Collisions with other Universes: the Optimal Analysis of the WMAP data

Understand

An appealing theory is that our current patch of universe was born as a nucleation bubble from a phase of false vacuum eternal inflation.

• We search for evidence for this theory by looking for the signal imprinted on the CMB that is generated when another bubble "universe" collides with our own.
• We create an efficient and optimal estimator for the signal in the WMAP 7-year data.
• We find no detectable signal, and constrain the amplitude, a, of the initial curvature perturbation that would be generated by a collision: -4.66 \times 10^{-8} < a (\sin{\thetabubble})^{4/3} < 4.73 \times 10^{-8} [Mpc^{-1}] at 95% confidence where \thetabubble is the angular radius of the bubble signal.