This article proves that the immersions of compact manifolds into a fixed compact Riernannian manifold, with bounds on the second fundamental forms and either the diameter or volume of the induced metrics, fall into only finitely many topological types.
FORMULATION OF THE RESULTCheeger's finiteness theorem [-1] yields control over the diffeomorphism class of a compact Riemannian manifold, given bounds on its geometric invariants. The purpose of this paper is to prove an analogous result for immersions of compact manifolds into a fixed Riemannian manifold.Suppose that N is a Riemannian manifold, and f: M ---, N andf': M' ---, N are immersions of compact manifolds into N. DEFINITION 0.1. The immersions f and f' are said to be equivalent if there is a diffeomorphism ~p: M--, M' and a homotopy F: M x [-0, 1]--, N with Fo = f' o ~p, F1 = f, and F, an immersion for any t ~ [0, 1]. F is called a regular homotopy. Associated with an immersion f: M --, N are: the normal bundle vM of M in N, the second fundamental form l-I: TM ® TM -, vM, and Riemannian invariants of the metric on M induced by the immersion, e.g. the volume and diameter of M. The main result is the following. THEOREM 0.2. Let N be a compact Riemannian manifold (without boundary), B, d, and v three positive constants, and J the set of all immersions f: M --, N satisfying: 1. M is a compact manifold (without boundary) 2. I III <<. B, where IH[ is the pointwise operator norm of the second fundamental form, and 3. either diam (M) <<. d or vol(M) ~< v.
J contains only finitely many equivalence classes of immersions.A similar result can be given when N is a homogeneous complete Riemannian manifold, by minor modifications of the argument to be given here.Theorem 0.2 probably reflects a compactness result, in much the same way Geometriae Dedicata 33: [153][154][155][156][157][158][159][160][161] 1990.