Equivalence between different classical treatments of the O(N) nonlinear sigma model and their functional Schrodinger equations

In this work we derive the Hamiltonian formalism of the O(N) non-linear sigma model in its original version as a second-class constrained field theory and then as a first-class constrained field theory. We treat the model as a second-class constrained field theory by two different methods: the unconstrained and the Dirac second-class formalisms. We show that the Hamiltonians for all these versions of the model are equivalent. Then, for a particular factor-ordering choice, we write the functional Schrodinger equation for each derived Hamiltonian. We show that they are all identical which justifies our factor-ordering choice and opens the way for a future quantization of the model via the functional Schrodinger representation.Comment: Revtex version, 17 pages, substantial change

Efeito do nivel de saturação de alumínio em solo ácido sobre os danos de Spodoptera frugiperda (J.E.Smith) em milho.

Estudou-se a influencia de niveis de calagem na intensidade dos danos provocados pela lagarta-do-cartucho, S.frugiperda (J.E. Smith), em milho. Foram conduzidos experimentos durante tres anos consecutivos, em parcelas que receberam calagem de modo a manter tres niveis de saturacao de aluminio: nivel toxico (m < 50%), intermediario (m < 20%) e sem aluminio (m < 5%). Foram utilizadas duas cultivares de milho, a BR 136, tolerante a toxidez de aluminio, e a CMS 28, sensivel. Foram tambem utilizadas unidades experimentais infestadas artificialmente com lagartas recem-nascidas, e nao infestadas, controladas com inseticidas granulados aplicados diretamente no cartucho da planta. Independente da cultivar utilizada ou do nivel de fertilidade do solo, as perdas quantitativas ocasionadas a cultura do milho foram de 17,7% (848 kg/ha), considerando uma produtividade maxima, sem o ataque da praga, de 4.792 kg/ha

Thermal dependence of the zero-bias conductance through a nanostructure

We show that the conductance of a quantum wire side-coupled to a quantum dot, with a gate potential favoring the formation of a dot magnetic moment, is a universal function of the temperature. Universality prevails even if the currents through the dot and the wire interfere. We apply this result to the experimental data of Sato et al.[Phys. Rev. Lett. 95, 066801 (2005)].Comment: 6 pages, 3 figures. More detailed presentation, and updated references. Final version

Universal zero-bias conductance through a quantum wire side-coupled to a quantum dot

A numerical renormalization-group study of the conductance through a quantum wire side-coupled to a quantum dot is reported. The temperature and the dot-energy dependence of the conductance are examined in the light of a recently derived linear mapping between the Kondo-regime temperature-dependent conductance and the universal function describing the conductance for the symmetric Anderson model of a quantum wire with an embedded quantum dot. Two conduction paths, one traversing the wire, the other a bypass through the quantum dot, are identified. A gate potential applied to the quantum wire is shown to control the flow through the bypass. When the potential favors transport through the wire, the conductance in the Kondo regime rises from nearly zero at low temperatures to nearly ballistic at high temperatures. When it favors the dot, the pattern is reversed: the conductance decays from nearly ballistic to nearly zero. When the fluxes through the two paths are comparable, the conductance is nearly temperature-independent in the Kondo regime, and a Fano antiresonance in the fixed-temperature plot of the conductance as a function of the dot energy signals interference. Throughout the Kondo regime and, at low temperatures, even in the mixed-valence regime, the numerical data are in excellent agreement with the universal mapping.Comment: 12 pages, with 9 figures. Submitted to PR