http://arxiv.org/abs/2203.03124
We formulate axion-electrodynamics and magnetohydrodynamics (MHD) in the cosmological context assuming weak gravity. The two formulations are made for a general scalar field with general $f(\phi)$-coupling, and an axion as a massive scalar field with $\phi^2$-coupling, with the helical electromagnetic field. The $\alpha$-dynamo term appears naturally from the helical-coupling in the MHD formulation. In the presence of the electromagnetic coupling, however, the Schr\”odinger and hydrodynamic formulations of the coherently oscillating axion are not available for the conventional $\phi$ coupling; instead, $\phi^2$ coupling allows successful formulations preserving the dark matter nature of the axion to nonlinear order.
J. Hwang and H. Noh
Tue, 8 Mar 22
53/100
Comments: 7 pages, no figure
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