Stepping Into the Forest: Confronting Interacting Dark Sector Models for the Hubble Tension With Lyα Data

Speaker: Melissa Joseph

Date: Monday, March 18, 2024

Time: 4:00 – 5:00 pm

Location: 472 Willamette Hall

Abstract: Models of dark sectors with a mass threshold can have important cosmological signatures. If, in the era prior to recombination, a relativistic species becomes nonrelativistic and is then depopulated in equilibrium, there can be measurable impacts on the cosmic microwave background as the entropy is transferred to lighter relativistic particles. In particular, if this step occurs near z ∼ 20,000, the model can naturally accommodate larger values of H₀. If this stepped radiation is additionally coupled to dark matter, there can be a meaningful impact on the matter power spectrum as dark matter can be coupled via a species that becomes nonrelativistic and depleted. This can naturally lead to suppressed power at scales inside the sound horizon before the step, while leaving conventional cold dark matter signatures for power outside the sound horizon. I will discuss the cosmological signatures of such models and assess their ability to address the 5σ Hubble tension in concert with tensions in Large Scale Structure data including the eBOSS Lyα forest measurement.

Host: Pouya Asadi