782 research outputs found
Unitary evolution of perturbations of a two-dimensional black hole
We discuss massive scalar perturbations of a two-dimensional dilaton black
hole. We employ a Pauli-Villars reqularization scheme to calculate the effect
of the scalar perturbation on the Bekenstein-Hawking entropy. By concentrating
on the dynamics of the scalar field near the horizon, we argue that quantum
effects alter the effective potential. We calculate the two-point function
explicitly and show that it exhibits Poincare recurrences.Comment: 11 page
Newton constant, contact terms and entropy
We discuss the renormalization of the Newton constant due to fields of
various spin . We first briefly review the cases of already discussed in the literature and notice the appearance of the
well-known contact terms for the vector bosons. We then extend this discussion
of the contact terms to massive vector fields, -forms and to the case of
spin particles (gravitons). We observe that, in general, the contact
terms originate from the fields which mediate the interactions (such as vector
gauge bosons and gravitons). We then discuss entanglement entropy and the
conical entropy and their relation to the renormalized Newton constant. We
address the puzzle of the non-analytic terms due to fields of spin and
suggest that the resolution of this puzzle comes from the non-equivalence of
the orbifold and -fold cover constructions which are used in the entropy
calculations. Finally, we propose a mechanism by which the Bekenstein-Hawking
entropy is identified with entanglement entropy in any theory which includes
both matter fields and the mediators of interactions (vector gauge bosons and
gravitons).Comment: 31 pages; new ref. adde
Conformal a-charge, correlation functions and conical defects
In this note we demonstrate that, as we conjectured earlier in [1], the
a-charge in the conformal anomaly in dimension manifests in a -point
correlation function of energy momentum tensor of a CFT considered in flat
spacetime with a conical defect. We consider in detail dimensions and give a general formula for arbitrary .Comment: 10 pages; v2: new references added + several remarks on absence of
contribution from anomaly of type B adde
How to make the gravitational action on non-compact space finite
The recently proposed technique to regularize the divergences of the
gravitational action on non-compact space by adding boundary counterterms is
studied. We propose prescription for constructing the boundary counterterms
which are polynomial in the boundary curvature. This prescription is efficient
for both asymptotically Anti-de Sitter and asymptotically flat spaces. Being
mostly interested in the asymptotically flat case we demonstrate how our
procedure works for known examples of non-compact spaces: Eguchi-Hanson metric,
Kerr-Newman metric, Taub-NUT and Taub-bolt metrics and others. Analyzing the
regularization procedure when boundary is not round sphere we observe that our
counterterm helps to cancel large divergence of the action in the zero and
first orders in small deviations of the geometry of the boundary from that of
the round sphere. In order to cancel the divergence in the second order in
deviations a new quadratic in boundary curvature counterterm is introduced. We
argue that cancelation of the divergence for finite deviations possibly
requires infinite series of (higher order in the boundary curvature) boundary
counterterms.Comment: 27 pages, latex, no figure
Entanglement entropy of round spheres
We propose that the logarithmic term in the entanglement entropy computed in
a conformal field theory for a -dimensional round sphere in Minkowski
spacetime is identical to the logarithmic term in the entanglement entropy of
extreme black hole. The near-horizon geometry of the latter is . For a scalar field this proposal is checked by direct calculation. We
comment on relation of this and earlier calculations to the ``brick wall''
model of 't Hooft. The case of generic 4d conformal field theory is discussed.Comment: 11 pages, no figures, minor modificatio
Metric Redefinition and UV Divergences in Quantum Einstein Gravity
I formulate several statements demonstrating that the local metric
redefinition can be used to reduce the UV divergences present in the quantum
action for the Einstein gravity in dimensions. In its most general form,
the proposal is that any UV divergences in the quantum action can be removed by
an appropriate field re-definition and a renormalization of cosmological
constant.Comment: 10 pages; v2: minor typos corrected; v3a: more remarks + discussion
of S-matrix + 1 new reference added, v3b: more references added, version to
appear in PL
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