BRANE INFLATION: FROM SUPERGRAVITY TO TACHYONIC

Abstract

We report on results obtained for a class of TV = 1 supergravity inflationary models in which the evolution of the inflaton dynamics is controlled by a single power (quadratic or cubic in the inflaton field) at the point where the observed density fluctuations are produced. We find that the so-called rj-problem encountered in such models can be naturally solved in the context of braneworld scenario for some range of a, the ratio of the dominant term in the inflationary potential and the brane tension, and the value of the inflaton field at the end of inflation, (j>p. We have also shown that successful tachyonic inflation can be achieved in the context of a five-dimensional ADS braneworld scenario. We argue that the bosonic String Field Theory action around the top of the tachyon potential does allow a sufficiently long period of inflation provided the string remains very weakly coupled and the string energy density T3 is sufficiently below the Planck scale to render the low-energy four-dimensional gravity theory description reliable.