Cosmological Perturbation Theory With Background Anisotropic Curvature
  The theory of cosmological perturbations is extended to spacetimes displaying
isotropic expansion but anisotropic curvature. The perturbed Einstein equation
and Boltzmann equations for massless and massive particles are derived in a
general gauge and a decomposition of perturbations into harmonic modes and
moments is proposed. Generalization to the case where anisotropic expansion is
also present in the background is discussed.
