Thoughts on Tachyon Cosmology

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.

34 pages, no figures. This is the written version of a lecture delivered at the Workshop on the Quantum Structure of Spacetime and the Geometric Nature of Fundamental Interactions held in Leuven from Sept 13th to Sept 19th(2002) which is to appear in the Proceedings in a special issue of Quantum and Classical Gravity