• Differential invariants of Kundt waves 

      Kruglikov, Boris; McNutt, David Duncan; Schneider, Eivind (Peer reviewed; Journal article, 2019-07)
      Kundt waves belong to the class of spacetimes which are not distinguished by their scalar curvature invariants. We address the equivalence problem for the metrics in this class via scalar differential invariants with respect ...
    • A mathematical approach to Wick rotations 

      Helleland, Christer (PhD thesis UiS;536, Doctoral thesis, 2020-09)
      In this thesis we define Wick-rotations mathematically using pseudo-Riemannian geometry, and relate Wick-rotations to real geometric invariant theory (GIT). We discover some new results concerning the existence of Wick ...
    • On a class of integrable systems of Monge-Ampère type 

      Doubrov, Boris; Ferapontov, Eugene V.; Kruglikov, Boris; Novikov, Vladimir (Journal article; Peer reviewed, 2017-06)
      We investigate a class of multi-dimensional two-component systems of Monge-Ampère type that can be viewed as generalisations of heavenly type equations appearing in a self-dual Ricci-flat geometry. Based on the Jordan-Kronecker ...
    • Second-Order PDEs in 3D with Einstein–Weyl Conformal Structure 

      Berjawi, S.; Ferapontov, E.V.; Kruglikov, Boris; Novikov, V.S. (Peer reviewed; Journal article, 2021)
      Einstein–Weyl geometry is a triple (D,g,ω) where D is a symmetric connection, [g] is a conformal structure and ω is a covector such that ∙ connection D preserves the conformal class [g], that is, Dg=ωg ; ∙ trace-free part ...