Curvature perturbation from velocity modulation
  We propose a new variant model of the modulated reheating. If particles have
large scale fluctuations on their velocities, or equivalently their Lorentz
factors, the decay rate also fluctuates and the curvature perturbation is
induced via their decay processes in analogy with modulated reheating. For
example, if they are produced nonthermally by the decay of another field with
its mass fluctuating on large scales, such a situation is realized. We
explicitly calculate the resulting curvature perturbation and non-linearity
parameters and show that the effect of velocity-modulation is not negligible if
the particles are semi-relativistic at the decay.
