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

Thermodynamical properties of metric fluctuations during inflation

I study a thermodynamical approach to scalar metric perturbations during the inflationary stage. In the power-law expanding universe here studied, I find a negative heat capacity as a manifestation of superexponential growing for the number of states in super Hubble scales. The power spectrum depends on the Gibbons-Hawking and Hagedorn temperatures.Comment: 7 pages, no figures (accepted to publication in General Relativity and Gravitation

Fresh inflation and decoherence of super Hubble fluctuations

I study a stochastic approach to the recently introduced fresh inflation model for super Hubble scales. I find that the state loses its coherence at the end of the fresh inflationary period as a consequence of the damping of the interference function in the reduced density matrix. This fact should be a consequence of a) the relative evolutions of both the scale factor and the horizon and b) the additional thermal and dissipative effects. This implies a relevant difference with respect to supercooled inflationary scenarios which require a very rapid expansion of the scale factor to give the decoherence of super Hubble fluctuations.Comment: version with minor changes. To appear in Phys. Rev.

Warm inflation and scalar perturbations of the metric

A second-order expansion for the quantum fluctuations of the matter field was considered in the framework of the warm inflation scenario. The friction and Hubble parameters were expended by means of a semiclassical approach. The fluctuations of the Hubble parameter generates fluctuations of the metric. These metric fluctuations produce an effective term of curvature. The power spectrum for the metric fluctuations can be calculated on the infrared sector.Comment: 10 pages, no figures, to be published in General Rel. and Gravitatio

Astrometry and photometry with HST-WFC3. I. Geometric distortion corrections of F225W, F275W, F336W bands of the UVIS-channel

An accurate geometric distortion solution for the Hubble Space Telescope UVIS-channel of Wide Field Camera 3 is the first step towards its use for high precision astrometry. In this work we present an average correction that enables a relative astrometric accuracy of ~1 mas (in each axis for well exposed stars) in three broad-band ultraviolet filters (F225W, F275W, and F336W). More data and a better understanding of the instrument are required to constrain the solution to a higher level of accuracy.Comment: 20 pages, 7 figures (3 in low resolution), 3 tables. Accepted for publication in PASP on October 16 200

Fresh inflation: a warm inflationary model from a zero temperature initial state

A two-components mixture fluid which complies with the gamma law is considered in the framework of inflation with finite temperature. The model is developed for a quartic scalar potential without symmetry breaking. The radiation energy density is assumed to be zero when inflation starts and remains below the GUT temperature during the inflationary stage. Furthermore, provides the necessary number of e-folds and sufficient radiation energy density to GUT baryogenesis can take place near the minimum energetic configuration.Comment: 11 pages, no figures, to be published in Phys. Rev.

Geometric back-reaction in pre-inflation from relativistic quantum geometry

The pre-inflationary evolution of the universe describes the beginning of the expansion from a static initial state, such that the Hubble parameter is initially zero, but increases to an asymptotic constant value, in which it could achieve a de Sitter (inflationary) expansion. The expansion is driven by a background phantom field. The back-reaction effects at this moment should describe vacuum geometrical excitations, which are studied with detail in this work using Relativistic Quantum Geometry.Comment: improved versio

A confirmation of agreement of different approaches for scalar gauge-invariant metric perturbations during inflation

We revisit an extension of the well-known formalism for gauge-invariant scalar metric fluctuations, to study the spectrums for both, the inflaton and gauge invariant (scalar) metric fluctuations in the framework of a single field inflationary model where the quasi-exponential expansion is driven by an inflation which is minimally coupled to gravity. The proposal here examined is valid also for fluctuations with large amplitude, but for cosmological scales, where vector and tensor perturbations can be neglected and the fluid is irrotacional.Comment: Version accepted in EPJC with new title. 11 pages, no figure

Charged and electromagnetic fields from relativistic quantum geometry

In the Relativistic Quantum Geometry (RQG) formalism recently introduced, was explored the possibility that the variation of the tensor metric can be done in a Weylian integrable manifold using a geometric displacement, from a Riemannian to a Weylian integrable manifold, described by the dynamics of an auxiliary geometrical scalar field $\theta$, in order that the Einstein tensor (and the Einstein equations) can be represented on a Weyl-like manifold. In this framework we study jointly the dynamics of electromagnetic fields produced by quantum complex vector fields, which describes charges without charges. We demonstrate that complex fields act as a source of tetra-vector fields which describe an extended Maxwell dynamics.Comment: improved versio