On the Initial Conditions for Brane Inflation

TL;DR

This paper investigates how initial conditions, including initial momentum, affect the likelihood of achieving sufficient inflation in brane inflation models derived from string theory.

Contribution

It analyzes the initial condition phase space for brane inflation, highlighting the impact of initial momentum on reducing fine-tuning requirements.

Findings

Nonzero initial momentum broadens the initial conditions for successful inflation.

Considering initial momentum reduces the fine-tuning needed for initial conditions.

The phase space for inflationary trajectories is significantly affected by initial velocities.

Abstract

String theory gives rise to various mechanisms to generate primordial inflation, of which ``brane inflation'' is one of the most widely considered. In this scenario, inflation takes place while two branes are approaching each other, and the modulus field representing the separation between the branes plays the role of the inflaton field. We study the phase space of initial conditions which can lead to a sufficiently long period of cosmological inflation, and find that taking into account the possibility of nonvanishing initial momentum can significantly change the degree of fine tuning of the required initial conditions.