Thermal Inflation and the Moduli Problem

Abstract

In supersymmetric theories a field can develop a vacuum expectation value $M\gg 10^3\mathrm{GeV}$, even though its mass $m$ is of order $10^2$ to $10^3\mathrm{GeV}$. The finite temperature in the early Universe can hold such a field at zero, corresponding to a false vacuum with energy density $V_0\sim m^2{M}^2$. When the temperature falls below $V_0^{1/4}$, the thermal energy density becomes negligible and an era of thermal inflation begins. It ends when the field rolls away from zero at a temperature of order $m$, corresponding to of order 10 $e$-folds of inflation which does not affect the density perturbation generated during ordinary inflation. Thermal inflation can solve the Polonyi/moduli problem if $M$ is within one or two orders of magnitude of $10^{12}\mathrm{GeV}$.

Comments: Revised version to appear in Phys Rev D. Improved discussion of the possible effect of parametric resonance. Latex, 31 pages