Inflation from a Tachyon Fluid?

TL;DR

The paper investigates whether inflation can be driven by Sen’s tachyon matter in a flat FRW universe. It derives the tachyon cosmology equations, defines slow-roll conditions in terms of the tachyon field, and analyzes the required near-peak potential and the resulting e-folds and density perturbations, linking them to COBE normalization. It then translates the phenomenology into string-theoretic parameters and shows significant tensions between typical choices and observational constraints, proposing potential resolutions such as a large number of branes but highlighting reheating and the tachyon-fluid fate as open issues. Overall, the work presents a phenomenological tachyon-inflation scenario with automatic exit but faces substantial hurdles in embedding it consistently within concrete string theory.

Abstract

Motivated by recent works of Sen and Gibbons, we study the evolution of a flat and homogeneous universe dominated by tachyon matter. In particular, we analyse the necessary conditions for inflation in the early roll of a single tachyon field.

Figures (2)

• Figure 1: $\dot T^2$ as a function of $T/T_0$, for various values of $X_0$. Inflation stops when $\dot T^2 > 2/3$.
• Figure 2: Number of e-folds during tachyon rolling as a function of $X_0$.