Cosmological Moduli Problem and Thermal Inflation Models

In superstring theories, there exist various dilaton and modulus fields which masses are expected to be of the order of the gravitino mass m3/2. These fields lead to serious cosmological difficulties, so called “cosmological moduli problem”, because a large number of moduli particles are produced as the coherent oscillations after the primordial inflation. We make a comprehensive study whether the thermal inflation can solve the cosmological moduli problem in the whole modulus mass region mφ ∼ 10 eV–104 GeV predicted by both hidden sector supersymmetry (SUSY) breaking and gauge-mediated SUSY breaking models. In particular, we take into account the primordial inflation model whose reheating temperature is so low that its reheating process finishes after the thermal inflation ends. We find that the above mass region mφ(' m3/2) ∼ 10 eV–104 GeV survives from various cosmological constraints in the presence of the thermal inflation.