On Darboux-integrable semi-discrete chains
Journal of Physics A: Mathematical and Theoretical
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A differential-difference equation d/dx t(n + 1, x) = f (x, t(n, x), t(n + 1, x), d/dx t(n, x)) with unknown t(n, x) depending on the continuous and discrete variables x and n is studied. We call an equation of such kind Darboux integrable if there exist two functions (called integrals) F and I of a finite number of dynamical variables such that DxF = 0 and DI = I, where Dx is the operator of total differentiation with respect to x and D is the shift operator: Dp(n) = p(n + 1). It is proved that the integrals can be brought to some canonical form. A method of construction of an explicit formula for a general solution to Darboux-integrable chains is discussed and such solutions are found for a class of chains. © 2010 IOP Publishing Ltd.