Event

Gravitational lensing of the cosmic microwave background (CMB) encodes information from the low-redshift universe. Therefore, its measurement is useful for constraining cosmological parameters that describe structure formation, e.g. Omega_m, sigma_8, and the sum of neutrino masses. In this talk, I will present a measurement of and the cosmological constraints from the CMB lensing potential and its power spectrum using data from the SPTpol 500 deg^2 survey.  From the minimum-variance combination of the lensing estimators from all combinations of SPTpol temperature and polarization data, we measure the lensing amplitude A_MV = 0.944 \pm 0.058 (Stat.) \pm 0.025 (Sys.), which constitutes the tightest lensing amplitude measurement using ground-based CMB data alone. Using this lensing spectrum measurement, we constrain sigma_8*Omega_m^0.25 to 4%, compared to Planck lensing’s 3% measurement. In combination with galaxy BAO and a BBN prior, SPTpol lensing measures H0 to be 1.6 sigma higher than the Planck measurement. Looking to the future, high signal-to-noise measurements of lensing enabled by deep polarization maps is crucial for constraining the sum of neutrino masses and the amplitude of inflationary gravitational waves through delensing. If time permits, I will give an update on the current effort of delensing the BICEP/Keck telescope data.