Recursion Operators and Nonlocal Symmetries for Integrable rmdKP and rdDym Equations

We find direct and inverse recursion operators for integrable cases of the rmdKP and rdDym equations. Also, we study actions of these operators on the contact symmetries and find shadows of nonlocal symmetries of these equations

Structure of Symmetry Groups via Cartan's Method: Survey of Four Approaches

In this review article we discuss four recent methods for computing Maurer-Cartan structure equations of symmetry groups of differential equations. Examples include solution of the contact equivalence problem for linear hyperbolic equations and finding a contact transformation between the generalized Hunter-Saxton equation and the Euler-Poisson equation.Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA

Integrable dispersionless PDE in 4D, their symmetry pseudogroups and deformations

We study integrable non-degenerate Monge-Ampere equations of Hirota type in 4D and demonstrate that their symmetry algebras have a distinguished graded structure, uniquely determining the equations. This is used to deform these heavenly type equations into new integrable PDE of the second order with large symmetry pseudogroups. We classify the obtained symmetric deformations and discuss self-dual hyper-Hermitian geometry of their solutions, which encode integrability via the twistor theory.Comment: This version is updated with an appendix about multi-component extensions of the integrable equations. Our deformations can be considered as reductions of such extensions (as they are reductions of the self-duality equation), but we stress that second order deformations carry the natural geometry which encodes integrability. We also expanded the introduction a bi