Post-recombination gravity-generated contributions to the cosmic microwave background anisotropies and cosmological parameter estimation

Abstract

Gravitational interaction of cosmic microwave background (CMB) photons with matter perturbations present along the line-of-sight to the surface of last scattering modifies the shape of the CMB anisotropy power spectrum. Here I focus on (linear) integrated Sachs-Wolfe and (non-linear) gravitational lensing effects and discuss the detectability of the resulting distortions and their possible consequences for the CMB-based estimation of cosmological parameters. Specifically, I discuss if any of those effects may allow us to use CMB experiments to put independent constraints on the curvature of the universe and the cosmological constant, i.e. breaking the so-called geometrical degeneracy in CMB parameter estimation discussed by Bond, Efstathiou and Tegmark (1997) and Zaldarriaga, Spergel and Seljak (1997). I address that issue using the Fisher matrix approach and show that gravitational lensing of the CMB temperature and polarisation patterns might be detectable by the Planck Surveyor satellite, leading to useful independent and precise constraints on the cosmological constant and spatial curvature. The integrated Sachs-Wolfe effect though bound to restrict those parameters only very weakly still may set constraints more stringent than those currently available.