Diagnosing structure and evolution of clusters with neutron star binaries

A key problem in using binaries as a tool for diagnosing cluster evolution is that the tool itself is not very well understood. The theory of binary evolution, despite real successes that can be exploited, has serious problems in many areas relevant to cluster evolution. At least as important but often neglected are connective problems, which arise when theoretical model binaries need to be related to observed classes of object, which often requires poorly understood parts of their physics which can be quite irrelevant to their bulk properties. I shall discuss these issues in general briefly, and then illustrate them with the specific example of X-ray binaries and millisecond pulsars.