The continuum spectrum of the 4N system : Results and challenges

The recent calculation of the four nucleon continuum spectrum are reviewed. Faddeev-Yakubovsky equations in configuration space have been solved for the four nucleon system with special interest in their scattering states. We present results concerning the structure of the first $^4$He, scattering states in different (T,S) channels including the first inelatic threshold N+3N$\to$NN+NN and the n-t cross section using realistic potentials