  We present a new technique for constraining the topology of the universe. The
method exploits the existence of correlations in the phases of the spherical
harmonic coefficients of the CMB temperature pattern associated with matched
pairs of circles seen in the sky in universes with non-trivial topology. The
method is computationally faster than all other statistics developed to hunt
for these matched circles. We applied the method to a range of simulations with
topologies of various forms and on different scales. A characteristic form of
phase correlation is found in the simulations. We also applied the method to
preliminary CMB maps derived from WMAP, but the separation of topological
effects from, e.g., foregrounds is not straightforward.
