D-brane Anti-brane Annihilation in an Expanding Universe

TL;DR

This paper investigates the annihilation dynamics of D-branes and anti-D-branes in an expanding universe, revealing that annihilation rates are insufficient to prevent branes from dominating the universe's energy density, with implications for braneworld models.

Contribution

It demonstrates that D-brane anti-brane annihilation is too slow to counteract cosmic expansion, and shows that lower-dimensional branes persist longer, offering a new perspective on braneworld cosmology.

Findings

Annihilation rate is too small to compete with universe expansion.

Lower-dimensional branes annihilate more slowly than higher-dimensional ones.

A brane-dominated universe can be consistent with late-time inflation.

Abstract

The time-varying density of D-branes and anti-D-branes in an expanding universe is calculated. The D-brane anti-brane annihilation rate is shown to be too small to compete with the expansion rate of a FRW type universe and the branes over-close the universe. This brane problem is analogous to the old monopole problem. Interestingly however, it is shown that small dimension D-branes annihilate more slowly than high dimension branes. Hence, an initially brany universe may be filled with only low dimension branes at late times. When combined with an appropriate late inflationary theory this leads to an attractive dynamical way to create a realistic braneworld scenario.