The generation of helical magnetic field in a viable scenario of Inflationary Magnetogenesis

Understand

We study the generation of helical magnetic fields in a model of inflationary magnetogenesis which is free from the strong coupling and back-reaction problems.

• To generate helical magnetic fields, we add an $f^2 \tilde{F}^{\mu\nu} F_{\mu\nu}$ term to the lagrangian of Ratra model.
• The strong coupling and back-reaction problems are avoided if we take a particular behaviour of coupling function $f$, in which $f$ increases during inflation and decreases post inflation to reheating.
• The generated magnetic field is fully helical and has a blue spectrum, $d\rho_B/d\ln k \propto k^4$.