Generating curvature perturbations with or without MSSM flat directions

We consider instant preheating as the mechanism for generating the curvature perturbation at the end of chaotic inflation. Then we examine if inflation could be driven by a Minimal Supersymmetric Standard Model (MSSM) flat direction or a sneutrino. Our simple mechanism relaxes some serious constraints that appeared in past studies, making inflation driven by a MSSM flat direction or a sneutrino more plausible.