Primordial gravity wave helicity from tidal imprints in large-scale structure

Abstract: Parity violating processes in the early Universe could have resulted in net helicity in the primordial gravity-wave background – the preferred excitation of one circular polarization over the other. In principle, parity violating EB and TB correlations in the cosmic microwave background offer a probe of helicity, however these turn out to be undetectable except in the most optimistic scenarios. I will describe a tidal effect whereby primordial gravity waves leave an imprint in the statistics of the large-scale structure, which could be used to study helicity. In contrast to the CMB, these tidal imprints allow gravity- waves to be reconstructed without loss of geometric information, which I will show is critical to detecting helicity.