Phase diagram of the extended Hubbard model in one spatial dimension

We report results obtained for the phase diagram and critical behavior of the extended Hubbard model in one spatial dimension at half-filling. We show that umklapp scattering is responsible for the tricritical behavior. We calculate the critical exponents at the tricritical point, and along the critical line separating the charge- and spin-density-wave phases. In addition, using Monte Carlo simulations we estimate the position of the tricritical point to occur at approximately U=1.5 and V=3.1 in units of the hopping energy.