ICE-TCS seminar: Michael Albert
DATE/TIME: Tuesday, 9 June 2015 at 2pm
PLACE: Room V1.02
SPEAKER: Michael Albert (University of Otago, New Zealand; WWW: http://www.cs.otago.ac.nz/staff/michael.html)
TITLE: Catalan coincidences
ABSTRACT: The Catalan numbers arise in counting combinatorial structures in an enormous variety of contexts, so themselves are exemplary of the notion of "combinatorial coincidence". I will discuss enumerative coincidences that arise between naturally defined subcollections in a particular "Catalan universe". Such coincidences are first discovered computationally and then systematically classified according to some rules derived from observation. Since it turns out that from a set of (roughly) 4^n potentially different sequences, fewer than (2.5)^n actually arise, calling these coincidence ("a remarkable concurrence of events or circumstances without apparent causal connection") is perhaps a misnomer.
(joint work with Mathilde Bouvel, CNRS and University of Zurich)