Palatini approach and large-scale magnetogenesis. (arXiv:2110.02632v2 [hep-th] UPDATED)
<a href="http://arxiv.org/find/hep-th/1/au:+Giovannini_M/0/1/0/all/0/1">Massimo Giovannini</a>
Large-scale magnetogenesis is analyzed within the Palatini approach when the
gravitational action is supplemented by a contribution that is nonlinear in the
Einstein-Hilbert term. While the addition of the nonlinear terms does not
affect the scalar modes of the geometry during the inflationary phase, the
tensor-to-scalar ratio is nonetheless suppressed. In this context it is
plausible to have a stiff phase following the standard inflationary stage
provided the potential has a quintessential form. The large-scale magnetic
fields can even be a fraction of the nG over typical length scales of the order
of the Mpc prior to the gravitational collapse of the protogalaxy.
Large-scale magnetogenesis is analyzed within the Palatini approach when the
gravitational action is supplemented by a contribution that is nonlinear in the
Einstein-Hilbert term. While the addition of the nonlinear terms does not
affect the scalar modes of the geometry during the inflationary phase, the
tensor-to-scalar ratio is nonetheless suppressed. In this context it is
plausible to have a stiff phase following the standard inflationary stage
provided the potential has a quintessential form. The large-scale magnetic
fields can even be a fraction of the nG over typical length scales of the order
of the Mpc prior to the gravitational collapse of the protogalaxy.
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