Abstract
An exact quantum decimation is performed on an extended Hubbard model for a three-site cluster by taking the partial trace of the Boltzmann factor over states of the central site. The resulting temperature-dependent Hamiltonian for the outer two sites of the cluster contains higher order three- and four-particle interactions, t-J model, pairing and superexchange interactions, and two-particle interactions which are predominantly attractive. Possible implications for high-temperature superconductivity are briefly discussed.