Radio Halos, cluster mergers and the role of future LOFAR observations
  A radio bimodality is observed in galaxy clusters: a fraction of clusters
host giant radio halos while the majority of clusters do not show evidence of
diffuse cluster-scale radio emission. Present data clearly suggest that the
radio bi-modality has a correspondence in terms of dynamical state of the
hosting clusters. I will report on these evidences in some details and discuss
the role of cluster mergers in the generation of giant radio halos and their
evolution. Finally I will report on expectations on the statistical properties
of radio halos assuming that the emitting electrons are re-accelerated by
merger-turbulence, and discuss the role of incoming LOFAR surveys.
