Related papers: String Gas Cosmology
String theory can (in principle) describe gravity at all curvature scales, and can be applied to cosmology to look back in time beyond the Planck epoch. The duality symmetries of string theory suggest a cosmological picture in which the…
We study string-gas cosmology in dilaton gravity, inspired by the fact that it naturally arises in a string theory context. Our main interest is the thermodynamical treatment of the string-gas and the resulting implications for the…
The predictions of the inflationary LCDM paradigm match today's high-precision measurements of the cosmic microwave background anisotropy extremely well. The same data put tight limits on other sources of anisotropy. Cosmic strings are a…
Cosmic strings are topological defects which can be formed as a result of phase transitions with a spontaneous symmetry breaking in the early Universe. The possibility of the generation of a magnetic field around a cosmic string on the…
String cosmology models predict a stochastic cosmic background of gravitational waves with a characteristic spectrum. I describe the background, present astrophysical and cosmological bounds on it, and outline how it may be possible to…
We consider the spacetime dynamics of a gas of closed strings in the context of General Relativity in a background of arbitrary spatial dimensions. Our motivation is primarily late time String Gas Cosmology, where such a spacetime picture…
A class of grand unified theories with symmetry breaking scale of order $10^{16} GeV$ have a Higgs particle with mass in the $TeV$ scale. The cosmology of such theories is very different from usual. We study the cosmic strings obtained in…
The mystery of the cosmological constant is probably the most pressing obstacle to significantly improving the models of elementary particle physics derived from string theory. The problem arises because in the standard framework of low…
String theory avoids the ultraviolet infinities that arise in trying to quantize gravity. It is also more predictive than conventional quantum field theory, one aspect of this being the way that it contributed to the emergence of the…
One of the main virtues of string gas cosmology is that it resolves cosmological singularities. Since the Universe can be approximated by a locally asymptotically de Sitter spacetime by the end of the inflationary era, a singularity theorem…
In this paper we will discuss how cosmic strings can be used to bridge the gap between the local geometry of our spacetime model and the global topology. The primary tool is the theory of foliations and surfaces, and together with…
We consider an ensemble of closed strings in a compact space with stable one cycles and compute the speed of sound resulting from string thermodynamics. Possible applications to the issue of Jeans instability in string gas cosmology are…
String theory is the leading contemporary framework to explore the synthesis of quantum mechanics with gravity. String phenomenology aims to study string theory while maintaining contact with observational data. The fermionic $Z_2\times…
A generalized second law in string cosmology accounts for geometric and quantum entropy in addition to ordinary sources of entropy. The proposed generalized second law forbids singular string cosmologies, under certain conditions, and…
String Field Theory is a formulation of String Theory as a Quantum Field Theory in target space. It allows to tame the infrared divergences of String Theory and to approach its non-perturbative structure and background independence. This…
The cosmological constant problem is turned around to argue for a new foundational physics postulate underlying a consistent quantum theory of gravity and matter, such as string theory. This postulate is a quantum equivalence principle…
We consider a toy cosmological model in string theory involving the winding and momentum modes of (m,n) strings, i.e. bound states of m fundamental and n D-strings. The model is invariant under S-duality provided that m and n are…
The established cosmological theory which describes the history of the Universe since shortly after the "Big Bang" until today is remarkably successful. Thanks to the increasing precision of available observational data, we are now able to…
In the light of $\phi$-mapping topological current theory, the structure of cosmic strings are obtained from the Abelian Higgs model, which is an effective description to the brane world cosmic string system. In this topological description…
A brief discussion is presented assessing the achievements and challenges of string phenomenology: the subfield dedicated to study the potential for string theory to make contact with particle physics and cosmology. Building from the well…