• Integrable Systems in Four Dimensions Associated with Six-Folds in Gr(4, 6) 

      Doubrov, Boris; Ferapontov, Evgeny V; Kruglikov, Boris; Novikov, Vladimir S (Journal article; Tidsskriftartikkel, 2018-01-29)
      Let Gr(d, n) be the Grassmannian of <i>d</i>-dimensional linear subspaces of an <i>n</i>-dimensional vector space <i>V</i>. A submanifold <i>X</i> ⊂ Gr(<i>d, n</i>) gives rise to a differential system Σ(X) that governs <i>d</i>-dimensional submanifolds of <i>V</i> whose Gaussian image is contained in <i>X</i>. We investigate a special case of this construction where <i>X</i> is a six-fold in Gr(4, ...
    • Second-order PDEs in four dimensions with half-flat conformal structure 

      Berjawi, S.; Ferapontov, Eugene V.; Kruglikov, Boris; Novikov, Vladimir S (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-29)
      We study second-order partial differential equations (PDEs) in four dimensions for which the conformal structure defined by the characteristic variety of the equation is half-flat (self-dual or anti-self-dual) on every solution. We prove that this requirement implies the Monge–Ampère property. Since half-flatness of the conformal structure is equivalent to the existence of a non-trivial dispersionless ...