Magnetogenesis from axion and dilaton electromagnetism in torsioned spacetime

TL;DR

This paper explores how torsion and dilaton fields in modified gravity theories can generate primordial magnetic fields, potentially explaining cosmic magnetogenesis and supporting theories involving torsion and axions.

Contribution

It demonstrates that torsion-dilatonic Lagrangians can produce primordial magnetic fields consistent with observational bounds, linking modified gravity theories to magnetogenesis.

Findings

Cosmological magnetic fields of order 10^{-10} G can be generated.

Results align with teleparallel gravity and Einstein-Cartan theories.

Magnetogenesis bounds support torsion-based modified gravity models.

Abstract

Recently much controversy has been shed on BICEP 2 experiments for the concerning this validity or not and a possible set of new experiments to detect primordial inflation and gravitational waves. Since gravitational waves imply the existence of primordial magnetic fields in this context, C Bonvin, R Durrer and R Marteens [Phys Rev Lett (2014)] have tried to associate the presence of primordial magnetic fields to BICEP 2 by making use of CMB tensor modes. Here we show that by considering torsion dilatonic lagrangean one obtains cosmological magnetic fields of the order of $B\sim{10^{-10}G}$ which may seed galactic dynamos. Actually this new result came out of a mistake of a recent paper published by myself in JCAP (2014). These results are more in accordance with Bamba results [JCAP (2014)] in the context of teleparallel theory of gravity with Einstein's distant parallelism and torsion. These results also support Einstein-Cartan sort of theories of gravity from well-known recent data. Another example which supports the use of modified gravities with torsion to investigate magnetogenesis is the alternative exampleof using axions with transmutation into torsion to obtain cosmic magnetic seed bound of $10^{-12}G$.This coincides with the lower bound obtained by Barrow et al [Phys Rev D (2012)] in the interval of $10^{-20}G$ to $10^{-12}G$ in Friedmann universes.