Second-order gravitational effects of local inhomogeneities on cmb anisotropies and non-gaussian signatures

Based on the second-order nonlinear theory of perturbations in nonzero $\ensuremath{\Lambda}$ flat cosmological models, we study the gravitational effects of local inhomogeneities on cosmic microwave background (CMB) anisotropies. As the local inhomogeneities we consider first large-scale dipole and quadrupole distributions of galaxies around us and next an isolated cluster-scale matter distribution. It is found that, due to the second-order integral Sachs-Wolfe effect, the north-south asymmetry of CMB anisotropies and non-Gaussian signatures (in terms of scale-dependent estimators of kurtosis) in a spotlike object are caused from these matter distributions along light paths. Our theoretical results seem to be consistent with recent various observational results which have been shown by Hansen et al., Eriksen et al., Vielva et al. and Cruz et al.