367 research outputs found
On the "Universal" Quantum Area Spectrum
There has been much debate over the form of the quantum area spectrum for a
black hole horizon, with the evenly spaced conception of Bekenstein having
featured prominently in the discourse. In this letter, we refine a very
recently proposed method for calibrating the Bekenstein form of the spectrum.
Our refined treatment predicts, as did its predecessor, a uniform spacing
between adjacent spectral levels of in Planck units; notably, an outcome
that already has a pedigree as a proposed ``universal'' value for this
intrinsically quantum-gravitational measure. Although the two approaches are
somewhat similar in logic and quite agreeable in outcome, we argue that our
version is conceptually more elegant and formally simpler than its precursor.
Moreover, our rendition is able to circumvent a couple of previously unnoticed
technical issues and, as an added bonus, translates to generic theories of
gravity in a very direct manner.Comment: 7 Pages; (v2) now 9 full pages, significant changes to the text and
material added but the general theme and conclusions are unchange
Gender differences in identities and their socio-structural correlates: how gendered lives shape parental and work identities
This study draws on identity theory to explore parental and work identities. It examined gender differences in identities, as well as the moderating role of gender in the effects of individualsâ socio-structural characteristics. A sample of 148 couples with young children completed extensive questionnaires. As hypothesized, couplesâ paid work strategy moderated gender differences in the salience and centrality of parental and work identities. Whereas significant differences in identities were found between stay-at-home mothers and their breadwinning husbands, no differences were found among dual-earner couples. Moreover, menâs work identity centrality increased when they had more and younger children, whereas womenâs work identity centrality decreased. Finally, menâs parental identity centrality increased with their income, whereas womenâs parental identity centrality decreased the more they earned. These findings attest to the importance of examining differences within as well as between genders, by taking into account the interactive effects of gender with other socio-structural characteristics
Radiation via Tunneling from a de Sitter Cosmological Horizon
Hawking radiation can usefully be viewed as a semi-classical tunneling
process that originates at the black hole horizon. The same basic premise
should apply to de Sitter background radiation, with the cosmological horizon
of de Sitter space now playing the featured role. In fact, a recent work
[hep-th/0204107] has gone a long way to verifying the validity of this de
Sitter-tunneling picture. In the current paper, we extend these prior
considerations to arbitrary-dimensional de Sitter space, as well as
Schwarzschild-de Sitter spacetimes. It is shown that the tunneling formalism
naturally censors against any black hole with a mass in excess of the Nariai
value; thus enforcing a ``third law'' of Schwarzschild-de Sitter
thermodynamics. We also provide commentary on the dS/CFT correspondence in the
context of this tunneling framework.Comment: 19 pages, Latex; citation added; Eqs.(36,37) correcte
Quantum Gravity and Recovery of Information in Black Hole Evaporation
The Generalized Uncertainty Principle (GUP), motivated by current
alternatives of quantum gravity, produces significant modifications to the
Hawking radiation and the final stage of black hole evaporation. We show that
incorporation of the GUP into the quantum tunneling process (based on the
null-geodesic method) causes correlations between the tunneling probability of
different modes in the black hole radiation spectrum. In this manner, the
quantum information becomes encrypted in the Hawking radiation, and information
can be recovered as non-thermal GUP correlations between tunneling
probabilities of different modes.Comment: 7 pages, no figure, final revisio
Anatomy of a Bounce
Holographic considerations are used in the scrutiny of a special class of
brane-world cosmologies. Inherently to this class, the brane typically bounces,
at a finite size, as a consequence of a charged black hole in the bulk. Whereas
a prior treatment [hep-th/0301010] emphasized a brane that is void of
standard-model matter, the analysis is now extended to include an intrinsic
(radiation-dominated) matter source. An interesting feature of this generalized
model is that a bounce is no longer guaranteed but, rather, depends on the
initial conditions. Ultimately, we demonstrate that compliance with an
appropriate holographic bound is a sufficient prerequisite for a bounce to
occur.Comment: 14 pages, Revtex; (v2) minor revisions; (v3) reference adde
Of Bounces, Branes and Bounds
Some recent studies have considered a Randall-Sundrum-like brane world
evolving in the background of an anti-de Sitter Reissner-Nordstrom black hole.
For this scenario, it has been shown that, when the bulk charge is
non-vanishing, a singularity-free ``bounce'' universe will always be obtained.
However, for the physically relevant case of a de Sitter brane world, we have
recently argued that, from a holographic (c-theorem) perspective, such brane
worlds may not be physically viable. In the current paper, we reconsider the
validity of such models by appealing to the so-called ``causal entropy bound''.
In this framework, a paradoxical outcome is obtained: these brane worlds are
indeed holographically viable, provided that the bulk charge is not too small.
We go on to argue that this new finding is likely the more reliable one.Comment: 15 pages, Revtex; references added and very minor change
Area spectra versus entropy spectra in black holes in topologically massive gravity
We consider the area and entropy spectra of black holes in topologically
massive gravity with gravitational Chern-Simons term. The examples we consider
are the BTZ black hole and the warped AdS black hole. For the non-rotating BTZ
black hole, the area and entropy spectra are equally spaced and independent of
the coupling constant \v of the Chern-Simons term. For the rotating BTZ black
hole case, the spectra of the inner and outer horizon areas are not equally
spaced in general and dependent of the coupling constant \v. However the
entropy spectrum is equally spaced and independent of the coupling constant
\v. For the warped AdS black holes for by using the quasinormal modes
obtained without imposing the boundary condition at radial infinity we find
again that the entropy spectrum is equally spaced and independent of the
coupling constant \v, while the spectra of the inner and outer horizon areas
are not equally spaced and dependent of the coupling constant \v. Our result
implies that the entropy spectrum has a universal behavior regardless of the
presence of the gravitational Chern-Simons term, and therefore it implies that
the entropy is more `fundamental' than the horizon area.Comment: 16 page
On the Kerr Quantum Area Spectrum
Suppose that there is a quantum operator that describes the horizon area of a
black hole. Then what would be the form of the ensuing quantum spectrum? In
this regard, it has been conjectured that the characteristic frequencies of the
black hole oscillations can be used to calibrate the spacing between the
spectral levels. The current article begins with a brief review of this
conjecture and some of its subsequent developments. We then suggest a simple
but vital modification to a recent treatment on the Kerr (or rotating black
hole) spectrum. As a consequence of this refinement, we are able to rectify a
prior inconsistency (as was found between two distinct calculations) and to
establish, unambiguously, a universal form for the Kerr and Schwarzschild
spectra.Comment: Roughly 8 pages; (v2) added references and very minor change
Exact braneworld cosmology induced from bulk black holes
We use a new, exact approach in calculating the energy density measured by an
observer living on a brane embedded in a charged black hole spacetime. We find
that the bulk Weyl tensor gives rise to non-linear terms in the energy density
and pressure in the FRW equations for the brane. Remarkably, these take exactly
the same form as the ``unconventional'' terms found in the cosmology of branes
embedded in pure AdS, with extra matter living on the brane. Black hole driven
cosmologies have the benefit that there is no ambiguity in splitting the
braneword energy momentum into tension and additional matter. We propose a new,
enlarged relationship between the two descriptions of braneworld cosmology. We
also study the exact thermodynamics of the field theory and present a
generalised Cardy-Verlinde formula in this set up.Comment: 17 pages, no figures; v3: Minor change, References added, Version to
appear in CQ
The Highly Damped Quasinormal Modes of -dimensional Reissner-Nordstrom Black Holes in the Small Charge Limit
We analyze in detail the highly damped quasinormal modes of -dimensional
Reissner-Nordstrm black holes with small charge, paying
particular attention to the large but finite damping limit in which the
Schwarzschild results should be valid. In the infinite damping limit, we
confirm using different methods the results obtained previously in the
literature for higher dimensional Reissner-Nordstrm black holes.
Using a combination of analytic and numerical techniques we also calculate the
transition of the real part of the quasinormal mode frequency from the
Reissner-Nordstrm value for very large damping to the
Schwarzschild value of for intermediate damping. The real
frequency does not interpolate smoothly between the two values. Instead there
is a critical value of the damping at which the topology of the
Stokes/anti-Stokes lines change, and the real part of the quasinormal mode
frequency dips to zero.Comment: 18 pages, 8 figure
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