A note on Weyl transformations in two-dimensional dilaton gravity

We discuss Weyl (conformal) transformations in two-dimensional matterless dilaton gravity. We argue that both classical and quantum dilaton gravity theories are invariant under Weyl transformations.Comment: 8 pages, accepted for publication in Mod. Phys. Lett.

Canonical and path integral quantisation of string cosmology models

We discuss the quantisation of a class of string cosmology models that are characterized by scale factor duality invariance. We compute the amplitudes for the full set of classically allowed and forbidden transitions by applying the reduce phase space and the path integral methods. We show that these approaches are consistent. The path integral calculation clarifies the meaning of the instanton-like behaviour of the transition amplitudes that has been first pointed out in previous investigations.Comment: 18 pages,2 eps figures, LaTeX2e, macro files included (epsf.tex,epsf.sty), macros of Classical and Quantum Gravity used; accepted for publication on Classical and Quantum Gravit

Geometrodynamical Formulation of Two-Dimensional Dilaton Gravity

Two-dimensional matterless dilaton gravity with arbitrary dilatonic potential can be discussed in a unitary way, both in the Lagrangian and canonical frameworks, by introducing suitable field redefinitions. The new fields are directly related to the original spacetime geometry and in the canonical picture they generalize the well-known geometrodynamical variables used in the discussion of the Schwarzschild black hole. So the model can be quantized using the techniques developed for the latter case. The resulting quantum theory exhibits the Birkhoff theorem at the quantum level.Comment: 15 pages, LATE

Recent developments in quantum string cosmology

In this talk we discuss the quantisation of a class of string cosmology models characterised by scale factor duality invariance. The amplitudes for the full set of classically allowed and forbidden transitions are computed by applying the reduced phase space and path integral methods. In particular, the path integral calculation clarifies the meaning of the instanton-like behaviour of the transition amplitudes that has been first pointed out in previous investigations.Comment: 4 pages, one eps figures, uses espcrc2.sty. Talk given at the Third Conference on Constrained Dynamics and Quantum Gravit

Supersymmetry versus black holes at the LHC

Supersymmetry and extra dimensions are the two most promising candidates for new physics at the TeV scale. Supersymmetric particles or extra-dimensional effects could soon be observed at the Large Hadron Collider. We propose a simple but powerful method to discriminate the two models: the analysis of isolated leptons with high transverse momentum. Black hole events are simulated with the CATFISH black hole generator. Supersymmetry simulations use a combination of PYTHIA and ISAJET, the latter providing the mass spectrum. Our results show the measure of the dilepton invariant mass provides a strong signature to differentiate supersymmetry and black hole events at the Large Hadron Collider. Analysis of event-shape variables and multilepton events complement and strengthen this conclusion.Comment: 12 pages, 5 figure

Time Gauge Fixing and Hilbert Space in Quantum String Cosmology

Recently the low-energy effective string theory has been used by Gasperini and Veneziano to elaborate a very interesting scenario for the early history of the universe (``birth of the universe as quantum scattering''). Here we investigate the gauge fixing and the problem of the definition of a global time parameter for this model, and we obtain the positive norm Hilbert space of states.Comment: 13 pages, Plain TEX, no figure

Pre-big bang in M-theory

We discuss a simple cosmological model derived from M-theory. Three assumptions lead naturally to a pre-big bang scenario: (a) 11-dimensional supergravity describes the low-energy world; (b) non-gravitational fields live on a three-dimensional brane; and (c) asymptotically past triviality.Comment: 16 pages, 8 figures, LaTeX (requires epsf

Quantum gravity corrections to the Schwarzschild mass

Vacuum spherically symmetric Einstein gravity in $N\ge 4$ dimensions can be cast in a two-dimensional conformal nonlinear sigma model form by first integrating on the $(N-2)$-dimensional (hyper)sphere and then performing a canonical transformation. The conformal sigma model is described by two fields which are related to the Arnowitt-Deser-Misner mass and to the radius of the $(N-2)$-dimensional (hyper)sphere, respectively. By quantizing perturbatively the theory we estimate the quantum corrections to the ADM mass of a black hole.Comment: 18 pages, 8 figures, LaTeX2e, uses epsfig package, accepted for publication in Phys. Rev.