39 research outputs found
zeta-function regularization and one-loop renormalization of field fluctuations in curved space-times
A method to regularize and renormalize the fluctuations of a quantum field in
a curved background in the -function approach is presented. The method
produces finite quantities directly and finite scale-parametrized counterterms
at most. These finite couterterms are related to the presence of a particular
pole of the effective-action function as well as to the heat kernel
coefficients. The method is checked in several examples obtaining known or
reasonable results. Finally, comments are given for as it concerns the recent
proposal by Frolov et al. to get the finite Bekenstein-Hawking entropy from
Sakharov's induced gravity theory.Comment: 9 pages, standard LaTeX, no figure
Euclidean Thermal Green Functions of Photons in Generalized Euclidean Rindler Spaces for any Feynman-like Gauge
The thermal Euclidean Green functions for Photons propagating in the Rindler
wedge are computed employing an Euclidean approach within any covariant
Feynman-like gauge. This is done by generalizing a formula which holds in the
Minkowskian case. The coincidence of the found (\be=2\pi)-Green functions and
the corresponding Minkowskian vacuum Green functions is discussed in relation
to the remaining static gauge ambiguity already found in previous papers.
Further generalizations to more complicated manifolds are discussed. Ward
identities are verified in the general case.Comment: 12 pages, standard latex, no figures, some signs changed, more
comments added, final version to appear on Int. J. Mod. Phys.
On the Dimensional Reduction Procedure
The issue related to the so-called dimensional reduction procedure is
revisited within the Euclidean formalism. First, it is shown that for symmetric
spaces, the local exact heat-kernel density is equal to the reduced one, once
the harmonic sum has been succesfully performed. In the general case, due to
the impossibility to deal with exact results, the short time heat-kernel
asymptotics is considered. It is found that the exact heat-kernel and the
dimensionally reduced one coincide up to two non trivial leading contributions
in the short time expansion. Implications of these results with regard to
dimensional-reduction anomaly are discussed.Comment: 15 pages, Latex, enlarged discussion added in Sec 3 and typos
corrected. Version to appear in Nucl. Phys.
Ambiguity in the evaluation of the effective action on the cone
An ambiguity in the computation of the one-loop effective action for fields
living on a cone is illustrated. It is shown that the ambiguity arises due to
the non-commutativity of the regularization of ultraviolet and (conical)
boundary divergencies.Comment: REVTeX file, 10 pages. Comments on recent papers have been adde
Quantum fluctuations on a thick de Sitter brane
We investigate quantum fluctuations on a de Sitter (dS) brane, which has its
own thickness, in order to examine whether or not the finite thickness of the
brane can act as a natural cut-off for the Kaluza-Klein (KK) spectrum. We
calculate the amplitude of the KK modes and the bound state by using the zeta
function method after a dimensional reduction.We show that the KK amplitude is
finite for a given brane thickness and in the thin wall limit the standard
surface divergent behavior is recovered. The strength of the divergence in the
thin wall limit depends on the number of dimensions, e.g., logarithmic on a two
dimensional brane and quadratic on a four dimensional brane. We also find that
the amplitude of the bound state mode and KK modes depends on the choice of
renormalization scale; and for fixed renormalization scales the bound state
mode is insensitive to the brane thickness both for two and four-dimensional dS
branes.Comment: 23 pages, typos correcte
Dynamical Chiral Symmetry Breaking and its Restoration for an Accelerated Observer
Based on the Hawking-Unruh thermalization theorem, we investigate the
phenomenon of the dynamical chiral symmetry breaking and its restoration for a
uniformly accelerated observer. We employ the NambuJona-Lasinio model in
Rindler coordinates, and calculate the effective potential and the gap
equation. The critical coupling and the critical acceleration for symmetry
restoration are obtained.Comment: 7 pages. Phys. Lett. B (2004), in pres
Massive scalar field near a cosmic string
The function of a massive scalar field near a cosmic string is
computed and then employed to find the vacuum fluctuation of the field. The
vacuum expectation value of the energy-momentum tensor is also computed using a
point-splitting approach. The obtained results could be useful also for the
case of self-interacting scalar fields and for the finite-temperature Rindler
space theory.Comment: 15 pages, standard LaTeX, no figures. Reference [14] correcte