828 research outputs found
Conformal anomaly for dilaton coupled electromagnetic field
The derivation of the conformal anomaly for dilaton coupled electromagnetic
field in curved space is presented. The models of this sort naturally appear in
stringy gravity or after spherical reduction of multidimensional
Einstein-Maxwell theory. It is shown that unlike the case of minimal vector in
curved space or dilaton coupled scalar the anomaly induced effective action
cannot be derived. The reason is the same why anomaly induced effective action
cannot be constructed for interacting theories (like QED) in curved space.Comment: Latex file, 10 page
Conformal dynamics of quantum gravity with torsion
The trace anomaly induced dynamics of the conformal factor is investigated in
four-dimensional quantum gravity with torsion. The constraints for the coupling
constants of torsion matter interaction are obtained in the infrared stable
fixed point of the effective scalar theory.Comment: 10 pages, CPTH-A213.1292 -- HUPD-921
General dilatonic gravity with an asymptotically free gravitational coupling constant near two dimensions
We study a renormalizable, general theory of dilatonic gravity (with a
kinetic-like term for the dilaton) interacting with scalar matter near two
dimensions. The one-loop effective action and the beta functions for this
general theory are written down. It is proven that the theory possesses a
non-trivial ultraviolet fixed point which yields an asymptotically free
gravitational coupling constant (at ) in this regime.
Moreover, at the fixed point the theory can be cast under the form of a
string-inspired model with free scalar matter. The renormalization of the
Jackiw-Teitelboim model and of lineal gravity in dimensions is
also discussed. We show that these two theories are distinguished at the
quantum level. Finally, fermion-dilatonic gravity near two dimensions is
considered.Comment: LaTeX, 13 pages, no figure
Gravitational Phase Transitions in Infrared Quantum Gravity
The conformal anomaly induced sector of four-dimensional quantum gravity
(infrared quantum gravity) ---which has been introduced by Antoniadis and
Mottola--- is here studied on a curved fiducial background. The one-loop
effective potential for the effective conformal factor theory is calculated
with accuracy, including terms linear in the curvature. It is proven that a
curvature induced phase transition can actually take place. An estimation of
the critical curvature for different choices of the parameters of the theory is
given.Comment: 9 pages, LaTeX file, 3 figures (not included), HUPD-92-10, UB-ECM-PF
92/2
Non-Critical Bosonic String Corrections to the Black Hole Entropy
We calculate the quantum corrections to the entropy of a very large black
hole, coming from the theory of a -dimensional, non-critical bosonic string.
We show that, for , as a result of modular invariance the entropy is
ultraviolet finite, although it diverges in the infrared (while for the
entropy contains both ultraviolet and infrared divergences). The issue of
modular invariance in field theory, in connection with black-hole entropy, is
also investigated.Comment: 8 pages, latex, no figure
Covariant Generalized Holographic Dark Energy and Accelerating Universe
We proposed the generalized holographic dark energy model where infrared
cutoff is identified with the combination of the FRW universe parameters: the
Hubble rate, particle and future horizons, cosmological constant, the universe
life-time (if finite) and their derivatives. It is demonstrated that with the
corresponding choice of the cutoff one can map such holographic dark energy to
modified gravity or gravity with general fluid. Explicitly, F(R) gravity and
general perfect fluid are worked out in detail and corresponding infrared
cutoff is found. Using this correspondence, we get realistic inflation or
viable dark energy or unified inflationary-dark energy universe in terms of
covariant holographic dark energy.Comment: LaTeX 9 pages, version to appear in EPJ
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