Covariant perturbation theory and the Randall-Sundrum picture

The effective action for quantum fields on a $d$-dimensional spacetime can be computed using a non local expansion in powers of the curvature. We show explicitly that, for conformal fields and up to quadratic order in the curvature, the non local effective action is equivalent to the $d+1$ action for classical gravity in $AdS_{d+1}$ restricted to a $d-1$-brane. This generalizes previous results about quantum corrections to the Newtonian potential and provides an alternative method for making local a non-local effective action. The equivalence can be easily understood by comparing the Kallen-Lehmann decomposition of the classical propagator with the spectral representation of the non local form factors in the quantum effective action.Comment: 8 pages, Latex. Minor corrections. To appear in Phys. Lett.

Anomaly-Induced Effective Action and Inflation

In the early Universe matter can be described as a conformal invariant ultra-relativistic perfect fluid, which does not contribute, on classical level, to the evolution of the isotropic and homogeneous metric. If we suppose that there is some desert in the particle spectrum just below the Planck mass, then the effect of conformal trace anomaly is dominating at the corresponding energies. With some additional constraints on the particle content of the underlying gauge model (which favor extended or supersymmetric versions of the Standard Model rather than the minimal one), one arrives at the stable inflation. We review the model and report about the calculation of the gravitational waves on the background of the anomaly-induced inflation. The result for the perturbation spectrum is close to the one for the conventional inflaton model, and is in agreement with the existing Cobe data (see also [hep-th/0009197]).Comment: 4 pages, LaTeX. Contribution to the Proceedings of the EuroConference on Frontiers in Particle Astrophysics and Cosmology, 30 September - 5 October 2000. San Feliu, Spai

The graceful exit from the anomaly-induced inflation: Supersymmetry as a key

The stable version of the anomaly-induced inflation does not need a fine tuning and leads to sufficient expansion of the Universe. The non-stable version (Starobinsky model) provides the graceful exit to the FRW phase. We indicate the possibility of the inflation which is stable at the beginning and unstable at the end. The effect is due to the soft supersymmetry breaking and the decoupling of the massive sparticles at low energy.Comment: 10 pages, 2 figures using axodraw. Modified version. Discussion concerning the gravitational scale modified, the effect of massive particles in the last stage of inflation taken into accoun

Quantum dynamics of N=1N=1, D=4D=4 supergravity compensator

A new $N=1$ superfield theory in $D=4$ flat superspace is suggested. It describes dynamics of supergravity compensator and can be considered as a low-energy limit for $N=1$, $D=4$ superfield supergravity. The theory is shown to be renormalizable in infrared limit and infrared free. A quantum effective action is investigated in infrared domain

On the inflationary solutions in higher-derivative gravity with dilaton field

We discuss the existence of de Sitter inflationary solutions for the string-inspired fourth-derivative gravity theories with dilaton field. We consider a space-time of arbitrary dimension D and an arbitrary parametrization of the target space metric. The specific features of the theory in dimension D=4 and those of the special ghost-free parametrization of the metric are found. We also consider similar string-inspired theories with torsion and construct an inflationary solution with torsion and dilaton for D=4. The stability of the inflationary solutions is also investigated.Comment: 13 pages, LaTeX, no figure

Conformal symmetry, anomaly and effective action for metric-scalar gravity with torsion

We consider some aspects of conformal symmetry in a metric-scalar-torsion system. It is shown that, for some special choice of the action, torsion acts as a compensating field and the full theory is conformally equivalent to General Relativity on classical level. Due to the introduction of torsion, this equivalence can be provided for the positively-defined gravitational and scalar actions. One-loop divergences arising from the scalar loop are calculated and both the consequent anomaly and the anomaly-induced effective action are derived.Comment: 15 pages, LaTeX. Essentially extended version, in particular the discussion of the stability of the conformal factor in gravity theory with torsion and scalar added. Title also modified. To be published in Physics Letters

Massive fields temper anomaly-induced inflation: the clue to graceful exit?

A method of calculating the vacuum effective action for massive quantum fields in curved space-time is outlined. Our approach is based on the conformal representation of the fields action and on the integration of the corresponding conformal anomaly. As a relevant cosmological application, we find that if taking the masses of the fields into account, then the anomaly-induced inflation automatically slows down. The only relevant massive fields for this purpose turn out to be the fermion fields. So in supersymmetric theories this mechanism can be specially efficient, for it may naturally provide the graceful exit from the inflationary to the FLRW phase. Taking the SUSY breaking into account, the anomaly-induced inflation could be free of the well-known difficulties with the initial data and also with the amplitude of the gravitational waves.Comment: 12 pages, 2 figures. Extended version, in particular an important discussion concerning the gravitational waves adde

Anomaly induced effective actions and Hawking radiation

The quantum stress tensor in the Unruh state for a conformal scalar propagating in a 4D Schwarzschild black hole spacetime is reconstructed in its leading behaviour at infinity and near the horizon by means of an effective action derived by functionally integrating the trace anomaly.Comment: 4 pages, revte

Effective action for scalar fields and generalised zeta-function regularisation

Motivated by the study of quantum fields in a Friedman-Robertson-Walker (FRW) spacetime, the one-loop effective action for a scalar field defined in the ultrastatic manifold $R\times H^3/\Gamma$, $H^3/\Gamma$ being the finite volume, non-compact, hyperbolic spatial section, is investigated by a generalisation of zeta-function regularisation. It is shown that additional divergences may appear at one-loop level. The one-loop renormalisability of the model is discussed and making use of a generalisation of zeta-function regularisation, the one-loop renormalisation group equations are derived.Comment: Latex, 16 pages, no figures; Latex mistakes corrected; accepted for publication in Physical Review

Vacuum polarization in Schwarzschild space-time by anomaly induced effective actions

The characteristic features of $$ in the Boulware, Unruh and Hartle-Hawking states for a conformal massless scalar field propagating in the Schwarzschild space-time are obtained by means of effective actions deduced by the trace anomaly. The actions are made local by the introduction of auxiliary fields and boundary conditions are carefully imposed on them in order to select the different quantum states.Comment: 20 pages, latex; misprints corrected and references adde