Related papers: Evolution of Entropy with Cosmic Time
There is sufficient amount of internal evidence in the nature of gravitational theories to indicate that gravity is an emergent phenomenon like, e.g, elasticity. Such an emergent nature is most apparent in the structure of gravitational…
Understanding the origins and distribution of matter in the Universe is one of the most important quests in physics and astronomy. Themes range from astro-particle physics to chemical evolution in the Galaxy to cosmic nucleosynthesis and…
In an expanding universe the vacuum energy density \rho_{\Lambda} is expected to be a dynamical quantity. In quantum field theory in curved space-time \rho_{\Lambda} should exhibit a slow evolution, determined by the expansion rate of the…
Cosmology and astroparticle physics give strongest possible evidence for the incompleteness of the Standard Model of particle physics. Leaving aside misterious dark energy, which may or may not be just the cosmological constant, two…
In this paper, we investigate the evolution of the early universe within an emergent fractional cosmological framework. The underlying formulation is conceptually rooted in generalized measure constructions, closely related to fractal…
We discuss a cosmology in which cold dark matter begins to decay into relativistic particles at a recent epoch (z < 1). We show that the large entropy production and associated bulk viscosity from such decays leads to an accelerating…
A quantum expansion parameter, analogous to the Hubble parameter in cosmology, is defined for a free particle quantum wavefunction. By considering the universe as an initial single Gaussian quantum wavepacket whose mass is that of…
The puzzle of the thermodynamic arrow of time reduces to the question of how the universe could have had lower entropy in the past. I show that no special entropy lowering mechanism (or fluctuation) is necessary. As a consequence of…
A cosmological model has been constructed in the framework of Brans-Dicke (BD) gravity, based on an inter-conversion between matter and dark energy, for a spatially flat universe in the era of pressureless dust. To account for the…
In contrast to the phenomenon of nullification of the cosmological constant in the equilibrium vacuum, which is the general property of any quantum vacuum, there are many options in modifying the Einstein equation to allow the cosmological…
The vacuum fluctuations of all quantum fields filling the universe are supposed to leave enormous energy and pressure contributions which are incompatible with observations. It has been recently suggested that, when the effective nature of…
We sketch the average behaviour of the temperatures and densities of the main components of the $\Lambda$CDM universe after inflation. It is modelled as a perfect fluid with dark energy associated with the macroscopic effect of conformal…
By considering the logarithmic correction to the energy density, we study the behavior of Hubble parameter in the holographic dark energy model. We assume that the universe is dominated by interacting dark energy and matter and the…
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…
The expansion of our universe, when followed backward in time, implies that it emerged from a phase of huge density, the big bang. These stages are so extreme that classical general relativity combined with matter theories is not able to…
The present work is an example of the application of the dynamical system analysis in the context of cosmology. Here cosmic evolution is considered in the background of homogeneous and isotropic flat Friedmann-Lema\^{i}tre-Robertson-Walker…
An introductory account is given of the modern understanding of the physics of the early Universe. Particular emphasis is placed on the paradigm of cosmological inflation, which postulates a period of accelerated expansion during the…
Dark energy (DE) is not necessarily uniform when other sources of gravity are present: interaction with matter leads to its variation in space and time. We study cosmological implications of this fact by analyzing cosmological models in…
We determine the behaviour of a time-varying fine structure 'constant' $\alpha (t)$ during the early and late phases of universes dominated by the kinetic energy of changing $\alpha (t)$, radiation, dust, curvature, and lambda,…
We examine the evolution of magnetic fields in an expanding fluid composed of matter and radiation with particular interest in the evolution of cosmic magnetic fields. We derive the propagation velocities and damping rates for relativistic…