Related papers: Quantum Corrections to the Cosmological Evolution …
In this work, we have developed an elegant algorithm to study the cosmological consequences from a huge class of quantum field theories (i.e. superstring theory, supergravity, extra dimensional theory, modified gravity etc.), which are…
We investigate quantum corrections for a cosmological solution of the string effective action. Starting point is a classical solution containing an antisymmetric tensor field, a dilaton and a modulus field which has singularities in the…
A basic problem that confronts the standard cosmological models is the problem of initial singularity characterised by infinite material density, infinite temperature and infinite spacetime curvature. The inevitable existence of such a…
It is often the case that scalar fields are produced in the early Universe in the form of coherent oscillation. These scalar fields may have huge abundances and affect the evolution of the Universe. In particular, if the lifetime is long…
Non-Abelian gauge fields are traditionally not coupled to torsion due to violation of gauge invariance. However, it is possible to couple torsion to Yang-Mills fields while maintaining gauge invariance provided one accepts that the gauge…
We derive a generalized equation for the evolution of tensor perturbations in a cosmological background, taking into account higher-curvature contributions and a tree-level coupling to the dilaton in the string frame. The equation is…
We study the damping of an oscillating scalar field in a Friedmann-Robertson-Walker spacetime by perturbative processes, taking into account the finite density effects that interactions with the plasma of decay products have on the damping…
Gauss-Bonnet-dilatonic coupling in four dimension plays an important role to explain late time cosmic evolution. However, this term is an outcome of low energy string effective action and thus ought to be important in the early universe…
Gravitation and the standard model of particle physics are incorporated within a single conformal scalar-tensor theory, where the scalar field is complex. The Higgs field has a dynamical expectation value, as has the Planck mass, but the…
Theoretical and observational arguments are listed in favor of a new principle of relativity of units of measurements as the basis of a conformal-invariant unification of General Relativity and Standard Model by replacement of all masses…
In order to satisfy limits on the allowed variation of particle masses from big bang nucleosynthesis (BBN) until today, the chameleon scalar field is required to reach its attractor solution early on in its cosmological evolution. Brax et…
Starting from an initial classical four dimensional flat background of the heterotic or type II superstrings, we are able to determine at the string one-loop level the quantum corrections to the effective potential due to the spontaneous…
The quantum evolution of a model of the universe with account of two scalar fields ({\it dilaton} and {\it inflaton}) is considered. For this case, the closed and flat models has been examined. It is shown that in both cases the realization…
We investigate the evolution of the linear cosmological perturbations in f(R) gravity, an alternative to dark energy for explaining the late-time cosmic acceleration. We numerically calculate the early-time evolution with an approximation…
The classical and quantum models of the Friedmann universe originally filled with a scalar field and radiation have been studied. The radiation has been used to specify a reference frame that makes it possible to remove ambiguities in…
Despite its great successes in accounting for the current observations, the so called `standard' model of cosmology faces a number of fundamental unresolved questions. Paramount among these are those relating to the nature of the origin of…
We investigate a conformal invariant gravitational model which is taken to hold at pre-inflationary era. The conformal invariance allows to make a dynamical distinction between the two unit systems (or conformal frames) usually used in…
Our Universe is ruled by quantum mechanics and its extension Quantum Field Theory (QFT). However, the explanations for a number of cosmological phenomena such as inflation, dark energy, symmetry breakings, and phase transitions need the…
We establish a connection between the trace anomaly and a thermal radiation in the context of the standard cosmology. This is done by solving the covariant conservation equation of the stress tensor associated with a conformally invariant…
One possibility to explain the current accelerated expansion of the universe may be related with the presence of cosmologically evolving scalar whose mass depends on the local matter density (chameleon cosmology). We point out that matter…