1 research outputs found
N^N^N does not satisfy Normann's condition
We prove that the Kleene-Kreisel space N^N^N does not satisfy Normann's
condition. A topological space is said to fulfil Normann's condition, if
every functionally closed subset of is an intersection of clopen sets. The
investigation of this property is motivated by its strong relationship to a
problem in Computable Analysis. D. Normann has proved that in order to
establish non-coincidence of the extensional hierarchy and the intensional
hierarchy of functionals over the reals it is enough to show that N^N^N fails
the above condition.Comment: 10 page