arXiv subjects
Publications and source records attributed to Ramon Herrera.
We study one-field open inflationary models in a universe dominated by tachyon matter. In these scenarios, we determine and characterize the existence of the Coleman-De Lucia (CDL) instanton. Also, we study the Lorentzian regime, that is, the period of inflation after tunnelling has occurred.
The coincidence problem of late cosmic acceleration is a serious riddle in connection with our understanding of the evolution of the Universe. In this paper we show that an interaction between the dark energy component (either phantom or quintessence) and dark matter can alleviate it. In this scenario the baryon component is independently conserved. This generalizes a previous study [S. del Campo, R. Herrera, and D. Pavon, Phys. Rev. D 71, 123529 (2005)] in which neither baryons nor phantom energy were considered.
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 results to be quite different when compared with that obtained from Einstein`s theory of gravity.
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 $10^{14}$--$10^{16}$GeV.
We study the coincidence problem of late cosmic acceleration by assuming that the present ratio between dark matter and dark energy is a slowly varying function of the scale factor. As dark energy component we consider two different candidates, first a quintessence scalar field, and then a tachyon field. In either cases analytical solutions for the scale factor, the field and the potential are derived. Both models show a good fit to the recent magnitude-redshift supernovae data. However, the likelihood contours disfavor the tachyon field model as it seems to prefer a excessively high value for the matter component.
In this paper we study a type of model for closed inflationary universe models using the Jordan-Brans-Dicke theory. Herein we determine and characterize the existence of $Ω>$1, together with the period of inflation. We have found that our model, which takes into account a Jordan-Brans-Dicke type of theory, is less restrictive than the one used in Einstein's theory of general relativity. Our results are compared to those found in Einstein's theory of Relativity.
In this article we study closed inflationary universe models proposed by Linde in a brane world cosmological context. In this scenario we determine and characterize the existence of a closed universe, in presence of one self-interacting scalar field with an inflationary stage. Our results are compared to those found in General Relativity.
In this paper we show that a universe dominated by two components, namely domain walls and dissipative dark matter such that the former slowly decays into the latter may drive power law cosmological acceleration consistent with the high redshift supernovae data, while the ratio between the energy densities of both components remains fixed at late times thus solving the coincidence problem of present acceleration. Likewise, we estimate the aforesaid ratio at early times.
In this paper, we study a type of one-field model for open inflationary universe models in the context of the brane world models. In the scenario of a one-bubble universe model, we determine and characterize the existence of the Coleman-De Lucia instanton, together with the period of inflation after tunneling has occurred. Our results are compared to those found in the Einstein theory of Relativistic Models.
We find exact solutions leading to power law accelerated expansion for a homogeneous, isotropic and spatially flat universe, dominated by an interacting mixture of cold dark matter and a tachyonic field such that the ratio of the energy densities of both components at late times is constant and no coincidence problem arises.
Scalar density cosmological perturbations, spectral indices and reheating in a chaotic inflationary universe model, in which a higher derivative term is added, are investigated. This term is supposed to play an important role in the early evolution of the Universe, specifically at times closer to the Planck era.
In this paper we study a type of one-field model for open inflationary universe models in the context of the Jordan-Brans-Dicke theory. In the scenario of a one-bubble universe model we determine and characterize the existence of the Coleman-De Lucia instanton, together with the period of inflation after tunnelling has occurred. Our results are analogous to those found in the Einstein General Relativity models.
We investigate the possibility that the matter of the universe has a significant component (the quintessence component) determined by the equation of state $p=wρ$, with $w<0$. Here, we find conditions under which a closed model may look like a flat Friedmann-Robertson-Walker universe at low redshift. We study this problem in Einstein's general relativity and Brans-Dicke theories. In both cases we obtain explicit expressions for the quintessence scalar potential $V(Q)$, and the angular size as a function of the redshift.