Resumen de On Unions and Intersections of Simply Connected Planar Sets

Umed H. Karimov, Dusan Repovs, Matjaz Zeljko

• We construct several simple examples of planar compacta which show that without additional conditions, a theorem of Breen and a direct generalization of the Seifert-van Kampen theorem fail. We give answers to two conjectures of Bogatyi and a partial solution to his third conjecture. We give a counterexample to a statement in the classical survey paper by Danzer¿Grünbaum¿Klee, related to Molnár¿s result on intersections of simply connected planar sets