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

The evolution of the Universe

With the recent measurements of temperature and polarization anisotropies in the microwave background by WMAP, we have entered a new era of precision cosmology, with the cosmological parameters of a Standard Cosmological Model determined to 1%. This Standard Model is based on the Big Bang theory and the inflationary paradigm, a period of exponential expansion in the early universe responsible for the large-scale homogeneity and spatial flatness of our observable patch of the Universe. The spectrum of metric perturbations, seen in the microwave background as temperature anisotropies, were produced during inflation from quantum fluctuations that were stretched to cosmological size by the expansion, and later gave rise, via gravitational collapse, to the observed large-scale structure of clusters and superclusters of galaxies. Furthermore, the same theory predicts that all the matter and radiation in the universe today originated at the end of inflation from an explosive production of particles that could also have been the origin of the present baryon asymmetry, before the universe reached thermal equilibrium at a very large temperature. From there on, the universe cooled down as it expanded, in the way described by the standard hot Big Bang model.Comment: 15 pages, 6 figures, LaTeX, uses ws-procs975x65.cls (included). Invited Plenary Talk at the international colloquium on TIME AND MATTER, Venice, Italy, August 11 - 17, 200

Dual inflation

We propose a new model of inflation based on the soft-breaking of N=2 supersymmetric SU(2) Yang-Mills theory. The advantage of such a model is the fact that we can write an exact expression for the effective scalar potential, including non-perturbative effects, which preserves the analyticity and duality properties of the Seiberg-Witten solution. We find that the scalar condensate that plays the role of the inflaton can drive a long period of cosmological expansion, produce the right amount of temperature anisotropies in the microwave background, and end inflation when the monopole acquires a vacuum expectation value. Duality properties relate the weak coupling Higgs region where inflation takes place with the strong coupling monopole region, where reheating occurs, creating particles corresponding to the light degrees of freedom in the true vacuum.Comment: 5 pages, RevTeX, epsf, 2 figures (included in the text). Slightly improved version, accepted in Physics Letters