Can Quintessence Be The Rolling Tachyon?

TL;DR

This paper investigates whether a rolling tachyon field from string theory can serve as quintessence, analyzing phase-plane stability and potential forms, and concludes it is possible under certain conditions.

Contribution

It provides a phase-plane analysis showing the instability of tachyon as quintessence with typical potentials and explores conditions for stability with alternative potentials.

Findings

No stable critical point with typical potentials.

Stable critical point possible with an exactly solvable toy potential.

Tachyon can be quintessence if the potential is suitably chosen.

Abstract

In light of the recent work by Sen and Gibbons, we present a phase-plane analysis on the cosmology containing a rolling tachyon field in a potential resulted from string theory. We show that there is no stable point on the phase-plane, which indicated that there is a coincidence problem if one consider tachyon as a candidate of quintessence. Furthermore, we also analyze the phase-plane of the cosmology containing a rolling tachyon field for an exactly solvable toy potential in which the critical point is stable. Therefore, it is possible for rolling tachyon to be quintessence if one give up the strict constraint on the potential or find a more appropriate effective potential for the tachyon from M/string theory.