Related papers: Adiabatic fluctuations from cosmic strings in a co…
During the inflationary phase of the early universe, quantum fluctuations in the vacuum generate particles as they stretch beyond the Hubble length. These fluctuations are thought to result in the density fluctuations and gravitational…
We consider the classical fluctuations of the gravitational constant generated by bubbles in the inflationary universe. For extended inflation, we demonstrate numerically how and how large fluctuations are produced during bubble expansion.…
The evolution of superhorizon curvature perturbations in a two-component interacting universe is considered. It is found that adiabatic modes conserve the total curvature perturbation $\zeta$, unless there are stages in which the rate of…
We study the behaviour of cosmic string networks in contracting universes, and discuss some of their possible consequences. We note that there is a fundamental time asymmetry between defect network evolution for an expanding universe and a…
According to the inflationary scenario, all structure in the Universe can be traced back to quantum fluctuations of the metric and scalar field(s) during inflation. The seeds of this structure can be observed as classical anisotropies in…
A key prediction of cosmological theories for the origin and evolution of structure in the Universe is the existence of a `Doppler peak' in the angular power spectrum of cosmic microwave background (CMB) fluctuations. We present new results…
In D-term inflation models, the fluctuations of squark fields in the flat directions give rise to isocurvature density fluctuations stored in the Affleck-Dine condensate. After the condensate breaks up in B-balls, these can be perturbations…
Topological defects form at cosmological phase transitions by the Kibble mechanism, with cosmic strings and superstrings having the most interesting phenomenology. A rigorous analysis of their astrophysical consequences is limited by the…
I propose a reinterpretation of cosmic dark matter in which a rigid network of cosmic strings formed at the end of inflation. The cosmic strings fulfill three functions: At recombination they provide an accretion mechanism for virializing…
We develop a numerical statistical method to study linear cosmological fluctuations in inflationary scenarios with multiple fields, and apply it to an ensemble of six-field inflection point models in string theory. The latter are concrete…
Cosmic strings, a hot subject in the 1980's and early 1990's, lost its appeal when it was found that it leads to inconsistencies in the power spectrum of the measured cosmic microwave background temperature anisotropies. However,…
We study the evolution of cosmological perturbations in an anti-de-Sitter (AdS) bulk through a cosmological singularity by mapping the dynamics onto the boundary conformal fields theory by means of the AdS/CFT correspondence. We consider a…
We study cosmological perturbations produced by the most general two-derivative actions involving two scalar fields, coupled to Einstein gravity, with an arbitrary field space metric, that admit scaling solutions. For contracting universes,…
Turbulence influences the behavior of many astrophysical systems, frequently by providing non-thermal pressure support through random bulk motions. Although turbulence is commonly studied in systems with constant volume and mean density,…
It is shown that density fluctuations obey a scaling law in an open Friedmann universe. In a flat universe, the fluctuations are not scale-invariant. We compute the growth rate of adiabatic scale-invariant density fluctuations in flat, open…
A novel mechanism to produce a cosmic network of fundamental superstrings based on a time-varying string tension has been recently proposed. It has been found that fundamental superstrings can grow in a kinating background driven by the…
It is shown that the evolution of the density perturbations during certain eras of substantial entropy generation in the universe can be described in the scheme of the KPZ equation. Therefore, the influence on cosmological structure…
Cosmological perturbations in an expanding universe back-react on the space-time in which they propagate. Calculations to lowest non-vanishing order in perturbation theory indicate that super-Hubble-scale fluctuations act as a negative and…
Comparison of theobservedanisotropy with that predicted iadiabaticDM models suggest that much of thserved signal may be due to long wavelenh gravitational waves. In inflationary models this requires the generation of tensor fluctuations to…
We include the effect of the frictional force caused by interactions between cosmic strings and the particles of the background plasma in the computation of the stochastic gravitational wave background generated by cosmic string loops.…