Non-BPS D9-branes in the Early Universe

TL;DR

This paper explores how non-BPS D9-branes could have influenced the early universe's evolution, focusing on their stability at high temperatures and decay at lower temperatures via tachyon condensation.

Contribution

It presents a novel scenario for the early universe involving non-BPS D9-branes, analyzing their stability and decay using boundary string field theory and classical gravity solutions.

Findings

Non-BPS D9-branes are stable near the Hagedorn temperature.

The universe's temperature decreases as it expands, leading to brane decay.

Classical solutions for Einstein and dilaton gravity are obtained.

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-anti-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.