Stochastic Approach to Flat Direction during Inflation

We revisit the time evolution of a flat and non-flat direction system during inflation. In order to take into account quantum noises in the analysis, we base on stochastic formalism and solve coupled Langevin equations numerically. We focus on a class of models in which tree-level Hubble-induced mass is not generated. Although the non-flat directions can block the growth of the flat direction's variance in principle, the blocking effects are suppressed by the effective masses of the non-flat directions. We find that the fate of the flat direction during inflation is determined by one-loop radiative corrections and non-renormalizable terms as usually considered, if we remove the zero-point fluctuation from the noise terms.Comment: 17 pages, 4 figures, v2: minor corrections made, published in JCA

Remarks on Hubble Induced Mass from Fermion Kinetic Term

We evaluate the effective mass of a scalar field which interacts with visible sector via Planck-suppressed coupling in supergravity framework. We focus on the radiation-dominated (RD) era after inflation and the contribution from a fermionic field in the thermal bath. We find that, in RD era, the fermion kinetic term gives the effective mass of the order of Hubble scale to the scalar field.Comment: 8 pages, v2: minor corrections made, published in PL