To prove that our moment matching algorithm results in a nearly minimal number of phases, we need to know the minimal number of phases needed to well-represent an input distribution, , by an acyclic PH distribution (namely, OPT()). Thus, we will provide a formal characterization of the set of distributions, , that are well-represented by an -phase acyclic PH distribution for each .

Takayuki Osogami 2005-07-19