Warm inflation with back - reaction: a stochastic approach

I study a stochastic approach for warm inflation considering back - reaction of the metric with the fluctuations of matter field. This formalism takes into account the local inhomogeneities fo the spacetime in a globally flat Friedmann - Robertson - Walker metric. The stochastic equations for the fluctuations of the matter field and the metric are obtained. Finally, the dynamics for the amplitude of these fluctuations in a power - law expansion for the universe are examined.Comment: minor changes, 6 pages, no figures, accepted for publication in Classical and Quantum Gravit

Primordial fluctuations in the warm inflation scenario with a more realistic coarse - grained field

I study a semiclassical approach to warm inflation scenario introduced in previous works. In this work, I define the fluctuations for the matter field by means of a new coarse - grained field with a suppression factor G. This field describes the matter field fluctuations on the now observable scale of the universe. The power spectrum for the fluctuations of the matter field is analyzed in both, de Sitter and power - law expansions for the universe. The constraint for the spectral index gives a constraint for the mass of the matter field in the de Sitter expansion and a constraint for the friction parameter in the power - law expansion for the universe.Comment: 11 pages, no figures (revtex file

Geometrical origin of entropy during inflation from the STM theory of gravity

Using a recently introduced 5D Riemann flat metric, we investigate the possibility of introducing dissipation in the dynamics of the inflaton field on an effective 4D FRW metric, in the framework of the STM theory of gravity.Comment: Final version, to be published in Phys. Lett.

Ground-based CCD astrometry with wide field imagers. IV. An improved Geometric Distortion Correction for the Blue prime-focus Camera at the LBT

High precision astrometry requires an accurate geometric distortion solution. In this work, we present an average correction for the Blue Camera of the Large Binocular Telescope which enables a relative astrometric precision of ~15 mas for the B_Bessel and V_Bessel broad-band filters. The result of this effort is used in two companion papers: the first to measure the absolute proper motion of the open cluster M67 with respect to the background galaxies; the second to decontaminate the color-magnitude diagram of M67 from field objects, enabling the study of the end of its white dwarf cooling sequence. Many other applications might find this distortion correction useful.Comment: 13 pages, 11 figures, 4 tables. accepted for publication on Astronomy and Astrophysic

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 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.Comment: to appear in Nuclear Physics B (version with some changes and some references added

Towards a theory of Warm Inflation of the Universe

The warm inflation scenario is an alternative mechanism which can explain the isotropic and homogeneous Universe which we are living in. In this work I extend a previously introduced formalism, without the restriction of slow - roll regime. Quantum to classical transition of the fluctuations is studied by means of the "transition function" here introduced. I found that the fluctuations of radiation energy density decrease with time and the thermal equilibrium at the end of inflation holds.Comment: 14 pages, no figures, to appear in Classical and Quantum Gravit