First Chen Inequality for General Warped Product Submanifolds of a Riemannian Space Form and Applications; [Premi�re in�galit� de Chen pour des produits tordus de sous-vari�t�s d�un espace forme riemannien et applications]

Abstract

In this paper, the first Chen inequality is proved for general warped product submanifolds in Riemannian space forms, this inequality involves intrinsic invariants (?-invariant and sectional curvature) controlled by an extrinsic one (the mean curvature vector), which provides an answer for Chen�s Problem 1 relating to establish simple relationships between the main extrinsic invariants and the main intrinsic invariants of a submanifold. As a geometric application, this inequality is applied to derive a necessary condition for the immersed submanifold to be minimal in Riemannian space forms, which presents a partial answer for the well-known problem proposed by S.S. Chern, Problem 2. For further research directions, we address a couple of open problems; namely Problem 3 and Problem 4. � 2023 ISTE OpenScience � Published by ISTE Ltd. London, UK.