38212869
Stochastic approach to inflation: Classicality conditions.
The stochastic approach to inflation relies on one key assumption, the emergence of a long-wave classical field that drives the inflation and is subject to a shortwave classical noise. In this work we consider explicitly the potential that acts on the inflaton field, and analyze classicality conditions that must be satisfied to have an effective classical stochastic approach. When these hold, the dynamics is given by a two-dimensional classical Fokker-Planck equation. We develop some examples, already widely considered in different approaches, and find a very suggestive result, which is the damping of the quantum fluctuations by the effect of the inflaton interaction potential. @S0556-2821~96!01624-4#
14666799
Scalar metric fluctuations in space-time matter inflation
Abstract Using the Ponce de Leon background metric, which describes a 5D universe in an apparent vacuum: G ¯ A B = 0 , we study the effective 4D evolution of both, the inflaton and gauge-invariant scalar metric fluctuations, in the recently introduced model of space–time matter inflation.
14603990
Quintessential inflation from a variable cosmological constant in a 5D vacuum
We explore an effective 4D cosmological model for the universe where the variable cosmological constant governs its evolution and the pressure remains negative along all the expansion. This model is introduced from a 5D vacuum state where the (space-like) extra coordinate is considered as noncompact. The expansion is produced by the inflaton field, which is considered as nonminimally coupled to gravity. We conclude from experimental data that the coupling of the inflaton with gravity should be weak, but variable in different epochs of the evolution of the universe.
14646411
Coarse-grained field wave function in stochastic inflation
The wave function for the matter field fluctuations in the infrared sector is studied within the framework of inflationary cosmology. These fluctuations are described by a coarse-grained field which takes into account only the modes with wavelength much bigger than the size of the Hubble horizon. The case of a power-law expanding universe is considered and it is found that the relevant phase-space (φcg,Pφcg) remains coherent under certain circumstances. In this case the classical stochastic treatment for matter field fluctuations is not valid, however, for p>4.6, the system loses its coherence and a classical stochastic approximation is allowed.
1448222
The bang of a white hole in the early universe from a 6D vacuum state: origin of astrophysical spectrum
Using a previously introduced model in which the expansion of the universe is driven by a single scalar field subject to gravitational attraction induced by a white hole during the expansion (from a 6D vacuum state), we study the origin of squared inflaton fluctuations spectrum on astrophysical scales.
118446723
Super-exponential inflation from a dynamical foliation of a 5D vacuum state
Abstract We introduce super-exponential inflation ( ω − 1 ) from a 5D Riemann-flat canonical metric on which we make a dynamical foliation. The resulting metric describes a super accelerated expansion for the early universe well known as super-exponential inflation that, for very large times, tends to an asymptotic de Sitter (vacuum dominated) expansion. The scalar field fluctuations are analyzed. The important result here obtained is that the spectral index for energy density fluctuations is not scale invariant, and for cosmological scales becomes n s ( k k ⁎ ) ≃ 1 . However, for astrophysical scales this spectrum changes to negative values n s ( k > k ⁎ ) 0 .
121128941
Compton scattering and pi(+) photo-production at GRAAL
A polarized and tagged gamma ray beam is produced at GRAAL by the Compton scattering of laser light on the high energy electron circulating in the ESRF storage ring. We present results on the beam polarization asymmetries in the Compton Scattering and positive pion photo-production on proton target in the energy region 500-1500 MeV. These very precise results cover the angular range 30-150 degrees, providing stringent constraints to theoretical models.