Inflationary reheating in grand unified theories

Grand unified theories may display multiply interacting fields with strong coupling dynamics. This poses two new problems: (1) What is the nature of chaotic reheating after inflation, and (2) how is reheating sensitive to the mass spectrum of these theories? We answer these questions in two interesting limiting cases and demonstrate an increased efficiency of reheating which strongly enhances nonthermal topological defect formation, including monopoles and domain walls. Nevertheless, the large fluctuations may resolve this monopole problem via a modified Dvali-Liu-Vachaspati mechanism in which nonthermal destabilization of discrete symmetries occurs at reheating. [S0031-9007(98)07221-4].