Speaker
Kylar Greene
(University of New Mexico)
Description
Primordial B-mode polarization is often viewed as a smoking-gun signature of inflationary gravitational waves. However, as experiments such as LiteBIRD, the Simons Observatory, and CMB-S4 push toward sensitivities near r ~ 0.001, non-inflationary tensor sources may become observationally relevant. In this talk, I will introduce early causal tensor sources (ECTs), including dark-sector first-order phase transitions and topological defects (cosmic strings, domain walls), and explain how causality gives rise to a characteristic B-mode signal distinct from inflation. I will also present current state-of-the-art constraints on the ECT amplitude from South Pole Telescope B-mode measurements.