S. Kumar | Dark Radiation Isocurvature: Constraints and Application to the H0 Tension

Parallel Talk | Cosmology from Home 2021

Talk title:
Dark Radiation Isocurvature: Constraints and Application to the H0 Tension
Speaker:
Soubhik Kumar

Talk abstract:
Dark radiation (DR) appears as a new-physics candidate in various scenarios beyond the Standard Model and, quite plausibly, one can obtain isocurvature fluctuations from the inflationary era. In this talk, I describe the constraints on DR isocurvature perturbations from the full Planck 2018 data and the role it plays in the context of the H0 problem. While free-streaming DR is degenerate with the well-studied neutrino density isocurvature perturbation with varying ΔN_{eff}, qualitatively new physical effects arise when DR evolves as a coupled fluid.