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81.
82.
Sorella S Martins GB Becca F Gazza C Capriotti L Parola A Dagotto E 《Physical review letters》2002,88(11):117002
Using computational techniques, it is shown that pairing is a robust property of hole-doped antiferromagnetic insulators. In one dimension and for two-leg ladder systems, a BCS-like variational wave function with long-bond spin singlets and a Jastrow factor provides an accurate representation of the ground state of the t-J model, even though strong quantum fluctuations destroy the off-diagonal superconducting long-range order in this case. However, in two dimensions it is argued-and numerically confirmed using several techniques, especially quantum Monte Carlo-that quantum fluctuations are not strong enough to suppress superconductivity. 相似文献
83.
M. Madalena Martins 《BIT Numerical Mathematics》1982,22(1):73-78
With the definition of generalized diagonal dominant matrices we improve the known results about the intervals of convergence of the (AOR) method for linear systems. We consider this problem for different kinds of matrices and we get some important results forH-matrices.Supported by Instituto Nacional de Investigação Cientifica. 相似文献
84.
85.
E.?BrigattiEmail author J. S.?Sá Martins I.?Roditi 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(4):529-532
We use a microscopic model of population dynamics, a modified version
of the well known Penna model, to study some aspects of microevolution. This
research is motivated by recent reports on the effect of selective hunting on the
gene pool of bighorn sheep living in the Ram Mountain region, in Canada. Our
model finds a sharp transition in the structure of the gene pool as some
threshold for the number of animals hunted is reached. 相似文献
86.
The linear conductance of a molecular conductor oscillating between two metallic leads is investigated numerically both for Hubbard interacting and noninteracting electrons. The molecule-leads tunneling barriers depend on the molecule displacement from its equilibrium position. The results present an interesting interference which leads to a conductance dip at the electron-hole symmetry point that could be experimentally observable. It is shown that this dip is caused by the destructive interference between the purely electronic and phonon-assisted tunneling channels, which are found to carry opposite phases. When an internal vibrational mode is also active, the electron-hole symmetry is broken but a Fano-like interference is still observed. 相似文献
87.
E.?BrigattiEmail author J.?S.?Sá Martins I.?Roditi 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,42(3):431-434
We investigate the scaling properties of the Penna model, which has become a popular tool for the study of population dynamics and evolutionary problems in recent years. We find that the model generates a normalised age distribution for which a simple scaling rule is proposed, that is able to reproduce qualitative features for all genome sizes.Received: 9 October 2004, Published online: 23 December 2004PACS:
87.23.Cc Population dynamics and ecological pattern formation - 89.75.Da Systems obeying scaling laws - 05.10.Ln Monte Carlo methods 相似文献
88.
Ergodic dynamics in a natural threshold system 总被引:1,自引:0,他引:1
Numerical simulations suggest that certain driven, dissipative mean-field threshold systems, including earthquake models, can be characterized by statistical properties often associated with ergodic dynamics, in the same sense as stochastic Brownian motion. We applied a fluctuation metric proposed by Thirumalai and Mountain [Phys. Rev. E 47, 479 (1993)]] for statistically stationary systems and find that the natural earthquake fault system in California demonstrates similar ergodic dynamics. 相似文献
89.
Duarte MF Martins F Fernandez MT Langley GJ Rodrigues P Barros MT Costa ML 《Rapid communications in mass spectrometry : RCM》2003,17(9):957-962
A series of derivatives of 2-azidoacetic acid and 2-azidoacetone were synthesized and their behaviour under electron ionization conditions was investigated. This paper reports the electron ionization fragmentation mechanisms for five aliphatic alpha-carbonyl azides, which were clarified by accurate mass measurements and B/E linked scans. The substituent influences the abundance and the nature of the ions resulting from the molecular ion fragmentation. 相似文献
90.
Rundle PB Rundle JB Tiampo KF Martins JS McGinnis S Klein W 《Physical review letters》2001,87(14):148501
Earthquake faults occur in interacting networks having emergent space-time modes of behavior not displayed by isolated faults. Using simulations of the major faults in southern California, we find that the physics depends on the elastic interactions among the faults defined by network topology, as well as on the nonlinear physics of stress dissipation arising from friction on the faults. Our results have broad applications to other leaky threshold systems such as integrate-and-fire neural networks. 相似文献