A CLASS OF ALMOST CONTACT METRIC MANIFOLDS AND DOUBLE-TWISTED PRODUCTS

Abstract

We determine the Chinea-Gonzales class of almost contact metricmanifolds locally realized as double-twisted product manifolds I ×(λ1,λ2)F ,I being an open interval, F an almost Hermitian manifold and λ1, λ2smoothpositive functions. Several subclasses are studied. We also give an explicitexpression for the cosymplectic defect of any manifold in the considered classand derive several consequences in dimensions 2n + 1 ≥ 5. Explicit formulasfor two algebraic curvature tensor fields are obtained. In particular cases, thisallows to state interesting curvature relations