Magnetogenesis in cyclical Universe

Abstract

We propose a simple solution to the magnetogenesis problem based on cyclic cosmology. It is demonstrated that magnetic fields, of sufficient strengths to account for the present observational bounds, can be created in the contracting phase preceding the beginning of the current cosmological cycle. The basic assumption of this model is that the Universe enters a contraction phase essentially empty, characterized by small seed electric fields. We discuss how such small seed electric fields can be naturally created due to charge separation of astrophysical currents during the expansion of the Universe or, alternatively, due to ionization as a consequence of the growth of the effective dark energy contribution reaching the hydrogen atom ionization potential. In this framework, there is no need for any new theoretical additions to explain magnetogenesis, such as new scalar fields or the non-minimal coupling between curvature, scalar fields and the electromagnetic sector. Moreover, the proposed model is general in the sense that it does not assume any specific modified gravity theory to enable the cosmological bounce. When compared to the inflationary magnetogenesis paradigm, the proposed model also has the advantage of not leading to the backreaction and strong coupling problems.