Particle horizon

About: Particle horizon is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 69137 citations.

Non-BPS D9-Branes in the Early Universe

Abstract: We have investigated the finite temperature systems of non-BPS D-branes and D-brane?anti-D-brane pairs in the previous papers. It has been shown that non-BPS D9-branes and D9- pairs become stable near the Hagedorn temperature on the basis of boundary string field theory. This implies that there is a possibility that these spacetime-filling branes exist in the early universe. We study the time evolution of the universe in the presence of non-BPS D9-branes on the basis of boundary string field theory in this paper. We try to construct the following scenario for the early universe: The universe expands at high temperature and the open string gas on the non-BPS D9-branes dominates the total energy of the system at first. The temperature decreases as the universe expands. Then the non-BPS D9-branes become unstable at low temperature and decay through tachyon condensation. We obtain some classical solutions for Einstein gravity and dilaton gravity in the very simple cases.

A Note on The Origin of Time in Archaic Universe

Abstract: The problem of initial singularity in cosmology, beyond the technical aspects, set the insurmountable limits of every description purely dynamics of the universe. In this brief note we present the main conceptual aspects of the Archaic Universe cosmological program. The adoption of a de Sitter pre- space as a structure of the quantum vacuum allows you to rethink the problem of time in cosmology by the relationship between the archaic non-local phase and the local observable Universe.

Separate universe and the back reaction of long wavelength fluctuations

Abstract: We investigate the back reaction of cosmological long wavelength perturbations on the evolution of the Universe By applying the renormalization group method to a Friedmann-Robertson-Walker universe with long wavelength fluctuations, we demonstrate that the renormalized solution with the back reaction effect is equivalent to that of the separate universe Then, using the effective Friedmann equation, we show that only the nonadiabatic mode of long wavelength fluctuations affects the expansion law of the spatially averaged universe

Topological defects in an open universe

Abstract: This talk will explore the evolution of topological defects in an open universe The rapid expansion of the universe in an open model slows defects and suppresses the generation of CBR fluctuations at large angular scale as does the altered relationship between angle and lenght in an open universe Defect models, when normalized to COBE in an open universe, predict a galaxy power spectrum consistent with the galaxy power spectrum inferred from the galaxy surveys and do not require an extreme bias Neither defect models in a flat universe nor standard inflationary models can fit either the multipole spectrum or the power spectrum inferred from galaxy surveys