ON THE FUNDAMENTAL TONE OF IMMERSIONS AND SUBMERSIONS.

In this paper we obtain lower bound estimates of the spectrum of the Laplace-Beltrami operator on complete submanifolds with bounded mean curvature, whose ambient space admits a Riemannian submersion over a Riemannian manifold with negative sectional curvature. Our main theorem generalizes many previously known estimates and applies for both immersions and submersions. [ABSTRACT FROM AUTHOR]