Second Order perturbation Theory: A covariant approach involving a barotropic equation of state

摘要

We present a covariant and gauge invariant formalism suited to the study ofsecond-order effects associated with higher order tensor perturbations. Theanalytical method we have developed enables us to characterize puresecond-order tensor perturbations about FLRW model having different kinds ofequations of state. Our analysis of the radiation case suggests that it may befeasible to examine the CMB polarization arising from higher orderperturbations.