Transverse Riemann-Lorentz type-changing metrics with tangent radical

Abstract

Consider a smooth manifold with a smooth metric which changes bilinear type on a hypersurface Σ and whose radical line field is everywhere tangent to Σ. We describe two natural tensors on Σ and use them to describe “integrability conditions” which are similar to the Gauss–Codazzi conditions. We show that these forms control the smooth extendibility to Σ of ambient curvatures.