22 research outputs found
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.
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
Vacuum Expectation Value of the Spinor Massive field in the Cosmic String Space-Time
We found the contribution to the vacuum expectation value of the
energy-momentum tensor of a massive Dirac field due to the conical geometry of
the cosmic string space-time. The heat kernel and heat kernel expansion for the
squared Dirac operator in this background are also considered and the first
three coefficients were found in an explicity form.Comment: 9 pages, 1 figure (2 ref added) (enlarged version
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
Thermal partition function of photons and gravitons in a Rindler wedge
The thermal partition function of photons in any covariant gauge and
gravitons in the harmonic gauge, propagating in a Rindler wedge, are computed
using a local -function regularization approach. The correct Planckian
leading order temperature dependence is obtained in both cases. For the
photons, the existence of a surface term giving a negative contribution to the
entropy is confirmed, as earlier obtained by Kabat, but this term is shown to
be gauge dependent in the four-dimensional case and, therefore is discarded. It
is argued that similar terms could appear dealing with any integer spin in the massless case and in more general manifolds. Our conjecture is
checked in the case of a graviton in the harmonic gauge, where different
surface terms also appear, and physically consistent results arise dropping
these terms. The results are discussed in relation to the quantum corrections
to the black hole entropy.Comment: 29 pages, RevTeX, no figures. Minor errors corrected and a few
comments changed since first submission. To be published on Phys.Rev.
Thermal fluctuations of a quantized massive scalar field in Rindler background
Thermal fluctuations for a massive scalar field in the Rindler wedge are
obtained by applying the point-splitting procedure to the zero temperature
Feynman propagator in a conical spacetime. Renormalization is implemented by
removing the zero temperature contribution. It is shown that for a field of non
vanishing mass the thermal fluctuations, when expressed in terms of the local
temperature, do not have Minkowski form. As a by product, Minkowski vacuum
fluctuations seen by an uniformly accelerated observer are determined and
confronted with the literature.Comment: 10 pages; Latex fil
Thermodynamics of scalar fields in Kerr's geometry
The one-loop contributions to the entropy for a massive scalar field in a
Kerr black hole are investigated using an approximation of the metric, which,
after a conformal transformation, permits to work in a Rindler-like spacetime.
Of course, as for the Schwarzschild case, the entropy is divergent in the
proximity of the event horizon.Comment: 7 pages, LaTex, (revised version-last section modified
Fluctuations of quantum fields via zeta function regularization
Explicit expressions for the expectation values and the variances of some
observables, which are bilinear quantities in the quantum fields on a
D-dimensional manifold, are derived making use of zeta function regularization.
It is found that the variance, related to the second functional variation of
the effective action, requires a further regularization and that the relative
regularized variance turns out to be 2/N, where N is the number of the fields,
thus being independent on the dimension D. Some illustrating examples are
worked through.Comment: 15 pages, latex, typographical mistakes correcte
Quantum Scalar Field on the Massless (2+1)-Dimensional Black Hole Background
The behavior of a quantum scalar field is studied in the metric ground state
of the (2+1)-dimensional black hole of Ba\~nados, Teitelboim and Zanelli which
contains a naked singularity. The one-loop BTZ partition function and the
associate black hole effective entropy, the expectation value of the quantum
fluctuation as well as the renormalized expectation value of the stress tensor
are explicitly computed in the framework of the -function procedure.
This is done for all values of the coupling with the curvature, the mass of the
field and the temperature of the quantum state. In the massless conformally
coupled case, the found stress tensor is used for determining the quantum back
reaction on the metric due to the scalar field in the quantum vacuum state, by
solving the semiclassical Einstein equations. It is finally argued that, within
the framework of the 1/N expansion, the Cosmic Censorship Hypothesis is
implemented since the naked singularity of the ground state metric is shielded
by an event horizon created by the back reaction.Comment: 18 pages, RevTeX, no figures, minor changes, final version accepted
for publication in Phys. Rev.
An approach for the calculation of one-loop effective actions, vacuum energies, and spectral counting functions
In this paper, we provide an approach for the calculation of one-loop
effective actions, vacuum energies, and spectral counting functions and discuss
the application of this approach in some physical problems. Concretely, we
construct the equations for these three quantities; this allows us to achieve
them by directly solving equations. In order to construct the equations, we
introduce shifted local one-loop effective actions, shifted local vacuum
energies, and local spectral counting functions. We solve the equations of
one-loop effective actions, vacuum energies, and spectral counting functions
for free massive scalar fields in , scalar fields in
three-dimensional hyperbolic space (the Euclidean Anti-de Sitter space
), in (the geometry of the Euclidean BTZ black hole), and in
, and the Higgs model in a -dimensional finite interval.
Moreover, in the above cases, we also calculate the spectra from the counting
functions. Besides exact solutions, we give a general discussion on approximate
solutions and construct the general series expansion for one-loop effective
actions, vacuum energies, and spectral counting functions. In doing this, we
encounter divergences. In order to remove the divergences, renormalization
procedures are used. In this approach, these three physical quantities are
regarded as spectral functions in the spectral problem.Comment: 37 pages, no figure. This is an enlarged and improved version of the
paper published in JHE