Related papers: Inhomogeneous post-inflationary Lambda-CDM cosmolo…
Starting from an inhomogeneous space-time model of the universe we could recreate a scenario of recent time accelerating universe dominated by Dark Energy type of fluid. The background matter component of such a universe was considered to…
We consider cosmological scenarios in which density perturbations are generated by the quantum fluctuations of the inflaton field at early times; the late time dynamics involves a modulus which first dominates the energy density of the…
In this Letter we discuss the issues of the graceful exit from inflation and of matter creation in the context of a recent scenario \cite{RHBrev} in which the back-reaction of long wavelength cosmological perturbations induces a negative…
Current and upcoming surveys will measure the cosmological parameters with an extremely high accuracy. The primary goal of these observations is to eliminate some of the currently viable cosmological models created to explain the late time…
We establish the future nonlinear stability of a large class of FLRW models as solutions to the Einstein-Dust system. We consider the case of a vanishing cosmological constant, which in particular implies that the expansion rate of the…
Starting from the inhomogeneous shear--free Nariai metric we show, by solving the Einstein--Klein--Gordon field equations, how a self--interacting scalar field plus a material fluid, a variable cosmological term and a heat flux can drive…
In simple inflationary cosmological scenarios the near-exponential growth can be followed by a long period in which the Universe is dominated by the oscillating inflaton condensate. The condensate is initially almost homogeneous, but…
In the framework of polynomial Palatini cosmology, we investigate a simple cosmological homogeneous and isotropic model with matter in the Einstein frame. We show that in this model during cosmic evolution, it appears the early inflation…
We study cosmological evolution in a flat FLRW spacetime in the context of modified STEGR gravity or $f(Q)$, using an exponential two-parameter model which represents a smooth perturbative expansion around the $\Lambda$CDM model. The…
We study the dynamics of the FLRW flat cosmological models in which the vacuum energy varies with time, $\Lambda(t)$. In this model we find that the main cosmological functions such as the scale factor of the universe and the Hubble flow…
We present a new cosmological model, based on the holographic principle, which shares many of the virtues of inflation. The very earliest semiclassical era of the universe is dominated by a dense gas of black holes, with equation of state…
Observational cosmology provides us with a large number of high precision data which are used to derive models trying to reproduce ``on the mean'' our observable patch of the Universe. Most of these attempts are achieved in the framework of…
The integrated Sachs-Wolfe (ISW) effect in a Lambda dominated universe can be an important factor in the evolution of cosmic microwave background fluctuations. With the inclusion of cosmological constant we present the complete analytic…
We investigate the properties of the FLRW flat cosmological models in which the vacuum energy density evolves with time, $\Lambda(t)$. Using different versions of the $\Lambda(t)$ model, namely quantum field vacuum, power series vacuum and…
Fluctuations in the intensity and polarization of the cosmic microwave background (CMB) and the large-scale distribution of matter in the universe each contain clues about the nature of the earliest moments of time. The next generation of…
We analyze constraints on parameters characterizing the pre-inflating universe in an open inflation model with a present slightly open $\Lambda$CDM universe. We employ an analytic model to show that for a broad class of inflation-generating…
We present a cosmological model arising from a gravitational theory with an infinite tower of higher-order curvature invariants that can reproduce the entire evolution of the Universe: from inflation to late-time acceleration, without…
Despite the ultraviolet problems with canonical quantum gravity, as an effective field theory its infrared phenomena should enjoy fully quantum mechanical unitary time evolution. Currently this is not possible, the impediment being what is…
We provide exact solutions to the Einstein equations when the Universe contains vacuum energy plus a uniform arrangements of magnetic fields, strings, or domain walls. Such a universe has planar symmetry, i. e., it is homogeneous but, not…
The standard model of cosmology assumes a homogeneous and isotropic universe that undergoes a period of exponential expansion very early on, named inflation. This stretches quantum fluctuations from the onset of inflation to cosmological…