arXiv subjects
Publications and source records attributed to Sergio del Campo.
We study a model in which a closed universe with dust and quintessence matter components may look like an accelerated flat Friedmann-Robertson-Walker (FRW) universe at low redshifts. Several quantities relevant to the model are expressed in terms of observed density parameters, $Ω_M$ and $Ω_Λ$, and of the associated density parameter $Ω_Q$ related to the quintessence scalar field $Q$.
We study a closed model of the universe filled with viscous fluid and quintessence matter components in a Brans-Dicke type cosmological model. The dynamical equations imply that the universe may look like an accelerated flat Friedmann-Robertson-Walker universe at low redshift. We consider here dissipative processes which follow a causal thermodynamics. The theory is applied to viscous fluid inflation, where accepted values for the total entropy in the observable universe is obtained.
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 discuss different aspects of modern cosmology through a scalar field potential construction method. We discuss the case of negative potential cosmologies and its relation with oscillatory cosmic evolution, models with a explicit interaction between dark energy and dark matter which address the coincidence problem and also the case of non-zero curvature space.
We describe an accelerating universe model in the context of a scalar-tensor theory. This model is intrinsically closed, and is filled with quintessence-like scalar field components, in addition to the Cold Dark Matter component. With a background geometry specified by the Friedman-Robertson-Walker metric, we establish conditions under which this closed cosmological model, described in a scalar-tensor theory, may look flat in a genuine Jordan-Brans-Dicke theory. Both models become indistinguishable at low enough redshift.
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.
The flatness of an accelerating universe model (characterized by a dark energy scalar field $χ$) is mimicked from a curved model that is filled with, apart from the cold dark matter component, a quintessencelike scalar field $Q$. In this process, we characterize the original scalar potential $V(Q)$ and the mimicked scalar potential $V(χ)$ associated to the scalar fields $Q$ and $χ$, respectively. The parameters of the original model are fixed through the mimicked quantities that we relate to the present astronomical data, such that the equation state parameter $w_{_χ}$ and the dark energy density parameter $Ω_χ$.
We study universe models which are intrinsically closed and are full of a quintessence scalar field, besides the Cold Dark Matter component. We use these to depict diverse flat Cold Dark Matter models. With the background geometry specified by the Friedman-Robertson-Walker metric, we include among them the standard Cold Dark Matter, the Cosmological Constant Cold Dark Matter and the Dark Energy or Quintessence Cold Dark Matter models. After describing these models, we determine the position of the first Doppler peak of the Cosmic Microwave Background anisotropy spectrum for $Ω_T$ close to one; we also study the shift parameter $R$.
In this letter we study adiabatic anisotropic matter filled Bianchi type I models of the Kasner form together with the cosmological holographic bound. We find that the dominant energy condition and the holographic bound give precisely the same constraint on the scale factor parameters that appear in the metric.
We study in this article a class of homogeneous, but anisotropic cosmological models in which shear viscosity is included. Within the matter content we consider a component (the quintessence component) determined by the barotropic equations of state, $p=αρ$, with $α< 0$. We establish conditions under which a closed axisymmetrical cosmological model may look flat al low redshift.
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.