相关论文: Phenomenological Dark Energy model with hybrid dyn…
In this work we study the evolution of matter-density perturbations for an arbitrary $\Lambda(t)$ model, and specialize our analysis to the particular phenomenological law $\Lambda = \Lambda_0 + 3\beta H^2$. We study the evolution of the…
This study investigates the cosmological dynamics of an accelerating universe within the framework of teleparallel gravity using an exponential f(T) functional form. To obtain exact cosmological solutions, a hybrid scale factor is employed…
Nearly seventy per cent of the energy density in the universe is unclustered and exerts negative pressure. This conclusion -- now supported by numerous observations -- poses the greatest challenge for theoretical physics today. I discuss…
In this PhD thesis a wide variety of cosmological models beyond the $\Lambda$CDM are studied in detail. Great emphasis is put on the running vacuum models (RVM's), which can be motivated in the context of Quantum Field Theory in curved…
Dynamic dark energy (DDE) models are often designed to solve the cosmic coincidence (why, just now, is the dark energy density $\rho_{de}$, the same order of magnitude as the matter density $\rho_m$?) by guaranteeing $\rho_{de} \sim \rho_m$…
We consider new models of dark energy with finite time future singularities, by introducing the pressure density as a function of the scale factor. This approach gives acceptable phenomenological models of dark energy, practically…
The $\Lambda$CDM framework offers a remarkably good description of our universe with a very small number of free parameters, which can be determined with high accuracy from currently available data. However, this does not mean that the…
It is extraordinary that a number of observations indicate that we live in a spatially flat, low matter density Universe, which is currently undergoing a period of accelerating expansion. The effort to explain this current state has focused…
We consider ever-expanding Big Bang models with a cosmological constant, $\Lambda$, and investigate in detail the evolution of the observable part of the universe. We also discuss quintessence models from the same point of view. A new…
Motivated by results implying that the constituents of dark matter (DM) might be collisional, we consider a cosmological (toy-) model, in which the DM itself possesses some sort of thermodynamic properties. In this case, not only can the…
In the present work, we study a cosmological model composed of a viscous dark matter interacting with decaying vacuum energy in a spatially flat Universe. In the first part, we find the analytical solution of different cosmological…
We discuss models that can account for today's dark energy. The underlying cosmological constant may be Planck scale but starts as a redundant coupling which can be eliminated by a field redefinition. The observed vacuum energy arises when…
We analyze a model for Dark Energy - Dark Matter interaction, based on a decaying process of the former into the latter. The dynamical equations are constructed following a kinetic formulation, which separates the interacting fluctuations…
We study a cosmological model featuring evolutionary dark energy, according to the idea that the creation of its constituents arises from the gravitational field of the expanding universe, whose non-equilibrium physics is described by a…
To explore whether there is new physics going beyond the standard cosmological model or not, we constrain seven cosmological models by combining the latest and largest Pantheon Type Ia supernovae sample with the data combination of baryonic…
Based on tensions between the early and late time cosmology, we proposed a double valued cosmological constant which could undergo a phase transition in its history. It is named "double-$\Lambda$ Cold Dark Matter": $\Lambda\Lambda$CDM. An…
The energy density of the vacuum, Lambda, is at least 60 orders of magnitude smaller than several known contributions to it. Approaches to this problem are tightly constrained by data ranging from elementary observations to precision…
A phenomenological model is proposed to explain the recent observed cosmological variation of the fine structure constant as an effect of the quantum vacuum, assuming a flat universe with cosmological constant $\Lambda$ in the cases…
We consider the perturbation dynamics for the cosmic baryon fluid and determine the corresponding power spectrum for a $\Lambda(t)$CDM model in which a cosmological term decays into dark matter linearly with the Hubble rate. The model is…
A range of cosmological observations demonstrate an accelerated expansion of the Universe, and the most likely explanation of this phenomenon is a cosmological constant. Given the importance of understanding the underlying physics, it is…