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Theory of cosmological perturbations
We present in a manifestly gauge-invariant form the theory of classical linear gravitational perturbations in part I, and a quantum theory of cosmological perturbations in part II. Part I includesExpand
Superstrings in the Early Universe
We investigate some aspects of thermodynamics and cosmology for superstrings. By a rather delicate computation using the microcanonical ensemble we show that the thermodynamic description of stringsExpand
Formation of structure in the universe
An introduction to modern theories for the origin of structure in the Universe is given. After a brief review of the growth of cosmological perturbations in an expanding Universe and a summary ofExpand
Towards a nonsingular bouncing cosmology
We present a nonsingular bouncing cosmology using single scalar field matter with non-trivial potential and non-standard kinetic term. The potential sources a dynamical attractor solution withExpand
Generation of a scale-invariant spectrum of adiabatic fluctuations in cosmological models with a contracting phase
In pre-big-bang and in ekpyrotic cosmology, perturbations on cosmological scales today are generated from quantum vacuum fluctuations during a phase when the Universe is contracting (viewed in theExpand
Decay of correlations in surface models
A convergent low-temperature expansion for a variety of models of twodimensional surfaces is presented. It yields existence of the thermodynamic limit for the pressure and correlation functions asExpand
Trans-Planckian problem of inflationary cosmology
In most current models of inflation based on a weakly self-coupled scalar matter field minimally coupled to gravity, the period of inflation lasts so long that, at the beginning of the inflationaryExpand
Loitering phase in brane gas cosmology
Abstract Brane gas cosmology (BGC) is an approach to M-theory cosmology in which the initial state of the Universe is taken to be small, dense and hot, with all fundamental degrees of freedom nearExpand
Producing a scale-invariant spectrum of perturbations in a Hagedorn phase of string cosmology.
In this cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period ofcosmological inflation. Expand
Trans-Planckian censorship and inflationary cosmology
We study the implications of the recently proposed Trans-Planckian Censorship Conjecture (TCC) for early universe cosmology and in particular inflationary cosmology. The TCC leads to the conclusionExpand