Speaker
Description
As compelling cold dark matter candidates, the mechanism underlying axion generation in the early Universe remains a central focus of contemporary research. Conventional misalignment mechanisms, however, have not systematically incorporated key physical effects including the initial velocity and initial field value of the axion. In this Letter, we comprehensively investigate the impact of pri- mordial magnetic fields (PMFs) on axion production abundance. Specifically, considering the axion coupling to the Chern-Simons term of the U(1) hypercharge gauge field, its equation of motion is modified into that of a driven oscillator. This modification effectively shifts the onset time of axion oscillations, which in turn significantly alters the relic abundance of axions in the early Universe. We term this novel axion production effect the axion helical misalignment mechanism. Furthermore, if chiral asymmetries exist in the early Universe, the chiral magnetic effect (CME) will also contribute to axion evolution. The coexistence of the axion field and the CME exerts a profound influence on the evolution of Standard Model (SM) chiral fermions, and this modification to fermion evolution ultimately leads to the generation of the baryon asymmetry of the Universe.
