Cosmological Perturbations with Multiple Scalar Fields

In this brief note we present a set of equations describing the evolution of perturbed scalar fields in a cosmological spacetime with multiple scalar fields. We take into account of the simultaneously excited full metric perturbations in the context of the uniform-curvature gauge which is known to be the best choice. The equations presented in a compact form will be useful for handling the structure formation processes under the multiple episodes of inflation.