Theory: Implications from spatial fluctuations of primordial magnetic helicity

by Fumio Uchida (KEK)

Tuesday 1 Oct 2024, 15:00 → 16:00 Europe/Berlin

SR2

A recently proposed concept in magneto-hydrodynamics, known as the Hosking integral, simplifies the analysis of decaying homogeneous and isotropic magnetic fields as an approximately conserved quantity. The Hosking integral quantifies spatial fluctuations of magnetic helicity, which also play a key role in constraining primordial magnetic fields. These fluctuations, especially above the electroweak scale, results in baryon isocurvature perturbations, which increase the primordial deuterium abundance at the Big Bang Nucleosynthesis. In the talk, I will address two key topics, the Hosking integral and the baryon isocurvature problem, highlighting their shared idea, spatial fluctuations of primordial magnetic helicity.