Resumen de On the idempotency of the set function
In 1980, Bellamy asked: If X and Y are indecomposable continua, is T idempotent on their product? Even for only the closed sets of their product? (see Problem 164 of the Houston Problem Book). We present a negative answer to the first question by showing that the set function T is not idempotent on the product of two continua one of which is indecomposable. In particular, T is not idempotent on the product of two indecomposable continua. The second question remains open
