2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/68598In this work we define a relative version of the flux homomorphism, introduced by Calabi in 1969, for a symplectic manifold. We use it to study (the universal cover of) the group of symplectomorphisms of a symplectic manifold leaving a Lagrangian submanifold invariant. We show that some quotients of this group are stable under symplectic reduction.9 pages, corrected typosSymplectic Geometry53D22, 53D12 (Primary), 53D20 (Secondary)text