Brane inflation and reheating

Abstract

We study inflation and reheating in a brane world model derived from Type IIA string theory. This particular setup is based on a model of string mediated supersymmetry breaking. The inflaton is one of the transverse scalars of a D4-brane which has one of its spatial dimensions stretched between two NS5-branes, so that it is effectively three-dimensional. This D4-brane is attracted to a D6-brane that is separated from the 5-branes by a fixed amount. The potential of the transverse scalar due to the D4/D6 interaction makes a good inflaton potential. As the D4-brane slides along the two 5-branes towards the 6-brane it begins to oscillate near the minimum of the potential. The inflaton field couples to the massless Standard Model fields through Yukawa couplings. In the brane picture these couplings are introduced by having another D6'-brane intersect the D4-brane such that the 4-6' strings, whose lowest lying modes are the Standard Model matter, couple to the scalar mode of the 4-4 strings, the inflaton. The inflaton can decay into scalar and spinor particles on the 4-6' strings, reheating the universe. Observational data is used to place constraints on the parameters of the model.