Isospin effects in heavy-ion reactions: Results from transport theories

We discuss recent studies, within the framework of transport theories, on heavy ion reactions between charge asymmetric systems, from low up to Fermi energies. We focus on isospin sensitive observables, aiming at extracting information on the density dependence of the isovector part of the nuclear effective interaction and of the nuclear symmetry energy. Results are critically reviewed, also trying to establish a link, when possible, between the outcome of different transport models