Metric-torsion decay of non-adiabatic chiral helical magnetic fields against chiral dynamo action in bouncing cosmological models

Abstract

Metric-torsion effects on chiral massless fermions are investigated in the realm of the adiabatic amplification of cosmological magnetic fields (CMFs) in a general relativistic framework and in the framework of Einstein-Cartan (EC) bouncing cosmologies. In GR the chiral effect is proportional to the Hubble factor and the solution of the dynamo equation leads to an adiabatic magnetic field, while in Einstein-Cartan bouncing cosmology we have non-adiabatic magnetic fields where the breaking of adiabaticity is given by a torsion term. Using a EWPT magnetic field of the order of B seed ∼ 10 24 G at 5 pc scale, we obtain a CMF in EC of the order of 10 −10 G, which is still able to seed a galactic dynamo which amplifies this field up to galactic magnetic fields of four orders of magnitude, which is a mild dynamo. In the case of massive chiral fermions it is shown that torsion actually attenuated the convective dynamo term in the dynamo equation obtained from the QED of an electron-positron pair e − e + . Chiral effects on general relativity may lead to strong magnetic fields of the order of ∼ 10 18 G at the early universe resulting from pure metric effects. Strong magnetic fields of the order of B metric−torsion ∼ 10 8 G may be obtained from very strong seed fields. At 1 Mpc scale of the present universe a galactic dynamo seed of the order of 10 −19 G is found. It is shown in this paper that chiral dynamo effects in the expanded universe can be obtained if one takes into account the speed of the cosmic plasma.

Magnetogenesis in cyclical Universe

“…Bouncing cosmological solutions [41][42][43][44][45][46][47], representing the transition from a contracting to an expanding phase of the Universe, are also a necessary ingredient of cyclic Universe models, but for that purpose, the bouncing phase needs moreover to be combined with the approximately standard cosmological evolution following it (radiation dominated, matter dominated, effective cosmological term dominated phases) and with a turnaround phasethe transition from the expanding to the contracting phase, which happens at the end of each cycle. The problem of magnetogenesis could be one of the problems and limitations of the Big Bang paradigm, and this naturally leads to the program of solving magnetogenesis beyond the Big Bang cosmology, i.e.…”

Spontaneous CPT Violation and Quantum Anomalies in a Model for Matter–Antimatter Asymmetry in the Cosmos

“…The above results invalidate any arguments [53] in of the axial background playing a rôle in the generation of instabilities and thus magnification of the magnetic fields in neutron stars. However the KR torsion might play a non-trivial rôle in the dynamo equation for the generation of magnetic fields [56], and thus affect their strength independent of the CME. We hope to come back to a discussion of such effects in a future work.…”