Overproduction of cosmic superstrings

TL;DR

This paper demonstrates that the initial density of cosmic superstrings formed during brane annihilation is much higher than previously estimated, potentially leading to cosmological overclosure issues in certain inflation models.

Contribution

It provides analytical and numerical analysis showing that defect formation during brane annihilation results in higher density of cosmic superstrings than the naive Kibble mechanism predicts.

Findings

Defects form with correlation lengths of order M_s^{-1}

Potential overclosure of the universe by relic defects

Implications for brane-antibrane inflation models

Abstract

We show that the naive application of the Kibble mechanism seriously underestimates the initial density of cosmic superstrings that can be formed during the annihilation of D-branes in the early universe, as in models of brane-antibrane inflation. We study the formation of defects in effective field theories of the string theory tachyon both analytically, by solving the equation of motion of the tachyon field near the core of the defect, and numerically, by evolving the tachyon field on a lattice. We find that defects generically form with correlation lengths of order M_s^{-1} rather than H^{-1}. Hence, defects localized in extra dimensions may be formed at the end of inflation. This implies that brane-antibrane inflation models where inflation is driven by branes which wrap the compact manifold may have problems with overclosure by cosmological relics, such as domain walls and monopoles.