Resumen de On universal central extensions of precrossed and crossed modules

Daniel Arias Mosquera, José María Casas Sabata, Manuel Ladra González

• We study the connection between universal central extensions in the categories of precrossed and crossed modules. They are compared with several kinds of universal central extensions in the categories of groups, epimorphisms of groups, groups with operators and modules over a group. We study the relationship between the homologies defined in these categories. Applications to relative algebraic K-theory are also obtained.