Séminaire / Seminar GReCO |
| « Inflationary magnetogenesis: Effects due to non-trivial dynamics » |
|
L. Sriramkumar |
| The primordial magnetic fields are generated during inflation by breaking the conformal invariance of the electromagnetic action through a coupling to the inflaton. Often, a parity violating term is also added to generate helical magnetic fields. I will first show that departures from slow roll inflation, which generate sharp features in the scalar power spectrum, inevitably lead to strong features in the power spectra of the electromagnetic fields as well. We point out that, in single-field models of inflation, the strong features in the spectra of electromagnetic fields can be undone only at the cost of severe fine-tuning. We find that such challenges can be circumvented in two-field models (with suitably chosen non-conformal coupling functions) to arrive at spectra of magnetic fields of the required strength and shape. Thereafter, I will discuss the evaluation of the three-point cross-correlation between the curvature perturbations and magnetic fields in slow roll and ultra slow roll inflation, and discuss their behavior in the squeezed limit wherein a consistency relation is expected to be valid. Lastly, I will describe the evolution of the quantum state associated with the Fourier modes of the electromagnetic field during inflation. I will show that the violation of parity leads to an enhancement of the squeezing amplitude and quantum discord associated with one of the two states of polarization. I will conclude the talk with a short summary and outlook. |
|
lundi 16 juin 2025 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |