id stringlengths 16 29 | text stringlengths 86 3.49k | source stringlengths 14 112 |
|---|---|---|
arxiv_dataset-20001007.0762 | Adhesive Penetration in Beech Wood Part I: Experiments
cond-mat.mtrl-sci
A study with synchrotron radiation X-ray tomographic microscopy (SRXTM) of
PUR, PVAC, and UF adhesive bond lines in beech wood, bonded under various
growth ring angles is presented. After determining the hardening
characteristics of the adhesives, we evaluate the bond line morphologies, and
the adhesive penetration into the wood structure. We find distinct bond line
imperfections for the different adhesive systems. To describe the adhesive
distribution inside the bond line we propose the saturation of the pore space
instead of the commonly used maximum penetration depth. The results are the
basis for a penetration model of hardening fluids into hardwood (part II).
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-20011007.0862 | Supercriticality of Annealed Approximations of Boolean Networks
math.PR
We consider a model recently proposed by Chatterjee and Durrett [CD2011] as
an "annealed approximation" of boolean networks, which are a class of cellular
automata on a random graph, as defined by S. Kauffman [K69]. The starting point
is a random directed graph on $n$ vertices; each vertex has $r$ input vertices
pointing to it. For the model of [CD2011], a discrete time threshold contact
process is then considered on this graph: at each instant, each vertex has
probability $q$ of choosing to receive input; if it does, and if at least one
of its input vertices were in state 1 at the previous instant, then it is
labelled with a 1; in all other cases, it is labelled with a 0. $r$ and $q$ are
kept fixed and $n$ is taken to infinity. Improving a result of [CD2011], we
show that if $qr > 1$, then the time of persistence of activity of the dynamics
is exponential in $n$.
| arxiv topic:math.PR |
arxiv_dataset-20021007.0962 | Self-Similar Blowup Solutions to the 2-Component Camassa-Holm Equations
math-ph math.AP math.MP
In this article, we study the self-similar solutions of the 2-component
Camassa-Holm equations% \begin{equation} \left\{ \begin{array} [c]{c}%
\rho_{t}+u\rho_{x}+\rho u_{x}=0
m_{t}+2u_{x}m+um_{x}+\sigma\rho\rho_{x}=0 \end{array} \right. \end{equation}
with \begin{equation} m=u-\alpha^{2}u_{xx}. \end{equation} By the separation
method, we can obtain a class of blowup or global solutions for $\sigma=1$ or
$-1$. In particular, for the integrable system with $\sigma=1$, we have the
global solutions:% \begin{equation} \left\{ \begin{array} [c]{c}%
\rho(t,x)=\left\{ \begin{array} [c]{c}% \frac{f\left( \eta\right)
}{a(3t)^{1/3}},\text{ for }\eta^{2}<\frac {\alpha^{2}}{\xi}
0,\text{ for }\eta^{2}\geq\frac{\alpha^{2}}{\xi}% \end{array} \right.
,u(t,x)=\frac{\overset{\cdot}{a}(3t)}{a(3t)}x
\overset{\cdot\cdot}{a}(s)-\frac{\xi}{3a(s)^{1/3}}=0,\text{ }a(0)=a_{0}%
>0,\text{ }\overset{\cdot}{a}(0)=a_{1}
f(\eta)=\xi\sqrt{-\frac{1}{\xi}\eta^{2}+\left( \frac{\alpha}{\xi}\right)
^{2}}% \end{array} \right. \end{equation}
where $\eta=\frac{x}{a(s)^{1/3}}$ with $s=3t;$ $\xi>0$ and $\alpha\geq0$ are
arbitrary constants.\newline Our analytical solutions could provide concrete
examples for testing the validation and stabilities of numerical methods for
the systems.
| arxiv topic:math-ph math.AP math.MP |
arxiv_dataset-20031007.1062 | Preparation of carbon nanotubes from graphite powder at room temperature
cond-mat.mtrl-sci
We develop a new chemical route to prepare carbon nanotubes at room
temperature. Graphite powder is immersed in a mixed solution of nitric and
sulfuric acid with potassium chlorate. After heating the solution up to
70{\deg}C and leaving them in the air for 3 days, we obtained carbon nanotube
bundles. This process could provide an easy and inexpensive method for the
preparation of carbon nanotubes.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-20041007.1162 | Evolution of a mass-less test scalar field on Boson Stars space-times
gr-qc astro-ph.CO
We numerically solve the mass-less test scalar field equation on the
space-time background of boson stars and black holes. In order to do so, we use
a numerical domain that contains future null infinity. We achieve this
construction using a scri-fixing conformal compactification technique based on
hyperboloidal constant mean curvature foliations of the space-time and solve
the conformally invariant wave equation. We present two results: the scalar
field shows oscillations of the quasi- normal-mode type found for black holes
only for boson star configurations that are compact, and no signs of tail decay
is found in the parameter space we explored. Even though our results do not
correspond to the master equation of perturbations of boson star solutions,
they indicate that the parameter space of boson stars as black hole mimickers
is restricted to compact configurations.
| arxiv topic:gr-qc astro-ph.CO |
arxiv_dataset-20051007.1262 | Magnetic Quenching of Turbulent Diffusivity: Reconciling Mixing-length
Theory Estimates with Kinematic Dynamo Models of the Solar Cycle
astro-ph.SR
The turbulent magnetic diffusivity in the solar convection zone is one of the
most poorly constrained ingredients of mean-field dynamo models. This lack of
constraint has previously led to controversy regarding the most appropriate set
of parameters, as different assumptions on the value of turbulent diffusivity
lead to radically different solar cycle predictions. Typically, the dynamo
community uses double step diffusivity profiles characterized by low values of
diffusivity in the bulk of the convection zone. However, these low diffusivity
values are not consistent with theoretical estimates based on mixing-length
theory -- which suggest much higher values for turbulent diffusivity. To make
matters worse, kinematic dynamo simulations cannot yield sustainable magnetic
cycles using these theoretical estimates. In this work we show that magnetic
cycles become viable if we combine the theoretically estimated diffusivity
profile with magnetic quenching of the diffusivity. Furthermore, we find that
the main features of this solution can be reproduced by a dynamo simulation
using a prescribed (kinematic) diffusivity profile that is based on the
spatiotemporal geometric-average of the dynamically quenched diffusivity. Here,
we provide an analytic fit to the dynamically quenched diffusivity profile,
which can be used in kinematic dynamo simulations. Having successfully
reconciled the mixing-length theory estimated diffusivity profile with
kinematic dynamo models, we argue that they remain a viable tool for
understanding the solar magnetic cycle.
| arxiv topic:astro-ph.SR |
arxiv_dataset-20061007.1362 | On Whitney type inequalities for local anisotropic polynomial
approximation
math.FA
We prove a multivariate Whitney type theorem for the local anisotropic
polynomial approximation in $L_p(Q)$ with $1\leq p\leq \infty$. Here $Q$ is a
$d$-parallelepiped in $\RR^d$ with sides parallel to the coordinate axes. We
consider the error of best approximation of a function $f$ by algebraic
polynomials of fixed degree at most $r_i - 1$ in variable $x_i,\ i=1,...,d$,
and relate it to a so-called total mixed modulus of smoothness appropriate to
characterizing the convergence rate of the approximation error. This theorem is
derived from a Johnen type theorem on equivalence between a certain
K-functional and the total mixed modulus of smoothness which is proved in the
present paper.
| arxiv topic:math.FA |
arxiv_dataset-20071007.1462 | Trispectrum estimator in equilateral type non-Gaussian models
hep-th astro-ph.CO gr-qc
We investigate an estimator to measure the primordial trispectrum in
equilateral type non-Gaussian models such as k-inflation, single field DBI
inflation and multi-field DBI inflation models from Cosmic Microwave Background
(CMB) anisotropies. The shape of the trispectrum whose amplitude is not
constrained by the bispectrum in the context of effective theory of inflation
and k-inflation is known to admit a separable form of the estimator for CMB
anisotropies. We show that this shape is $87 \%$ correlated with the full
quantum trispectrum in single field DBI inflation, while it is $33 \%$
correlated with the one in multi-field DBI inflation when curvature
perturbation is originated from purely entropic contribution. This suggests
that $g_{\rm NL} ^{equil}$, the amplitude of this particular shape, provides a
reasonable measure of the non-Gaussianity from the trispectrum in equilateral
non-Gaussian models. We relate model parameters such as the sound speed, $c_s$
and the transfer coefficient from entropy perturbations to the curvature
perturbation, $T_{\mathcal{R} S}$ with $g_{\rm NL} ^{equil}$, which enables us
to constrain model parameters in these models once $g_{\rm NL}^{equil}$ is
measured in WMAP and Planck.
| arxiv topic:hep-th astro-ph.CO gr-qc |
arxiv_dataset-20081007.1562 | Azimuthal asymmetries of charged hadrons produced by high-energy muons
scattered off longitudinally polarised deuterons
hep-ex
Azimuthal asymmetries in semi-inclusive production of positive (h^+) and
negative hadrons (h^-) have been measured by scattering 160 GeV muons off
longitudinally polarised deuterons at CERN. The asymmetries were decomposed in
several terms according to their expected modulation in the azimuthal angle phi
of the outgoing hadron. Each term receives contributions from one or several
spin and transverse-momentum-dependent parton distribution and fragmentation
functions. The amplitudes of all phi-modulation terms of the hadron asymmetries
integrated over the kinematic variables are found to be consistent with zero
within statistical errors, while the constant terms are nonzero and equal for
h^+ and h^- within the statistical errors. The dependencies of the
phi-modulated terms versus the Bjorken momentum fraction x, the hadron
fractional momentum z, and the hadron transverse momentum p_h^T were studied.
The x dependence of the constant terms for both positive and negative hadrons
is in agreement with the longitudinal double-spin hadron asymmetries, measured
in semi-inclusive deep-inelastic scattering. The x dependence of the sin
phi-modulation term is less pronounced than that in the corresponding HERMES
data. All other dependencies of the phi-modulation amplitudes are consistent
with zero within the statistical errors.
| arxiv topic:hep-ex |
arxiv_dataset-20091007.1662 | Cracking the Taub-NUT
gr-qc astro-ph.CO hep-th
We present further analysis of an anisotropic, non-singular early universe
model that leads to the viable cosmology presented in Dechant et al
(arXiv:0809.4335). Although this model (the DLH model) contains scalar field
matter, it is reminiscent of the Taub-NUT vacuum solution in that it has
biaxial Bianchi IX geometry and its evolution exhibits a dimensionality
reduction at a quasi-regular singularity that one can identify with the
big-bang. We show that the DLH and Taub-NUT metrics are related by a coordinate
transformation, in which the DLH time coordinate plays the role of conformal
time for Taub-NUT. Since both models continue through the big-bang, the
coordinate transformation can become multivalued. In particular, in mapping
from DLH to Taub-NUT, the Taub-NUT time can take only positive values. We
present explicit maps between the DLH and Taub-NUT models, with and without a
scalar field. In the vacuum DLH model, we find a periodic solution expressible
in terms of elliptic integrals. Mapping the vacuum solution over to Taub-NUT
coordinates, recovers the standard (non-periodic) Taub-NUT solution in the Taub
region, where Taub-NUT time takes positive values, but does not exhibit the two
NUT regions known in the standard Taub-NUT solution. Conversely, mapping the
complete Taub-NUT solution to the DLH case reveals that the NUT regions
correspond to imaginary time and space in DLH coordinates. We show that many of
the well-known `pathologies' of the Taub-NUT solution arise because the
traditional coordinates are connected by a multivalued transformation to the
physically more meaningful DLH coordinates. In particular, the
`open-to-closed-to-open' transition and the Taub and NUT regions of the
(Lorentzian) Taub-NUT model are replaced by a closed pancaking universe with
spacelike homogeneous sections at all times.
| arxiv topic:gr-qc astro-ph.CO hep-th |
arxiv_dataset-20101007.1762 | Cosmological intersecting brane solutions
hep-th gr-qc
The recent discovery of an explicit dynamical description of p-branes makes
it possible to investigate the existence of intersection of such objects. We
generalize the solutions depending on the overall transverse space coordinates
and time to those which depend also on the relative transverse space and
satisfy new intersection rules. We give classification of these dynamical
intersecting brane solutions involving two branes, and discuss the application
of these solutions to cosmology and show that these give
Friedmann-Lemaitre-Robertson-Walker cosmological solutions. Finally, we
construct the brane world models, using the (cut-)copy-paste method after
compactifying the trivial spatial dimensions. We then find that interesting
brane world models can be obtained from codimension-one branes and several
static branes with higher codimensions. We also classify the behaviors of the
brane world near the future/past singularity.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-20111007.1862 | Surface roughness induced electric field enhancement and
triboluminescence
cond-mat.soft
The separation of solids in adhesive contact, or the fracture of solid
bodies, often results in the emission of high energy photons, e.g., visible
light and X-rays. This is believed to be related to charge separation. We
propose that the emission of high energy photons involves surface roughness and
surface diffusion of ions or electrons, resulting in the concentration of
charge at the tips of high asperities, and to electric field enhancement, which
facilitate the discharging process which result in the high energy photons. If
the surface diffusion is too fast, or the separation of the solid surfaces too
slow, discharging start at small interfacial separation resulting in low energy
photons.
| arxiv topic:cond-mat.soft |
arxiv_dataset-20121007.1962 | Self-isospectrality, mirror symmetry, and exotic nonlinear supersymmetry
hep-th math-ph math.MP quant-ph
We study supersymmetry of a self-isospectral one-gap Poschl-Teller system in
the light of a mirror symmetry that is based on spatial and shift reflections.
The revealed exotic, partially broken nonlinear supersymmetry admits seven
alternatives for a grading operator. One of its local, first order supercharges
may be identified as a Hamiltonian of an associated one-gap, non-periodic
Bogoliubov-de Gennes system. The latter possesses a nonlinear supersymmetric
structure, in which any of the three non-local generators of a Clifford algebra
may be chosen as the grading operator. We find that the supersymmetry
generators for the both systems are the Darboux-dressed integrals of a free
spin-1/2 particle in the Schrodinger picture, or of a free massive Dirac
particle. Nonlocal Foldy- Wouthuysen transformations are shown to be involved
in the supersymmetric structure.
| arxiv topic:hep-th math-ph math.MP quant-ph |
arxiv_dataset-20131007.2062 | Constructive role of non-adiabaticity for quantized charge pumping
cond-mat.mes-hall
We investigate a recently developed scheme for quantized charge pumping based
on single-parameter modulation. The device was realized in an AlGaAl-GaAs gated
nanowire. It has been shown theoretically that non-adiabaticity is
fundamentally required to realize single-parameter pumping, while in previous
multi-parameter pumping schemes it caused unwanted and less controllable
currents. In this paper we demonstrate experimentally the constructive and
destructive role of non-adiabaticity by analysing the pumping current over a
broad frequency range.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-20141007.2162 | Tuning Jammed Frictionless Disk Packings from Isostatic to Hyperstatic
cond-mat.soft cond-mat.stat-mech
We perform extensive computational studies of two-dimensional static
bidisperse disk packings using two distinct packing-generation protocols. The
first involves thermally quenching equilibrated liquid configurations to zero
temperature over a range of thermal quench rates $r$ and initial packing
fractions followed by compression and decompression in small steps to reach
packing fractions $\phi_J$ at jamming onset. For the second, we seed the system
with initial configurations that promote micro- and macrophase-separated
packings followed by compression and decompression to $\phi_J$. We find that
amorphous, isostatic packings exist over a finite range of packing fractions
from $\phi_{\rm min} \le \phi_J \le \phi_{\rm max}$ in the large-system limit,
with $\phi_{\rm max} \approx 0.853$. In agreement with previous calculations,
we obtain $\phi_{\rm min} \approx 0.84$ for $r > r^*$, where $r^*$ is the rate
above which $\phi_J$ is insensitive to rate. We further compare the structural
and mechanical properties of isostatic versus hyperstatic packings. The
structural characterizations include the contact number, bond orientational
order, and mixing ratios of the large and small particles. We find that the
isostatic packings are positionally and compositionally disordered, whereas
bond-orientational and compositional order increase with contact number for
hyperstatic packings. In addition, we calculate the static shear modulus and
normal mode frequencies of the static packings to understand the extent to
which the mechanical properties of amorphous, isostatic packings are different
from partially ordered packings. We find that the mechanical properties of the
packings change continuously as the contact number increases from isostatic to
hyperstatic.
| arxiv topic:cond-mat.soft cond-mat.stat-mech |
arxiv_dataset-20151007.2262 | Markov Chain Monte Carlo Method without Detailed Balance
cond-mat.stat-mech math-ph math.MP
We present a specific algorithm that generally satisfies the balance
condition without imposing the detailed balance in the Markov chain Monte
Carlo. In our algorithm, the average rejection rate is minimized, and even
reduced to zero in many relevant cases. The absence of the detailed balance
also introduces a net stochastic flow in a configuration space, which further
boosts up the convergence. We demonstrate that the autocorrelation time of the
Potts model becomes more than 6 times shorter than that by the conventional
Metropolis algorithm. Based on the same concept, a bounce-free worm algorithm
for generic quantum spin models is formulated as well.
| arxiv topic:cond-mat.stat-mech math-ph math.MP |
arxiv_dataset-20161007.2362 | Introduction to metric spaces with dilations
math.MG math.FA
This paper gives a short introduction into the metric theory of spaces with
dilations.
| arxiv topic:math.MG math.FA |
arxiv_dataset-20171007.2462 | QCD inspired relativistic bound state model and meson structures
hep-th
A QCD inspired relativistic effective Hamiltonian model for the bound states
of mesons has been constructed, which integrates the advantages of several QCD
effective Hamiltonian models. Based on light-front QCD effective Hamiltonian
model, the squared invariant mass operator of meson is used as the effective
Hamiltonian. The model has been improved significantly in four major aspects:
i)it is proved that in center of mass frame and in internal coordinate Hilbert
subspace, the total angular momentum $J$ of meson is conserved and the mass
eigen equation can be expressed in total angular momentum representation and in
terms of a set of coupled radial eigen equations for each $J$. ii)Based on
lattice QCD results, a relativistic confining potential is introduced into the
effective interaction and the excited states of mesons can be well described.
iii)an SU(3) flavor mixing interaction is introduced phenomenologically to
describe the flavor mixing mesons and the mass eigen equations contain the
coupling among different flavor components. iv)the mass eigen equations are of
relativistic covariance and the coupled radial mass eigen equations take full
account of $L-S $ coupling and tensor interactions. The model has been applied
to describe the whole meson spectra of about 265 mesons with available data.
The agreement of the calculated masses, squared radii, and decay constants with
data is quite well. For the mesons whose mass data have large experimental
uncertainty, the model produces certain mass values for test. For some mesons
whose total angular momenta and parity are not assigned experimentally, the
model gives a prediction of the spectroscopic configuration$^{2S+1}L_J$. The
connection between our model and the recent low energy QCD issues-the infrared
conformal scaling invariance and holographic QCD hadron models is discussed.
| arxiv topic:hep-th |
arxiv_dataset-20181007.2562 | Pointwise weighted approximation of functions with inner singularities
by Bernstein operators
math.FA
We consider the pointwise weighted approximation by Bernstein operators with
inner singularities. The related weight functions are weights
$\bar{w}(x)=|x-\xi|^\alpha(0<\xi<1,\ \alpha>0).$ In this paper we give direct
and inverse results of this type of Bernstein polynomials.
| arxiv topic:math.FA |
arxiv_dataset-20191007.2662 | Solving the Effective Field Equations for the Newtonian Potential
gr-qc hep-th
Loop corrections to the gravitational potential are usually inferred from
scattering amplitudes, which seems quite different from how the linearized
Einstein equations are solved with a static, point mass to give the classical
potential. In this study we show how the Schwinger-Keldysh effective field
equations can be used to compute loop corrections to the potential in a way
which parallels the classical treatment. We derive explicit results for the one
loop correction from the graviton self-energy induced by a massless, minimally
coupled scalar.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-20201007.2762 | Generalizations of Hagge's Theorems
math.MG
Two generalizations of Hagge's theorems are described. In the first we
consider what happens when one moves from the orthocentre to a general point.
What one loses by doing so is the indirect similarity and hence one loses the
centre of indirect similarity. Instead one proceeds from the centre of the
circle under consideration. In the second generalization we consider pairs of
triangles that have orthologic centres with respect to each other, so that an
indirect similarity is the main feature preserved.
| arxiv topic:math.MG |
arxiv_dataset-20211007.2862 | Minimal resonances in annular non-Euclidean strips
cond-mat.mtrl-sci cond-mat.soft physics.bio-ph
Differential growth processes play a prominent role in shaping leaves and
biological tissues. Using both analytical and numerical calculations, we
consider the shapes of closed, elastic strips which have been subjected to an
inhomogeneous pattern of swelling. The stretching and bending energies of a
closed strip are frustrated by compatibility constraints between the curvatures
and metric of the strip. To analyze this frustration, we study the class of
"conical" closed strips with a prescribed metric tensor on their center line.
The resulting strip shapes can be classified according to their number of
wrinkles and the prescribed pattern of swelling. We use this class of strips as
a variational ansatz to obtain the minimal energy shapes of closed strips and
find excellent agreement with the results of a numerical bead-spring model.
Within this class of strips, we derive a condition under which a strip can have
vanishing mean curvature along the center line.
| arxiv topic:cond-mat.mtrl-sci cond-mat.soft physics.bio-ph |
arxiv_dataset-20221007.2962 | Strangeness production in jets from p+p \sqrt{s} = 200 GeV collisions
nucl-ex
Measurements of strangeness production in jets help illuminate the QCD
mechanisms in fragmentation. Furthermore, they provide a crucial baseline for
heavy-ion studies where modifications in jet chemistry have recently been
predicted. We present new results on strange particle production in jets from
p+p \sqrt{s} = 200 GeV collisions measured by the STAR experiment. The momentum
distributions of the \Lambda, \bar{\Lambda} and K0Short particles are obtained
using various jet finding algorithms, and then compared to various models.
Strange particle ratios in jets are obtained and compared to values obtained
from the inclusive spectra. Finally, we show jets tagged with leading strange
baryons and mesons, in order to investigate whether gluon or quark jets can be
isolated in this way.
| arxiv topic:nucl-ex |
arxiv_dataset-20231007.3062 | Standing spin-wave mode structure and linewidth in partially disordered
perpendicularly magnetized sub-micron Permalloy disc arrays
cond-mat.mes-hall
Standing spin wave mode frequencies and linewidths in partially disordered
perpendicular magnetized arrays of sub-micron Permalloy discs are measured
using broadband ferromagnetic resonance and compared to analytical results from
a single, isolated disc. The measured mode structure qualitatively reproduces
the structure expected from the theory. Fitted demagnetizing parameters
decrease with increasing array disorder. The frequency difference between the
first and second radial modes is found to be higher in the measured array
systems than predicted by theory for an isolated disc. The relative frequencies
between successive spin wave modes are unaffected by reduction of the
long-range ordering of discs in the array. An increase in standing spin wave
resonance linewidth at low applied magnetic fields is observed and grows more
severe with increased array disorder.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-20241007.3162 | Green functions of the spectral ball and symmetrized polydisk
math.CV math.FA
The Green function of the spectral ball is constant over the isospectral
varieties, is never less than the pullback of its counterpart on the
symmetrized polydisk, and is equal to it in the generic case where the pole is
a cyclic (non-derogatory) matrix. When the pole is derogatory, the inequality
is always strict, and the difference between the two functions depends on the
order of nilpotence of the strictly upper triangular blocks that appear in the
Jordan decomposition of the pole. In particular, the Green function of the
spectral ball is not symmetric in its arguments. Additionally, some estimates
are given for invariant functions in the symmetrized polydisc, e.g.
(infinitesimal versions of) the Carath\'eodory distance and the Green function,
that show that they are distinct in dimension greater or equal to $3$.
| arxiv topic:math.CV math.FA |
arxiv_dataset-20251007.3262 | The Evolution of Lyman Limit Absorption Systems to Redshift Six
astro-ph.CO
We have measured the redshift evolution of the density of Lyman limit systems
(LLS) in the intergalactic medium over the redshift range 0 < z < 6. We have
used two new quasar samples to (1) improve coverage at z ~ 1, with GALEX grism
spectrograph observations of 50 quasars with 0.8 < z_em < 1.3, and (2) extend
coverage to z ~ 6, with Keck ESI spectra of 25 quasars with 4.17 < z_em < 5.99.
Using these samples together with published data, we find that the number
density of LLS per unit redshift, n(z), can be well fit by a simple evolution
of the form n(z) = n_3.5 [(1+z)/4.5]^gamma, with n_3.5 = 2.80 +/- 0.33 and
gamma = 1.94^(+0.36)_(-0.32) for the entire range 0 < z < 6. We have also
reanalyzed the evolution of damped Lyman alpha systems (DLAs) in the redshift
range 4 < z < 5 using our high-redshift quasar sample. We find a total of 17
DLAs and sub-DLAs, which we have analyzed in combination with published data.
The DLAs with log (HI column density) > 20.3 show the same redshift evolution
as the LLS. When combined with previous results, our DLA sample is also
consistent with a constant Omega_DLA= 9 x 10^(-4) from z = 2 to z = 5. We have
used the LLS number density evolution to compute the evolution in the mean free
path of ionizing photons. We find a smooth evolution to z ~ 6, very similar in
shape to that of Madau, Haardt & Rees (1999) but about a factor of two higher.
Recent theoretical models roughly match to the z < 6 data but diverge from the
measured power law at z > 6 in different ways, cautioning against extrapolating
the fit to the mean free path outside the measured redshift range.
| arxiv topic:astro-ph.CO |
arxiv_dataset-20261007.3362 | Picard approximation of stochastic differential equations and
application to LIBOR models
q-fin.CP math.PR q-fin.PR
The aim of this work is to provide fast and accurate approximation schemes
for the Monte Carlo pricing of derivatives in LIBOR market models. Standard
methods can be applied to solve the stochastic differential equations of the
successive LIBOR rates but the methods are generally slow. Our contribution is
twofold. Firstly, we propose an alternative approximation scheme based on
Picard iterations. This approach is similar in accuracy to the Euler
discretization, but with the feature that each rate is evolved independently of
the other rates in the term structure. This enables simultaneous calculation of
derivative prices of different maturities using parallel computing. Secondly,
the product terms occurring in the drift of a LIBOR market model driven by a
jump process grow exponentially as a function of the number of rates, quickly
rendering the model intractable. We reduce this growth from exponential to
quadratic using truncated expansions of the product terms. We include numerical
illustrations of the accuracy and speed of our method pricing caplets,
swaptions and forward rate agreements.
| arxiv topic:q-fin.CP math.PR q-fin.PR |
arxiv_dataset-20271007.3462 | Multiple Scattering: Dispersion, Temperature Dependence, and Annular
Pistons
hep-th quant-ph
We review various applications of the multiple scattering approach to the
calculation of Casimir forces between separate bodies, including dispersion,
wedge geometries, annular pistons, and temperature dependence. Exact results
are obtained in many cases.
| arxiv topic:hep-th quant-ph |
arxiv_dataset-20281007.3562 | Differently knotted symplectic surfaces in D^4 bounded by the same
transverse knot
math.GT math.SG
In this paper we show that there are two symplectic surfaces in the 4-ball
which bound the same transverse knot, have the same topology (as abstract
surfaces), and are distinguished by the fundamental groups of their
complements.
| arxiv topic:math.GT math.SG |
arxiv_dataset-20291007.3662 | An extended Stein-type covariance identity for the Pearson family with
applications to lower variance bounds
math.ST stat.TH
For an absolutely continuous (integer-valued) r.v. $X$ of the Pearson (Ord)
family, we show that, under natural moment conditions, a Stein-type covariance
identity of order $k$ holds (cf. [Goldstein and Reinert, J. Theoret. Probab. 18
(2005) 237--260]). This identity is closely related to the corresponding
sequence of orthogonal polynomials, obtained by a Rodrigues-type formula, and
provides convenient expressions for the Fourier coefficients of an arbitrary
function. Application of the covariance identity yields some novel expressions
for the corresponding lower variance bounds for a function of the r.v. $X$,
expressions that seem to be known only in particular cases (for the Normal, see
[Houdr\'{e} and Kagan, J. Theoret. Probab. 8 (1995) 23--30]; see also
[Houdr\'{e} and P\'{e}rez-Abreu, Ann. Probab. 23 (1995) 400--419] for
corresponding results related to the Wiener and Poisson processes). Some
applications are also given.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-20301007.3762 | Geometry of Lipschitz percolation
math.PR
We prove several facts concerning Lipschitz percolation, including the
following. The critical probability p_L for the existence of an open Lipschitz
surface in site percolation on Z^d with d\ge 2 satisfies the improved bound p_L
\le 1-1/[8(d-1)]. Whenever p > p_L, the height of the lowest Lipschitz surface
above the origin has an exponentially decaying tail. The lowest surface is
dominated stochastically by the boundary of a union of certain independent,
identically distributed random subsets of Z^d. As a consequence, for p
sufficiently close to 1, the connected regions of Z^{d-1} above which the
surface has height 2 or more exhibit stretched-exponential tail behaviour.
| arxiv topic:math.PR |
arxiv_dataset-20311007.3862 | Breaking an image encryption algorithm based on chaos
cs.CR
Recently, a chaos-based image encryption algorithm called MCKBA (Modified
Chaotic-Key Based Algorithm) was proposed. This paper analyzes the security of
MCKBA and finds that it can be broken with a differential attack, which
requires only four chosen plain-images. Performance of the attack is verified
by experimental results. In addition, some defects of MCKBA, including
insensitivity with respect to changes of plain-image/secret key, are reported.
| arxiv topic:cs.CR |
arxiv_dataset-20321007.3962 | Energy in one dimensional linear waves in a string
physics.class-ph
We consider the energy density and energy transfer in small amplitude,
one-dimensional waves on a string, and find that the common expressions used in
textbooks for the introductory physics with calculus course give wrong results
for some cases, including standing waves. We discuss the origin of the problem,
and how it can be corrected in a way appropriate for the introductory calculus
based physics course.
| arxiv topic:physics.class-ph |
arxiv_dataset-20331007.4062 | Support Vector Machines for Additive Models: Consistency and Robustness
stat.ML
Support vector machines (SVMs) are special kernel based methods and belong to
the most successful learning methods since more than a decade. SVMs can
informally be described as a kind of regularized M-estimators for functions and
have demonstrated their usefulness in many complicated real-life problems.
During the last years a great part of the statistical research on SVMs has
concentrated on the question how to design SVMs such that they are universally
consistent and statistically robust for nonparametric classification or
nonparametric regression purposes. In many applications, some qualitative prior
knowledge of the distribution P or of the unknown function f to be estimated is
present or the prediction function with a good interpretability is desired,
such that a semiparametric model or an additive model is of interest.
In this paper we mainly address the question how to design SVMs by choosing
the reproducing kernel Hilbert space (RKHS) or its corresponding kernel to
obtain consistent and statistically robust estimators in additive models. We
give an explicit construction of kernels - and thus of their RKHSs - which
leads in combination with a Lipschitz continuous loss function to consistent
and statistically robust SMVs for additive models. Examples are quantile
regression based on the pinball loss function, regression based on the
epsilon-insensitive loss function, and classification based on the hinge loss
function.
| arxiv topic:stat.ML |
arxiv_dataset-20341007.4162 | Grain sedimentation inside giant planet embryos
astro-ph.EP astro-ph.SR
In the context of massive fragmenting protoplanetary discs, Boss (1998)
suggested that grains can grow and sediment inside giant planet embryos formed
at R ~ 5 AU away from the star. Several authors since then criticised the
suggestion. Convection may prevent grain sedimentation, and the embryos cannot
even form so close to the parent star as cooling is too inefficient at these
distances. Here we reconsider the grain sedimentation process suggested by Boss
(1998) but inside an embryo formed, as expected in the light of the cooling
constraints, at R ~ 100 AU. Such embryos are much less dense and are also
cooler. We make analytical estimates of the process and also perform simple
spherically symmetric radiation hydrodynamics simulations to test these ideas.
We find that convection in our models does not become important before a
somewhat massive (~ an Earth mass, this is clarified in a followup paper) solid
core is built. Turbulent mixing slows down dust sedimentation but is
overwhelmed by grain sedimentation when the latter grow to a centimetres size.
The minimum time required for dust sedimentation to occur is a few thousand
years, and is a strong function of the embryo's mass, dust content and opacity.
An approximate analytical criterion is given to delineate conditions in which a
giant embryo contracts and heats up faster than dust can sediment. As Boss et
al (2002), we argue that core formation through grain sedimentation inside the
giant planet embryos may yield an unexplored route to form giant gas and giant
ice planets. The present model also stands at the basis of paper III, where we
study the possibility of forming terrestrial planet cores by tidal disruption
and photoevaporation of the planetary envelope.
| arxiv topic:astro-ph.EP astro-ph.SR |
arxiv_dataset-20351007.4262 | Optimal waveform for the entrainment of a weakly forced oscillator
nlin.CD
A theory for obtaining waveform for the effective entrainment of a weakly
forced oscillator is presented. Phase model analysis is combined with calculus
of variation to derive a waveform with which entrainment of an oscillator is
achieved with minimum power forcing signal. Optimal waveforms are calculated
from the phase response curve and a solution to a balancing condition. The
theory is tested in chemical entrainment experiments in which oscillations
close to and further away from a Hopf bifurcation exhibited sinusoidal and
higher harmonic nontrivial optimal waveforms, respectively.
| arxiv topic:nlin.CD |
arxiv_dataset-20361007.4362 | Holographic model for dilepton production in p-p collisions
hep-th hep-ph
We propose a holographic model for dilepton production in proton-proton
collisions based on the exchange of vector mesons. The holographic hard wall
model is used to describe the dynamics and interactions of vector mesons and
baryons. We estimate the parameters lambda, mu, nu that characterize the
angular distribution of the produced dileptons in a region of q_T^2 << Q^2,
where perturbative QCD presents an effective strong coupling due to large
logarithm corrections.
| arxiv topic:hep-th hep-ph |
arxiv_dataset-20371007.4462 | Radioactive 26Al from the Scorpius-Centaurus Association
astro-ph.HE
The Scorpius-Centaurus association is the most-nearby group of massive and
young stars. As nuclear-fusion products are ejected by massive stars and
supernovae into the surrounding interstellar medium, the search for
characteristic gamma-rays from radioactivity is one way to probe the history of
activity of such nearby massive stars on a My time scale through their
nucleosynthesis. 26Al decays within ~1 My, 1809 keV gamma-rays from its decay
can be measured with current gamma-ray telescopes, such as INTEGRAL's gamma-ray
spectrometer SPI. Following earlier 26Al gamma-ray mapping with NASA's Compton
observatory, we test spatial emission skymaps of 26Al for a component which
could be attributed to ejecta from massive stars in the Scorpius-Centaurus
group of stars. Such a model fit of spatial distributions for large-scale and
local components is able to discriminate 26Al emission associated with
Scorpius-Centaurus, in spite of the strong underlying nucleosynthesis signal
from the Galaxy at large. We find an 26Al signal above 5 sigma significance,
which we associate with the Sco-Cen group. The observed flux of 6 *10^{-5}ph
cm^{-2} s^{-1} corresponds to 1.1 *10^{-4} M_sol of 26Al. This traces the
nucleosynthesis ejecta of several massive stars within the past several million
years. We confirm through direct detection of radioactive 26Al the recent
ejection of massive-star nucleosynthesis products from the Sco-Cen association.
Its youngest subgroup in Upper Scorpius appears to dominate 26Al contributions
from this association. Our 26Al signal can be interpreted as a measure of the
age and richness of this youngest subgroup. We also estimate a kinematic
imprint of these nearby massive-star ejecta from the bulk motion of 26Al and
compare this to other indications of Scorpius-Centaurus massive-star activity .
| arxiv topic:astro-ph.HE |
arxiv_dataset-20381007.4562 | Type IIB construction of flavoured ABJ(M) and fractional M2 branes
hep-th
We study type IIB brane configurations engineering 3d flavoured ABJ(M)
theories with Yang-Mills kinetic terms, which flow to IR fixed points
describing M2 branes at a class of toric Calabi-Yau fourfold singularities. The
type IIB construction provides a bridge between M-theory geometry and field
theory, and allows to identify the superconformal field theories with fixed
quiver diagram, Chern-Simons levels and superpotential, differing by the ranks
of the gauge groups, which we associate to dual AdS_4\timesY_7 backgrounds of
M-theory without or with torsion G-fluxes sourced by fractional M2 branes in
Y_7, when Y_7 is smooth. The analysis includes the Q^{1,1,1} and Y^{1,2}(CP^2)
geometries. We also comment on duality cascades and on the interplay between
torsion G-fluxes in M-theory and partial resolutions.
| arxiv topic:hep-th |
arxiv_dataset-20391007.4662 | Non-boost-invariant motion of dissipative and highly anisotropic fluid
nucl-th hep-ph
The recently formulated framework of anisotropic and dissipative
hydrodynamics (ADHYDRO) is used to describe non-boost-invariant motion of the
fluid created at the early stages of heavy-ion collisions. Very strong initial
asymmetries of pressure are reduced by the entropy production processes. By the
appropriate choice of the form of the entropy source we can reproduce realistic
scenarios for the isotropization expected in heavy-ion collisions. Our previous
results are generalized by including the realistic equation of state as the
limit of the isotropization processes.
| arxiv topic:nucl-th hep-ph |
arxiv_dataset-20401007.4762 | FERO: Finding Extreme Relativistic Objects. I. Statistics of
Relativistic Fe Kalpha lines in Radio-Quiet Type 1 AGN
astro-ph.HE
Accretion models predict that fluorescence lines broadened by relativistic
effects should arise from reflection of X-ray emission onto the inner region of
the accretion disc surrounding the central black hole of active galactic nuclei
(AGN). The theory behind the origin of relativistic lines is well established,
and observational evidence from a moderate number of sources seems to support
the existence of these lines. The aim of this work is to establish the fraction
of AGN with relativistic Fe Kalpha lines, and study possible correlations with
source physical properties. An XMM-Newton collection of 149 radio-quiet Type 1
AGN has been systematically and uniformly analyzed in order to search for
significant evidence of a relativistically broadened Fe Kalpha line. To enable
statistical studies, an almost complete, flux-limited subsample of 31 sources
has been defined. The 2-10 keV spectra of the FERO sources have been compared
with a complex model including most of the physical components observed in the
X-ray spectra of Seyfert galaxies: a power law primary continuum modified by
non-relativistic Compton reflection and warm absorption, plus a series of
narrow Fe line reflection features. The observed fraction of sources in the
flux-limited sample that show significant evidence of a relativistic Fe Kalpha
line is 36%. The average line Equivalent Width (EW) is of the order of 100 eV,
while the average disc inclination angle is 28+/-5 deg and the average
power-law index of the radial disc emissivity law is 2.4+/-0.4. The spin value
is well constrained only in 2 cases (MCG-6-30-15 and MRK509), and in the rest
of the cases, whenever a constraint can be placed, it always implies the
rejection of the static black hole solution. The Fe Kalpha line EW does not
correlate with disc parameters or with system physical properties, such as
black hole mass, accretion rate and hard X-ray luminosity.
| arxiv topic:astro-ph.HE |
arxiv_dataset-20411007.4862 | No Indications of Axion-Like Particles From Fermi
astro-ph.HE hep-ph
As very high energy (~100 GeV) gamma rays travel over cosmological distances,
their flux is attenuated through interactions with the extragalactic background
light. Observations of distant gamma ray sources at energies between ~200 GeV
and a few TeV by ground-based gamma ray telescopes such as HESS, however,
suggest that the universe is more transparent to very high energy photons than
had been anticipated. One possible explanation for this is the existence of
axion-like-particles (ALPs) which gamma rays can efficiently oscillate into,
enabling them to travel cosmological distances without attenuation. In this
article, we use data from the Fermi Gamma Ray Space Telescope to calculate the
spectra at 1-100 GeV of two gamma ray sources, 1ES1101-232 at redshift z=0.186
and H2356-309 at z=0.165, and use this in conjunction with the measurements of
ground-based telescopes to test the ALP hypothesis. We find that the
observations can be well-fit by an intrinsic power-law source spectrum with
indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that
no ALPs or other exotic physics is necessary to explain the observed degree of
attenuation.
| arxiv topic:astro-ph.HE hep-ph |
arxiv_dataset-20421007.4962 | The Formation of Spheroids in Early-Type Spirals: Clues From Their
Globular Clusters
astro-ph.CO
We use deep Hubble Space Telescope images taken with the Advanced Camera for
Surveys (ACS) in the F475W and F814W filters to investigate the globular
cluster systems in four edge-on Sa spiral galaxies covering a factor of 4 in
luminosity. The specific frequencies of the blue globular clusters in the
galaxies in our sample fall in the range 0.34 -- 0.84, similar to typical
values found for later-type spirals. The number of red globular clusters
associated with the bulges generally increases with the bulge luminosity,
similar to what is observed for elliptical galaxies, although the specific
frequency of bulge clusters is a factor of 2-3 lower for the lowest luminosity
bulges than for the higher luminosity bulges. We present a new empirical
relation between the fraction of red globular clusters and total bulge
luminosity based on the elliptical galaxies studied by ACSVCS (ACS Virgo
Cluster Survey), and discuss how this diagram can be used to assess the
importance that dissipative processes played in building spiral bulges. Our
results suggest a picture where dissipative processes, which are expected
during gas-rich major mergers, were more important for building luminous bulges
of Sa galaxies, whereas secular evolution may have played a larger role in
building lower-luminosity bulges in spirals.
| arxiv topic:astro-ph.CO |
arxiv_dataset-20431007.5062 | A hot compact dust disk around a massive young stellar object
astro-ph.SR astro-ph.GA astro-ph.IM
Circumstellar disks are an essential ingredient of the formation of low-mass
stars. It is unclear, however, whether the accretion-disk paradigm can also
account for the formation of stars more massive than about 10 solar masses, in
which strong radiation pressure might halt mass infall. Massive stars may form
by stellar merging, although more recent theoretical investigations suggest
that the radiative-pressure limit may be overcome by considering more complex,
nonspherical infall geometries. Clear observational evidence, such as the
detection of compact dusty disks around massive young stellar objects, is
needed to identify unambiguously the formation mode of the most massive stars.
Here we report near-infrared interferometric observations that spatially
resolve the astronomical unit-scale distribution of hot material around a
high-mass (approx. 20 solar masses) young stellar object. The image shows an
elongated structure with a size of about 13 x 19 astronomical units, consistent
with a disk seen at an inclination angle of 45 degree. Using geometric and
detailed physical models, we found a radial temperature gradient in the disk,
with a dust-free region less than 9.5 astronomical units from the star,
qualitatively and quantitatively similar to the disks observed in low-mass star
formation. Perpendicular to the disk plane we observed a molecular outflow and
two bow shocks, indicating that a bipolar outflow emanates from the inner
regions of the system.
| arxiv topic:astro-ph.SR astro-ph.GA astro-ph.IM |
arxiv_dataset-20441007.5162 | The effect of disorder on the free-energy for the Random Walk Pinning
Model: smoothing of the phase transition and low temperature asymptotics
math-ph math.MP math.PR
We consider the continuous time version of the Random Walk Pinning Model
(RWPM), studied in [5,6,7]. Given a fixed realization of a random walk Y$ on
Z^d with jump rate rho (that plays the role of the random medium), we modify
the law of a random walk X on Z^d with jump rate 1 by reweighting the paths,
giving an energy reward proportional to the intersection time L_t(X,Y)=\int_0^t
\ind_{X_s=Y_s}\dd s: the weight of the path under the new measure is exp(beta
L_t(X,Y)), beta in R. As beta increases, the system exhibits a
delocalization/localization transition: there is a critical value beta_c, such
that if beta>beta_c the two walks stick together for almost-all Y realizations.
A natural question is that of disorder relevance, that is whether the quenched
and annealed systems have the same behavior. In this paper we investigate how
the disorder modifies the shape of the free energy curve: (1) We prove that, in
dimension d larger or equal to three 3, the presence of disorder makes the
phase transition at least of second order. This, in dimension larger or equal
to 4, contrasts with the fact that the phase transition of the annealed system
is of first order. (2) In any dimension, we prove that disorder modifies the
low temperature asymptotic of the free energy.
| arxiv topic:math-ph math.MP math.PR |
arxiv_dataset-20451007.5262 | Metastability of solitary roll wave solutions of the St. Venant
equations with viscosity
math.AP
We study by a combination of numerical and analytical Evans function
techniques the stability of solitary wave solutions of the St. Venant equations
for viscous shallow-water flow down an incline, and related models. Our main
result is to exhibit examples of metastable solitary waves for the St. Venant
equations, with stable point spectrum indicating coherence of the wave profile
but unstable essential spectrum indicating oscillatory convective instabilities
shed in its wake. We propose a mechanism based on ``dynamic spectrum'' of the
wave profile, by which a wave train of solitary pulses can stabilize each other
by de-amplification of convective instabilities as they pass through successive
waves. We present numerical time evolution studies supporting these
conclusions, which bear also on the possibility of stable periodic solutions
close to the homoclinic. For the closely related viscous Jin-Xin model, by
contrast, for which the essential spectrum is stable, we show using the
stability index of Gardner--Zumbrun that solitary wave pulses are always
exponentially unstable, possessing point spectra with positive real part.
| arxiv topic:math.AP |
arxiv_dataset-20461007.5362 | Dynamics of Neptune's Trojans: II. Eccentric orbits and observed ones
astro-ph.EP
In a previous paper, we have presented a global view of the stability of
Neptune Trojan (NT hereafter) on inclined orbit. We discuss in this paper the
dependence of stability of NT orbits on the eccentricity. High-resolution
dynamical maps are constructed using the results of extensive numerical
integrations of orbits initialized on the fine grids of initial semimajor axis
(a0) versus eccentricity (e0). The extensions of regions of stable orbits on
the (a0, e0) plane at different inclinations are shown. The maximum
eccentricities of stable orbits in three most stable regions at low (0,
12deg.), medium (22,36deg.) and high (51, 59deg.) inclination, are found to be
0.10, 0.12 and 0.04, respectively. The fine structures in the dynamical maps
are described. Via the frequency analysis method, the mechanisms that portray
the dynamical maps are revealed. The secondary resonances, concerning the
frequency of the librating resonant angle and the frequency of the quasi 2:1
mean motion resonance between Neptune and Uranus, are found deeply involved in
the motion of NTs. Secular resonances are detected and they also contribute
significantly to the triggering of chaos in the motion. Particularly, the
effects of the secular resonance v8, v18 are clarified.
We also investigate the orbital stabilities of six observed NTs by checking
the orbits of hundreds clones of them generated within the observing error
bars. We conclude that four of them, except 2001 QR322 and 2005 TO74, are
deeply inside the stable region. The 2001 QR322 is in the close vicinity of the
most significant secondary resonance. The 2005 TO74 locates close to the
boundary separating stable orbits from unstable ones, and it may be influenced
by a secular resonance.
| arxiv topic:astro-ph.EP |
arxiv_dataset-20471007.5462 | Multiscale analysis: Fisher-Wright diffusions with rare mutations and
selection, logistic branching system
math.PR
We study two types of stochastic processes, a mean-field spatial system of
interacting Fisher-Wright diffusions with an inferior and an advantageous type
with rare mutation (inferior to advantageous) and a (mean-field) spatial system
of supercritical branching random walks with an additional deathrate which is
quadratic in the local number of particles. The former describes a standard
two-type population under selection, mutation, the latter models describe a
population under scarce resources causing additional death at high local
population intensity. Geographic space is modelled by $\{1, \cdots, N\}$. The
first process starts in an initial state with only the inferior type present or
an exchangeable configuration and the second one with a single initial
particle. {This material is a special case of the theory developed in
\cite{DGsel}.}
We study the behaviour in two time windows, first between time 0 and $T$ and
secondly after a large time when in the Fisher-Wright model the rare mutants
succeed respectively in the branching random walk the particle population
reaches a positive spatial intensity. It is shown that the second phase for
both models sets in after time $\alpha^{-1} \log N$, if $N$ is the size of
geographic space and $N^{-1}$ the rare mutation rate and $\alpha \in (0,
\infty)$ depends on the other parameters. We identify the limit dynamics in
both time windows and for both models as a nonlinear Markov dynamic
(McKean-Vlasov dynamic) respectively a corresponding random entrance law from
time $-\infty$ of this dynamic.
Finally we explain that the two processes are just two sides of the very same
coin, a fact arising from duality, in particular the particle model generates
the genealogy of the Fisher-Wright diffusions with selection and mutation. We
discuss the extension of this duality relation to a multitype model with more
than two types.
| arxiv topic:math.PR |
arxiv_dataset-20481008.0041 | Dual Superconformal Symmetry of N=6 Chern-Simons Theory
hep-th
We demonstrate that the four and six-point tree-level amplitudes of N=6
superconformal Chern-Simons theory (ABJM) enjoy OSp(6|4) dual superconformal
symmetry if one enlarges the dual superspace to include three additional
Grassmann-even coordinates which correspond to an abelian isometry of CP3. The
inclusion of these coordinates enables us to match the nontrivial dual
superconformal generators with level-one Yangian generators when acting on
on-shell amplitudes. We also discuss some implications of dual conformal
symmetry for loop-level amplitudes.
| arxiv topic:hep-th |
arxiv_dataset-20491008.0141 | Impurity effect on weak anti-localization in the topological insulator
Bi2Te3
cond-mat.mes-hall cond-mat.dis-nn
We study weak anti-localization (WAL) effect in topological insulator Bi2Te3
thin films at low temperatures. Two-dimensional WAL effect associated with
surface carriers is revealed in the tilted magnetic field dependence of
magneto-conductance. Our data demonstrates that the observed WAL is robust
against deposition of non-magnetic Au impurities on the surface of the thin
films. But it is quenched by deposition of magnetic Fe impurities which destroy
the pi Berry's phase of the topological surface states. The magneto-conductance
data of a 5 nm Bi2Te3 film suggests that a crossover from symplectic to unitary
classes is observed with the deposition of Fe impurities.
| arxiv topic:cond-mat.mes-hall cond-mat.dis-nn |
arxiv_dataset-20501008.0241 | Multi-shocks in asymmetric simple exclusions processes: Insights from
fixed-point analysis of the boundary-layers
cond-mat.stat-mech
The boundary-induced phase transitions in an asymmetric simple exclusion
process with inter-particle repulsion and bulk non-conservation are analyzed
through the fixed points of the boundary layers. This system is known to have
phases in which particle density profiles have different kinds of shocks. We
show how this boundary-layer fixed-point method allows us to gain physical
insights on the nature of the phases and also to obtain several quantitative
results on the density profiles especially on the nature of the boundary-layers
and shocks.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-20511008.0341 | Temperature and bias voltage dependence of Co/Pd multilayer-based
magnetic tunnel junctions with perpendicular magnetic anisotropy
cond-mat.mtrl-sci
Temperature- and bias voltage-dependent transport measurements of magnetic
tunnel junctions (MTJs) with perpendicularly magnetized Co/Pd electrodes are
presented. Magnetization measurements of the Co/Pd multilayers are performed to
characterize the electrodes. The effects of the Co layer thickness in the Co/Pd
bilayers, the annealing temperature, the Co thickness at the MgO barrier
interface, and the number of bilayers on the tunneling magneto resistance (TMR)
effect are investigated. TMR-ratios of about 11 % at room temperature and 18.5
% at 13 K are measured and two well-defined switching fields are observed. The
results are compared to measurements of MTJs with Co-Fe-B electrodes and
in-plane anisotropy.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-20521008.0441 | An Optimal Trade-off between Content Freshness and Refresh Cost
cs.IR
Caching is an effective mechanism for reducing bandwidth usage and
alleviating server load. However, the use of caching entails a compromise
between content freshness and refresh cost. An excessive refresh allows a high
degree of content freshness at a greater cost of system resource. Conversely, a
deficient refresh inhibits content freshness but saves the cost of resource
usages. To address the freshness-cost problem, we formulate the refresh
scheduling problem with a generic cost model and use this cost model to
determine an optimal refresh frequency that gives the best tradeoff between
refresh cost and content freshness. We prove the existence and uniqueness of an
optimal refresh frequency under the assumptions that the arrival of content
update is Poisson and the age-related cost monotonically increases with
decreasing freshness. In addition, we provide an analytic comparison of system
performance under fixed refresh scheduling and random refresh scheduling,
showing that with the same average refresh frequency two refresh schedulings
are mathematically equivalent in terms of the long-run average cost.
| arxiv topic:cs.IR |
arxiv_dataset-20531008.0541 | Determinant Sums for Undirected Hamiltonicity
cs.DS
We present a Monte Carlo algorithm for Hamiltonicity detection in an
$n$-vertex undirected graph running in $O^*(1.657^{n})$ time. To the best of
our knowledge, this is the first superpolynomial improvement on the worst case
runtime for the problem since the $O^*(2^n)$ bound established for TSP almost
fifty years ago (Bellman 1962, Held and Karp 1962). It answers in part the
first open problem in Woeginger's 2003 survey on exact algorithms for NP-hard
problems.
For bipartite graphs, we improve the bound to $O^*(1.414^{n})$ time. Both the
bipartite and the general algorithm can be implemented to use space polynomial
in $n$.
We combine several recently resurrected ideas to get the results. Our main
technical contribution is a new reduction inspired by the algebraic sieving
method for $k$-Path (Koutis ICALP 2008, Williams IPL 2009). We introduce the
Labeled Cycle Cover Sum in which we are set to count weighted arc labeled cycle
covers over a finite field of characteristic two. We reduce Hamiltonicity to
Labeled Cycle Cover Sum and apply the determinant summation technique for Exact
Set Covers (Bj\"orklund STACS 2010) to evaluate it.
| arxiv topic:cs.DS |
arxiv_dataset-20541008.0641 | An Alternative Approach To Measuring Reverberation Lags in Active
Galactic Nuclei
astro-ph.CO astro-ph.IM
Motivated by recent progress in the statistical modeling of quasar
variability, we develop a new approach to measuring emission-line reverberation
lags to estimate the size of broad-line regions (BLRs) in active galactic
nuclei. Assuming that all emission-line light curves are scaled, smoothed, and
displaced versions of the continuum, this alternative approach fits the light
curves directly using a damped random walk model and aligns them to recover the
time lag and its statistical confidence limits. We introduce the mathematical
formalism of this approach and demonstrate its ability to cope with some of the
problems for traditional methods, such as irregular sampling, correlated
errors, and seasonal gaps. We redetermine the lags for 87 emission lines in 31
quasars and reassess the BLR size--luminosity relationship using 60 H-beta
lags. We confirm the general results from the traditional cross-correlation
methods, with a few exceptions. Our method, however, also supports a broad
range of extensions. In particular, it can simultaneously fit multiple lines
and continuum light curves which improves the lag estimate for the lines and
provides estimates of the error correlations between them. Determining these
correlations is of particular importance for interpreting emission-line
velocity--delay maps. We can also include parameters for luminosity-dependent
lags or line responses. We use this to detect the scaling of the BLR size with
continuum luminosity in NGC 5548.
| arxiv topic:astro-ph.CO astro-ph.IM |
arxiv_dataset-20551008.0741 | Strong impact of light induced conical intersections on the spectrum of
diatomic molecules
physics.atom-ph physics.chem-ph
We show that dressing of diatomic molecules by running laser waves gives rise
to conical intersections (CIs). Due to presence of such CIs, the rovibronic
molecular motions are strongly coupled. A pronounced impact of the CI on the
spectrum of $Na_2$ molecule is demonstrated via numerical calculation for weak
and moderate laser intensity, and an experiment is suggested on this basis. The
position of the light induced CI and the strength of its non-adiabatic
couplings can be chosen by changing the frequency and intensity of the used
running laser wave. This offers new possibilities to control the photo-induced
rovibronic molecular dynamics.
| arxiv topic:physics.atom-ph physics.chem-ph |
arxiv_dataset-20561008.0841 | Support Theorems for Horocycles on Hyperbolic Spaces
math.DG
A support theorem for the horocycle Radon transform f \to \hat{f} is a
property of the form \hat{f} of compact support \rightarrow f of compact
support. Here we prove a variation of this result where support (\hat{f}) is
outside a fixed horocycle in hyperbolic space.
| arxiv topic:math.DG |
arxiv_dataset-20571008.0941 | Timing matters: Lessons From The CA Literature On Updating
cs.MA nlin.AO nlin.CG
In the present article we emphasize the importance of modeling time in the
context of agent-based models. To this end, we present a (selective) survey of
the Cellular Automata-literature on updating and draw parallels to the issue of
agent activation in agent-based models. By means of two simple models,
Schelling's segregation model and Epstein's demographic prisoner's dilemma we
investigate the influence of choosing different regimes of agent activation.
Our experiments indicate that timing is not a critical issue for very simple
models but bears huge influence on model behavior and results as soon as the
degree of complexity increases only so slightly. After a brief review of the
way commonly used ABM simulation environments handle the issue of timing, we
draw some tentative conclusions about the importance of timing and the need for
more research towards that direction, similar to the concerted effort on
updating in cellular automata.
| arxiv topic:cs.MA nlin.AO nlin.CG |
arxiv_dataset-20581008.1041 | Anisotropic magnetocaloric effect in all-ferromagnetic
(La0.7Sr0.3MnO3/SrRuO3) superlattices
cond-mat.mtrl-sci cond-mat.str-el
We exploit the magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3
superlattices to realize a crossover between inverse and conventional magnetic
entropy changes. Our data reveal a strong anisotropic nature of the
magnetocaloric effect due to the magnetic anisotropy of the superlattice.
Therefore, artificial superlattices built from ferromagnetic materials that can
be used to alter the magnetic structure as well as the magnetic anisotropy,
could also be utilized for tuning the magnetocaloric properties, which may open
a constructive approach for magnetic refrigeration applications.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-20591008.1141 | Feshbach resonances in 3He*-4He* mixtures
cond-mat.quant-gas
We discuss the stability of homonuclear and heteronuclear mixtures of 3He and
4He atoms in the metastable 2^3S_1 state (He*) and predict positions and widths
of Feshbach resonances by using the Asymptotic Bound-state Model (ABM). All
calculations are performed without fit parameters, using \emph{ab-initio}
calculations of molecular potentials. One promising very broad Feshbach
resonance (\Delta B=72.9^{+18.3}_{-19.3} mT) is found that allows for tuning of
the inter-isotope scattering length.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-20601008.1241 | Muon Tomography of Ice-filled Cleft Systems in Steep Bedrock Permafrost:
A Proposal
physics.geo-ph physics.acc-ph physics.ins-det
In this note, we propose a novel application of geoparticle physics, namely
using a muon tomograph to study ice-filled cleft systems in steep bedrock
permafrost. This research could significantly improve our understanding of high
alpine permafrost in general and climate-permafrost induced rockfall in
particular.
| arxiv topic:physics.geo-ph physics.acc-ph physics.ins-det |
arxiv_dataset-20611008.1341 | Seismic pulse propagation with constant Q and stable probability
distributions
math-ph math.MP math.PR physics.geo-ph
The one-dimensional propagation of seismic waves with constant Q is shown to
be governed by an evolution equation of fractional order in time, which
interpolates the heat equation and the wave equation. The fundamental solutions
for the Cauchy and Signalling problems are expressed in terms of entire
functions (of Wright type) in the similarity variable and their behaviours turn
out to be intermediate between those for the limiting cases of a perfectly
viscous fluid and a perfectly elastic solid. In view of the small dissipation
exhibited by the seismic pulses, the nearly elastic limit is considered.
Furthermore, the fundamental solutions for the Cauchy and Signalling problems
are shown to be related to stable probability distributions with index of
stability determined by the order of the fractional time derivative in the
evolution equation.
| arxiv topic:math-ph math.MP math.PR physics.geo-ph |
arxiv_dataset-20621008.1441 | Parametric oscillators from factorizations employing a constant-shifted
Riccati solution of the harmonic oscillator
math-ph math.MP
We determine the kind of parametric oscillators that are generated in the
usual factorization procedure of second-order linear differential equations
when one introduces a constant shift of the Riccati solution of the classical
harmonic oscillator. The mathematical results show that some of these
oscillators could be of physical nature. We give the solutions of the obtained
second-order differential equations and the values of the shift parameter
providing strictly periodic and antiperiodic solutions. We also notice that
this simple problem presents parity-time (PT) symmetry. Possible applications
are mentioned
| arxiv topic:math-ph math.MP |
arxiv_dataset-20631008.1541 | SuperB Progress Reports -- Physics
hep-ex hep-ph
SuperB is a high luminosity e+e- collider that will be able to indirectly
probe new physics at energy scales far beyond the reach of any man made
accelerator planned or in existence. Just as detailed understanding of the
Standard Model of particle physics was developed from stringent constraints
imposed by flavour changing processes between quarks, the detailed structure of
any new physics is severely constrained by flavour processes. In order to
elucidate this structure it is necessary to perform a number of complementary
studies of a set of golden channels. With these measurements in hand, the
pattern of deviations from the Standard Model behavior can be used as a test of
the structure of new physics. If new physics is found at the LHC, then the many
golden measurements from SuperB will help decode the subtle nature of the new
physics. However if no new particles are found at the LHC, SuperB will be able
to search for new physics at energy scales up to 10-100 TeV. In either
scenario, flavour physics measurements that can be made at SuperB play a
pivotal role in understanding the nature of physics beyond the Standard Model.
Examples for using the interplay between measurements to discriminate New
Physics models are discussed in this document. SuperB is a Super Flavour
Factory, in addition to studying large samples of B_{u,d,s}, D and tau decays,
SuperB has a broad physics programme that includes spectroscopy both in terms
of the Standard Model and exotica, and precision measurements of sin^2theta_W.
In addition to performing CP violation measurements at the Y(4S) and phi(3770),
SuperB will test CPT in these systems, and lepton universality in a number of
different processes. The multitude of rare decay measurements possible at
SuperB can be used to constrain scenarios of physics beyond the Standard Model.
...
| arxiv topic:hep-ex hep-ph |
arxiv_dataset-20641008.1641 | An approximate method for controlling solid elastic waves by
transformation media
physics.class-ph
By idealizing a general mapping as a series of local affine ones, we derive
approximately transformed material parameters necessary to control solid
elastic waves within classical elasticity theory. The transformed elastic
moduli are symmetric, and can be used with Navier's equation to manipulate
elastic waves. It is shown numerically that the method can provide a powerful
tool to control elastic waves in solids in case of high frequency or small
material gradient. Potential applications can be anticipated in nondestructive
testing, structure impact protection, petroleum exploration and seismology.
| arxiv topic:physics.class-ph |
arxiv_dataset-20651008.1741 | BCS as Foundation and Inspiration: The Transmutation of Symmetry
cond-mat.supr-con cond-mat.str-el hep-th
The BCS theory injected two powerful ideas into the collective consciousness
of theoretical physics: pairing and spontaneous symmetry breaking. In the 50
years since the seminal work of Bardeen, Cooper, and Schrieffer, those ideas
have found important use in areas quite remote from the stem application to
metallic superconductivity. This is a brief and eclectic sketch of some
highlights, emphasizing relatively recent developments in QCD and in the theory
of quantum statistics, and including a few thoughts about future directions. A
common theme is the importance of symmetry {\it transmutation}, as opposed to
the simple {\it breaking} of electromagnetic $U(1)$ symmetry in classic
metallic superconductors.
| arxiv topic:cond-mat.supr-con cond-mat.str-el hep-th |
arxiv_dataset-20661008.1841 | Hadron production in p+p, p+Pb, and Pb+Pb collisions with the HIJING 2.0
model at energies available at the CERN Large Hadron Collider
hep-ph nucl-th
The HIJING (Heavy-ion Jet Interaction Generator) Monte Carlo model is updated
with the latest parton distributions functions (PDF) and new set of the
parameters in the two-component mini-jet model that controls total $p+p$ cross
section and the central pseudorapity density. We study hadron spectra and
multiplicity distributions using the HIJING 2.0 model and compare to recent
experimental data from $p+p$ collisions at the LHC energies. We also give
predictions of hadron production in $p+p$, $p+Pb$ and $Pb+Pb$ collisions at the
full LHC energy.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-20671008.1941 | Comparison of covariant and orthogonal Lyapunov vectors
nlin.CD
Two sets of vectors, covariant and orthogonal Lyapunov vectors (CLVs/OLVs),
are currently used to characterize the linear stability of chaotic systems. A
comparison is made to show their similarity and difference, especially with
respect to the influence on hydrodynamic Lyapunov modes (HLMs). Our numerical
simulations show that in both Hamiltonian and dissipative systems HLMs formerly
detected via OLVs survive if CLVs are used instead. Moreover the previous
classification of two universality classes works for CLVs as well, i.e. the
dispersion relation is linear for Hamiltonian systems and quadratic for
dissipative systems respectively. The significance of HLMs changes in different
ways for Hamiltonian and dissipative systems with the replacement of OLVs by
CLVs. For general dissipative systems with nonhyperbolic dynamics the long wave
length structure in Lyapunov vectors corresponding to near-zero Lyapunov
exponents is strongly reduced if CLVs are used instead, whereas for highly
hyperbolic dissipative systems the significance of HLMs is nearly identical for
CLVs and OLVs. In contrast the HLM significance of Hamiltonian systems is
always comparable for CLVs and OLVs irrespective of hyperbolicity. We also find
that in Hamiltonian systems different symmetry relations between conjugate
pairs are observed for CLVs and OLVs. Especially, CLVs in a conjugate pair are
statistically indistinguishable in consequence of the micro- reversibility of
Hamiltonian systems. Transformation properties of Lyapunov exponents, CLVs and
hyperbolicity under changes of coordinate are discussed in appendices.
| arxiv topic:nlin.CD |
arxiv_dataset-20681008.2041 | Least squares approximations of measures via geometric condition numbers
math.FA math.MG
For a probability measure on a real separable Hilbert space, we are
interested in "volume-based" approximations of the d-dimensional least squares
error of it, i.e., least squares error with respect to a best fit d-dimensional
affine subspace. Such approximations are given by averaging real-valued
multivariate functions which are typically scalings of squared (d+1)-volumes of
(d+1)-simplices. Specifically, we show that such averages are comparable to the
square of the d-dimensional least squares error of that measure, where the
comparison depends on a simple quantitative geometric property of it. This
result is a higher dimensional generalization of the elementary fact that the
double integral of the squared distances between points is proportional to the
variance of measure. We relate our work to two recent algorithms, one for
clustering affine subspaces and the other for Monte-Carlo SVD based on volume
sampling.
| arxiv topic:math.FA math.MG |
arxiv_dataset-20691008.2141 | Interplay of p-d and d-d charge transfer transitions in rare-earth
perovskite manganites
cond-mat.str-el cond-mat.mtrl-sci
We have performed both theoretical and experimental study of optical response
of parent perovskite manganites RMnO_3 with a main goal to elucidate nature of
clearly visible optical features. Starting with a simple cluster model approach
we addressed the both one-center (p-d) and two-center (d-d) charge transfer
(CT) transitions, their polarization properties, the role played by structural
parameters, orbital mixing, and spin degree of freedom. Optical complex
dielectric function of single crystalline samples of RMnO_3 (R=La, Pr, Nd, Sm,
Eu) was measured by ellipsometric technique at room temperature in the spectral
range from 1.0 to 5.0 eV for two light polarizations: E \parallel c and E \perp
c. The comparative analysis of the spectral behavior of \varepsilon _1 and
\varepsilon _2 is believed to provide a more reliable assignment of spectral
features. We have found an overall agreement between experimental spectra and
theoretical predictions based on the theory of one-center p-d CT transitions
and inter-site d-d CT transitions. Our experimental data and theoretical
analysis evidence a dual nature of the dielectric gap in nominally
stoichiometric matrix of perovskite manganites RMnO_3, it is formed by a
superposition of forbidden or weak dipole allowed p-d CT transitions and
inter-site d-d CT transitions. In fact, the parent perovskite manganites RMnO_3
should rather be sorted neither into the CT insulator nor the Mott-Hubbard
insulator in the Zaanen, Sawatzky, Allen scheme.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci |
arxiv_dataset-20701008.2241 | Theoretical prediction of topological insulator in ternary rare earth
chalcogenides
cond-mat.mtrl-sci
A new class of three-dimensional topological insulator, ternary rare earth
chalcogenides, is theoretically investigated with ab initio calculations. Based
on both bulk band structure analysis and the direct calculation of topological
surface states, we demonstrate that LaBiTe3 is a topological insulator. La can
be substituted by other rare earth elements, which provide candidates for novel
topological states such as quantum anomalous Hall insulator, axionic insulator
and topological Kondo insulator. Moreover, YBiTe3 and YSbTe3 are found to be
normal insulators. They can be used as protecting barrier materials for both
LaBiTe3 and Bi2Te3 families of topological insulators for their well matched
lattice constants and chemical composition.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-20711008.2341 | Active feedback of a Fabry-Perot cavity to the emission of a single
InAs/GaAs quantum dot
cond-mat.mes-hall physics.optics
We present a detailed study of the use of Fabry-Perot (FP) cavities for the
spectroscopy of single InAs quantum dots (QDs). We derive optimal cavity
characteristics and resolution limits, and measure photoluminescence linewidths
as low as 0.9 GHz. By embedding the QDs in a planar cavity, we obtain a
sufficiently large signal to actively feed back on the length of the FP to lock
to the emission of a single QD with a stability below 2% of the QD linewidth.
An integration time of approximately two seconds is found to yield an optimum
compromise between shot noise and cavity length fluctuations.
| arxiv topic:cond-mat.mes-hall physics.optics |
arxiv_dataset-20721008.2441 | Tensorial Reconstruction at the Integrand Level
hep-ph
We present a new approach to the reduction of one-loop amplitudes obtained by
reconstructing the tensorial expression of the scattering amplitudes. The
reconstruction is performed at the integrand level by means of a sampling in
the integration momentum. There are several interesting applications of this
novel method within existing techniques for the reduction of one-loop multi-leg
amplitudes: to deal with numerically unstable points, such as in the vicinity
of a vanishing Gram determinant; to allow for a sampling of the numerator
function based on real values of the integration momentum; to optimize the
numerical reduction in the case of long expressions for the numerator
functions.
| arxiv topic:hep-ph |
arxiv_dataset-20731008.2541 | On "soft" physics at the CERN Large Hadron Collider
hep-ph
Three tightly inter-related topics have been discussed: the $pp(p\bar p)$
total cross section; the single diffraction dissociation cross section; the
$p(\bar p)d$ total cross section and the defect of the total cross section in
scattering from deuteron.
| arxiv topic:hep-ph |
arxiv_dataset-20741008.2641 | Negative spectral index of $f_{NL}$ in the axion-type curvaton model
astro-ph.CO gr-qc hep-ph hep-th
We derive the spectral index of $f_{NL}$ and its running from isocurvature
single field and investigate the curvaton models with a negative spectral index
of $f_{NL}$ in detail. In particular, a numerical study of the axion-type
curvaton model is illustrated, and we find that the spectral index of $f_{NL}$
is negative and its absolute value is maximized around $\sigma_*=\pi f/2$ for
the potential $V(\sigma)=m^2f^2(1-\cos{\sigma\over f})$. The spectral index of
$f_{NL}$ can be ${\cal O}(-0.1)$ for the axion-type curvaton model. A
convincing detection of a positive $n_{f_{NL}}$ will rule out the axion-type
curvaton model. In addition, we also give a general discussion about the
detectable parameter space for the curvaton model with a polynomial potential.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
arxiv_dataset-20751008.2741 | Thermal Histories of Chondrules in Solar Nebula Shocks
astro-ph.EP
Chondrules are important early Solar System materials that can provide a
wealth of information on conditions in the solar nebula, if their formation
mechanism can be understood. The theory most consistent with observational
constraints, especially thermal histories, is the so-called "shock model", in
which chondrules were melted in solar nebula shocks. However, several problems
have been identified with previous shock models. These problems all pertained
to the treatment of the radiation field, namely the input boundary condition to
the radiation field, the proper treatment of the opacity of solids, and the
proper treatment of molecular line cooling. In this paper, we present the
results of our updated shock model, which corrects for the problems listed
above. Our new hydrodynamic shock code includes a complete treatment of
molecular line cooling due to H2O. Previously, shock models including line
cooling predicted chondrule cooling rates exceeding 100,000 K/hr. Contrary to
these expectations, we have found that the effect of line cooling is minimal;
after the inclusion of line cooling, the cooling rates of chondrules are
10-1000 K/hr. The reduction in the otherwise rapid cooling rates attributable
to line cooling is due to a combination of factors, including buffering due to
hydrogen recombination/dissociation, high column densities of water, and
backwarming. Our model demonstrates that the shock model for chondrule
formation remains consistent with observational constraints.
| arxiv topic:astro-ph.EP |
arxiv_dataset-20761008.2841 | Comparison of different Broadcast Schemes for Multi-Hop Wireless Sensor
Networks
cs.NI
In this paper, we present the performance of different broadcast schemes for
multihop sensor networks based on mathematical modeling. In near future many
applications will demand multicast (Broadcast) communication feature from the
sensor networks. This broadcast feature does not use virtual carrier sensing
but relies on physical carrier sensing to reduce collision. For this paper, we
analyze the different broadcast schemes for multihop wireless sensor networks
and also calculated the achievable throughput.
| arxiv topic:cs.NI |
arxiv_dataset-20771008.2941 | Comment on "Entanglement transformation between two-qubit mixed states
by LOCC" [Phys. Lett. A 373 (2009) 3610]
quant-ph
The paper [Phys. Lett. A 373 (2009) 3610] by D.-C. Li analyzes the
transformation between two-qubit mixed states by local operations and classical
communication. We show that the proof of the main theorem, Theorem 2.6 in
[Phys. Lett. A 373 (2009) 3610] is not complete. Therefore the generalization
of Nielsen's theorem to mixed states still remains an open problem.
| arxiv topic:quant-ph |
arxiv_dataset-20781008.3041 | Finite-time singularities in modified $\mathcal{F}(R,G)$-gravity and
singularity avoidance
gr-qc
We study finite-time future singularities in $\mathcal{F}(R,G)$-gravity,
where $R$ and $G$ are the Ricci scalar and the Gauss-Bonnet invariant,
respectively. In particular, we reconstruct the $F(G)$-gravity and
$\mathcal{F}(R,G)$-gravity models realizing the finite-time future
singularities. We discuss a possible way to cure the finite-time future
singularities in $\mathcal{F}(R,G)$-gravity by taking into account higher-order
curvature corrections or effects of viscous fluids.
| arxiv topic:gr-qc |
arxiv_dataset-20791008.3142 | Brownian motion in a truncated Weyl chamber
math.PR
We examine the non-exit probability of a multidimensional Brownian motion
from a growing truncated Weyl chamber. Different regimes are identified
according to the growth speed, ranging from polynomial decay over
stretched-exponential to exponential decay. Furthermore we derive associated
large deviation principles for the empirical measure of the properly rescaled
and transformed Brownian motion as the dimension grows to infinity. Our main
tool is an explicit eigenvalue expansion for the transition probabilities
before exiting the truncated Weyl chamber.
| arxiv topic:math.PR |
arxiv_dataset-20801008.3243 | Multi-black rings and the phase diagram of higher-dimensional black
holes
hep-th gr-qc
Configurations of multiple concentric black rings play an important role in
determining the pattern of branchings, connections and mergers between
different phases of higher-dimensional black holes. We examine them using both
approximate and (in five dimensions) exact methods. By identifying the role of
the different scales in the system, we argue that it is possible to have
multiple black ring configurations in which all the rings have equal
temperature and angular velocity. This allows us to correct and improve in a
simple, natural manner, an earlier proposal for the phase diagram of
singly-rotating black holes in $D\geq 6$.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-20811008.3343 | A Simple Method to Measure the Interaction Potential of Dielectric
Grains in a Dusty Plasma
physics.plasm-ph
A simple minimally perturbative method is introduced which provides the
ability to experimentally measure both the radial confining potential and the
interaction potential between two individual dust particles, levitated in the
sheath of a radio-frequency (RF) argon discharge. In this technique, a single
dust particle is dropped into the plasma sheath to interact with a second
individual dust particle already situated at the system's equilibrium point,
without introducing any external perturbation. The resulting data is analyzed
using a method employing a polynomial fit to the particle displacement(s),
X(t), to reduce uncertainty in calculation. Employing this technique, the
horizontal confinement is shown to be parabolic over a wide range of pressures
and displacements from the equilibrium point. The interaction potential is also
measured and shown to be well-described by a screened Coulomb potential and to
decrease with increasing pressure. Finally, the charge on the particle and the
effective dust screening distance are calculated. It is shown for the first
time experimentally that the charge on a particle in the sheath of an RF plasma
decreases with increasing pressure, in agreement with theoretical predictions.
The screening distance also decreases with increasing pressure as expected.
This technique can be used for rapid determination of particle parameters in
dusty plasma.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-20821008.3443 | On weakly optimal partitions in modular networks
cs.SI cond-mat.stat-mech physics.soc-ph
Modularity was introduced as a measure of goodness for the community
structure induced by a partition of the set of vertices in a graph. Then, it
also became an objective function used to find good partitions, with high
success. Nevertheless, some works have shown a scaling limit and certain
instabilities when finding communities with this criterion. Modularity has been
studied proposing several formalisms, as hamiltonians in a Potts model or
laplacians in spectral partitioning. In this paper we present a new
probabilistic formalism to analyze modularity, and from it we derive an
algorithm based on weakly optimal partitions. This algorithm obtains good
quality partitions and also scales to large graphs.
| arxiv topic:cs.SI cond-mat.stat-mech physics.soc-ph |
arxiv_dataset-20831008.3543 | Test of the Universality of Naive-time-reversal-odd Fragmentation
Functions
hep-ph
We investigate the ''spontaneous'' hyperon transverse polarization in
$e^+e^-$ annihilation and semi-inclusive deep inelastic scattering processes as
a test of the universality of the naive-time-reversal-odd transverse momentum
dependent fragmentation functions. We find that universality implies definite
sign relations among various observables. This provides a unique opportunity to
study initial/final state interaction effects in the fragmentation process and
test the associated factorization.
| arxiv topic:hep-ph |
arxiv_dataset-20841008.3643 | Inferring the Gibbs state of a small quantum system
quant-ph cond-mat.stat-mech
Gibbs states are familiar from statistical mechanics, yet their use is not
limited to that domain. For instance, they also feature in the maximum entropy
reconstruction of quantum states from incomplete measurement data. Outside the
macroscopic realm, however, estimating a Gibbs state is a nontrivial inference
task, due to two complicating factors: the proper set of relevant observables
might not be evident a priori; and whenever data are gathered from a small
sample only, the best estimate for the Lagrange parameters is invariably
affected by the experimenter's prior bias. I show how the two issues can be
tackled with the help of Bayesian model selection and Bayesian interpolation,
respectively, and illustrate the use of these Bayesian techniques with a number
of simple examples.
| arxiv topic:quant-ph cond-mat.stat-mech |
arxiv_dataset-20851008.3743 | Data Cleaning and Query Answering with Matching Dependencies and
Matching Functions
cs.DB
Matching dependencies were recently introduced as declarative rules for data
cleaning and entity resolution. Enforcing a matching dependency on a database
instance identifies the values of some attributes for two tuples, provided that
the values of some other attributes are sufficiently similar. Assuming the
existence of matching functions for making two attributes values equal, we
formally introduce the process of cleaning an instance using matching
dependencies, as a chase-like procedure. We show that matching functions
naturally introduce a lattice structure on attribute domains, and a partial
order of semantic domination between instances. Using the latter, we define the
semantics of clean query answering in terms of certain/possible answers as the
greatest lower bound/least upper bound of all possible answers obtained from
the clean instances. We show that clean query answering is intractable in some
cases. Then we study queries that behave monotonically wrt semantic domination
order, and show that we can provide an under/over approximation for clean
answers to monotone queries. Moreover, non-monotone positive queries can be
relaxed into monotone queries.
| arxiv topic:cs.DB |
arxiv_dataset-20861008.3843 | The determinantal ideals of extended Hankel matrices
math.AC math.CO
In this paper, we use the tools of Gr\"{o}bner bases and combinatorial secant
varieties to study the determinantal ideals $I_t$ of the extended Hankel
matrices. Denote by $c$-chain a sequence $a_1,\...,a_k$ with $a_i+c<a_{i+1}$
for all $i=1,\...,k-1$. Using the results of $c$-chain, we solve the membership
problem for the symbolic powers $I_t^{(s)}$ and we compute the primary
decomposition of the product $I_{t_1}\... I_{t_k}$ of the determinantal ideals.
Passing through the initial ideals and algebras we prove that the product
$I_{t_1}\... I_{t_k}$ has a linear resolution and the multi-homogeneous Rees
algebra $\Rees(I_{t_1},\...,I_{t_k})$ is defined by a Gr\"obner basis of
quadrics.
| arxiv topic:math.AC math.CO |
arxiv_dataset-20871008.3943 | On Muckenhoupt-Wheeden Conjecture
math.CA
Let M denote the dyadic Maximal Function. We show that there is a weight w,
and Haar multiplier T for which the following weak-type inequality fails: $$
\sup_{t>0}t w\left\{x\in\mathbb R \mid |Tf(x)|>t\right\}\le C \int_{\mathbb
R}|f|Mw(x)dx. $$ (With T replaced by M, this is a well-known fact.) This shows
that a dyadic version of the so-called Muckenhoupt-Wheeden Conjecture is false.
This accomplished by using current techniques in weighted inequalities to show
that a particular $L^2$ consequence of the inequality above does not hold.
| arxiv topic:math.CA |
arxiv_dataset-20881008.4043 | Metabifurcation analysis of a mean field model of the cortex
math.DS physics.bio-ph q-bio.NC
Mean field models (MFMs) of cortical tissue incorporate salient features of
neural masses to model activity at the population level. One of the common
aspects of MFM descriptions is the presence of a high dimensional parameter
space capturing neurobiological attributes relevant to brain dynamics. We study
the physiological parameter space of a MFM of electrocortical activity and
discover robust correlations between physiological attributes of the model
cortex and its dynamical features. These correlations are revealed by the study
of bifurcation plots, which show that the model responses to changes in
inhibition belong to two families. After investigating and characterizing
these, we discuss their essential differences in terms of four important
aspects: power responses with respect to the modeled action of anesthetics,
reaction to exogenous stimuli, distribution of model parameters and oscillatory
repertoires when inhibition is enhanced. Furthermore, while the complexity of
sustained periodic orbits differs significantly between families, we are able
to show how metamorphoses between the families can be brought about by
exogenous stimuli. We unveil links between measurable physiological attributes
of the brain and dynamical patterns that are not accessible by linear methods.
They emerge when the parameter space is partitioned according to bifurcation
responses. This partitioning cannot be achieved by the investigation of only a
small number of parameter sets, but is the result of an automated bifurcation
analysis of a representative sample of 73,454 physiologically admissible sets.
Our approach generalizes straightforwardly and is well suited to probing the
dynamics of other models with large and complex parameter spaces.
| arxiv topic:math.DS physics.bio-ph q-bio.NC |
arxiv_dataset-20891008.4143 | Bose-Einstein condensation in perfect crystals
quant-ph cond-mat.quant-gas
To investigate the phenomenon of Bose-Einstein condensation in perfect
crystals a hierarchy of equations for reduced density matrices that describes a
thermodynamically equilibrium quantum system is employed, the hierarchy being
obtained earlier by the author. The thermodynamics of a crystal with a
condensate and the one of a crystal with no condensate are constructed in
parallel, which is required for studying the phase transition involving
Bose-Einstein condensation. The transition is analysed also with the help of
the Landau theory of phase transitions which shows that a superfluid state can
result either from two consecutive phase transitions or from only one. To
demonstrate how the general equations obtained can be applied for a concrete
crystal the bifurcation method for solving the equations is utilized. New
results concerning properties of the condensate crystals at zero temperature
are obtained as well. In the concluding section, the physical concept of the
condensate is discussed.
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-20901008.4243 | Quantifying non-Gaussianity for quantum information
quant-ph
We address the quantification of non-Gaussianity of states and operations in
continuous-variable systems and its use in quantum information. We start by
illustrating in details the properties and the relationships of two recently
proposed measures of non-Gaussianity based on the Hilbert-Schmidt (HS) distance
and the quantum relative entropy (QRE) between the state under examination and
a reference Gaussian state. We then evaluate the non-Gaussianities of several
families of non-Gaussian quantum states and show that the two measures have the
same basic properties and also share the same qualitative behaviour on most of
the examples taken into account. However, we also show that they introduce a
different relation of order, i.e. they are not strictly monotone each other. We
exploit the non-Gaussianity measures for states in order to introduce a measure
of non-Gaussianity for quantum operations, to assess Gaussification and
de-Gaussification protocols, and to investigate in details the role played by
non-Gaussianity in entanglement distillation protocols. Besides, we exploit the
QRE-based non-Gaussianity measure to provide new insight on the extremality of
Gaussian states for some entropic quantities such as conditional entropy,
mutual information and the Holevo bound. We also deal with parameter estimation
and present a theorem connecting the QRE nonG to the quantum Fisher
information. Finally, since evaluation of the QRE nonG measure requires the
knowledge of the full density matrix, we derive some {\em experimentally
friendly} lower bounds to nonG for some class of states and by considering the
possibility to perform on the states only certain efficient or inefficient
measurements.
| arxiv topic:quant-ph |
arxiv_dataset-20911008.4343 | X-ray emission processes in stars
astro-ph.SR astro-ph.HE
A decade of X-ray stellar observations with Chandra and XMM-Newton has led to
significant advances in our understanding of the physical processes at work in
hot (magnetized) plasmas in stars and their immediate environment, providing
new perspectives and challenges, and in turn the need for improved models. The
wealth of high-quality stellar spectra has allowed us to investigate, in
detail, the characteristics of the X-ray emission across the HR diagram.
Progress has been made in addressing issues ranging from classical stellar
activity in stars with solar-like dynamos (such as flares, activity cycles,
spatial and thermal structuring of the X-ray emitting plasma, evolution of
X-ray activity with age), to X-ray generating processes (e.g. accretion, jets,
magnetically confined winds) that were poorly understood in the
pre-Chandra/XMM-Newton era. I discuss the progress made in the study of high
energy stellar physics and its impact in a wider astrophysical context,
focusing on the role of spectral diagnostics now accessible.
| arxiv topic:astro-ph.SR astro-ph.HE |
arxiv_dataset-20921008.4443 | Spectral sequences of colored Jones polynomials, colored Rasmussen
invariants and nanophrases
math.GT math.CO math.QA
We introduce three spectral sequences which give some expressions of colored
Jones polynomials. Each spectral sequence contains a Khovanov-type homology
groups. Two of them are derived from a bicomplex of the colored Jones
polynomial. The other is the spectral sequence that deduces a colored Rasmussen
invariant of links. We also introduce three functors between categories of
nanophrases, generalizations of links, and obtain their applications using
colored Jones polynomials and their categorifications.
| arxiv topic:math.GT math.CO math.QA |
arxiv_dataset-20931008.4543 | Reply to the comment on "Topological phase in two flavor neutrino
oscillations"
hep-ph hep-th quant-ph
In a recent paper [arXiv:0901.0790], we showed that there is a neat geometric
interpretation of two flavor neutrino oscillation formulae, and that the
geometric phase involved in the physics of oscillations is restricted to be
topological as long as CP is conserved. This paper has been criticised by
Bhandari [arXiv:1006.5935]. In the present note, we show that the criticisms
are not valid and only reflect his failure to understand some crucial points.
| arxiv topic:hep-ph hep-th quant-ph |
arxiv_dataset-20941008.4643 | Quantum Oracles in Terms of Universal Gate Set
quant-ph
We present a systematic construction of quantum circuits implementing
Grover's database search algorithm for arbitrary number of targets. We
introduce a new operator which flips the sign of the targets and evaluate its
circuit complexity. We find the condition under which the circuit complexity of
the database search algorithm based on this operator is less than that of the
conventional one.
| arxiv topic:quant-ph |
arxiv_dataset-20951008.4743 | High-energy asymptotics of D-brane decay amplitudes from Coulomb gas
electrostatics
hep-th cond-mat.stat-mech
We study the high-energy limit of tree-level string production amplitudes
from decaying D-branes in bosonic string theory, interpreting the vertex
operators as external charges interacting with a Coulomb gas corresponding to
the rolling tachyon background, and performing an electrostatic analysis. In
particular, we consider two open string - one closed string amplitudes and four
open string amplitudes, and calculate explicit formulas for the leading
exponential behavior.
| arxiv topic:hep-th cond-mat.stat-mech |
arxiv_dataset-20961008.4843 | Renormalization Group Functions for the Radiative Symmetry Breaking
Scheme with Multi Mass Scale
hep-ph hep-th
We obtain the renormalization group(RG) functions for the $O(N)$ scalar field
theory and the Higgs-Yukawa field theory with the Coleman-Weinberg mechanism in
which the symmetry breaking occurs radiatively by using the method proposed
previously in case of the neutral scalar field theory.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-20971008.4943 | Tensor factorizations of local second-order M{\o}ller Plesset theory
physics.comp-ph quant-ph
Efficient electronic structure methods can be built around efficient tensor
representations of the wavefunction. Here we describe a general view of tensor
factorization for the compact representation of electronic wavefunctions. We
use these ideas to construct low-complexity representations of the doubles
amplitudes in local second order M{\o}ller-Plesset perturbation theory. We
introduce two approximations - the direct orbital specific virtual
approximation and the full orbital specific virtual approximation. In these
approximations, each occupied orbital is associated with a small set of
correlating virtual orbitals. Conceptually, the representation lies between the
projected atomic orbital representation in Pulay-Saeb{\o} local correlation
theories and pair natural orbital correlation theories. We have tested the
orbital specific virtual approximations on a variety of systems and properties
including total energies, reaction energies, and potential energy curves.
Compared to the Pulay-Saeb{\o} ansatz, we find that these approximations
exhibit favourable accuracy and computational times, while yielding smooth
potential energy curves.
| arxiv topic:physics.comp-ph quant-ph |
arxiv_dataset-20981008.5043 | The case of 3C326: VLA 74 MHz observations during a geomagnetic storm
astro-ph.IM
Reaching the thermal noise at low frequencies with the next generation of
instruments (e.g. SKA, LOFAR etc.) is going to be a challenge. It requires the
development of more advanced techniques of calibration compared to those used
from the traditional radio astronomy until now. This revolution has slowly
started, from self-cal, going through field based correction and SPAM up to the
formulation and application of a general Measurement Equation. We will describe
and compare the several approaches of calibration used so far to reduce low
frequency data. We will present some results of a 74 MHz VLA observation in
exceptional ionospheric conditions of the giant radio galaxy 3C326 for which
some of these methods have been successfully applied.
| arxiv topic:astro-ph.IM |
arxiv_dataset-20991008.5143 | Combining individually valid and conditionally i.i.d. P-variables
stat.ME
For a given testing problem, let $U_1,...,U_n$ be individually valid and
conditionally on the data i.i.d.\ P-variables (often called P-values). For
example, the data could come in groups, and each $U_i$ could be based on
subsampling just one datum from each group in order to satisfy an independence
assumption under the hypothesis. The problem is then to deterministically
combine the $U_i$ into a valid summary P-variable. Restricting here our
attention to functions of a given order statistic $U_{k:n}$ of the $U_i$, we
compute the function $f_{n,k}$ which is smallest among all increasing functions
$f$ such that $f(U_{k:n})$ is always a valid P-variable under the stated
assumptions. Since $f_{n,k}(u)\le 1\wedge (\frac {n}{k} u)$, with the right
hand side being a good approximation for the left when $k$ is large, one may in
particular always take the minimum of 1 and twice the left sample median of the
given P-variables.
We sketch the original application of the above in a recent study of
associations between various primate species by Astaras et al.
| arxiv topic:stat.ME |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.