2,191 research outputs found
Cosmic Censorship: As Strong As Ever
Spacetimes which have been considered counter-examples to strong cosmic
censorship are revisited. We demonstrate the classical instability of the
Cauchy horizon inside charged black holes embedded in de Sitter spacetime for
all values of the physical parameters. The relevant modes which maintain the
instability, in the regime which was previously considered stable, originate as
outgoing modes near to the black hole event horizon. This same mechanism is
also relevant for the instability of Cauchy horizons in other proposed
counter-examples of strong cosmic censorship.Comment: 4 pages RevTeX style, 1 figure included using epsfi
Gravitational quasinormal modes for Anti-de Sitter black holes
Quasinormal mode spectra for gravitational perturbations of black holes in
four dimensional de Sitter and anti-de Sitter space are investigated. The
anti-de Sitter case is relevant to the ADS-CFT correspondence in superstring
theory. The ADS-CFT correspondence suggests a prefered set of boundary
conditions.Comment: 12 pages, 6 figures in ReVTe
Duality between Electric and Magnetic Black Holes
A number of attempts have recently been made to extend the conjectured
duality of Yang Mills theory to gravity. Central to these speculations has been
the belief that electrically and magnetically charged black holes, the solitons
of quantum gravity, have identical quantum properties. This is not obvious,
because although duality is a symmetry of the classical equations of motion, it
changes the sign of the Maxwell action. Nevertheless, we show that the chemical
potential and charge projection that one has to introduce for electric but not
magnetic black holes exactly compensate for the difference in action in the
semi-classical approximation. In particular, we show that the pair production
of electric black holes is not a runaway process, as one might think if one
just went by the action of the relevant instanton. We also comment on the
definition of the entropy in cosmological situations, and show that we need to
be more careful when defining the entropy than we are in an asymptotically-flat
case.Comment: 23 pages, revtex, no figures. Major revision: two sections on the
electric Ernst solution adde
Genome-wide functional analysis of human 5' untranslated region introns
Genes with short 5'UTR introns have higher expression than genes with no or long 5'UTR introns. Complex evolutionary forces act on these introns
Cosmological Multi-Black Hole Solutions
We present simple, analytic solutions to the Einstein-Maxwell equation, which
describe an arbitrary number of charged black holes in a spacetime with
positive cosmological constant . In the limit , these
solutions reduce to the well known Majumdar-Papapetrou (MP) solutions. Like the
MP solutions, each black hole in a solution has charge equal
to its mass , up to a possible overall sign. Unlike the limit,
however, solutions with are highly dynamical. The black holes move
with respect to one another, following natural trajectories in the background
deSitter spacetime. Black holes moving apart eventually go out of causal
contact. Black holes on approaching trajectories ultimately merge. To our
knowledge, these solutions give the first analytic description of coalescing
black holes. Likewise, the thermodynamics of the solutions is
quite interesting. Taken individually, a black hole is in thermal
equilibrium with the background deSitter Hawking radiation. With more than one
black hole, because the solutions are not static, no global equilibrium
temperature can be defined. In appropriate limits, however, when the black
holes are either close together or far apart, approximate equilibrium states
are established.Comment: 15 pages (phyzzx), UMHEP-380 (minor referencing error corrected
Particle Production and Positive Energy Theorems for Charged Black Holes in deSitter
We study quantum mechanical and classical stability properties of
Reissner-Nordstrom deSitter spacetimes, which describe black holes with mass
and charge in a background with cosmological constant .
There are two sources of particle production in these spacetimes; the black
hole horizon and the cosmological horizon. A scattering calculation is done to
compute the Hawking radiation in these spacetimes. We find that the flux from
the black hole horizon equals the flux from the cosmological horizon, if and
only if , indicating that this is a state of thermodynamic equilibrium.
The spectrum, however, is not thermal. We also show that spacetimes containing
a number of charge equal to mass black holes with , have
supercovariantly constant spinors, suggesting that they may be minimum energy
states in a positive energy construction. As a first step in this direction, we
present a positive energy construction for asymptotically deSitter spacetimes
with vanishing charge. Because the construction depends only on a spatial
slice, our result also holds for spacetimes which are asymptotically
Robertson-Walker.Comment: 11 pages (1 figure not included), UMHEP-39
Characterization of the nonequilibrium steady state of a heterogeneous nonlinear q-voter model with zealotry
We introduce an heterogeneous nonlinear q-voter model with zealots and two types of susceptible voters, and study its non-equilibrium properties when the population is finite and well mixed. In this two-opinion model, each individual supports one of two parties and is either a zealot or a susceptible voter of type q1 or q2. While here zealots never change their opinion, a qi-susceptible voter (i = 1, 2) consults a group of qi neighbors at each time step, and adopts their opinion if all group members agree. We show that this model violates the detailed balance whenever q1 â q2 and has surprisingly rich properties. Here, we focus on the characterization of the modelâs non-equilibrium stationary state (NESS) in terms of its probability distribution and currents in the distinct regimes of low and high density of zealotry. We unveil the NESS properties in each of these phases by computing the opinion distribution and the circulation of probability currents, as well as the two-point correlation functions at unequal times (formally related to a âprobability angular momentumâ). Our analytical calculations obtained in the realm of a linear Gaussian approximation are compared with numerical results
Pair of accelerated black holes in a de Sitter background: the dS C-metric
Following the work of Kinnersley and Walker for flat spacetimes, we have
analyzed the anti-de Sitter C-metric in a previous paper. In the de Sitter
case, Podolsky and Griffiths have established that the de Sitter C-metric (dS
C-metric) found by Plebanski and Demianski describes a pair of accelerated
black holes in the dS background with the acceleration being provided (in
addition to the cosmological constant) by a strut that pushes away the two
black holes or, alternatively, by a string that pulls them. We extend their
analysis mainly in four directions. First, we draw the Carter-Penrose diagrams
of the massless uncharged dS C-metric, of the massive uncharged dS C-metric and
of the massive charged dS C-metric. These diagrams allow us to clearly identify
the presence of two dS black holes and to conclude that they cannot interact
gravitationally. Second, we revisit the embedding of the dS C-metric in the 5D
Minkowski spacetime and we represent the motion of the dS C-metric origin in
the dS 4-hyperboloid as well as the localization of the strut. Third, we
comment on the physical properties of the strut that connects the two black
holes. Finally, we find the range of parameters that correspond to non-extreme
black holes, extreme black holes, and naked particles.Comment: 11 pages, 11 figures (RevTeX4). Published version: references adde
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
Scalar Wave Falloff in Asymptotically Anti-de Sitter Backgrounds
Conformally invariant scalar waves in black hole spacetimes which are
asymptotically anti-de Sitter are investigated. We consider both the
-dimensional black hole and -dimensional Schwarzschild-anti-de
Sitter spacetime as backgrounds. Analytical and numerical methods show that the
waves decay exponentially in the dimensional black hole background.
However the falloff pattern of the conformal scalar waves in the
Schwarzschild-anti-de Sitter background is generally neither exponential nor an
inverse power rate, although the approximate falloff of the maximal peak is
weakly exponential. We discuss the implications of these results for mass
inflation.Comment: 34 pages, Latex, 26 figures, uses psfi
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