SEMI-INVARIANT $\xi ^{\bot}$-SUBMANIFOLDS OF GENERALIZED QUASI-SASAKIAN MANIFOLDS

Abstract

A structure on an almost contact metric manifold is defined as a generalization of well-known cases: Sasakian, quasi-Sasakian, Kenmotsu and cosymplectic. This was suggested by a local formula of Eum [9]. Then we consider a semi-invariant $\xi^{\bot}$-submanifold of a manifold endowed with such a structure and two topics are studied: the integrability of distributions defined by this submanifold and characterizations for the totally umbilical case. In particular we recover results of Kenmotsu [11], Eum [9,10] and Papaghiuc [16].