Quantum Fluctuations of Planck Mass as Mutation Mechanism in a Theory of Evolution of the Universe

Contributed talk at the Seventh Marcel Grossman Meeting on Gravity, June 24-30. A theory of evolution of the universe requires both a mutation mechanism and a selection mechanism. We believe that both can be encountered in the stochastic approach to quantum cosmology. In Brans-Dicke chaotic inflation, the quantum fluctuations of Planck mass behave as mutations, such that new inflationary domains may contain values of Planck mass that differ slightly from their parent's. The selection mechanism establishes that the value of Planck mass should be such as to increase the proper volume of the inflationary domain, which will then generate more offsprings. This mechanism predicts that the effective Planck scale at the end of inflation should be much larger than any given scale in the model.Comment: 3 pages, Stanford University preprint SU-ITP-94-32, IEM-FT-92/9

Preheating the universe in hybrid inflation

One of the fundamental problems of modern cosmology is to explain the origin of all the matter and radiation in the Universe today. The inflationary model predicts that the oscillations of the scalar field at the end of inflation will convert the coherent energy density of the inflaton into a large number of particles, responsible for the present entropy of the Universe. The transition from the inflationary era to the radiation era was originally called reheating, and we now understand that it may consist of three different stages: preheating, in which the homogeneous inflaton field decays coherently into bosonic waves (scalars and/or vectors) with large occupation numbers; backreaction and rescattering, in which different energy bands get mixed; and finally decoherence and thermalization, in which those waves break up into particles that thermalize and acquire a black body spectrum at a certain temperature. These three stages are non-perturbative, non-linear and out of equilibrium, and we are just beginning to understand them. In this talk I will concentrate on the preheating part, putting emphasis on the differences between preheating in chaotic and in hybrid inflation.Comment: 6 pages, LaTeX, uses moriond.sty (included), no figures. Contribution to the proceedings of Moriond 98, Fundamental Parameters in Cosmology, Les Arcs, France (January 17-24, 1998

Primordial Gravitational Waves and the local B-mode polarization of the CMB

A stochastic background of primordial gravitational waves could be detected soon in the polarization of the CMB and/or with laser interferometers. There are at least three GWB coming from inflation: those produced during inflation and associated with the stretching of space-time modes; those produced at the violent stage of preheating after inflation; and those associated with the self-ordering of Goldstone modes if inflation ends via a global symmetry breaking scenario, like in hybrid inflation. Each GW background has its own characteristic spectrum with specific features. We discuss the prospects for detecting each GWB and distinguishing between them with a very sensitive probe, the local B-mode of CMB polarization.Comment: 5 pages, 6 figures, to appear in the Proceedings of Moriond Cosmology 201

Particle Physics and Cosmology

In this talk I review the present status of inflationary cosmology and its emergence as the basic paradigm behind the Standard Cosmological Model, with parameters determined today at better than 10% level from CMB and LSS observations.Comment: 12 pages, LaTeX, uses frascatiphys_R.sty (included). Plenary talk, to appear in the Proceedings of the First International Workshop on Frontier Science, October 6-11, 2002, Frascati (Italy

Single-bubble Open Inflation: An Overview

The idea that the universe might be open is an old one, and the possibility of having an open universe arise form inflation is not new either. However, a concrete realization of a consistent single-bubble open inflation model is known only recently. There has been great progress in the last two years in the development of models of inflation consistent with observations in such an open universe. In this overview I will describe the basic features and the phenomenological consequences of such models, making emphasis in the predictions of the CMB temperature anisotropies that differ from ordinary inflation.Comment: 20 pages, LaTeX, crckapb.sty macro included, 6 figures included in the text with epsf. Review talk, to appear in the Proceedings of the ``Birth of the Universe II'' Conference in Roma, May 199