Searching for Stringy Topologies in the Cosmic Microwave Background
  We consider a universe with a non-classical stringy topology that has fixed
points. We concentrate on the simplest example, an orbifold point, and study
its observable imprints on the cosmic microwave background (CMB). We show that
an orbifold preserves the Gaussian nature of the temperature fluctuations, yet
modifies the angular correlation function. A direct signature of an orbifold is
a single circle in the CMB that is invariant under rotation by 180 degrees.
Searching the 7-year ILC map of WMAP, we find one candidate circle with high
statistical significance. However, a closer look reveals that the temperature
profile does not fit an orbifold. We place a lower bound on the distance to an
orbifold point at ~85% of the distance to the surface of last scattering.
