Exact Solution of the Isovector Proton Neutron Pairing Hamiltonian
  The complete exact solution of the T=1 neutron-proton pairing Hamiltonian is presented in the context of the SO(5) Richardson-Gaudin model with non-degenerate single-particle levels and including isospin-symmetry breaking terms. The power of the method is illustrated with a numerical calculation for $^{64}$Ge for a $pf+g_{9/2}$ model space which is out of reach of modern shell-model codes. 
J. Dukelsky, V. G. Gueorguiev, P. Van Isacker, S. Dimitrova, B. Errea,   S. Lerma H