Coherent State Path Integrals in the Weyl Representation

We construct a representation of the coherent state path integral using the Weyl symbol of the Hamiltonian operator. This representation is very different from the usual path integral forms suggested by Klauder and Skagerstan in \cite{Klau85}, which involve the normal or the antinormal ordering of the Hamiltonian. These different representations, although equivalent quantum mechanically, lead to different semiclassical limits. We show that the semiclassical limit of the coherent state propagator in Weyl representation is involves classical trajectories that are independent on the coherent states width. This propagator is also free from the phase corrections found in \cite{Bar01} for the two Klauder forms and provides an explicit connection between the Wigner and the Husimi representations of the evolution operator.Comment: 23 page

Tecnologia para produção orgância de cenoura consorciada com alface em Sergipe.

bitstream/CPATC/19935/1/ct-50.pd

Tecnologia para biodegradação da casca de coco sem gerar outros resíduos.

bitstream/CPATC/19770/1/f_07_2007.pdfExiste o documento impresso

Tecnologia para biodegradação da casca de coco seco e de outros resíduos do coqueiro.

bitstream/item/158629/1/ct-46.pd

Perfil de distribuição de água de miniaspersor Rondo XL da "Plastro", em irrigação de hortas comunitárias.

O manejo adequado de um sistema de irrigação localizada visando obter ificiência de uso de água, requer a determinação do perfil de distribuição de água dos emissores utilizados em condições de campo. O propósito deste trabalho foi avaliar o desempenho do miniaspersor Rondo XL da Plastro, utilizado na irrigação de hortas comunitárias. Foram testados os sistemas de irrigação instalados na comunidade de Tancão (município de Tremendal) e de Lagoa do Mato (município de Jânio Quadros) todos compreendidos pela área de abrangência do Pró-Gavião, visando a determinação, do coeficiente de uniformidade e do perfil de distribuição de água do emissor na superfície do solo. Foi observado um maior valor do coeficiente de uniformidade CU relacionado à faixa de pressão entre 244,80 a 280,50 kPa. Por outro lado, o Coeficiente de Uniformidade de Christiansen CUC mostrou-se maior quando relacionado à faixa de pressão entre 336,0 a 408,0 kPa

Emergence of Hierarchy on a Network of Complementary Agents

Complementarity is one of the main features underlying the interactions in biological and biochemical systems. Inspired by those systems we propose a model for the dynamical evolution of a system composed by agents that interact due to their complementary attributes rather than their similarities. Each agent is represented by a bit-string and has an activity associated to it; the coupling among complementary peers depends on their activity. The connectivity of the system changes in time respecting the constraint of complementarity. We observe the formation of a network of active agents whose stability depends on the rate at which activity diffuses in the system. The model exhibits a non-equilibrium phase transition between the ordered phase, where a stable network is generated, and a disordered phase characterized by the absence of correlation among the agents. The ordered phase exhibits multi-modal distributions of connectivity and activity, indicating a hierarchy of interaction among different populations characterized by different degrees of activity. This model may be used to study the hierarchy observed in social organizations as well as in business and other networks.Comment: 13 pages, 4 figures, submitte

Fluctuating local moments, itinerant electrons and the magnetocaloric effect: the compositional hypersensitivity of FeRh

We describe an ab-initio Disordered Local Moment Theory for materials with quenched static compositional disorder traversing first order magnetic phase transitions. It accounts quantitatively for metamagnetic changes and the magnetocaloric effect. For perfect stoichiometric B2-ordered FeRh, we calculate the transition temperature of the ferromagnetic-antiferromagnetic transition to be $T_t =$ 495K and a maximum isothermal entropy change in 2 Tesla of $|\Delta S|= 21.1$ J~K$^{-1}$~kg$^{-1}$. A large (40\%) component of $|\Delta S|$ is electronic. The transition results from a fine balance of competing electronic effects which is disturbed by small compositional changes - e.g. swapping just 2\% Fe of `defects' onto the Rh sublattice makes $T_t$ drop by 290K. This hypersensitivity explains the narrow compositional range of the transition and impurity doping effects.Comment: 11 pages, 4 figure

Immunization and Aging: a Learning Process in the Immune Network

The immune system can be thought as a complex network of different interacting elements. A cellular automaton, defined in shape-space, was recently shown to exhibit self-regulation and complex behavior and is, therefore, a good candidate to model the immune system. Using this model to simulate a real immune system we find good agreement with recent experiments on mice. The model exhibits the experimentally observed refractory behavior of the immune system under multiple antigen presentations as well as loss of its plasticity caused by aging.Comment: 4 latex pages, 3 postscript figures attached. To be published in Physical Review Letters (Tentatively scheduled for 5th Oct. issue