2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67869For a Poincare duality space X and a map X -> B, consider the homotopy fiber product X x^B X. If X is orientable with respect to a multiplicative cohomology theory E, then, after suitably regrading, it is shown that the E-homology of X x^B X has the structure of a graded associative algebra. When X -> B is the diagonal map of a manifold X, one recovers a result of Chas and Sullivan about the homology of the free loop space LX.12 pagesAlgebraic TopologyGeometric Topology55N91;57R19 (Primary) 55P10;55B20 (Secondary)text