Lattice Hamiltonian approach to the massless Schwinger model: precise   extraction of the mass gap
  We present results of applying the Hamiltonian approach to the massless Schwinger model. A finite basis is constructed using the strong coupling expansion to a very high order. Using exact diagonalization, the continuum limit can be reliably approached. This allows to reproduce the analytical results for the ground state energy, as well as the vector and scalar mass gaps to an outstanding precision better than 10^{-6} %. 
Krzysztof Cichy, Agnieszka Kujawa-Cichy, Marcin Szyniszewski
hep-lat