Related papers: A Relationship between the Comoving Particle Numbe…
I describe an approach which relates classical gravity to the quantum microstructure of spacetime. In this approach, the field equations arise from maximizing the density of states of the matter plus geometry. The former is identified using…
A late epoch cosmic acceleration may be naturally entangled with cosmic coincidence -- the observation that at the onset of acceleration the vacuum energy density fraction nearly coincides with the matter density fraction. In this Letter we…
We analyze various phases of inflation based on the anomaly-induced effective action of gravity (modified Starobinsky model), taking the cosmological constant Lambda and k=0, +/- 1 topologies into account. The total number of the…
We construct the cosmological model to explain the cosmological constant problem. We built the extension of the standard cosmological model $\Lambda$CDM by consideration of decaying vacuum energy represented by the running cosmological…
Using the scalar and tensor virial equations, the Lane-Emden equation expressing the hydrostatic equilibrium and small oscillations around the equilibrium, we show how the cosmological constant $\Lambda$ affects various astrophysical…
We phenomenologically derive a cosmological model that includes both a cosmological constant term $\Lambda/3$ and a dissipative driving term $\beta (2 H^{2} + \dot{H})$ by applying both the first law of thermodynamics and an effective…
The idea that the cosmological term, Lambda, should be a time dependent quantity in cosmology is a most natural one. It is difficult to conceive an expanding universe with a strictly constant vacuum energy density, namely one that has…
We extend the usual gravitational action principle by promoting the bare cosmological constant (CC) from a parameter to a field which can take many possible values. Variation leads to a new integral constraint equation which determines the…
We introduce an effective Lagrangian which describes the classical and semiclassical dynamics of spherically symmetric, self-gravitating objects that may populate the Universe at large and small (Planck) scale. These include wormholes,…
We provide a comprehensive discussion of the Everpresent $\Lambda$ cosmological model arising from fundamental principles in causal set theory and unimodular gravity. In this framework the value of the cosmological constant ($\Lambda$)…
In Ref. [1], it was claimed that in the spatially flat cosmological case there exists a unique conserved measure (up to normalization) on the $(\phi,\dot{\phi})$ phase space for scalar field with $m^2\phi^2$ potential by finding a unique…
With no free parameter (except the string scale $M_S$), dynamical flux compactification in Type IIB string theory determines both the cosmological constant (vacuum energy density) $\Lambda$ and the Planck mass $M_P$ in terms of $M_S$, thus…
We consider a non-singular origin for the Universe starting from an Einstein static Universe, the so called "emergent universe" scenario, in the framework of a theory which uses two volume elements $\sqrt{-{g}}d^{4}x$ and $\Phi d^{4}x$,…
If we want to explain the recently discovered accelerated stage of the universe, one of the option we have is to modify the Einstein tensor. The simplest such modification, in agreement with all observations, is the positive cosmological…
For several independent reasons, the idea that notorious sources of entropy could exist in the Universe has been recently revived. Taking advantage of a new framework accounting for non-equilibrium processes in cosmology, we explicitly…
It is shown, using quantum field theory in curved spacetime, how the expansion of the universe during inflation produces an aggregate of particles and inflaton vacuum fluctuations at a temperature of 5x10^17GeV and dense enough to make…
Using the Ricci and scalar curvatures of the configuration manifold of gravitational N-body systems, we study the exponential instability in their trajectories. It is found that the exponentiation time-scale for isotropic Plummer spheres…
We investigate the compatibility of cosmological constraints on inflation and the cosmological constant with the asymptotic safety scenario of quantum gravity. The effective action is taken to be of $f(R)$ form, truncated to second order.…
We consider a massless, minimally coupled quantum scalar field theory with an asymmetric self interaction, $V (\phi) = \lambda\phi^4/4!+\beta\phi^3/3!$ ($\lambda >0$) in the inflationary de Sitter spacetime. The potential is bounded from…
This paper deals with gravitational thermodynamics on the dynamical apparent horizon of an FLRW universe with dissipation. The dissipation is assumed to arise due to adiabatic gravitational particle creation. For the thermodynamic study, we…