Spin-isospin density fluctuations in nuclear collisions

The possible build-up of the spin-isospin fluctuation strength in nuclear collisions is investigated. In lack of quantum mechanical methods we rely on assumptions usually applied for heavy ion collisions. Based on a fluid dynamical picture we present our ‘isospin coupling in a nucleon cascade’. Within this framework it is possible to describe the mean isospin value as a function of the number of participants in a heavy ion collision and it is possible to study the effect of neutron excess. Since the pion field couples to the spin-isospin density a substantial size of this quantity gives rise to pion bremsstrahlung, the dominant subthreshold pion production mechanism.