Related papers: Cosmological Stasis from Field-Dependent Decay
We study cosmological solutions for the very early universe beginning at the Planck scale for a universe containing radiation, curvature and, as a simplification of a possible scalar field potential, a cosmological constant term. The…
Topologically protected sheet-like surfaces, called domain walls, form when the potential of a field has a discrete symmetry that is spontaneously broken. Since this condition is commonplace in field theory, it is plausible that many of…
Hysteresis is a phenomenon occurring naturally in several magnetic and electric materials in condensed matter physics. When applied to cosmology, aka cosmological hysteresis, has interesting and vivid implications in the scenario of a…
The current expansion of the Universe has been observed to be accelerating, and the widely accepted spatially-flat concordance model of general relativistic cosmology attributes this phenomenon to a constant dark energy, a cosmological…
We introduce a time-delay function in bulk viscosity cosmology. Even for bulk viscosity functions where closed-form solutions are known, because of the time-delay term the exact solutions are lost. Therefore in order to study the…
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…
The evolution of cosmological large-scale perturbations is described in terms of the concordant model based on the recent discovery of cosmic vacuum. It is demonstrated that the process is robustly controlled by a few epoch-independent…
The dynamical realisation of the equation of state $p +\rho =0$ is studied. A non-pathological dynamics for the perturbations of such a system mimicking a dynamical cosmological constant (DCC) requires to go beyond the perfect fluid…
Dense enough compact objects were recently shown to lead to an exponentially fast increase of the vacuum energy density for some free scalar fields properly coupled to the spacetime curvature as a consequence of a tachyonic-like…
We propose a novel explanation for the smallness of the observed cosmological constant (CC). Regions of space with a large CC are short lived and are dynamically driven to crunch soon after the end of inflation. Conversely, regions with a…
The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even…
In the present article we have investigated a very natural question regarding the dynamics of the universe, namely, the possibility of its decelerating phase immediately after the present accelerating phase. To begin with, we have focused…
We propose a natural solution to the cosmological constant problem consistent with the standard cosmology and successful over a broad range of energies. This solution is based on the existence of a new field, the devaluton, with its…
We deal with a dynamical mechanism in which a large cosmological constant, as suggested by inflationary scenarios, decays due to expansion of the universe. This mechanism has its origin in the gravitational coupling of the vacuum density.…
We discuss the cosmological constant problem in the light of dilatation symmetry and its possible anomaly. For dilatation symmetric quantum theories realistic asymptotic cosmology is obtained provided the effective potential has a…
The Cyclic Model is a radical, new cosmological scenario which proposes that the Universe undergoes an endless sequence of epochs which begin with a `big bang' and end in a `big crunch.' When the Universe bounces from contraction to…
An alternative cosmological model is presented, which avoids the requirement of dark energy and dark matter. Based on the proposition that energy conservation should be valid not only locally but also globally, the energy tensor of general…
One of the greatest problems of standard cosmology is the Big Bang singularity. Previously it has been shown that non-local ghostfree higher-derivative modifications of Einstein gravity in the ultra-violet regime can admit non-singular…
Five-dimensional cosmological models with two 3-branes and with a buck cosmological constant are studied. It is found that for all the three cases ($\Lambda =0$, $\Lambda >0$, and $\Lambda <0$), the conventional space-time singularity ``big…
We derive a model of dark energy which evolves with time via the scale factor. The equation of state $\omega=(1-2\alpha)/(1+2\alpha)$ is studied as a function of a parameter $\alpha$ introduced in this model. In addition to the recent…