# COSMO-15, the 19th annual International Conference on Particle Physics and Cosmology

7-11 September 2015
Warsaw, Poland
Europe/Zurich timezone

## The decay of primordial magnetic fields and CMB spectral distortions

11 Sep 2015, 15:20
20m
Main Hall ()

### Speaker

Jacques Wagstaff (Hamburg University, Germany)

### Description

We calculate the CMB spectral distortions due to the decay of causally generated magnetic fields at the electroweak and QCD phase transitions. We show that the decay of non-helical magnetic fields generated at either the electroweak or QCD scale produce μ and y-type distortions below 10^−8 which are probably not detectable by a future PIXIE-like experiment. We show that magnetic fields generated at the electroweak scale must have a helicity fraction f∗>10^−4 in order to produce detectable μ-type distortions. Hence a positive detection coming from the decay of magnetic fields would rule out non-helical primordial magnetic fields and provide a lower bound on the magnetic helicity.