2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/111537In this paper we prove a vanishing theorem for the contact Ozsvath--Szabo invariants of certain contact 3--manifolds having positive Giroux torsion. We use this result to establish similar vanishing results for contact structures with underlying 3--manifolds admitting either a torus fibration over the circle or a Seifert fibration over an orientable base. We also show -- using standard techniques from contact topology -- that if a contact 3--manifold (Y,ξ) has positive Giroux torsion then there exists a Stein cobordism from (Y,ξ) to a contact 3--manifold (Y,ξ') such that (Y,ξ) is obtained from (Y,ξ') by a Lutz modification.22 pages, 5 figures; rephrased abstract and introductionSymplectic GeometryGeometric Topology57R17; 57R57text