Lensed Cosmic Microwave Background Constraints on Post-General Relativity Parameters

In this contribution we describe the constraints on departures from general relativity (GR) at cosmological length scales due to cosmic microwave background (CMB). For a more detailed discussion, see Phys. Rev. D 79, 101301 (R) (2009).The departure from GR is measured by the ratio, parameterized as , between the gravitational potentials conventionally appearing in the geodesic equation and the Poisson equation. Current CMB data indicate at the 2σ confidence level, while S remains unconstrained. The departure from GR affects the lensing conversion of E-mode into B-mode polarization. Hence, the lensing measurements from a future CMBpol experiment should be able to improve the constraints to for a fiducial model and independent of S.