Multiple Scalar Fields

Abstract

Inflation is generally considered to be a reasonable solution to many of the fundamental problems within the standard cosmological model [167, 236, 327] . There are a variety of inflationary models which include scalar fields [291], and in scalar field models with an exponential potential [372] the universe inflates at a power-law rate, R(t) ∞ t ^p, where p > 1 [249]. As we have seen, all ever-expanding scalar field models with an exponential potential experience power-law inflation when the parameter k ² < 2; i.e., when the potential is sufficiently flat. Exponential potentials arise in many theories of the fundamental interactions including superstring and higherdimensional theories [164, 291] . Typically, “realistic” supergravity theories predict steep exponential potentials [164] (i.e., k ² > 2), effectively eliminating the possibility of power-law inflation. However, dimensionally reduced higher-dimensional theories also predict numerous scalar fields, and so it is of interest to study models with multiple scalar fields.