2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/62542These are notes of a mini-course given at Dennisfest in June 2001. The goal of these notes is to give a self-contained survey of deformation quantization, operad theory, and graph homology. Some new results related to "String Topology" and cacti are announced in Section 2.7.22 pages, 10 figures; In the revised version, a few minor errors are corrected, including some signs for the A_infty operad and algebrasQuantum AlgebraHigh Energy Physics - TheoryAlgebraic TopologyGeometric Topology18D50 (primary), 14H10, 53D55, 55P48, 58D15 (secondary)text