Making holes in second symmetric products
by
José G. Anaya
Instituto de Matemáticas, UNAM.

Let Z be a unicoherent topological space and let z be an element of Z. We say that z makes a hole in Z if Z-{z} is not unicoherent.

For a given a topological space Z, the second symmetric products is the space consisting of all nonempty subsets of Z, having at most two elements, with the Vietoris topology.

In this talk we present which elements of the second symmetric product of a tree make a hole.

Date received: April 19, 2007