Low-Temperature Behavior of the Large-U Hubbard Model from   High-Temperature Expansions
  We derive low-temperature properties of the large-U Hubbard model in two and three dimensions from exact series-expansion results for high temperatures. Convergence problems and limited available information prevent a direct or Pade'-type extrapolation. We propose a new method of extrapolation, which is restricted to large U and low hole densities, for which the problem can be mapped on that of a system of weakly interacting holes. In the new formulation an extrapolation down to T=0 can be obtained, but it can be trusted for the presently available series data for kT/t < 0.05 and for hole densities below 0.2 only. Implications for the magnetic phase diagram are discussed. 
D.F.B. ten Haaf, P.W. Brouwer, P.J.H. Denteneer, and J.M.J. van   Leeuwen (Instituut-Lorentz, Leiden University,2300 RA Leid...