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Abstract: In this paper, we investigate the back-reaction of $U1$ gauge fields into aclass of inflationary settings. To be more precise, we employ a Bianchi-Igeometry taken as an anisotropic perturbation of a flat FRW model within twotypes of Born-Infeld theories. Firstly we consider pure Born-Infeldelectromagnetism. For either a constant or a $b\phi$ coupling, inflationarytrajectories are modified but anisotropies increase; In particular, for theformer coupling we find that a quadratic inflaton potential, within a constantratio for the scalar and gauge energy densities, does not induce sufficientinflation, while in the latter the back-reaction in the cosmology determinesfrom the tensor-scalar ratio a narrow range where inflation can occur. ADirac-Born-Infeld framework is afterwards analysed in both non-relativistic andrelativistic regimes. In the former, for different cases of the couplingricher with respect to mere BI setups between scalar and gauge sectors, wefind that inflationary trajectories are modified, with anisotropy increasing ordecreasing. In particular, a tachyonic solution is studied, allowing for a nonstandard ratio between scalar and gauge matter densities, enhancing sufficientinflation, but with the anisotropy increasing. For the relativistic limit,inflationary trajectories are also modified and anisotropies increase fasterthan in the non-relativistic limit. Finally we discuss how magnetic seed fieldscould evolve in these settings.

Autor: Paulo Vargas Moniz, John Ward


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