Totally geodesic property of the unit tangent sphere bundle with g-natural metrics

In this paper, we consider the tangent bundle of a Riemannian manifold (M, g) with g-natural metrics and among all of these metrics, we specify those with respect to which the unit tangent sphere bundle with induced g-natural metric is totally geodesic. Also, we equip the unit tangent sphere bundle T1M with g-natural contact (paracontact) metric structures, and we show that such structures are totally geodesic K-contact (K-paracontact) submanifolds of TM, if and only if the base manifold (M, g) has positive (negative) constant sectional curvature. Moreover, we establish a condition for g-natural almost contact B-metric structures on T1Msuch that these structures be totally geodesic submanifolds of TM.

ALMOST PARACONTACT STRUCTURES ON TANGENT SPHERE BUNDLE

Using the almost product structure given by Druta, we introduce a metrical framed f(3, -1)-structure on the tangent bundle of a Riemannian manifold. Then by restricting this metrical framed f(3, -1)-structure to the tangent sphere bundle, we obtain an almost metrical paracontact structure on the tangent sphere bundle.

H-CONTACT UNIT TANGENT SPHERE BUNDLES OF FOUR-DIMENSIONAL RIEMANNIAN MANIFOLDS

We study the geometric properties of a base manifold whose unit tangent sphere bundle, equipped with the standard contact metric structure, is H-contact. We prove that a necessary and sufficient condition for the unit tangent sphere bundle of a four-dimensional Riemannian manifold to be H-contact is that the base manifold is 2-stein.

η-EINSTEIN TANGENT SPHERE BUNDLES OF CONSTANT RADII

We study the geometric properties of the base manifold for the tangent sphere bundle of radius r satisfying the η-Einstein condition with the standard contact metric structure. One of the main theorems is that the tangent sphere bundle of the n(≥3)-dimensional locally symmetric space, equipped with the standard contact metric structure, is an η-Einstein manifold if and only if the base manifold is a space of constant sectional curvature [Formula: see text] or [Formula: see text].

AN INTEGRAL FORMULA AND ITS APPLICATION TO NORMAL EULER NUMBER

We establish a general integral formula over sphere, and then apply it to give a geometrical proof of the celebrated topological theorem of Lashof and Smale, which asserts that the tangential degree of the tangent sphere bundle coincides with the normal Euler number for an immersion Mn → E2n of an oriented closed manifold into Euclidean space of twice dimension.