Measuring dark matter power spectrum from cosmic microwave background

We propose a method to extract the projected power spectrum of density perturbations from the distortions in the cosmic microwave background (CMB). The distortions are imprinted onto the CMB by the gravitational lensing effect and can be extracted using a combination of products of CMB derivatives. Future CMB experiments such as the Planck satellite experiment will be able to extract the power spectrum with high statistical significance over 2 orders of magnitude in angle. The method proposed here directly traces dark matter in the linear regime to higher redshift (up to z similar to 1100) and larger scale (a few Gpc) than any other currently known method. [S0031-9007(99)08558-0].