Physics of the pseudogap phase of high Tc cuprates, or, RVB meets umklapp

It is argued that the dominant feature of the phase diagram of the high T-c cuprates is the crossover to the pseudogap phase in the energy (temperature) region E(T). We argue that this scale is determined by the effective anti-ferromagnetic interaction which we calculate to be J(eff) = J(superexchange) - xt where x is the hole percentage and t the hopping integral. (C) 2002 Published by Elsevier Science.