  We consider cosmological perturbations caused by modulated inflaton velocity.
During inflation, the inflaton motion is damped and the velocity is determined
by the parameters such as couplings or masses that may depend on light
fields(moduli). The number of e-foldings is different in different patches if
there are spatial fluctuations of such parameters. Based on this simple idea,
we consider ``modulated inflation'' in which the curvature perturbation is
generated by the fluctuation of the inflaton velocity. This talk is based on
our recent papers.
