Polarizing Bubble Collisions

TL;DR

This paper predicts a distinctive polarization pattern in the CMB caused by cosmic bubble collisions, which could be detected by future surveys and provide evidence for string theory landscape.

Contribution

It introduces a specific polarization signature of bubble collisions in the CMB, aiding in distinguishing such events from other anomalies.

Findings

Polarization is purely E-mode and symmetric around the collision axis.

Radial dependence features can differentiate bubble collision signals.

Future measurements could confirm the collision hypothesis.

Abstract

We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous "cold spot" detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.