Using the dynamical cluster approximation and quantum monte carlo we
calculate the single-particle spectra of the Hubbard model with next-nearest
neighbor hopping t′. In the underdoped region, we find that the pseudogap
along the zone diagonal in the electron doped systems is due to long range
antiferromagnetic correlations. The physics in the proximity of (0,π) is
dramatically influenced by t′ and determined by the short range correlations.
The effect of t′ on the low energy ARPES spectra is weak except close to the
zone edge. The short range correlations are sufficient to yield a pseudogap
signal in the magnetic susceptibility, produce a concomitant gap in the
single-particle spectra near (π,π/2) but not necessarily at a location in
the proximity of Fermi surface.Comment: 5 pages, 4 figure