19,620 research outputs found
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
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