajectories of the non-Hermitian Hamiltonian.
In contrast to the eigenvalues characterizing an open quantum system, the
eigenvalues describing the PT symmetric optical lattice are real as long as the
influence of the environment (lattice) onto the optical wave equation is small.
In the regime of avoided level crossings, the symmetry is destroyed, the
eigenvalues become complex and a dynamical phase transition occurs similar as
in the open quantum system. The redistribution processes in the regime of
avoided level crossings allow to design systems with desired properties in a
broad parameter range.
| arxiv topic:quant-ph |
arxiv_dataset-1437909.1332 | Searching for a Gravitational Heating Signature in Nearby Luminous
Ellipticals
astro-ph.CO
We present a new deep optical study of a luminosity limited sample of nearby
elliptical galaxies, attempting to observe the effects of gravitational
interactions on the ISM of these objects. This study is motivated by recent
observations of M86, a nearby elliptical galaxy that shows possible evidence
for gas heating through a recent gravitational interaction. The complete sample
includes luminous ellipticals in clusters, groups and the field. For each of
the galaxies we objectively derive a tidal parameter which measures the
deviation of the stellar body from a smooth, relaxed model and find that 73% of
them show tidal disturbance signatures in their stellar bodies. This is the
first time that such an analysis is done on a statistically complete sample and
it confirms that elliptical galaxies continue to grow and evolve through
gravitational interactions even in the local Universe. Our study of ellipticals
in a wide range of interaction stages, along with available ISM data will
attempt to shed light on this possibly alternative mechanism for maintaining
the observed ISM temperatures of elliptical galaxies.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1438909.1432 | The effective force NL3 revisited
nucl-th
Covariant density functional theory based on the relativistic mean field
(RMF) Lagrangian with the parameter set NL3 has been used in the last ten years
with great success. Now we propose a modification of this parameter set, which
improves the description of the ground state properties of many nuclei and
simultaneously provides an excellent description of excited states with
collective character in spherical as well as in deformed nuclei.
| arxiv topic:nucl-th |
arxiv_dataset-1439909.1532 | Does Galactic Magnetic Field Disturb the Correlation of the Highest
Energy Cosmic Rays with their Sources?
astro-ph.HE astro-ph.CO
The propagation trajectories of the highest energy cosmic rays (HECRs) are
deflected by not only intergalactic magnetic field but also Galactic magnetic
field (GMF). These magnetic fields can weaken the positive correlation between
the arrival directions of HECRs and the positions of their sources. In order to
explore the effect of GMF on the expected correlation, we simulate the arrival
distribution of protons with the energy above $6 \times 10^{19}$ eV taking
several GMF models into account, and then test the correlation between the
protons and their sources assumed in the simulation. The dependence of the
correlation signals on GMF models are also investigated. The correlation can be
observed by accumulating $\sim 200$ protons in a half hemisphere. Typical
angular scale at which the positive signal of the correlation is maximized
depends on the spiral component of GMF models. That angular scale is $\sim 5^o$
for bisymmetric spiral (BS) GMF models and $\sim 7^o$ for axisymmetric spiral
(AS) GMF models if the number density of HECR sources, $n_s$, is $\sim 10^{-4}$
Mpc$^{-3}$. An additional vertical (dipole) component of GMF affects these
angular scale by $0.5^o$ - $1^o$. The difference between the correlation signal
for the BS models and that for the AS models is prominent in the northern sky.
Significance of the positive correlation depends on source distribution. The
probability that the number of simulated HECR events correlating with sources
is smaller than the number of random events correlating with the same sources
by chance is much less than $10^{-3}$ ($\sim 3\sigma$) in almost all the source
distributions with $n_s = 10^{-4}$ Mpc$^{-3}$ under 200 protons detection, but
$\sim 10\%$ of source distributions predicts the chance probability more than
$10^{-3}$ in the AS GMF model. In addition, we also briefly discuss the effect
of GMF for heavy-nuclei dominated composition.
| arxiv topic:astro-ph.HE astro-ph.CO |
arxiv_dataset-1440909.1632 | Sulfur Abundances in the Orion Association B Stars
astro-ph.SR
Sulfur abundances are derived for a sample of ten B main-sequence star
members of the Orion association. The analysis is based on LTE plane-parallel
model atmospheres and non-LTE line formation theory by means of a
self-consistent spectrum synthesis analysis of lines from two ionization states
of sulfur, SII and SIII. The observations are high-resolution spectra obtained
with the ARCES spectrograph at the Apache Point Observatory. The abundance
distribution obtained for the Orion targets is homogeneous within the expected
errors in the analysis: A(S)=7.15+/-0.05. This average abundance result is in
agreement with the recommended solar value (both from modelling of the
photospheres in 1-D and 3-D, and meteorites) and indicates that little, if any,
chemical evolution of sulfur has taken place in the last ~4.5 billion years.
The sulfur abundances of the young stars in Orion are found to agree well with
results for the Orion nebulae, and place strong constraints on the amount of
sulfur depletion onto grains as being very modest or nonexistent. The sulfur
abundances for Orion are consistent with other measurements at a similar
galactocentric radius: combined with previous results for other OB-type stars
produce a relatively shallow sulfur abundance gradient with a slope of
-0.037+/-0.012 dex/kpc.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1441909.1732 | Helices on del Pezzo surfaces and tilting Calabi-Yau algebras
math.RA math.AG
We study tilting for a class of Calabi-Yau algebras associated to helices on
Fano varieties. We do this by relating the tilting operation to mutations of
exceptional collections. For helices on del Pezzo surfaces the algebras are of
dimension three, and using an argument of Herzog, together with results of
Kuleshov and Orlov, we obtain a complete description of the tilting process in
terms of quiver mutations.
| arxiv topic:math.RA math.AG |
arxiv_dataset-1442909.1832 | Universality in the jamming limit for elongated hard particles in one
dimension
cond-mat.stat-mech
We study thermodynamics properties of a one dimensional gas of hard elongated
particles. The particle centers are restricted to a line, while they can rotate
in two-dimensional space. Correlations between orientations of the objects are
studied (by transfer matrix method) as a function of density and aspect ratio.
The behavior in the extreme high-density (jamming) limit is described by a few
universality classes depending on the object's shape. In particular, there is a
diverging correlation length when the contact point of adjacent objects is far
from the line along which their centers move, as for needles and rectangles.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-1443909.1932 | Optimal estimates for the gradient of harmonic functions in the
multidimensional half-space
math.AP math.CV
A representation of the sharp constant in a pointwise estimate of the
gradient of a harmonic function in a multidimensional half-space is obtained
under the assumption that function's boundary values belong to $L^p$. This
representation is concretized for the cases $p=1, 2,$ and $\infty$.
| arxiv topic:math.AP math.CV |
arxiv_dataset-1444909.2032 | The 10k zCOSMOS: morphological transformation of galaxies in the group
environment since z~1
astro-ph.CO
We study the evolution of galaxies inside and outside of the group
environment since z=1 using a large well defined set of groups and galaxies
from the zCOSMOS-bright redshift survey in the COSMOS field. The fraction of
galaxies with early-type morphologies increases monotonically with M_B
luminosity and stellar mass and with cosmic epoch. It is higher in the groups
than elsewhere, especially at later epochs. The emerging environmental effect
is superposed on a strong global mass-driven evolution, and at z~0.5 and
log(M*/Msol)~10.2, the "effect" of group environment is equivalent to (only)
about 0.2 dex in stellar mass or 2 Gyr in time. The stellar mass function of
galaxies in groups is enriched in massive galaxies. We directly determine the
transformation rates from late to early morphologies, and for transformations
involving colour and star formation indicators. The transformation rates are
systematically about twice as high in the groups as outside, or up to 3-4 times
higher correcting for infall and the appearance of new groups. The rates reach
values, for masses around the crossing mass 10^10.5 Msol, as high as
(0.3-0.7)/Gyr in the groups, implying transformation timescales of 1.4-3 Gyr,
compared with less than 0.2/Gyr, i.e. timescales >5 Gyr, outside of groups. All
three transformation rates decrease at higher stellar masses, and must decrease
also at the lower masses below 10^10 Msol which we cannot well probe. The rates
involving colour and star formation are consistently higher than those for
morphology, by a factor of about 50%. Our conclusion is that the
transformations which drive the evolution of the overall galaxy population
since z~1 must occur at a rate 2-4 times higher in groups than outside of them.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1445909.2132 | Kinetic Friction by a Small Number of Intervening Inelastic Particles
between Rough Surfaces
cond-mat.soft cond-mat.stat-mech
We investigate a mechanism of the appearance of kinetic friction in granular
materials. We consider a small number of intervening inelastic particles
between two rough surfaces as one of the simplest dynamical models to study
granular friction. The resistance force applied to the upper surface is
numerically calculated. We find that the resistance force F(t) is scaled as
F'(vt) for a small pulling velocity v. The time average F_0=<F(t)> in the limit
v->0 is not zero owing to the mutual collisions between the intervening
particles. The nonzero F_0 implies the appearance of kinetic friction in this
simple dynamical system.
| arxiv topic:cond-mat.soft cond-mat.stat-mech |
arxiv_dataset-1446909.2232 | Large Time existence For 1D Green-Naghdi equations
math.AP
We consider here the $1D $ Green-Naghdi equations that are commonly used in
coastal oceanography to describe the propagation of large amplitude surface
waves. We show that the solution of the Green-Naghdi equations can be
constructed by a standard Picard iterative scheme so that there is no loss of
regularity of the solution with respect to the initial condition.
| arxiv topic:math.AP |
arxiv_dataset-1447909.2332 | A Nonconformity Approach to Model Selection for SVMs
stat.ML stat.ME
We investigate the issue of model selection and the use of the nonconformity
(strangeness) measure in batch learning. Using the nonconformity measure we
propose a new training algorithm that helps avoid the need for Cross-Validation
or Leave-One-Out model selection strategies. We provide a new generalisation
error bound using the notion of nonconformity to upper bound the loss of each
test example and show that our proposed approach is comparable to standard
model selection methods, but with theoretical guarantees of success and faster
convergence. We demonstrate our novel model selection technique using the
Support Vector Machine.
| arxiv topic:stat.ML stat.ME |
arxiv_dataset-1448909.2432 | Optimal waveform estimation for classical and quantum systems via
time-symmetric smoothing. II. Applications to atomic magnetometry and Hardy's
paradox
quant-ph
The quantum smoothing theory [Tsang, Phys. Rev. Lett. 102, 250403 (2009);
Phys. Rev. A, in press (e-print arXiv:0906.4133)] is extended to account for
discrete jumps in the classical random process to be estimated, discrete
variables in the quantum system, such as spin, angular momentum, and photon
number, and Poissonian measurements, such as photon counting. The extended
theory is used to model atomic magnetometers and study Hardy's paradox in phase
space. In the phase-space picture of Hardy's proposed experiment, the
negativity of the predictive Wigner distribution is identified as the culprit
of the disagreement between classical reasoning and quantum mechanics.
| arxiv topic:quant-ph |
arxiv_dataset-1449909.2532 | Aller-retour vers l'inseparable
math.AG
We construct inseparable morphisms between curves of genus $\ge 2$ that are
degenerations of separable morphisms.
| arxiv topic:math.AG |
arxiv_dataset-1450909.2632 | Following the 2008 outburst decay of the black hole candidate H1743-322
in X-ray and radio
astro-ph.HE
In this Paper we report on radio (VLA and ATCA) and X-ray (RXTE, Chandra and
Swift) observations of the outburst decay of the transient black hole candidate
H1743-322 in early 2008. We find that the X-ray light curve followed an
exponential decay, leveling off towards its quiescent level. The exponential
decay timescale is ~4 days and the quiescent flux corresponds to a luminosity
of 3x10^32 (d/7.5 kpc)^2 erg/s. This together with the relation between
quiescent X-ray luminosity and orbital period reported in the literature
suggests that H1743-322 has an orbital period longer than ~10 hours. Both the
radio and X-ray light curve show evidence for flares. The radio - X-ray
correlation can be well described by a power-law with index ~0.18. This is much
lower than the index of 0.6-0.7 found for the decay of several black hole
transients before. The radio spectral index measured during one of the radio
flares while the source is in the low-hard state, is -0.5+-0.15, which
indicates that the radio emission is optically thin. This is unlike what has
been found before in black hole sources in the low-hard state. We attribute the
radio flares and the low index for the radio - X-ray correlation to the
presence of shocks downstream the jet flow, triggered by ejection events
earlier in the outburst. We find no evidence for a change in X-ray power law
spectral index during the decay, although the relatively high extinction of N_H
=2.3x10^22 cm^-2 limits the detected number of soft photons and thus the
accuracy of the spectral fits.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1451909.2732 | Relativistic Equilibrium Distribution by Relative Entropy Maximization
cond-mat.stat-mech
The equilibrium state of a relativistic gas has been calculated based on the
maximum entropy principle. Though the relativistic equilibrium state was long
believed to be the Juttner distribution, a number of papers have been published
in recent years proposing alternative equilibrium states. However, some of
these papers do not pay enough attention to the covariance of distribution
functions, resulting confusion in equilibrium states. Starting from a fully
covariant expression to avoid this confusion, it has been shown in the present
paper that the Juttner distribution is the maximum entropy state if we assume
the Lorentz symmetry.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-1452909.2832 | The first peptides: the evolutionary transition between prebiotic amino
acids and early proteins
q-bio.BM q-bio.PE
The issues we attempt to tackle here are what the first peptides did look
like when they emerged on the primitive earth, and what simple catalytic
activities they fulfilled. We conjecture that the early functional peptides
were short (3 to 8 amino acids long), were made of those amino acids, Gly, Ala,
Val and Asp, that are abundantly produced in many prebiotic synthesis
experiments and observed in meteorites, and that the neutralization of Asp's
negative charge is achieved by metal ions. We further assume that some traces
of these prebiotic peptides still exist, in the form of active sites in
present-day proteins. Searching these proteins for prebiotic peptide candidates
led us to identify three main classes of motifs, bound mainly to Mg^{2+} ions:
D(F/Y)DGD corresponding to the active site in RNA polymerases, DGD(G/A)D
present in some kinds of mutases, and DAKVGDGD in dihydroxyacetone kinase. All
three motifs contain a DGD submotif, which is suggested to be the common
ancestor of all active peptides. Moreover, all three manipulate phosphate
groups, which was probably a very important biological function in the very
first stages of life. The statistical significance of our results is supported
by the frequency of these motifs in today's proteins, which is three times
higher than expected by chance, with a P-value of 3 10^{-2}. The implications
of our findings in the context of the appearance of life and the possibility of
an experimental validation are discussed.
| arxiv topic:q-bio.BM q-bio.PE |
arxiv_dataset-1453909.2932 | Fluctuation Theorem, non linear response and the regularity of time
reversal symmetry
cond-mat.stat-mech
The Gallavotti - Cohen Fluctuation Theorem (FT) implies an infinite set of
identities between correlation functions that can be seen as a generalization
of Green Kubo formula to the nonlinear regime. As an application, we discuss a
perturbative check of the FT relation through these identities for a simple
Anosov reversible system; we find that the lack of differentiability of the
time reversal symmetry implies a violation of the Gallavotti - Cohen
fluctuation relation. Finally, a brief comparison with Lebowitz - Spohn FT is
reported.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-1454909.3032 | Measurement of dijet photoproduction for events with a leading neutron
at HERA
hep-ex
Differential cross sections for dijet photoproduction and this process in
association with a leading neutron, e+ + p -> e+ + jet + jet + X (+ n), have
been measured with the ZEUS detector at HERA using an integrated luminosity of
40 pb-1. The fraction of dijet events with a leading neutron was studied as a
function of different jet and event variables. Single- and double-differential
cross sections are presented as a function of the longitudinal fraction of the
proton momentum carried by the leading neutron, xL, and of its transverse
momentum squared, pT^2. The dijet data are compared to inclusive DIS and
photoproduction results; they are all consistent with a simple pion-exchange
model. The neutron yield as a function of xL was found to depend only on the
fraction of the proton beam energy going into the forward region, independent
of the hard process. No firm conclusion can be drawn on the presence of
rescattering effects.
| arxiv topic:hep-ex |
arxiv_dataset-1455909.3132 | Partial correlation analysis indicates causal relationships between
GC-content, exon density and recombination rate in the human genome
q-bio.GN q-bio.PE
{\bf Background}: Several features are known to correlate with the GC-content
in the human genome, including recombination rate, gene density and distance to
telomere. However, by testing for pairwise correlation only, it is impossible
to distinguish direct associations from indirect ones and to distinguish
between causes and effects. {\bf Results}: We use partial correlations to
construct partially directed graphs for the following four variables:
GC-content, recombination rate, exon density and distance-to-telomere.
Recombination rate and exon density are unconditionally uncorrelated, but
become inversely correlated by conditioning on GC-content. This pattern
indicates a model where recombination rate and exon density are two independent
causes of GC-content variation. {\bf Conclusions}: Causal inference and
graphical models are useful methods to understand genome evolution and the
mechanisms of isochore evolution in the human genome.
| arxiv topic:q-bio.GN q-bio.PE |
arxiv_dataset-1456909.3232 | On the origin of reverse polarity patches found by Hinode in sunspot
penumbrae
astro-ph.SR
The satellite Hinode has recently revealed penumbral structures with a
magnetic polarity opposite to the main sunspot polarity. They may be a direct
confirmation of magnetic field lines and mass flows returning to the solar
interior throughout the penumbra, a configuration previously inferred from
interpretation of observed Stokes profile asymmetries. The paper points out the
relationship between the reverse polarity features found by Hinode, and the
model Micro-Structured Magnetic Atmospheres (MISMAs) proposed for sunspots. We
show how the existing model MISMAs produce strongly redshifted reverse polarity
structures as found by Hinode. Ad hoc model MISMAs also explain the asymmetric
Stokes profiles observed by Hinode. The same modeling may be consistent with
magnetograms of dark cored penumbral filaments if the dark cores are associated
with the reverse polarity. Such hypothetical relationship will show up only in
the far red wings of the spectral lines.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1457909.3332 | The number of beams in IMRT - theoretical investigations and
implications for single-arc IMRT
physics.med-ph
The first purpose of this paper is to shed some new light on the old question
of selecting the number of beams in intensity-modulated radiation therapy
(IMRT). The second purpose is to illuminate the related issue of discrete
static beam angles vs. rotational techniques, which has recently re-surfaced
due to the advancement of volumetric arc therapy (VMAT). A specific objective
is to find analytical expressions that allow one to address the points raised
above. To make the problem mathematically tractable, it is assumed that the
depth dose is flat and that the lateral dose profile can be approximated by
polynomials, specifically Chebyshev polynomials of the first kind, of finite
degree. The application of methods known from image reconstruction then allows
one to answer the first question above as follows: The required number of beams
is determined by the maximum degree of the polynomials used in the
approximation of the beam profiles, which is a measure of the dose variability.
There is nothing to be gained by using more beams. In realistic cases, in which
the variability of the lateral dose profile is restricted in several ways, the
required number of beams is of the order of 10 to 20. The consequence of
delivering the beams with a `leaf sweep' technique during continuous rotation
of the gantry, as in VMAT, is also derived in analytical form. The main effect
is that the beams fan out, but the effect near the axis of rotation is small.
This result can serve as a theoretical justification of VMAT. Overall the
analytical derivations in this paper, albeit based on strong simplifications,
provide new insights into, and a deeper understanding of, the beam angle
problem in IMRT.
| arxiv topic:physics.med-ph |
arxiv_dataset-1458909.3432 | Electrostatics of Graphene: Charge Distribution and Capacitance
cond-mat.mes-hall cond-mat.mtrl-sci
The distribution of net electric charge in graphene is investigated, using
both a constitutive atomic charge-dipole interaction model and an approximate
analytical solution to Laplace's equation. We demonstrate a strong size
dependence of the charge distributions in finite-size, infinitely-long and
multi-layered rectangular graphene sheets, respectively. We found that the
charge density can be naturally enhanced up to 13 times at graphene's geometry
edges. This edge charge enhancement effect becomes more significant when the
length or the width of graphene increases. The charge enhancement ratio is
found to follow a linear relationship with the number of layers. These results
can be used to understand the newly experimentally observed electron emission,
charge impurity and chemical doping phenomena in 2-dimension nanostructure.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-1459909.3532 | On the symmetric formulation of the Painleve IV equation
math-ph math.MP nlin.SI
Symmetries and solutions of the Painleve IV equation are presented in an
alternative framework which provides the bridge between the Hamiltonian
formalism and the symmetric Painleve IV equation. This approach originates from
a method developed in the setting of pseudo-differential Lax formalism
describing AKNS hierarchy with the Darboux-Backlund and Miura transformations.
In the Hamiltonian formalism the Darboux-Backlund transformations are
introduced as maps between solutions of the Hamilton equations corresponding to
two allowed values of Hamiltonian's discrete parameter. The action of the
generators of the extended affine Weyl group of the $A_2$ root system is
realized in terms of three "square-roots" of such Darboux-Backlund
transformations defined on a multiplet of solutions of the Hamilton equations.
| arxiv topic:math-ph math.MP nlin.SI |
arxiv_dataset-1460909.3632 | Going out with a bang: compact object collisions resulting from
supernovae in binary systems
astro-ph.HE
Binary star systems containing a neutron star or a black hole with an
evolved, massive star are dynamically perturbed when the latter undergoes a
supernova explosion. It is possible that the natal kick received by the
newly-formed neutron star in the supernova may place the stellar remnants into
a bound, highly eccentric orbit. In this case, the two compact objects can
tidally interact and spiral into one another on a short timescale. The
interaction with an accretion disc of supernova debris is also considered. We
quantify the likelihood of such events and show that they would be expected to
produce a high-energy transient, possibly a short gamma-ray burst, typically
within a few days of the supernova.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1461909.3732 | Spectral modelling of 1 ES 1218+30.4
astro-ph.HE
We employ a time-dependent synchrotron-self-Compton code for modeling
contemporaneous multiwavelength data of the blazar 1 ES 1218+30.4 The input
parameters of the model are used to infer physical parameters of the emitting
region. An acceptable fit to the data is obtained by taking into account a
stellar emission component in the optical regime due to the host galaxy. The
physical parameters inferred from the fit are in line with particle
acceleration due to the Fermi mechanism providing s = 2.1 spectra. From the
properties of the host galaxy in the optical, we estimate the central black
hole mass and thus confirm that the jet power injected into the emission region
is in the sub-Eddington regime, as expected for BL Lacertae objects.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1462909.3832 | Lunar Outgassing, Transient Phenomena & the Return to the Moon, II:
Predictions and Tests for Outgassing/Regolith Interactions
astro-ph.EP
We follow Paper I with predictions of how gas leaking through the lunar
surface could influence the regolith, as might be observed via optical
Transient Lunar Phenomena (TLPs) and related effects. We touch on several
processes, but concentrate on low and high flow rate extremes, perhaps the most
likely. We model explosive outgassing for the smallest gas overpressure at the
regolith base that releases the regolith plug above it. This disturbance's
timescale and affected area are consistent with observed TLPs; we also discuss
other effects. For slow flow, escape through the regolith is prolonged by low
diffusivity. Water, found recently in deep magma samples, is unique among
candidate volatiles, capable of freezing between the regolith base and surface,
especially near the lunar poles. For major outgassing sites, we consider the
possible accumulation of water ice. Over geological time ice accumulation can
evolve downward through the regolith. Depending on gases additional to water,
regolith diffusivity might be suppressed chemically, blocking seepage and
forcing the ice zone to expand to larger areas, up to square km scales, again,
particularly at high latitudes. We propose an empirical path forward, wherein
current and forthcoming technologies provide controlled, sensitive probes of
outgassing. The optical transient/outgassing connection, addressed via
Earth-based remote sensing, suggests imaging and/or spectroscopy, but aspects
of lunar outgassing might be more covert, as indicated above. TLPs betray some
outgassing, but does outgassing necessarily produces TLPs? We also suggest more
intrusive techniques from radar to in-situ probes. Many of these approaches
should be practiced in a pristine lunar atmosphere, before significant
confusing signals likely to be produced upon humans returning to the Moon.
| arxiv topic:astro-ph.EP |
arxiv_dataset-1463909.3932 | Experimental study on the cyclic resistance of a natural loess from
Northern France
physics.class-ph
In order to analyze the instability phenomenon observed along the Northern
High Speed Line of R\'eseau Ferr\'e de France (RFF), soil blocks were taken at
a site near the railway, at four different depths (1.2, 2.2, 3.5 and 4.9 m).
Cyclic triaxial tests were carried out on saturated and unsaturated soil
specimens. The results from tests on initially saturated specimens showed that
the soil taken at 2.2 m depth has the lowest resistance to cyclic loading, in
relation to its highest porosity and lowest clay fraction. This soil was then
studied at unsaturated state with various initial water contents. Unsaturated
soil specimens were first subjected to cyclic loadings to decrease their
volume. These cyclic loadings was stopped when the volume decrease was
approximately equal to the initial pore air volume, or when the pores filled by
air were eliminated and the soil was considered to become saturated.
Afterwards, the back-pressure tubing was saturated with de-aired water and
cycles were applied under undrained condition. Significant effect of initial
water content was evidenced: the lower the initial water content, the higher
the cyclic resistance. This can be explained by the densification of the soil
during the initial cyclic loadings.
| arxiv topic:physics.class-ph |
arxiv_dataset-1464909.4032 | Soliton equations, vertex operators, and simple singularities
math.QA math.AG math.RT
We prove the equivalence of two hierarchies of soliton equations associated
to a simply-laced finite Dynkin diagram. The first was defined by Kac and
Wakimoto using the principal realization of the basic representations of the
corresponding affine Kac-Moody algebra. The second was defined in
arXiv:math/0307176 using the Frobenius structure on the local ring of the
corresponding simple singularity. We also obtain a deformation of the principal
realization of the basic representation over the space of miniversal
deformations of the corresponding singularity. As a by-product, we compute the
operator product expansions of pairs of vertex operators defined in terms of
Picard-Lefschetz periods for more general singularities. Thus, we establish a
surprising link between twisted vertex operators and deformation theory of
singularities.
| arxiv topic:math.QA math.AG math.RT |
arxiv_dataset-1465909.4132 | An Improvement to a Berezin-Li-Yau type inequality for the Klein-Gordon
Operator
math.SP
In this article we improve a lower bound for $\sum_{j=1}^k\beta_j$ (a
Berezin-Li-Yau type inequality) in [E. M. Harrell II and S. Yildirim Yolcu,
Eigenvalue inequalities for Klein-Gordon Operators, J. Funct. Analysis, 256(12)
(2009) 3977-3995]. Here $\beta_j$ denotes the $j$th eigenvalue of the Klein
Gordon Hamiltonian $H_{0,\Omega}=|p|$ when restricted to a bounded set
$\Omega\subset {\mathbb R}^n$. $H_{0,\Omega}$ can also be described as the
generator of the Cauchy stochastic process with a killing condition on
$\partial \Omega$. (cf. [R. Banuelos, T. Kulczycki, Eigenvalue gaps for the
Cauchy process and a Poincare inequality, J. Funct. Anal. 211 (2) (2004)
355-423]; [R. Banuelos, T. Kulczycki, The Cauchy process and the Steklov
problem, J. Funct. Anal. 234 (2006) 199-225].) To do this, we adapt the proof
of Melas ([ A. D. Melas, A lower bound for sums of eigenvalues of the
Laplacian, Proceedings of the American Mathematical Society, 131(2) (2002)
631-636]), who improved the estimate for the bound of $\sum_{j=1}^k\lambda_j$,
where $\lambda_j$ denotes the $j$th eigenvalue of the Dirichlet Laplacian on a
bounded domain in ${\mathbb R}^d$.
| arxiv topic:math.SP |
arxiv_dataset-1466909.4232 | Comment on the orthogonality of the Macdonald functions of imaginary
order
math.CA math-ph math.MP
Recently, Yakubovich [Opuscula Math. 26 (2006) 161--172] and Passian et al.
[J. Math. Anal. Appl. doi:10.1016/j.jmaa.2009.06.067] have presented
alternative proofs of an orthogonality relation obeyed by the Macdonald
functions of imaginary order. In this note, we show that the validity of that
relation may be also proved in a simpler way by applying a technique
occasionally used in mathematical physics to normalize scattering wave
functions to the Dirac delta distribution.
| arxiv topic:math.CA math-ph math.MP |
arxiv_dataset-1467909.4332 | Almost Morawetz estimates and global well-posedness for the defocusing
$L^2$-critical nonlinear Schr{\"o}dinger equation in higher dimensions
math.AP
In this paper, we consider the global well-posedness of the defocusing,
$L^{2}$ - critical nonlinear Schr{\"o}dinger equation in dimensions $n \geq 3$.
Using the I-method, we show the problem is globally well-posed in $n = 3$ when
$s > {2/5}$, and when $n \geq 4$, for $s > \frac{n - 2}{n}$. We combine energy
increments for the I-method, interaction Morawetz estimates, and almost
Morawetz estimates to prove the result.
| arxiv topic:math.AP |
arxiv_dataset-1468909.4432 | Spin density functional study on magnetism of potassium loaded Zeolite A
cond-mat.str-el cond-mat.mes-hall
In order to clarify the mechanism of spin polarization in potassium-loaded
zeolite A, we perform {\em ab initio} density-functional calculations. We find
that (i) the system comprising only non-magnetic elements (Al, Si, O and K) can
indeed exhibit ferromagnetism, (ii) while the host cage makes a confining
quantum-well potential in which $s$- and $p$-like states are formed, the
potassium-4$s$ electrons accommodated in the p-states are responsible for the
spin polarization, and (iii) the size of the magnetic moment sensitively
depends on the atomic configuration of the potassium atoms. We show that the
spin polarization can be described systematically in terms of the confining
potential and the crystal field splitting of the p-states.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall |
arxiv_dataset-1469909.4532 | Supersymmetric lattices - a brief introduction
hep-lat
Recently, new theoretical ideas have allowed the construction of lattice
actions which are explicitly invariant under one or more supersymmetries. These
theories are local and free of doublers and in the case of Yang-Mills theories
also possess exact gauge invariance. In this talk these ideas are reviewed with
particular emphasis being placed on ${\cal N}=4$ super Yang-Mills theory.
| arxiv topic:hep-lat |
arxiv_dataset-1470909.4632 | Wave-driven dynamo action in spherical MHD systems
physics.flu-dyn
Hydrodynamic and magnetohydrodynamic numerical studies of a mechanically
forced two-vortex flow inside a sphere are reported. The simulations are
performed in the intermediate regime between the laminar flow and developed
turbulence where a hydrodynamic instability is found to generate internal waves
with a characteristic m=2 zonal wave number. It is shown that this
time-periodic flow acts as a dynamo although snapshots of the flow as well as
the mean flow are not dynamos. The magnetic fields' growth rate exhibits
resonance effects depending on the wave frequency. Furthermore, a cyclic
self-killing and self-recovering dynamo based on the relative alignment of the
velocity and magnetic fields is presented. The phenomena are explained in terms
of a mixing of non-orthogonal eigenstates of the time dependent linear operator
of the magnetic induction equation. The potential relevance of this mechanism
to dynamo experiments is discussed.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-1471909.4732 | A Natural Bijection between Permutations and a Family of Descending
Plane Partitions
math.CO
We construct a direct natural bijection between descending plane partitions
without any special part and permutations. The directness is in the sense that
the bijection avoids any reference to nonintersecting lattice paths. The
advantage of the bijection is that it provides an interpretation for the
seemingly long list of conditions needed to define descending plane partitions.
Unfortunately, the bijection does not relate the number of parts of the
descending plane partition with the number of inversions of the permutation as
one might have expected from the conjecture of Mills, Robbins and Rumsey,
although there is a simple expression for the number of inversions of a
permutation in terms of the corresponding descending plane partition.
| arxiv topic:math.CO |
arxiv_dataset-1472909.4832 | Small world-Fractal Transition in Complex Networks: Renormalization
Group Approach
cond-mat.dis-nn cond-mat.stat-mech
We show that renormalization group (RG) theory applied to complex networks
are useful to classify network topologies into universality classes in the
space of configurations. The RG flow readily identifies a small-world/fractal
transition by finding (i) a trivial stable fixed point of a complete graph,
(ii) a non-trivial point of a pure fractal topology that is stable or unstable
according to the amount of long-range links in the network, and (iii) another
stable point of a fractal with short-cuts that exists exactly at the
small-world/fractal transition. As a collateral, the RG technique explains the
coexistence of the seemingly contradicting fractal and small-world phases and
allows to extract information on the distribution of short-cuts in real-world
networks, a problem of importance for information flow in the system.
| arxiv topic:cond-mat.dis-nn cond-mat.stat-mech |
arxiv_dataset-1473909.4932 | Dynamics of finite Fermi-Hubbard and Bose-Hubbard systems
cond-mat.quant-gas
This paper analyzes dynamical properties of small Fermi-Hubbard and
Bose-Hubbard systems, focusing on the structure of the underlying Hilbert
space. We evaluate time-dependent quantities such as the return probability to
the initial state and the spin imbalance of spin-1/2 fermions. The results are
compared with recent experimental observations in ultracold gases. For the
symmetric two-site Fermi-Hubbard model we find that the spin imbalance and the
return probability are controlled by two and three frequencies, respectively.
The spin imbalance and the return probability are identical for the asymmetric
Falicov-Kimball limit and controlled by only one frequency. In general, the
transition probabilities between the initial state and energy eigenstates
depend strongly on the particle-particle interaction. This is discussed for
"self trapping" of spinless bosons in a double-well potential. We observe that
the available Hilbert space is reduced significantly by strong interaction.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-1474909.5032 | Cartesian product of hypergraphs: properties and algorithms
cs.DM cs.DS
Cartesian products of graphs have been studied extensively since the 1960s.
They make it possible to decrease the algorithmic complexity of problems by
using the factorization of the product. Hypergraphs were introduced as a
generalization of graphs and the definition of Cartesian products extends
naturally to them. In this paper, we give new properties and algorithms
concerning coloring aspects of Cartesian products of hypergraphs. We also
extend a classical prime factorization algorithm initially designed for graphs
to connected conformal hypergraphs using 2-sections of hypergraphs.
| arxiv topic:cs.DM cs.DS |
arxiv_dataset-1475909.5132 | Cameron--Martin formula for the $ \sigma $-finite measure unifying
Brownian penalisations
math.PR math.FA
Quasi-invariance under translation is established for the $ \sigma $-finite
measure unifying Brownian penalisations, which has been introduced by Najnudel,
Roynette and Yor. For this purpose, the theory of Wiener integrals for centered
Bessel processes, due to Funaki, Hariya and Yor, plays a key role.
| arxiv topic:math.PR math.FA |
arxiv_dataset-1476909.5232 | Rationality of motivic Chow series modulo A^1-homotopy
math.AG
Consider the formal power series $\sum [C_{p, \alpha}(X)]t^{\alpha}$ (called
Motivic Chow Series), where $C_p(X)=\disjoint C_{p, \alpha}(X)$ is the Chow
variety of $X$ parametrizing the $p$-dimensional effective cycles on $X$ with
$C_{p, \alpha}(X)$ its connected components, and $[C_{p, \alpha}(X)]$ its class
in $K(ChM)_{A^1}$, the $K$-ring of Chow motives modulo $A^1$ homotopy. Using
Picard product formula and Torus action, we will show that the Motivic Chow
Series is rational in many cases. We have added the computation of the motivic
zeta series in some of our examples so the reader can compare both series in
each case.
| arxiv topic:math.AG |
arxiv_dataset-1477909.5332 | Photospheric high-frequency acoustic power excess in sunspot umbra:
signature of magneto-acoustic modes
astro-ph.SR
We present observational evidence for the presence of MHD waves in the solar
photosphere deduced from SOHO/MDI Dopplergram velocity observations. The
magneto-acoustic perturbations are observed as acoustic power enhancement in
the sunspot umbra at high-frequency bands in the velocity component
perpendicular to the magnetic field. We use numerical modelling of wave
propagation through localised non-uniform magnetic field concentration along
with the same filtering procedure as applied to the observations to identify
the observed waves. Guided by the results of the numerical simulations we
classify the observed oscillations as magneto-acoustic waves excited by the
trapped sub-photospheric acoustic waves. We consider the potential application
of the presented method as a diagnostic tool for magnetohelioseismology.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1478909.5432 | Complete Dynamical Localization in Disordered Quantum Multi-Particle
Systems
math-ph cond-mat.quant-gas math.MP
We present some recent results concerning the persistence of dynamical
localization for disordered systems of n particles under weak interactions.
| arxiv topic:math-ph cond-mat.quant-gas math.MP |
arxiv_dataset-1479909.5532 | He and Ne ages of large presolar silicon carbide grains: Solving the
recoil problem
astro-ph.EP astro-ph.GA
Knowledge about the age of presolar grains provides important insights into
Galactic chemical evolution and the dynamics of grain formation and destruction
processes in the Galaxy. Determination from the abundance of cosmic ray
interaction products is straightforward, but in the past has suffered from
uncertainties in correcting for recoil losses of spallation products. The
problem is less serious in a class of large (tens of micrometer) grains. We
describe the correction procedure and summarise results for He and Ne ages of
presolar SiC "Jumbo" grains that range from close to zero to ~850 Myr, with the
majority being less than 200 Myr. We also discuss the possibility of extending
our approach to the majority of smaller SiC grains and explore possible
contributions from trapping of cosmic rays.
| arxiv topic:astro-ph.EP astro-ph.GA |
arxiv_dataset-1480909.5632 | The Convenient Setting for Quasianalytic Denjoy--Carleman Differentiable
Mappings
math.FA math.CA
For quasianalytic Denjoy--Carleman differentiable function classes $C^Q$
where the weight sequence $Q=(Q_k)$ is log-convex, stable under derivations, of
moderate growth and also an $\mathcal L$-intersection (see 1.6), we prove the
following: The category of $C^Q$-mappings is cartesian closed in the sense that
$C^Q(E,C^Q(F,G))\cong C^Q(E\times F, G)$ for convenient vector spaces.
Applications to manifolds of mappings are given: The group of
$C^Q$-diffeomorphisms is a regular $C^Q$-Lie group but not better.
| arxiv topic:math.FA math.CA |
arxiv_dataset-1481910.0036 | Non--Vanishing functions and Toeplitz Operators on Tube--Type Domains
math.OA
We prove an index theorem for Toeplitz operators on irreducible tube--type
domains and we extend our results to Toeplitz operators with matrix symbols. In
order to prove our index theorem, we proved a result asserting that a
non--vanishing function on the Shilov boundary of a tube--type bounded
symmetric domain, not necessarily irreducible, is equal to a unimodular
function defined as the product of powers of generic norms times an exponential
function.
| arxiv topic:math.OA |
arxiv_dataset-1482910.0136 | A theory of the three-pulse electric-dipole echo in glasses in a
magnetic field
cond-mat.dis-nn
We extended existing theory of the two-pulse electric-dipole echo in glasses
in a magnetic field to the three-pulse echo. As is well known, at low
temperatures two-level systems (TLS's) are responsible for the echo phenomenon
in glasses. Using a diagram technique in the framework of perturbation theory
we derived a simple formula for the three-pulse echo amplitude. As in the case
of two-pulse echo the magnetic field dependence of the tree-pulse echo
amplitude in glasses is related to quadrupole electric moments of TLS's
non-spherical nuclei and/or dipole-dipole interaction of their nuclear spins.
These two mechanisms are responsible for the fine level splitting of TLS. As a
result TLS transforms to multi-level system with the fine level splitting
depending on a magnetic field. Due to existence in the theory the additional
parameter T - the time interval between the second and the third pulses we have
more reach spectrum of echo oscillations in a magnetic field in comparison with
the case of the two-pulse echo.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-1483910.0236 | Joint Modelling of Gas and Electricity spot prices
q-fin.ST math.PR q-fin.GN
The recent liberalization of the electricity and gas markets has resulted in
the growth of energy exchanges and modelling problems. In this paper, we
modelize jointly gas and electricity spot prices using a mean-reverting model
which fits the correlations structures for the two commodities. The dynamics
are based on Ornstein processes with parameterized diffusion coefficients.
Moreover, using the empirical distributions of the spot prices, we derive a
class of such parameterized diffusions which captures the most salient
statistical properties: stationarity, spikes and heavy-tailed distributions.
The associated calibration procedure is based on standard and efficient
statistical tools. We calibrate the model on French market for electricity and
on UK market for gas, and then simulate some trajectories which reproduce well
the observed prices behavior. Finally, we illustrate the importance of the
correlation structure and of the presence of spikes by measuring the risk on a
power plant portfolio.
| arxiv topic:q-fin.ST math.PR q-fin.GN |
arxiv_dataset-1484910.0336 | Signatures of nonadiabatic O2 dissociation at Al(111): First-principles
fewest-switches study
cond-mat.mtrl-sci
Recently, spin selection rules have been invoked to explain the discrepancy
between measured and calculated adsorption probabilities of molecular oxygen
reacting with Al(111). In this work, we inspect the impact of nonadiabatic spin
transitions on the dynamics of this system from first principles. For this
purpose the motion on two distinct potential-energy surfaces associated to
different spin configurations and possible transitions between them are
inspected by means of the Fewest Switches algorithm. Within this framework we
especially focus on the influence of such spin transitions on observables
accessible to molecular beam experiments. On this basis we suggest experimental
setups that can validate the occurrence of such transitions and discuss their
feasibility.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-1485910.0436 | IceCube: The Rationale for Kilometer-Scale Neutrino Detectors
astro-ph.HE
At a time when IceCube is nearing completion, we revisit the rationale for
constructing kilometer-scale neutrino detectors. We focus on the prospect that
such observatories reveal the still-enigmatic sources of cosmic rays. While
only a "smoking gun" is missing for the case that the Galactic component of the
cosmic-ray spectrum originates in supernova remnants, the origin of the
extragalactic component remains a mystery. We speculate on neutrino emission
from gamma-ray bursts and active galaxies.
| arxiv topic:astro-ph.HE |
arxiv_dataset-1486910.0536 | On similar matrices over the dual numbers
math.RA
Matrices over the dual numbers are considered. We propose an approach to
classify these matrices up to similarity. Some preliminary results on the
realization of this approach are obtained. In particular, we produce explicitly
canonical matrices of orders 2 and 3.
| arxiv topic:math.RA |
arxiv_dataset-1487910.0636 | Inverse scattering for Schr\"odinger operators with Miura potentials, I.
Unique Riccati representatives and ZS-AKNS systems
math.SP math-ph math.MP
This is the first in a series of papers on scattering theory for
one-dimensional Schr\"odinger operators with highly singular potentials $q\in
H^{-1}(R)$. In this paper, we study Miura potentials $q$ associated to positive
Schr\"odinger operators that admit a Riccati representation $q=u'+u^2$ for a
unique $u\in L^1(R)\cap L^2(R)$. Such potentials have a well-defined reflection
coefficient $r(k)$ that satisfies $|r(k)|<1$ and determines $u$ uniquely. We
show that the scattering map $S:u\mapsto r$ is real-analytic with real-analytic
inverse. To do so, we exploit a natural complexification of the scattering map
associated with the ZS-AKNS system. In subsequent papers, we will consider
larger classes of potentials including singular potentials with bound states.
| arxiv topic:math.SP math-ph math.MP |
arxiv_dataset-1488910.0736 | Isospin-breaking corrections to the pion-nucleon scattering lengths
hep-ph nucl-th
We analyze isospin breaking through quark mass differences and virtual
photons in the pion-nucleon scattering lengths in all physical channels in the
framework of covariant baryon chiral perturbation theory. The so-called
triangle relation is found to be violated by about 1.5 %. We encounter a
substantial isospin-breaking correction to neutral-pion-nucleon scattering
beyond Weinberg's prediction due to a cusp effect. Finally, the application to
hadronic atoms is briefly discussed.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-1489910.0836 | No Evidence of Quasar-Mode Feedback in a Four-Way Group Merger at z~0.84
astro-ph.CO astro-ph.HE
We report on the results of a Chandra search for evidence of triggered
nuclear activity within the Cl0023+0423 four-way group merger at z ~ 0.84. The
system consists of four interacting galaxy groups in the early stages of
hierarchical cluster formation and, as such, provides a unique look at the
level of processing and evolution already under way in the group environment
prior to cluster assembly. We present the number counts of X-ray point sources
detected in a field covering the entire Cl0023 structure, as well as a
cross-correlation of these sources with our extensive spectroscopic database.
Both the redshift distribution and cumulative number counts of X-ray sources
reveal little evidence to suggest that the system contains X-ray luminous
active galactic nuclei (AGNs) in excess to what is observed in the field
population. If preprocessing is under way in the Cl0023 system, our
observations suggest that powerful nuclear activity is not the predominant
mechanism quenching star formation and driving the evolution of Cl0023
galaxies. We speculate that this is due to a lack of sufficiently massive
nuclear black holes required to power such activity, as previous observations
have found a high late-type fraction among the Cl0023 population. It may be
that disruptive AGN-driven outflows become an important factor in the
preprocessing of galaxy populations only during a later stage in the evolution
of such groups and structures when sufficiently massive galaxies (and central
black holes) have built up, but prior to hydrodynamical processes stripping
them of their gas reservoirs.
| arxiv topic:astro-ph.CO astro-ph.HE |
arxiv_dataset-1490910.0936 | Minimax Goodness-of-Fit Testing in Multivariate Nonparametric Regression
math.ST stat.TH
We consider an unknown response function $f$ defined on $\Delta=[0,1]^d$,
$1\le d\le\infty$, taken at $n$ random uniform design points and observed with
Gaussian noise of known variance. Given a positive sequence $r_n\to 0$ as
$n\to\infty$ and a known function $f_0 \in L_2(\Delta)$, we propose, under
general conditions, a unified framework for the goodness-of-fit testing problem
for testing the null hypothesis $H_0: f=f_0$ against the alternative $H_1:
f\in\CF, \|f-f_0\|\ge r_n$, where $\CF$ is an ellipsoid in the Hilbert space $
L_2(\Delta)$ with respect to the tensor product Fourier basis and $\|\cdot\|$
is the norm in $ L_2(\Delta)$. We obtain both rate and sharp asymptotics for
the error probabilities in the minimax setup. The derived tests are inherently
non-adaptive.
Several illustrative examples are presented. In particular, we consider
functions belonging to ellipsoids arising from the well-known multidimensional
Sobolev and tensor product Sobolev norms as well as from the less-known
Sloan-Wo$\rm\acute{z}$niakowski norm and a norm constructed from multivariable
analytic functions on the complex strip.
Some extensions of the suggested minimax goodness-of-fit testing methodology,
covering the cases of general design schemes with a known product probability
density function, unknown variance, other basis functions and adaptivity of the
suggested tests, are also briefly discussed.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-1491910.1036 | Harmonic morphisms and bicomplex manifolds
math.DG
We use functions of a bicomplex variable to unify the existing constructions
of harmonic morphisms from a 3-dimensional Euclidean or pseudo-Euclidean space
to a Riemannian or Lorentzian surface. This is done by using the notion of
complex-harmonic morphism between complex-Riemannian manifolds and showing how
these are given by bicomplex-holomorphic functions when the codomain is
one-bicomplex dimensional. By taking real slices, we recover well-known
compactifications for the three possible real cases. On the way, we discuss
some interesting conformal compactifications of complex-Riemannian manifolds by
interpreting them as bicomplex manifolds.
| arxiv topic:math.DG |
arxiv_dataset-1492910.1136 | Tracing the merger rate of the Universe with APERTIF and ASKAP
astro-ph.CO
OH maser emission at 1.67 GHz is known to be associated with regions of
intense star formation within ULIRGs. As these galaxies are formed through
violent mergers, studying the co-moving density of OH maser galaxies across
cosmic time will allow the merger rate of the Universe to be determined in an
independent way. This merger rate is an important parameter in galaxy formation
and evolution scenarios. The sensitivity, wide field of view and spectral
coverage of both APERTIF on the WSRT and ASKAP will allow for the first time
all-sky blind surveys for OH maser galaxies to be carried out to redshift 1.4.
We describe the prospects for such surveys, including the expected number of OH
maser galaxies that will be discovered, and what limits can be placed on the OH
maser luminosity function, and hence the merger rate out to redshift 1.4 with
various survey strategies.
| arxiv topic:astro-ph.CO |
arxiv_dataset-1493910.1236 | On `maximal' poles of zeta functions, roots of b-functions and monodromy
Jordan blocks
math.AG
The main objects of study in this paper are the poles of several local zeta
functions: the Igusa, topological and motivic zeta function associated to a
polynomial or (germ of) holomorphic function in n variables. We are interested
in poles of maximal possible order n. In all known cases (curves,
non-degenerate polynomials) there is at most one pole of maximal order n which
is then given by the log canonical threshold of the function at the
corresponding singular point.
For an isolated singular point we prove that if the log canonical threshold
yields a pole of order n of the corresponding (local) zeta function, then it
induces a root of the Bernstein-Sato polynomial of the given function of
multiplicity n (proving one of the cases of the strongest form of a conjecture
of Igusa-Denef-Loeser). For an arbitrary singular point we show under the same
assumption that the monodromy eigenvalue induced by the pole has a Jordan block
of size n on the (perverse) complex of nearby cycles.
| arxiv topic:math.AG |
arxiv_dataset-1494910.1336 | Spontaneous CP violation in E6 SUSY GUT with SU(2) flavor and anomalous
U(1) symmetries
hep-ph
We construct a model of spontaneous CP violation in E6 supersymmetric grand
unified theory. In the model, we employ an SU(2)F flavor symmetry and an
anomalous U(1)A symmetry. The SU(2)F flavor symmetry is introduced to provide
the origin of hierarchical structures of Yukawa coupling and to ensure the
universality of sfermion soft masses. The anomalous U(1)A symmetry is
introduced to realize the doublet-triplet mass splitting, to provide the origin
of hierarchical structures of Yukawa couplings, and to solve the mu problem. In
the model, CP is spontaneously broken by the SU(2)F breaking in order to
provide a Kobayashi-Maskawa phase and to evade the supersymmetric CP problem.
However, a naive construction of the model generally leads to unwanted outcome,
Arg[mu b*]=O(1), when CP violating effects in the flavor sector are taken into
account. We cure this difficulty by imposing a discrete symmetry and find that
this prescription can play additional roles. It ensures that realistic up-quark
mass and Cabibbo angle are simultaneously realized without cancellation between
O(1) coefficients. Also, severe constraints from the chromo-electric dipole
moment of the quark can be satisfied without destabilizing the weak scale. The
discrete symmetry reduces the number of free parameters, but the model is
capable of reproducing quark and lepton mass spectra, mixing angles, and a
Jarlskog invariant. We obtain characteristic predictions Vub sim O(lambda^4)
(lambda=0.22) and |Vcb Yb| = |Yc| at the grand unified theory scale.
| arxiv topic:hep-ph |
arxiv_dataset-1495910.1436 | Sounding stellar cycles with Kepler - preliminary results from
ground-based chromospheric activity measurements
astro-ph.SR
Due to its unique long-term coverage and high photometric precision,
observations from the Kepler asteroseismic investigation will provide us with
the possibility to sound stellar cycles in a number of solar-type stars with
asteroseismology. By comparing these measurements with conventional
ground-based chromospheric activity measurements we might be able to increase
our understanding of the relation between the chromospheric changes and the
changes in the eigenmodes.
In parallel with the Kepler observations we have therefore started a
programme at the Nordic Optical Telescope to observe and monitor chromospheric
activity in the stars that are most likely to be selected for observations for
the whole satellite mission. The ground-based observations presented here can
be used both to guide the selection of the special Kepler targets and as the
first step in a monitoring programme for stellar cycles. Also, the
chromospheric activity measurements obtained from the ground-based observations
can be compared with stellar parameters such as ages and rotation in order to
improve stellar evolution models.
| arxiv topic:astro-ph.SR |
arxiv_dataset-1496910.1536 | An algebraic framework for information theory: Classical Information
cs.IT math.IT
This work proposes a complete algebraic model for classical information
theory. As a precursor the essential probabilistic concepts have been defined
and analyzed in the algebraic setting. Examples from probability and
information theory demonstrate that in addition to theoretical insights
provided by the algebraic model one obtains new computational and anlytical
tools. Several important theorems of classical probahility and information
theory are formulated and proved in the algebraic framework.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-1497910.1636 | Arctic circles, domino tilings and square Young tableaux
math.PR math.CO
The arctic circle theorem of Jockusch, Propp, and Shor asserts that uniformly
random domino tilings of an Aztec diamond of high order are frozen with
asymptotically high probability outside the "arctic circle" inscribed within
the diamond. A similar arctic circle phenomenon has been observed in the
limiting behavior of random square Young tableaux. In this paper, we show that
random domino tilings of the Aztec diamond are asymptotically related to random
square Young tableaux in a more refined sense that looks also at the behavior
inside the arctic circle. This is done by giving a new derivation of the
limiting shape of the height function of a random domino tiling of the Aztec
diamond that uses the large-deviation techniques developed for the square Young
tableaux problem in a previous paper by Pittel and the author. The solution of
the variational problem that arises for domino tilings is almost identical to
the solution for the case of square Young tableaux by Pittel and the author.
The analytic techniques used to solve the variational problem provide a
systematic, guess-free approach for solving problems of this type which have
appeared in a number of related combinatorial probability models.
| arxiv topic:math.PR math.CO |
arxiv_dataset-1498910.1736 | Arginine-rich peptides destabilize the plasma membrane, consistent with
a pore formation translocation mechanism of cell penetrating peptides
q-bio.BM q-bio.CB
Recent molecular dynamics simulations (Herce and Garcia, PNAS, 104: 20805
(2007)) have suggested that the arginine-rich HIV Tat peptides might be able to
translocate by destabilizing and inducing transient pores in phospholipid
bilayers. In this pathway for peptide translocation, arginine residues play a
fundamental role not only in the binding of the peptide to the surface of the
membrane but also in the destabilization and nucleation of transient pores
across the bilayer, despite being charged and highly hydrophilic. Here we
present a molecular dynamics simulation of a peptide composed of nine arginines
(Arg-9) that shows that this peptide follows the same translocation pathway
previously found for the Tat peptide. We test this hypothesis experimentally by
measuring ionic currents across phospholipid bilayers and cell membranes
through the pores induced by Arg-9 peptides. We find that Arg-9 peptides, in
the presence of an electrostatic potential gradient, induce ionic currents
across planar phospholipid bilayers, as well as in cultured osteosarcoma cells
and human smooth muscle cells freshly isolated from the umbilical artery. Our
results suggest that the mechanism of action of Arg-9 peptide involves the
creation of transient pores in lipid bilayers and cell membranes.
| arxiv topic:q-bio.BM q-bio.CB |
arxiv_dataset-1499910.1836 | Optical Spectroscopy of Distant Red Galaxies
astro-ph.CO
We present optical spectroscopic follow-up of a sample of Distant Red
Galaxies (DRGs) with K < 22.5 (Vega), selected by J-K > 2.3, in the Hubble Deep
Field South, the MS 1054-03 field, and the Chandra Deep Field South.
Spectroscopic redshifts were obtained for 15 DRGs. Only 2 out of 15 DRGs are
located at z < 2, suggesting a high efficiency to select high-redshift sources.
From other spectroscopic surveys in the CDFS targeting intermediate to high
redshift populations selected with different criteria, we find spectroscopic
redshifts for a further 30 DRGs. We use the sample of spectroscopically
confirmed DRGs to establish the high quality (scatter in \Delta z/(1+z) of ~
0.05) of their photometric redshifts in the considered deep fields, as derived
with EAZY (Brammer et al. 2008). Combining the spectroscopic and photometric
redshifts, we find that 74% of DRGs with K < 22.5 lie at z > 2. The combined
spectroscopic and photometric sample is used to analyze the distinct intrinsic
and observed properties of DRGs at z < 2 and z > 2. In our photometric sample
to K < 22.5, low-redshift DRGs are brighter in K than high-redshift DRGs by 0.7
mag, and more extincted by 1.2 mag in Av. Our analysis shows that the DRG
criterion selects galaxies with different properties at different redshifts.
Such biases can be largely avoided by selecting galaxies based on their
rest-frame properties, which requires very good multi-band photometry and high
quality photometric redshifts.
| arxiv topic:astro-ph.CO |
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