Hubbard-model description of the high-energy spin-spectral-weight distribution in La(2)CuO(4)

The spectral-weight distribution in recent neutron scattering experiments on the parent compound La$_2$CuO$_4$ (LCO), which are limited in energy range to about 450\,meV, is studied in the framework of the Hubbard model on the square lattice with effective nearest-neighbor transfer integral $t$ and on-site repulsion $U$. Our study combines a number of numerical and theoretical approaches, including, in addition to standard treatments, density matrix renormalization group calculations for Hubbard cylinders and a suitable spinon approach for the spin excitations. Our results confirm that the $U/8t$ magnitude suitable to LCO corresponds to intermediate $U$ values smaller than the bandwidth $8t$, which we estimate to be $8t \approx 2.36$ eV for $U/8t\approx 0.76$. This confirms the unsuitability of the conventional linear spin-wave theory. Our theoretical studies provide evidence for the occurrence of ground-state d-wave spinon pairing in the half-filled Hubbard model on the square lattice. This pairing applies only to the rotated-electron spin degrees of freedom, but it could play a role in a possible electron d-wave pairing formation upon hole doping. We find that the higher-energy spin spectral weight extends to about 566 meV and is located at and near the momentum $[\pi,\pi]$. The continuum weight energy-integrated intensity vanishes or is extremely small at momentum $[\pi,0]$. This behavior of this intensity is consistent with that of the spin waves observed in recent high-energy neutron scattering experiments, which are damped at the momentum $[\pi,0]$. We suggest that future LCO neutron scattering experiments scan the energies between 450 meV and 566 meV and momenta around $[\pi,\pi]$.Comment: 23 pages, 5 figure

Certificação e selos de qualidade asseguram requisitos na produção.

Em 2011, o Committee on Fisheries (Cofi) da Food and Agriculture Organization (FAO) comitê de pesca da FAO, órgão da Organização das Nações Unidas (ONU) aprovou o documento que contém as Diretrizes Técnicas para Certificação da Aquicultura, visando ao desenvolvimento, à organização e à implementação de regimes confiáveis de certificação de aquicultura. Os países signatários deverão internalizá-lo e usá-lo como base para adaptar ou criar as normas relacionadas ao tema. O documento abrange questões de saúde e bem-estar animal, segurança alimentar, integridade ambiental e aspectos socioeconômicos

Produção de papel e açúcares a partir de biomassa florestal.

Resumo

Ultraviolet and Infrared Divergences in Implicit Regularization: a Consistent Approach

Implicit Regularization is a 4-dimensional regularization initially conceived to treat ultraviolet divergences. It has been successfully tested in several instances in the literature, more specifically in those where Dimensional Regularization does not apply. In the present contribution we extend the method to handle infrared divergences as well. We show that the essential steps which rendered Implicit Regularization adequate in the case of ultraviolet divergences have their counterpart for infrared ones. Moreover we show that a new scale appears, typically an infrared scale which is completely independent of the ultraviolet one. Examples are given.Comment: 9 pages, version to appear in Mod. Phys. Lett.

Análise comparativa da postura ortostática entre mulheres fisicamente activas e sedentárias

Foi objectivo deste trabalho comparar a postura ortostática entre mulheres fisicamente activas e sedentárias. Foram estudados 60 sujeitos do sexo feminino, saudáveis e não grávidas. Trinta mulheres incluíram o grupo das fisicamente activas (GFA) e outras trinta no grupo das sedentárias (GS). Os sujeitos foram fotografados nos planos sagital direito e esquerdo, frontal anterior e posterior na posição ortostática, com uma câmara digital com uma resolução fotográfica de 10.1 Megapixéis (Exilim, EX-Z29, Casio, Tóquio, Japão). A avaliação postural foi efectuada com recurso a uma técnica fotogramétrica e utilizando um software específico (SAPo, v. 0.86, Universidade de São Paulo, Brasil). Os ângulos Q dos membros inferiores direito e esquerdo foram superiores no GFA do que no GS. A assimetria das omoplatas relativamente à T3 apresentou valores médios superiores no GFA do que no GS. Os alinhamento horizontal da cabeça foi superiores no GFA do que no GS. O alinhamento vertical do corpo foi inferior no GFA do que no GS. Em síntese, o GFA tende apresentar uma postura ortostática que procura promover uma quantidade inferior de esforço e/ou de sobrecarga mecânica sobre o aparelho locomotor do que o GS

Basketball game-related statistics that discriminate between teams season-long success

The aim of the present study was to identify the game-related statistics that discriminate between season-long successful and unsuccessful basketball teams participating in the Spanish Basketball League (LEB1). The sample included all 145 average records per season from the 870 games played between the 2000-2001 and the 2005-2006 regular seasons. The following game-related statistics were gathered from the official box scores of the Spanish Basketball Federation: 2- and 3-point field-goal attempts (both successful and unsuccessful), free-throws (both successful and unsuccessful), defensive and offensive rebounds, assists, steals, turnovers, blocks (both made and received), and fouls (both committed and received). To control for season variability, all results were normalized to minutes played each season and then converted to z-scores. The results allowed discrimination between best and worst teams' performances through the following game-related statistics: assists (SC=0.47), steals (SC=0.34), and blocks (SC=0.30). The function obtained correctly classified 82.4% of the cases. In conclusion, season-long performance may be supported by players' and teams' passing skills and defensive preparation