  We present cosmological perturbation theory based on generalized gravity
theories including string theory correction terms and a tachyonic complication.
The classical evolution as well as the quantum generation processes in these
variety of gravity theories are presented in unified forms. These apply both to
the scalar- and tensor-type perturbations. Analyses are made based on the
curvature variable in two different gauge conditions often used in the
literature in Einstein's gravity; these are the curvature variables in the
comoving (or uniform-field) gauge and the zero-shear gauge. Applications to
generalized slow-roll inflations and its consequent power spectra are derived
in unified forms which include wide range of inflationary scenarios based on
Einstein's gravity and others.
