Dependence of the Cosmic Microwave Background Lensing Power Spectrum on
  the Matter Density
  The anisotropies in the cosmic microwave background (CMB) provide our best
laboratory for testing models of the formation and evolution of large-scale
structure. The rich features in the cosmic microwave background anisotropy
spectrum, in combination with highly precise observations and theoretical
predictions, also allow us to simultaneously constrain a number of cosmological
parameters. As observations have progressed, measurements at smaller angular
scales have provided increasing leverage. These smaller angular scales provide
sensitive measures of the matter density through the effect of gravitational
lensing. In this work we provide an analytic explanation of the manner in which
the lensing of CMB anisotropies depends on the matter density, finding that the
dominant effect comes from the shape of the matter power spectrum set by the
decay of small-scale potentials between horizon crossing and matter-radiation
equality.
