Symbolic Computation of Recursion Operators for Nonlinear Differential-Difference Equations

An algorithm for the symbolic computation of recursion operators for systems of nonlinear differential-difference equations (DDEs) is presented. Recursion operators allow one to generate an infinite sequence of generalized symmetries. The existence of a recursion operator therefore guarantees the complete integrability of the DDE. The algo-rithm is based in part on the concept of dilation invariance and uses our earlier algorithms for the symbolic computation of conservation laws and generalized symmetries. The algorithm has been applied to a number of well-known DDEs, including the Kac-van Moerbeke (Volterra), Toda, and Ablowitz-Ladik lattices, for which recursion opera-tors are shown. The algorithm has been implemented in Mathematica, a leading com-puter algebra system. The package DDERecursionOperator.m is briefly discussed.