Speaker
Description
In this talk, I will discuss the phenomenology of a first-order phase transition that occurs after Big Bang nucleosynthesis (BBN) but before recombination in a sector that is secluded from the standard model. Such a rather late phase transition impacts curvature perturbations at a time when some of them have already re-entered the cosmological horizon. In particular, the trigger dynamics of the phase transition induces acoustic oscillations in the post-phase transition fluid, leading to observable signatures in the cosmic microwave background and the large-scale structure of the Universe. Following this general discussion, I will present a simple dark sector Higgs model where an SU(N) gauge symmetry undergoes spontaneous breaking to SU(N-1) via a supercooled first-order phase transition à la Coleman-Weinberg. The latent heat released in the phase transition acts as an early phase of dark energy before it is converted into strongly interacting dark radiation. This scenario, termed Hot New Early Dark Energy, can alleviate the Hubble tension while remaining consistent with Big Bang nucleosynthesis constraints.
