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Ivancevic_Applied-Diff-Geom

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598 <strong>Applied</strong> <strong>Diff</strong>erential <strong>Geom</strong>etry: A Modern Introductionfor example, nonlinear Faraday resonance in a vertically oscillating water,an easy–plane ferromagnet with a combination of a stationary anda high–frequency magnetic fields, and the effect of phase–sensitive amplifierson solitons propagating in optical fibers.(2) Korteveg–de Vries (KdV) equationΨ t = 6ΨΨ x − Ψ xxx ,with Hamiltonian (total conserved energy) given byH KdV =∫ +∞−∞(Ψ 3 + 1 )2 Ψ2 x dx.KdV is related to the ordinary Schrödinger equation by the inversescattering method. KdV is a well–known model of 1D turbulence thatwas derived in various physical contexts, including chemical–reactionwaves, propagation of combustion fronts in gases, surface waves in afilm of a viscous liquid flowing along an inclined plane, patterns inthermal convection, rapid solidification, and others. Its discretizationgives the Lotka–Voltera equationẋ j (t) = x j (t) ( x j+1 (t) − x j−1 (t) ) ,which appears in a model of struggle for existence of biological species.(3) Sine–Gordon (SG) equationΨ tt = Ψ xx − sin Ψ,with Hamiltonian (total conserved enegy) given byH SG =∫ +∞−∞(Ψ2t + Ψ 2 x + cos Ψ ) dx.SG gives one of the simplest models of the unified field theory, can befound in the theory of dislocations in metals, in the theory of Josephsonjunctions and so on. It can be used also in interpreting certain biologicalprocesses like DNA dynamics. Its discretization gives a system ofcoupled pendulums.Discrete solitons exist also in the form of the soliton celular automata(SCA) [Park et al. (1986)]. SCA is a 1(space)+1(time)–dimensional ‘boxand ball system’ made of infinite number of zeros (or, boxes) and finite

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