Related papers: On String Gas Cosmology at Finite Temperature
Using dynamical system analysis, we explore the cosmology of theories of order up to eight order of the form $f(R, \Box R)$. The phase space of these cosmology reveals that higher-order terms can have a dramatic influence on the evolution…
Recently a Hamiltonian formulation for the evolution of the universe dominated by multiple oscillatory scalar fields was developed by the present author and was applied to the investigation of the evolution of cosmological perturbations on…
The Modified Chaplygin Gas (MCG) model is revisited to examine its ability to describe the full cosmic evolution within a single framework. Because the field equations are highly nonlinear, no closed analytical solution for the scale factor…
We reconsider cosmological constraints on extra dimension theories from the excess production of Kaluza-Klein gravitons. We point out that, if the normalcy temperature is above 1 GeV, then graviton states produced at this temperature will…
The aim of this work is to model the evolution of the cosmic space based on thermodynamical parameters. The universe is considered to have an apparent horizon radius with a Kodama-Hayward temperature assigned to it. The method is founded on…
We have developed a phenomenological effective quantum-field theoretical model describing the "hadron gas" of the lightest pseudoscalar mesons, scalar {\sigma}-meson and {\sigma}-vacuum, i.e. the expectation value of the {\sigma}-field, at…
In braneworld models a variable vacuum energy may appear if the size of the extra dimension changes during the evolution of the universe. In this scenario the acceleration of the universe is related not only to the variation of the…
We investigate structure formation in a one dimensional model of a matter-dominated universe using a quasi-newtonian formulation. In addition to dark matter, luminous matter is introduced to examine the potential bias in the distributions.…
We describe the evolution of the early and late universe from thermodynamic considerations, using the generalized non-extensive Tsallis entropy with a variable exponent. A new element in our analysis is the inclusion of a bulk viscosity in…
We investigate a possibility for construction of the conventional Friedmann cosmology for our observable Universe if underlying theory is multidimensional Kaluza-Klein model endowed with a perfect fluid. We show that effective Friedmann…
We investigate the properties of a cosmological scenario which undergoes a gravitational phase transition at late times. In this scenario, the Universe evolves according to general relativity in the standard, hot Big Bang picture until a…
The study of cosmic phase transitions are of central interest in modern cosmology. In the standard model of cosmology the Universe begins in a very hot state, right after at the end of inflation via the process of reheating/preheating, and…
The Kaluza-Klein compactification in the limit of large number of extra dimensions is studied. Starting point is the Einstein-Hilbert action plus cosmological constant in 4+D dimensions. It is shown that in the large D limit the effective…
We consider evolution of compact extra dimensions in cosmology and try to see whether wrapped branes can prevent the expansion of the internal space. Some difficulties of Brandenberger and Vafa mechanism for decompactification are pointed…
Phase correlations, density fluctuations and three-body loss rates are relevant for many experiments in quasi one-dimensional geometries. Extended mean-field theory is used to evaluate correlation functions up to third order for a quasi…
We show that a relativistic gas may be at ``global'' equilibrium in the expanding universe for any equation of state $0 < p \leq \rho /3$, provided that the gas particles move under the influence of a self-interacting, effective…
We consider the evolution of the ground state in the Two Higgs Doublet Model during cooling down of the Universe after the Big Bang. Different regions in the space of free parameters of this model correspond to different sequences of…
Multidimensional cosmological models in the presence of a bare cosmological constant and a perfect fluid are investigated under dimensional reduction to 4-dimensional effective models. Stable compactification of the internal spaces is…
A six-dimensional universe with two branes in the "football-shaped" geometry leads to an almost realistic cosmology. We describe a family of exact solutions with time dependent characteristic size of internal space. After a short…
We compute the high energy entropy and the equation of state of a gas of open superstrings in the infinite volume limit focusing on the calculation of the number of strings as a function of energy and volume. We do it in the fixed…