Testing cosmic geometry without dynamic distortions using voids
  We propose a novel technique to probe the expansion history of the Universe
based on the clustering statistics of cosmic voids. In particular, we compute
their two-point statistics in redshift space on the basis of realistic mock
galaxy catalogs and apply the Alcock-Paczynski test. In contrast to galaxies,
we find void auto-correlations to be marginally affected by peculiar motions,
providing a model-independent measure of cosmological parameters without
systematics from redshift-space distortions. Because only galaxy-galaxy and
void-galaxy correlations have been considered in these types of studies before,
the presented method improves both statistical and systematic uncertainties on
the product of angular diameter distance and Hubble rate, furnishing the
potentially cleanest probe of cosmic geometry available to date.
