4,621 research outputs found
An analytically solvable model of probabilistic network dynamics
We present a simple model of network dynamics that can be solved analytically
for uniform networks. We obtain the dynamics of response of the system to
perturbations. The analytical solution is an excellent approximation for random
networks. A comparison with the scale-free network, though qualitatively
similar, shows the effect of distinct topology.Comment: 4 pages, 1 figur
Chaos in one-dimensional lattices under intense laser fields
A model is investigated where a monochromatic, spatially homogeneous laser
field interacts with an electron in a one-dimensional periodic lattice. The
classical Hamiltonian is presented and the technique of stroboscopic maps is
used to study the dynamical behavior of the model. The electron motion is found
to be completely regular only for small field amplitudes, developing a larger
chaotic region as the amplitude increases. The quantum counterpart of the
classical Hamiltonian is derived. Exact numerical diagonalizations show the
existence of universal, random-matrix fluctuations in the electronic energy
bands dressed by the laser field. A detailed analysis of the classical phase
space is compatible with the statistical spectral analysis of the quantum
model. The application of this model to describe transport and optical
absorption in semiconductor superlattices submitted to intense infrared laser
radiation is proposed.Comment: 9 pages, RevTex 3.0, EPSF (6 figures), to appear in Europhys. J.
Energy transfer dynamics and thermalization of two oscillators interacting via chaos
We consider the classical dynamics of two particles moving in harmonic
potential wells and interacting with the same external environment (HE),
consisting of N non-interacting chaotic systems. The parameters are set so that
when either particle is separately placed in contact with the environment, a
dissipative behavior is observed. When both particles are simultaneously in
contact with HE an indirect coupling between them is observed only if the
particles are in near resonance. We study the equilibrium properties of the
system considering ensemble averages for the case N=1 and single trajectory
dynamics for N large. In both cases, the particles and the environment reach an
equilibrium configuration at long times, but only for large N a temperature can
be assigned to the system.Comment: 8 pages, 6 figure
The Velocity of Gravitational Waves
We examine the propagation of gravitational waves in the new field theory of
gravitation recently proposed by Novello-De Lorenci-Luciane (NDL). This
examination is done on a solvable case corresponding to a spherically symmetric
static configuration. We show that in NDL theory the velocity of gravitational
waves is lower than light velocity. We point out some consequences of this
result and suggest a possible scenario for its verification
Semiclassical coherent state propagator for systems with spin
We derive the semiclassical limit of the coherent state propagator for
systems with two degrees of freedom of which one degree of freedom is canonical
and the other a spin. Systems in this category include those involving
spin-orbit interactions and the Jaynes-Cummings model in which a single
electromagnetic mode interacts with many independent two-level atoms. We
construct a path integral representation for the propagator of such systems and
derive its semiclassical limit. As special cases we consider separable systems,
the limit of very large spins and the case of spin 1/2.Comment: 19 pages, no figure
Utilização da mandioca na indústria de compensados de madeira.
bitstream/item/28293/1/ComTec80.pd
Índice de Ecossistemas Fluviais (IEF): uma proposta para monitoramento da qualidade de ecossistemas fluviais no Brasil.
O habitat ciliar desempenha um papel fundamental na determinação da saúde geral dos ecossistemas aquáticos . A análise dest e ecossistema em conjunto com os dados de análise s hidrológicas e geomorfoló gi c a s do canal nos permite avaliar e monitorar os ecossistemas fluviais . O objetivo do presente trabalho é descrever o desenvolvimento de um índice de monitoramento de ecossistemas fluviais que pode ser utilizado em campo com a análise de características quantitativas (composição química) e qualitativas ( análise visual do estado hidromorfológico e ecológico ) . O índice foi aplicado na caracterização de duas bacias hidrográficas na região de Ponta Grossa, no Paraná , e foi bastante eficiente como forma de avaliação primária . O índice IEF pode ser considerado uma ferramenta importante p ara gestores e pesquisadores que não possuem recursos para monitor amento de ecossistemas fluviais , para avaliação de bacias hidrográficas, a partir d as condições da vegetação ripá ria (seção 1) e do canal (seção 2)
A conjugate for the Bargmann representation
In the Bargmann representation of quantum mechanics, physical states are
mapped into entire functions of a complex variable z*, whereas the creation and
annihilation operators and play the role of
multiplication and differentiation with respect to z*, respectively. In this
paper we propose an alternative representation of quantum states, conjugate to
the Bargmann representation, where the roles of and
are reversed, much like the roles of the position and momentum operators in
their respective representations. We derive expressions for the inner product
that maintain the usual notion of distance between states in the Hilbert space.
Applications to simple systems and to the calculation of semiclassical
propagators are presented.Comment: 15 page
Quantum Dissipation and Decoherence via Interaction with Low-Dimensional Chaos: a Feynman-Vernon Approach
We study the effects of dissipation and decoherence induced on a harmonic
oscillator by the coupling to a chaotic system with two degrees of freedom.
Using the Feynman-Vernon approach and treating the chaotic system
semiclassically we show that the effects of the low dimensional chaotic
environment are in many ways similar to those produced by thermal baths. The
classical correlation and response functions play important roles in both
classical and quantum formulations. Our results are qualitatively similar to
the high temperature regime of the Caldeira-Leggett model.Comment: 31 pages, 4 figure
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