197 research outputs found
Cosmological significance of one-loop effective gravity
We study the one-loop effective action for gravity in a cosmological setup to
determine possible cosmological effects of quantum corrections to Einstein
theory. By considering the effect of the universal non-local terms in a toy
model, we show that they can play an important role in the very early universe.
We find that during inflation, the non-local terms are significant, leading to
deviations from the standard inflationary expansion.Comment: 8 pages (REVTeX
Massive uncharged and charged particles' tunneling from the Horowitz-Strominger Dilaton black hole
Originally, Parikh and Wilczek's work is only suitable for the massless
particles' tunneling. But their work has been further extended to the cases of
massive uncharged and charged particles' tunneling recently. In this paper, as
a particular black hole solution, we apply this extended method to reconsider
the tunneling effect of the H.S Dilaton black hole. We investigate the behavior
of both massive uncharged and charged particles, and respectively calculate the
emission rate at the event horizon. Our result shows that their emission rates
are also consistent with the unitary theory. Moreover, comparing with the case
of massless particles' tunneling, we find that this conclusion is independent
of the kind of particles. And it is probably caused by the underlying
relationship between this method and the laws of black hole thermodynamics.Comment: 6 pages, no figure, revtex 4, accepted by Int. J. Mod. Phys
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
Hawking radiation as tunneling from squashed Kaluza-Klein black hole
We discuss Hawking radiation from a five-dimensional squashed Kaluza-Klein
black hole on the basis of the tunneling mechanism. A simple manner, which was
recently suggested by Umetsu, is possible to extend the original derivation by
Parikh and Wilczek to various black holes. That is, we use the two-dimensional
effective metric, which is obtained by the dimensional reduction near the
horizon, as the background metric. By using same manner, we derive both the
desired result of the Hawking temperature and the effect of the back reaction
associated with the radiation in the squashed Kaluza-Klein black hole
background.Comment: 16 page
Gravitational anomalies: a recipe for Hawking radiation
We explore the method of Robinson and Wilczek for deriving the Hawking
temperature of a black hole. In this method, the Hawking radiation restores
general covariance in an effective theory of near-horizon physics which
otherwise exhibits a gravitational anomaly at the quantum level. The method has
been shown to work for broad classes of black holes in arbitrary spacetime
dimensions. These include static black holes, accreting or evaporating black
holes, charged black holes, rotating black holes, and even black rings. In the
case of charged and rotating black holes, the expected super-radiant current is
also reproduced.Comment: 7 pages; This essay received an "Honorable Mention" in the 2007 Essay
Competition of the Gravity Research Foundation; (v2) Short comments and
references added; (v3) Minor revisions and updated references to agree with
published versio
Energy and Momentum Distributions of a (2+1)-dimensional black hole background
Using Einstein, Landau-Lifshitz, Papapetrou and Weinberg energy-momentum
complexes we explicitly evaluate the energy and momentum distributions
associated with a non-static and circularly symmetric three-dimensional
spacetime. The gravitational background under study is an exact solution of the
Einstein's equations in the presence of a cosmological constant and a null
fluid. It can be regarded as the three-dimensional analogue of the Vaidya
metric and represents a non-static spinless (2+1)-dimensional black hole with
an outflux of null radiation. All four above-mentioned prescriptions give
exactly the same energy and momentum distributions for the specific black hole
background. Therefore, the results obtained here provide evidence in support of
the claim that for a given gravitational background, different energy-momentum
complexes can give identical results in three dimensions. Furthermore, in the
limit of zero cosmological constant the results presented here reproduce the
results obtained by Virbhadra who utilized the Landau-Lifshitz energy-momentum
complex for the same (2+1)-dimensional black hole background in the absence of
a cosmological constant.Comment: 19 pages, LaTeX, v3: references added, to appear in Int.J.Mod.Phys.
Hawking Radiation of Black p-Branes from Gravitational Anomaly
We investigate the Hawking radiation of black -branes of superstring
theories using the method of anomaly cancelation, specially, we use the method
of [S. Iso, H. Umetsu and F. Wilczek, {\sl Phys. Rev. Lett.} {\bf 96}, 151302
(2006); {\sl Phys. Rev. D} {\bf 74}, 044017 (2006)]. The metrics of black
-branes are spherically symmetric, but not the Schwarzschild type. In order
to simplify the calculation, we first make a coordinate transformation to
transform the metric to the Schwarzschild type. Then we calculate its
energy-momentum flux from the method of anomaly cancelation of the above
mentioned references. The obtained energy-momentum flux is equal to a black
body radiation, the thermodynamic temperature of the radiation is equal to its
Hawking temperature. And we find that the results are not changed for the
original non-Schwarzschild type spherically symmetric metric.Comment: 19 pages Latex, some mistakes correcte
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