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A precise definition of reduction of partial differential equations

Renat Z. Zhdanov·Ivan M. Tsyfra·Roman O. Popovych
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Abstract

We give a comprehensive analysis of interrelations between the basic concepts of the modern theory of symmetry (classical and non-classical) reductions of partial differential equations. Using the introduced definition of reduction of differential equations we establish equivalence of the non-classical (conditional symmetry) and direct (Ansatz) approaches to reduction of partial differential equations. As an illustration we give an example of non-classical reduction of the nonlinear wave equation in (1+3) dimensions. The conditional symmetry approach when applied to the equation in question yields a number of non-Lie reductions which are far-reaching generalization of the well-known symmetry reductions of the nonlinear wave equations.

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Renat Z. Zhdanov, Ivan M. Tsyfra, Roman O. Popovych. 2002-07-18. A precise definition of reduction of partial differential equations. https://doi.org/10.1006/jmaa.1999.6511

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