On conformally flat hypersurfaces, curved flats and cyclic systems

Abstract

It will be shown that suitable “Gaus maps” associated to a conformally flat hypersurface inS n+1 (n≥3) yield normal congruences of circles having a whole 1-parameter family of conformally flat orthogonal hypersurfaces. However such a “cyclic system” is not uniquely associated to a conformally flat hypersurface. The key idea is to show that these Gaus maps are “curved flats” in a pseudo Riemannian symmetric space. Additionally, in this context some characterizations of 3-dimensional conformally flat hypersurfaces arise with a new flavour. The curved flat approach allows us to handle conformally flat hypersurfaces in the context of integrable system theory.