Invariants of CR-manifolds associated with the tangent quadric (Q1358448)

Suppose \(M\) is a real smooth CR-manifold. The author constructs a system of CR-invariants of \(M\) which arise from projective invariants of a tangent quadric to \(M\). There is a description of the group of projective automorphisms of quadrics. Also \textit{A. E. Tumanov} [Math. USSR, Izv. 32, No. 3, 655-662 (1989); translation from Izv. Akad. Nauk USSR, Ser. Mat. 52, No. 3, 651-659 (1988; Zbl 0655.32026)] showed that every CR-map of a \((k,n)\)-quadric into a \((k,n)\)-quadric is given by a rational map whose degree is bounded by a constant depending on \(n\) and \(k\). An estimate for this constant is given by the author.