Professor Lakshmanan Sriramkumar (IIT Madras)

Inflationary magnetogenesis: Effects due to non-trivial dynamics

The primordial magnetic fields are generated during inflation by breaking the conformal invariance of the electromagnetic action by introducing a coupling to the inflaton. Often, a parity violating term is also added to the action to generate helical magnetic fields. In this talk, I will first illustrate that sharp features in the scalar power spectrum generated due to departures from slow roll inflation inevitably lead to strong features in the power spectra of the electromagnetic fields. I will also point out that, in single field inflationary models, the strong features in the spectra of the electromagnetic fields can be undone only at the cost of severe fine-tuning of the non-conformal coupling function. Thereafter, I will demonstrate that such challenges can be circumvented in two field inflationary models (with suitably chosen coupling functions) to arrive at spectra of magnetic fields of the required strength and shape. Lastly, I will discuss the evolution of the quantum state associated with the Fourier modes of the electromagnetic field during inflation. I will show that violation of parity leads to an enhancement of the squeezing amplitude and the quantum discord associated with one of the two states of polarization. I will conclude the talk with a short summary and outlook.