Related papers: Generalized Second Law in String Cosmology
The first and second laws of thermodynamics should lead to a consistent scenario for discussing the cosmological constant problem. In the present study, to establish such a thermodynamic scenario, cosmological equations in a flat…
Here, we study the generalized second law (GSL) of thermodynamics in the framework of massive gravity. To do this, we consider a FRW universe filled only with matter and enclosed by the apparent horizon. In addition, we consider two models…
The notion of inflation (past or present) in standard cosmological models is shown to be a consequence of a sufficiently high second law entropy production from the internal heating of the universal expansion. The longitudinal viscous…
In dilaton gravity theories, we consider a string-like topological defect formed during U(1) gauge symmetry-breaking phase transition in the early Universe, and far from the cosmic string we have vacuum solutions of the generalized Einstein…
It is shown that all generalized two--dimensional dilaton theories with arbitrary matter content (with a curvature independent coupling to gravity) do not only obey a first law of black hole mechanics (which follows from Wald's general…
The thermodynamic second law in the evaporating black hole space-time is examined in the context of two-dimensional dilaton black hole. The dynamical evolution of entropy is investigated by using the analytical perturbation method and the…
We consider the effects of graviton multiplet fields on transitions between string gas phases. Focusing on the dilaton field, we show that it may obstruct transitions between different thermodynamic phases of the string gas, because the…
We study the effect of higher-curvature terms in the string low-energy effective actions on the cosmological solutions of the theory, up to corrections quartic in the curvatures, for the bosonic and heterotic strings as well as the type II…
At its very beginning, the universe is believed to have grown exponentially in size via the mechanism of inflation. The almost scale-invariant density perturbation spectrum predicted by inflation is strongly supported by cosmological…
We study the validity of the generalized second law (GSL) of gravitational thermodynamics in a non-flat FRW universe containing the interacting in $f(T)$ gravity. We consider that the boundary of the universe to be confined by the dynamical…
We investigate $(n+1)$-dimensional string-dilaton cosmology with effective dilaton potential in presence of perfect-fluid matter.We get exact solutions parametrized by the constant $\gam$ of the state equation $p=(\gam-1)\rho$, the spatial…
We investigate the validity of the generalized second law of gravitational thermodynamics on the apparent and event horizons in a non-flat FRW universe containing the interacting dark energy with dark matter. We show that for the dynamical…
We discuss some aspects of string cosmology with an emphasis on the role played by the dilaton. A cosmological scenario based on the assumption that all spatial dimensions are periodic so that winding modes play an important role is…
A string cosmology scenario ("pre-big-bang") postulates that the evolution of the Universe starts from a state of very small curvature and coupling, undergoes a long phase of dilaton-driven kinetic inflation and at some later time joins…
We investigate the cosmological consequences of particle physics theories that admit stable loops of superconducting cosmic string - {\it vortons}. General symmetry breaking schemes are considered, in which strings are formed at one energy…
We examine the second law of thermodynamics in the context of horizon cosmology, in particular, whether the change of total entropy (i.e. the sum of the entropy for the apparent horizon and the entropy for the matter fields) proves to be…
We complement the low-energy gravi-dilaton effective action of string theory with a non-local, general-covariant dilaton potential, and obtain homogeneous solutions describing a non-singular (bouncing-curvature) cosmology. We then compute,…
In this paper we examine the classical evolution of a cosmological model derived from the low-energy tree-level limit of a generic string theory. The action contains the metric, dilaton, central charge and an antisymmetric tensor field. We…
`Old' String Theory is a theory of one-dimensional extended objects, whose vibrations correspond to excitations of various target-space field modes including gravity. In these lectures I will give an introduction to low-energy Effective…
The generalized uncertainty principle of string theory is derived in the framework of Quantum Geometry by taking into account the existence of an upper limit on the acceleration of massive particles.