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 " preceeding our present "Closed String Era".

D 3 ¯ $$ \overline{\mathrm{D}3} $$ and dS

“…which is the generalization of the classical condition first found by [24][25][26]. The analysis that we perform here, in the presence of the above-mentioned corrections, would precisely achieve that, allowing a positive curvature solution to exist in our set-up.…”

“…In appendix B we give an explicit example of the D3 brane action in a simple toroidal GKP background. Finally, in appendix C we revisit the no-go theorem by Gibbons-Maldacena-Núñez [24][25][26] and discuss how consistent de Sitter vacua are realized in our framework.…”

“…We expect a positive cosmological solution in the four space-time direction and therefore we should discuss how the no-go condition of Gibbons-Maldacena-Núñez [24][25][26], recently updated in [55], is averted. Our starting point will be a metric ansatz, originally due to [56], specified by a warp factor e 2A , see (1.4), with a compact six-dimensional internal manifold, and a general 4d metric g µν rather than η µν .…”

Quantum cosmology and tachyons

“…A need for understanding these new and rather surprising facts, including (cold) "dark matter", has motivated numerous authors to reconsider different inflation scenarios. Despite some evident problems [6] such as a non-sufficiently long period of inflation, tachyon-driven scenarios [7,8,9] remain highly interesting for study.…”

Breathers in the elliptic sine-Gordon model

“…For instance, recently there has been great activity in the context of string theory [5,6,7,8,9,10,11,12,13,14,15,16], where Tachyon condensates have turned out to be important. They also appear to be very useful in the context of cosmological considerations [17,18,19,20,21,22,23,24,25]. Here we want to adopt the lesson from string theory and cosmology and allow them to be present.…”