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

L. V. Bogdanov, B. G. Konopelchenko
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.
View original: http://arxiv.org/abs/1208.6129