Speaker
Description
We study cosmological perturbations sourced by a domain wall (DW) network with a finite lifetime. Allowing DWs to decay avoids the stringent CMB energy density constraints, enabling signals that are relevant for both the CMB and measurements sensitive to smaller scales (higher $k$-modes). Using the uncorrelated segment model (USM) to describe the DW energy-momentum tensor, we derive analytical expressions for the scalar and tensor power spectra and clarify their $k$-dependence. In contrast to the first-order phase transition (FOPT) that reheats into dark radiation, DW-induced superhorizon perturbations continue to grow on scales larger than the PT horizon, and only transition to a $k^{3}$ scaling for modes entering the horizon after DW collapse. By comparing with existing curvature perturbation constraints, we determine the maximal $B$-mode signal from DW-sourced tensor perturbations, which can easily exceed the inflationary signal with $r=10^{-3}$.