5,810 research outputs found
On critical behaviour in gravitational collapse
We give an approach to studying the critical behaviour that has been observed
in numerical studies of gravitational collapse. These studies suggest, among
other things, that black holes initially form with infinitesimal mass. We show
generally how a black hole mass formula can be extracted from a transcendental
equation.
Using our approach, we give an explicit one parameter set of metrics that are
asymptotically flat and describe the collapse of apriori unspecified but
physical matter fields. The black hole mass formula obtained from this metric
exhibits a mass gap - that is, at the onset of black hole formation, the mass
is finite and non-zero.Comment: 11 pages, RevTex, 2 figures (available from VH
Self-Similar Collapse of Scalar Field in Higher Dimensions
This paper constructs continuously self-similar solution of a spherically
symmetric gravitational collapse of a scalar field in n dimensions. The
qualitative behavior of these solutions is explained, and closed-form answers
are provided where possible. Equivalence of scalar field couplings is used to
show a way to generalize minimally coupled scalar field solutions to the model
with general coupling.Comment: RevTex 3.1, 15 pages, 3 figures; references adde
Black hole formation from massive scalar fields
It is shown that there exists a range of parameters in which gravitational
collapse with a spherically symmetric massive scalar field can be treated as if
it were collapsing dust. This implies a criterion for the formation of black
holes depending on the size and mass of the initial field configuration and the
mass of the scalar field.Comment: 11 pages, RevTeX, 3 eps figures. Submitted to Class. Quantum Gra
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
A coherent triggered search for single spin compact binary coalescences in gravitational wave data
In this paper we present a method for conducting a coherent search for single
spin compact binary coalescences in gravitational wave data and compare this
search to the existing coincidence method for single spin searches. We propose
a method to characterize the regions of the parameter space where the single
spin search, both coincident and coherent, will increase detection efficiency
over the existing non-precessing search. We also show example results of the
coherent search on a stretch of data from LIGO's fourth science run but note
that a set of signal based vetoes will be needed before this search can be run
to try to make detections.Comment: 14 pages, 4 figure
Stability of degenerate Cauchy horizons in black hole spacetimes
In the multihorizon black hole spacetimes, it is possible that there are
degenerate Cauchy horizons with vanishing surface gravities. We investigate the
stability of the degenerate Cauchy horizon in black hole spacetimes. Despite
the asymptotic behavior of spacetimes (flat, anti-de Sitter, or de Sitter), we
find that the Cauchy horizon is stable against the classical perturbations, but
unstable quantum mechanically.Comment: Revtex, 4 pages, no figures, references adde
Tidal Stabilization of Rigidly Rotating, Fully Relativistic Neutron Stars
It is shown analytically that an external tidal gravitational field increases
the secular stability of a fully general relativistic, rigidly rotating neutron
star that is near marginal stability, protecting it against gravitational
collapse. This stabilization is shown to result from the simple fact that the
energy required to raise a tide on such a star, divided by the
square of the tide's quadrupole moment , is a decreasing function of the
star's radius , (where, as changes, the
star's structure is changed in accord with the star's fundamental mode of
radial oscillation). If were positive, the tidal
coupling would destabilize the star. As an application, a rigidly rotating,
marginally secularly stable neutron star in an inspiraling binary system will
be protected against secular collapse, and against dynamical collapse, by tidal
interaction with its companion. The ``local-asymptotic-rest-frame'' tools used
in the analysis are somewhat unusual and may be powerful in other studies of
neutron stars and black holes interacting with an external environment. As a
byproduct of the analysis, in an appendix the influence of tidal interactions
on mass-energy conservation is elucidated.Comment: Revtex, 10 pages, 2 figures; accepted for publication in Physical
Review D. Revisions: Appendix rewritten to clarify how, in Newtonian
gravitation theory, ambiguity in localization of energy makes interaction
energy ambiguous but leaves work done on star by tidal gravity unambiguous.
New footnote 1 and Refs. [11] and [19
The central density of a neutron star is unaffected by a binary companion at linear order in
Recent numerical work by Wilson, Mathews, and Marronetti [J. R. Wilson, G. J.
Mathews and P. Marronetti, Phys. Rev. D 54, 1317 (1996)] on the coalescence of
massive binary neutron stars shows a striking instability as the stars come
close together: Each star's central density increases by an amount proportional
to 1/(orbital radius). This overwhelms any stabilizing effects of tidal
coupling [which are proportional to 1/(orbital radius)^6] and causes the stars
to collapse before they merge. Since the claimed increase of density scales
with the stars' mass, it should also show up in a perturbation limit where a
point particle of mass orbits a neutron star. We prove analytically that
this does not happen; the neutron star's central density is unaffected by the
companion's presence to linear order in . We show, further, that the
density increase observed by Wilson et. al. could arise as a consequence of not
faithfully maintaining boundary conditions.Comment: 3 pages, REVTeX, no figures, submitted to Phys Rev D as a Rapid
Communicatio
Binary-induced collapse of a compact, collisionless cluster
We improve and extend Shapiro's model of a relativistic, compact object which
is stable in isolation but is driven dynamically unstable by the tidal field of
a binary companion. Our compact object consists of a dense swarm of test
particles moving in randomly-oriented, initially circular, relativistic orbits
about a nonrotating black hole. The binary companion is a distant, slowly
inspiraling point mass. The tidal field of the companion is treated as a small
perturbation on the background Schwarzschild geometry near the hole; the
resulting metric is determined by solving the perturbation equations of Regge
and Wheeler and Zerilli in the quasi-static limit. The perturbed spacetime
supports Bekenstein's conjecture that the horizon area of a near-equilibrium
black hole is an adiabatic invariant. We follow the evolution of the system and
confirm that gravitational collapse can be induced in a compact collisionless
cluster by the tidal field of a binary companion.Comment: 9 Latex pages, 14 postscript figure
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