Modelling the non-thermal emission from galaxy clusters
  We discuss the relevant processes for the relativistic electrons in the ICM and the possible mechanisms responsible for the production of these electrons. We focus on the origin of the radio halos giving some of the observational diagnostics which may help in discriminating among the different models proposed so far. Finally, we briefly discuss the discrepancy between the value of the magnetic field assuming an inverse Compton (IC) origin of the hard X-ray emission (HXR) and that obtained from Faraday Rotation Measurements (RM). 
G. Brunetti (Istituto di Radioastronomia del CNR, Bologna, Italy)