http://arxiv.org/abs/2212.07929
It has been conjectured that a specific set of Cauchy data may lead to an unexpected growth of the gauge fields in conformally flat cosmological backgrounds. After introducing a class of models where the (hyper)magnetic fields are produced quantum mechanically from the early variation of the gauge coupling, we show that the standard evolution for wavelengths larger than the Hubble radius fully accounts for the anomalous scaling which is however unable to increase the magnetic power spectra. This dynamical evolution has nothing to do with a peculiar choice of the initial conditions but rather with the rate of variation of the gauge coupling during inflation. While the correct scaling follows from the properly normalized solutions of the mode functions and from the late dominance of the conductivity, a further amplification of the magnetic power spectra can only occur when the post-inflationary expansion rate is slower than radiation and it is again unrelated to the initial data possibly set during the inflationary stage.
M. Giovannini
Fri, 16 Dec 22
11/72
Comments: 10 pages, 1 figure