Assisted chaotic inflation in higher dimensional theories

We address the problem of the large initial field values in chaotic inflati on and propose a remedy in the framework of the so-called assisted inflatio n. We demonstrate that a 4-dimensional theory of multiple, scalar fields wi th initial field values considerably below the Planck scale, can give rise to inflation even though none of the individual scalar fields are capable o f driving inflation. The problems arising from the presence of possible non -renormalizable interactions is therefore removed. As a concrete example of a theory with multiple scalar fields, we consider a (4 + d)-dimensional fi eld theory of a single, non-interacting massive scaler field whose KK modes play the role of the assisted sector. For the KK modes to assist inflation , the extra dimensions must have a size larger than the inverse (4D) Planck scale. (C) 1999 Elsevier Science B.V. All rights reserved.