9,417 research outputs found
Surface roughness detector Patent
Roughness detector for recording surface pattern of irregularitie
Odd-parity perturbations of self-similar Vaidya spacetime
We carry out an analytic study of odd-parity perturbations of the
self-similar Vaidya space-times that admit a naked singularity. It is found
that an initially finite perturbation remains finite at the Cauchy horizon.
This holds not only for the gauge invariant metric and matter perturbation, but
also for all the gauge invariant perturbed Weyl curvature scalars, including
the gravitational radiation scalars. In each case, `finiteness' refers to
Sobolev norms of scalar quantities on naturally occurring spacelike
hypersurfaces, as well as pointwise values of these quantities.Comment: 28 page
Fractal to Nonfractal Phase Transition in the Dielectric Breakdown Model
A fast method is presented for simulating the dielectric-breakdown model
using iterated conformal mappings. Numerical results for the dimension and for
corrections to scaling are in good agreement with the recent RG prediction of
an upper critical , at which a transition occurs between branching
fractal clusters and one-dimensional nonfractal clusters.Comment: 5 pages, 7 figures; corrections to scaling include
Jamming transitions in a schematic model of suspension rheology
We study the steady-state response to applied stress in a simple scalar model
of sheared colloids. Our model is based on a schematic (F2) model of the glass
transition, with a memory term that depends on both stress and shear rate. For
suitable parameters, we find transitions from a fluid to a nonergodic, jammed
state, showing zero flow rate in an interval of applied stress. Although the
jammed state is a glass, we predict that jamming transitions have an analytical
structure distinct from that of the conventional mode coupling glass
transition. The static jamming transition we discuss is also distinct from
hydrodynamic shear thickening.Comment: 7 pages; 3 figures; improved version with added references. Accepted
for publication in Europhysics Letter
Incorporating information from source simulations into searches for gravitational-wave bursts
The detection of gravitational waves from astrophysical sources of
gravitational waves is a realistic goal for the current generation of
interferometric gravitational-wave detectors. Short duration bursts of
gravitational waves from core-collapse supernovae or mergers of binary black
holes may bring a wealth of astronomical and astrophysical information. The
weakness of the waves and the rarity of the events urges the development of
optimal methods to detect the waves. The waves from these sources are not
generally known well enough to use matched filtering however; this drives the
need to develop new ways to exploit source simulation information in both
detections and information extraction. We present an algorithmic approach to
using catalogs of gravitational-wave signals developed through numerical
simulation, or otherwise, to enhance our ability to detect these waves. As more
detailed simulations become available, it is straightforward to incorporate the
new information into the search method. This approach may also be useful when
trying to extract information from a gravitational-wave observation by allowing
direct comparison between the observation and simulations.Comment: 8 pages, 1 figur
Gauge symmetry breaking on orbifolds
We discuss a new method for gauge symmetry breaking in theories with one
extra dimension compactified on the orbifold S^1/Z_2. If we assume that fields
and their derivatives can jump at the orbifold fixed points, we can implement a
generalized Scherk-Schwarz mechanism that breaks the gauge symmetry. We show
that our model with discontinuous fields is equivalent to another with
continuous but non periodic fields; in our scheme localized lagrangian terms
for bulk fields appear.Comment: 6 pages, 2 figures. Talk given at the XXXVIIth Rencontres de Moriond,
"Electroweak interactions and unified theories", Les Arcs, France, 9-16 Mar
2002. Minor changes, one reference adde
Numerical simulation of the massive scalar field evolution in the Reissner-Nordstr\"{o}m black hole background
We studied the massive scalar wave propagation in the background of
Reissner-Nordstr\"{o}m black hole by using numerical simulations. We learned
that the value plays an important role in determining the properties of
the relaxation of the perturbation. For the relaxation process
depends only on the field parameter and does not depend on the spacetime
parameters. For , the dependence of the relaxation on the black hole
parameters appears. The bigger mass of the black hole, the faster the
perturbation decays. The difference of the relaxation process caused by the
black hole charge has also been exhibited.Comment: Accepted for publication in Phys. Rev.
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