Nonlocal Excitations and 1/8 Singularity in Cuprates

Momentum-dependent excitation spectra of the two-dimensional Hubbard model on the square lattice have been investigated at zero temperature on the basis of the full self-consistent projection operator method in order to clarify nonlocal effects of electron correlations on the spectra. It is found that intersite antiferromagnetic correlations cause shadow bands and enhance the Mott-Hubbard splittings near the half-filling. Furthermore nonlocal excitations are shown to move the critical doping concentration $\delta^{\ast}_{h}$, at which the singular quasiparticle peak is located just on the Fermi level, from $\delta^{\ast}_{h}=0.153$ (the single-site value) to $\delta^{\ast}_{h}=0.123$. The latter suggests the occurance of an instability such as the stripe at $\delta^{\ast}_{h}=1/8$.Comment: 4 pages, 5 figures; to be published in the Journal of Korean Physical Society (ICM12

Cultivar de soja BR-7 (Cariri).

A cultivar de soja BR-27 (Cariri), foi introduzida no Piaui atraves daEMBRAPA/UEPAE, no ano agricola de 1983/84, onde apresentou boas caracteristicas agronomicas para as regioes tropicais, como rendimento de graos, altura de plantas e de insercao das primeiras vagens. A floracao ocorre aos 47 dias e a maturacao aos 122 dias. Recomenda-se o cultivoda BR 27-9 Cariri para o estado do Piaui, onde apresenta boas condicoes de fertilidade de solo e tambem boa distribuicao de chuvas. Deve-se utilizar um espacamento de 0,50 m entre fileiras e uma densidade de 20sementes vaiaveis por metro linear.bitstream/item/95943/1/CT370001.pd