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oai:recercat.cat:2445/123092025-12-04T20:43:10Zcom_2072_1057col_2072_478822col_2072_478917

Noise induced transitions in semiclassical cosmology Calzetta, Esteban A., 1958- Verdaguer Oms, Enric, 1950- Matèria interstel·lar Relativitat (Física) Gravitació (Física) Teoria quàntica de camps Soroll Espai i temps Interstellar medium Relativity (Physics) Gravitation Quantum field theory Space and time Noise A semiclassical cosmological model is considered which consists of a closed Friedmann-Robertson-Walker spacetime in the presence of a cosmological constant, which mimics the effect of an inflaton field, and a massless, non-conformally coupled quantum scalar field. We show that the back-reaction of the quantum field, which consists basically of a nonlocal term due to gravitational particle creation and a noise term induced by the quantum fluctuations of the field, are able to drive the cosmological scale factor over the barrier of the classical potential so that if the universe starts near a zero scale factor (initial singularity), it can make the transition to an exponentially expanding de Sitter phase. We compute the probability of this transition and it turns out to be comparable with the probability that the universe tunnels from ``nothing'' into an inflationary stage in quantum cosmology. This suggests that in the presence of matter fields the back-reaction on the spacetime should not be neglected in quantum cosmology. 2010-05-06T08:23:36Z 2010-05-06T08:23:36Z 1999 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 0556-2821 https://hdl.handle.net/2445/12309 145498 eng Reproducció digital del document publicat en format paper, proporcionada per PROLA i http://dx.doi.org/10.1103/PhysRevD.59.083513 Physical Review D, 1999, vol. 59, núm. 8, p. 083513-1-083513-24 http://dx.doi.org/10.1103/PhysRevD.59.083513 (c) The American Physical Society, 1999 info:eu-repo/semantics/openAccess 24 p. application/pdf The American Physical Society Articles publicats en revistes (Física de la Matèria Condensada)