Grassmannians Gr(N-1,N+1), closed differential N-1 forms and N-dimensional integrable systems

Abstract

Integrable flows on the Grassmannians Gr(N-1,N+1) are defined by the requirement of closedness of the differential N-1 forms ${\Omega }_{N-1}$ of rank N-1 naturally associated with Gr(N-1,N+1). Gauge-invariant parts of these flows, given by the systems of the N-1 quasi-linear differential equations, describe coisotropic deformations of (N-1)-dimensional linear subspaces. For the class of solutions which are Laurent polynomials in one variable these systems coincide with N-dimensional integrable systems such as Liouville equation (N=2), dispersionless Kadomtsev-Petviashvili equation (N=3), dispersionless Toda equation (N=3), Plebanski second heavenly equation (N=4) and others. Gauge invariant part of the forms ${\Omega }_{N-1}$ provides us with the compact form of the corresponding hierarchies. Dual quasi-linear systems associated with the projectively dual Grassmannians Gr(2,N+1) are defined via the requirement of the closedness of the dual forms ${\Omega }_{N-1}^{\star }$. It is shown that at N=3 the self-dual quasi-linear system, which is associated with the harmonic (closed and co-closed) form ${\Omega }_2$, coincides with the Maxwell equations for orthogonal electric and magnetic fields.

26 pages, references added

References in corpus (3)

• On the solutions of the dKP equation: nonlinear Riemann Hilbert problem, longtime behaviour, implicit solutions and wave breaking
• Coisotropic deformations of associative algebras and dispersionless integrable hierarchies
• `Interpolating' differential reductions of multidimensional integrable hierarchies

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• Self-dual Einstein spaces and the general heavenly equation. Eigenfunctions as coordinates
• Dispersionless (3+1)-dimensional integrable hierarchies
• Projective differential geometry of multidimensional dispersionless integrable hierarchies