Non thermal emission from clusters of galaxies: the importance of a
  joint LOFAR/Simbol-X view
  Deep radio observations of galaxy clusters have revealed the existence of
diffuse radio sources ("halos" and "relics") related to the presence of
relativistic electrons and weak magnetic fields in the intracluster volume. I
will outline our current knowledge about the presence and properties of this
non-thermal cluster component. Despite the recent progress made in
observational and theoretical studies of the non-thermal emission in galaxy
clusters, a number of open questions about its origin and its effects on the
thermo-dynamical evolution of galaxy clusters need to be answered. I will show
the importance of combining galaxy cluster observations by new-generation
instruments such as LOFAR and Simbol-X. A deeper knowledge of the non-thermal
cluster component, together with statistical studies of radio halos and relics,
will allow to test the current cluster formation scenario and to better
constrain the physics of large scale structure evolution.
