Generalized notions of symmetry of ODEs and reduction procedures

This paper describes the notion of sigma-symmetry, which extends the one of lambda-symmetry, and its application to reduction procedures of systems of ordinary differential equations (ODEs) and of dynamical systems (DS) as well. We also consider orbital symmetries, which give rise to a different form of reduction of DS. Finally, we discuss how DS can be transformed into higher order ODEs, and how these symmetry properties of the DS can be transferred into reduction properties of the corresponding ODEs. Many examples illustrate the various situations. Copyright (C) 2013 John Wiley & Sons, Ltd.