3,595 research outputs found
Elasticity of Stiff Polymer Networks
We study the elasticity of a two-dimensional random network of rigid rods
(``Mikado model''). The essential features incorporated into the model are the
anisotropic elasticity of the rods and the random geometry of the network. We
show that there are three distinct scaling regimes, characterized by two
distinct length scales on the elastic backbone. In addition to a critical
rigidiy percolation region and a homogeneously elastic regime we find a novel
intermediate scaling regime, where elasticity is dominated by bending
deformations.Comment: 4 pages, 4 figure
Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': methodological problems with case-only survival analysis.
Tree Buffers
In runtime verification, the central problem is to decide if a given program execution violates a given property. In online runtime verification, a monitor observes a program’s execution as it happens. If the program being observed has hard real-time constraints, then the monitor inherits them. In the presence of hard real-time constraints it becomes a challenge to maintain enough information to produce error traces, should a property violation be observed. In this paper we introduce a data structure, called tree buffer, that solves this problem in the context of automata-based monitors: If the monitor itself respects hard real-time constraints, then enriching it by tree buffers makes it possible to provide error traces, which are essential for diagnosing defects. We show that tree buffers are also useful in other application domains. For example, they can be used to implement functionality of capturing groups in regular expressions. We prove optimal asymptotic bounds for our data structure, and validate them using empirical data from two sources: regular expression searching through Wikipedia, and runtime verification of execution traces obtained from the DaCapo test suite
Enhancing Acceleration Radiation from Ground-State Atoms via Cavity Quantum Electrodynamics
When ground state atoms are accelerated through a high Q microwave cavity,
radiation is produced with an intensity which can exceed the intensity of Unruh
acceleration radiation in free space by many orders of magnitude. The cavity
field at steady state is described by a thermal density matrix under most
conditions. However, under some conditions gain is possible, and when the atoms
are injected in a regular fashion, the radiation can be produced in a squeezed
state
Scaling relation for determining the critical threshold for continuum percolation of overlapping discs of two sizes
We study continuum percolation of overlapping circular discs of two sizes. We
propose a phenomenological scaling equation for the increase in the effective
size of the larger discs due to the presence of the smaller discs. The critical
percolation threshold as a function of the ratio of sizes of discs, for
different values of the relative areal densities of two discs, can be described
in terms of a scaling function of only one variable. The recent accurate Monte
Carlo estimates of critical threshold by Quintanilla and Ziff [Phys. Rev. E, 76
051115 (2007)] are in very good agreement with the proposed scaling relation.Comment: 4 pages, 3 figure
Revealing the spectral state transition of the Clocked Burster, GS 1826-238 with NuSTAR StrayCats
We present the long term analysis of GS 1826-238, a neutron star X-ray binary
known as the "Clocked Burster", using data from NuSTAR StrayCats. StrayCats, a
catalogue of NuSTAR stray light data, contains data from bright, off-axis X-ray
sources that have not been focused by the NuSTAR optics. We obtained stray
light observations of the source from 2014-2021, reduced and analyzed the data
using nustar-gen-utils Python tools, demonstrating the transition of source
from the "island" atoll state to a "banana" branch. We also present the
lightcurve analysis of Type I X-Ray bursts from the Clocked Burster and show
that the bursts from the banana/soft state are systematically shorter in
durations than those from the island/hard state and have a higher burst
fluence. From our analysis, we note an increase in mass accretion rate of the
source, and a decrease in burst frequency with the transition
Tunneling-percolation origin of nonuniversality: theory and experiments
A vast class of disordered conducting-insulating compounds close to the
percolation threshold is characterized by nonuniversal values of transport
critical exponent t, in disagreement with the standard theory of percolation
which predicts t = 2.0 for all three dimensional systems. Various models have
been proposed in order to explain the origin of such universality breakdown.
Among them, the tunneling-percolation model calls into play tunneling processes
between conducting particles which, under some general circumstances, could
lead to transport exponents dependent of the mean tunneling distance a. The
validity of such theory could be tested by changing the parameter a by means of
an applied mechanical strain. We have applied this idea to universal and
nonuniversal RuO2-glass composites. We show that when t > 2 the measured
piezoresistive response \Gamma, i. e., the relative change of resistivity under
applied strain, diverges logarithmically at the percolation threshold, while
for t = 2, \Gamma does not show an appreciable dependence upon the RuO2 volume
fraction. These results are consistent with a mean tunneling dependence of the
nonuniversal transport exponent as predicted by the tunneling-percolation
model. The experimental results are compared with analytical and numerical
calculations on a random-resistor network model of tunneling-percolation.Comment: 13 pages, 12 figure
Spectral weight function for the half-filled Hubbard model: a singular value decomposition approach
The singular value decomposition technique is used to reconstruct the
electronic spectral weight function for a half-filled Hubbard model with
on-site repulsion from Quantum Monte Carlo data. A two-band structure
for the single-particle excitation spectrum is found to persist as the lattice
size exceeds the spin-spin correlation length. The observed bands are flat in
the vicinity of the points in the Brillouin zone, in
accordance with experimental data for high-temperature superconducting
compounds.Comment: 4 pages, Revtex
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