Bryce Cyr, "Soft Photon Heating: A zeroth order correction to the global 21cm signal"

Thursday 6 Aug 2026, 16:04 → 18:04 Asia/Seoul

Abstract: In this talk I will discuss recent work highlighting the interplay between a cosmological low-frequency (soft) photon background, and the global 21cm brightness temperature. I will begin with a broad introduction to 21cm cosmology, putting special emphasis on describing the underlying physics of the signal to build intuition. Afterwards, I will tell the tale of two intriguing astrophysical anomalies (from the EDGES and ARCADE-2 experiments), and discuss attempts to connect them. After pointing out a critical flaw in our understanding circa 2018, I will describe a more accurate way to study the evolution of the global 21cm brightness temperature in the presence of soft photons. This will reveal a correction that enters at zeroth order, qualitatively altering the shape and amplitude of the expected 21cm signal in the presence of soft photons.