Phase diagram of the Hubbard model: Beyond the dynamical mean field M. Jarrell, Th. Maier, M. H. Hettler and A. N. Tahvildarzadeh Europhys. Lett., 56 4 (2001) 563-569 Published online: 01 December 2003 DOI: 10.1209/epl/i2001-00557-x