We consider resonant photon-axion conversions that may occur in the regions of the Universe where the effective photon mass is equal to the axion mass in the presence of magnetic fields. We review various contributions into the effective photon and typical values of this mass that can exist in the clusters of galaxies and the intergalactic medium. We also examine what is known about magnetic fields in the regions of possible resonances. Finally, we apply these considerations to obtain new constraints on the couple constant of the axion in the mass range below 10^-11 eV.
Zoom link: https://cern.zoom.us/j/98399499159?pwd=MkkyQWNWNnc0OTBoemhXYU1qZ2NMQT09
Meeting ID: 983 994 99159