Cuauhtemoc Campuzano

Tachyon warm inflationary universe models

Warm inflationary universe models in a tachyon field theory are studied. General conditions required for these models to be realizable are derived and discussed. We describe scalar perturbations (in the longitudinal gauge) and tensor perturbations for these scenarios. We develop our models for a constant dissipation parameter Γ in one case and one dependent on in the other case. We have been successful in describing such inflationary universe models. We use recent astronomical observations for constraining the parameters appearing in our model. Also, our results are compared with their analogues found in the cool inflationary case.

CURVATON REHEATING IN A LOGAMEDIATE INFLATIONARY MODEL

In a logamediate inflationary universe model we introduce the curvaton field in order to bring this inflationary model to an end. In this approach we determine the reheating temperature. We also outline some interesting constraints on the parameters that describe our models. Thus, we give the parameter space in this scenario.

Curvaton reheating in tachyonic inflationary models

The curvaton reheating in a tachyonic inflationary universe model with an exponential potential is studied. We have found that the energy density in the kinetic epoch, has a complicated dependencies of the scale factor. For different scenarios, the temperature of reheating is computed. These temperature result to be analogous to those obtained in the standard case of the curvaton scenario.

Curvaton reheating in tachyonic braneworld inflation

The curvaton reheating in a tachyonic braneworld inflationary universe model with an exponential potential is studied. We have found that the energy density in the kinetic epoch, has a complicated dependencies of the scale factor. For different scenarios the temperature of reheating is computed, finding an upper limit that lies in the range 10{sup 14}-10{sup 16} GeV.

Extended curvaton reheating in inflationary models

The curvaton reheating in a non-oscillatory inflationary universe model is studied in a Jordan–Brans–Dicke theory. For different scenarios, the temperature of reheating is computed. The result tells us that the reheating temperature becomes practically independent of the Jordan–Brans–Dicke parameter w. This reheating temperature turns out to be quite different when compared with that obtained from Einsteins theory of gravity.

Erratum: Conformally flat stationary axisymmetric spacetimes [Phys. Rev. D 66 , 124018 (2002)]

Garcia and Campuzano claim to have found a previously overlooked family of stationary and axisymmetric conformally flat spacetimes, contradicting an old theorem of Collinson. In both these papers it is tacitly assumed that the isometry group is orthogonally transitive. Under the same assumption, we point out here that Collinsons result still holds if one demands the existence of an axis of symmetry on which the axial Killing vector vanishes. On the other hand if the assumption of orthogonal transitivity is dropped, a wider class of metrics is allowed and it is possible to find explicit counterexamples to Collinsons result.

Curvaton reheating in non-minimal derivative coupling to gravity: NO models

The curvaton reheating mechanism in a non-minimal derivative coupling to gravity for any non-oscillating (NO) model is studied. In this framework, we analyze the energy density during the kinetic epoch and we find that this energy has a complicated dependencies of the scale factor. Considering this mechanism, we study the decay of the curvaton in two different scenarios and also we determine the reheating temperatures. As an example the NO model, we consider an exponential potential and we obtain the reheating temperature indirectly from the inflation through of the number of e-folds.

Mimicking the LCDM model with stealths

We present a new cosmological model that mimics the Lambda Cold Dark Matter by using a stealth field. This kind of field is characterized as not coupling directly to gravity; however, it is connected to the underlying matter content of the universe model. As is well known, stealth fields do not back-react on the space-time; however, their mimicry skills show how this field and its self-interaction potential determines the cosmic evolution. We show the study of the simplest model that can be developed with the stealth field.

Conformally flat noncircular spacetimes

The general metric for conformally flat stationary cyclic symmetric noncircular spacetimes is explicitly given. In spite of the complexity introduced by the inclusion of noncircular contributions, the related metric is derived via the full integration of the conformal flatness constraints. It is also shown that the conditions for the existence of a rotation axis (axisymmetry) are the same ones which restrict the above class of spacetimes to be static. As a consequence, a known theorem by Collinson is just part of a more general result: any conformally flat stationary cyclic symmetric spacetime, even a noncircular one, is additionally axisymmetric if and only if it is also static. Since recent astrophysical motivations point in the direction of considering noncircular configurations to describe magnetized neutron stars, the above results seem to be relevant in this context.

Stealths on \((1+1)\)-dimensional dilatonic gravity

We study gravitational stealth configurations emerging on a charged dilatonic