Thoughts on Tachyon Cosmology

TL;DR

This work surveys how standard cosmology confronts inflationary goals within M/String Theory and explores tachyon dynamics as a possible pre-inflationary stage. It introduces the Carollian confinement mechanism for open string states and sketches a scenario where an Open String Era transitions to a Closed String Era before a conventional inflationary epoch. The discussion covers Chaplygin-like tachyon matter, the violation of the strong energy condition, and challenges related to reheating, initial conditions, and measure in cosmology. Overall, it argues for a speculative but potentially fruitful integration of tachyon dynamics and Carroll/Galilei-symmetric structures into early-universe cosmology, warranting further theoretical development and phenomenological exploration.

Abstract

After a pedagogical review of elementary cosmology, I go on to discuss some obstacles to obtaining inflationary or accelerating universes in M/String Theory. In particular, I give an account of an old No-Go Theorem to this effect. I then describe some recent ideas about the possible rôle of the tachyon in cosmology. I stress that there are many objections to a naive inflationary model based on the tachyon, but there remains the possiblity that the tachyon was important in a possible pre-inflationary Open-String Era preceding our present Closed String Era.