In this post I’ll finally get to the “condensation of singularities” argument that was invented by Lindner and Seidel in the (free abelian) group context and generalized by Spakula and Willett to metric spaces.  (Calling this “condensation of singularities” is my idea, but it does seem to me to get at what is going on.  I can’t help feeling that there should be a way of replacing some of the explicit constructions with an abstract argument involving the Baire category theorem.  But I have not yet been able to come up with one.) Continue reading →