西南理论物理中心系列报告：Primordial magnetic field as a common solution of nanohertz gravitational waves and Hubble tension

报告摘要：The origin of interstellar and intergalactic magnetic fields remains largely unknown. One possibility is that they are related to the primordial magnetic fields (PMFs) produced by, for instance, the phase transitions of the early Universe. In this letter, the PMF-induced turbulence generated at around the QCD phase transition epoch—the characteristic magnetic field strength B∗ch ∼ O(1) μG and coherent length scale ℓ∗ch ∼ O(1) pc, can naturally accommodate with nanohertz gravitational waves reported by pulsar timing array collaborations. Moreover, the evolution of the PMFs to the recombination era with the form of Bch ∼ ℓch−αcan induce baryon density inhomogeneities, alter the recombination history, and alleviate the tension of the Hubble parameter H0 and the matter clumpiness parameter S8 between early and late-time measurements for 0.88 ≤ α ≤ 1.17 (approximate 95% credible region based on three PTA likelihoods). This allowed range of α is for the first time obtained by data-driven approach. The further evolved PMFs may account for the ∼ O(10−16) Gauss extra-galactic magnetic field inferred with GRB 221009A.

报告人介绍：李垚钰，现紫金山天文台硕士三年级，主要研究方向为宇宙学和原初磁场演化。