Brane Inflation is Attractive

TL;DR

This paper demonstrates that incorporating the Dirac-Born-Infeld kinetic term in brane inflation models significantly reduces the fine-tuning of initial conditions needed for inflation, especially when considering UV effects and the DBI regime.

Contribution

It provides a detailed phase space analysis showing how DBI effects expand the initial conditions space, lowering fine-tuning compared to standard models.

Findings

DBI effects expand the inflationary phase space.

Fine-tuning is reduced by several orders of magnitude.

UV effects impose restrictions on initial conditions.

Abstract

We study the phase space of initial conditions for brane inflation, and find that including the effects of the Dirac-Born-Infeld (DBI) kinetic term dramatically improves previous estimates on the amount of fine tuning of initial conditions necessary for inflation, even for models dominated by slow roll. Two effects turn out to be important for the phase space analysis: restrictions on the total available phase space due to UV effects in brane inflation, and the extension of the inflationary attractor to the DBI inflationary regime. We compare the amount of initial conditions fine tuning required for a brane inflation model and its standard field theory counterpart and find that brane inflation decreases the required tuning by several orders of magnitude.