PhD Thesis Proposal Defence "Counting Combinatorial Structures in Circulant Graphs" by Mr. Yiu Cho Leung Abstract: Circulants graphs are a well-studied subclass of regular graphs, partially because they model many practical computer network topologies. In this proposal, we focus on counting different combinatorial structures in circulant graphs with constant jumps and non-constant jumps. Our goal is to derive counting formulas in 'n' (the number of vertices). The combinatorial structures addressed include Spanning trees, Hamiltonian cycles, directed cycle covers and more. It was known that the number of spanning trees in constant-jump circulant graphs satisfy recurrences relation with constant coefficients. The proofs were algebraic in structure and only worked for constant jump circulants and only for spanning trees. In this proposal we discuss general combinatorial techniques for counting different types of structures in circulants, both with constant and non-constant jumps. We will also extend our approach of counting to count structures in grid graphs and tori. Date: Friday, 1 December 2006 Time: 3:00p.m.-5:00p.m. Venue: Room 4480 lifts 25-26 Committee Members: Dr. Mordecai Golin (Supervisor) Dr. Cunsheng Ding (Chairperson) Dr. Sunil Arya Dr. Siu Wing Cheng **** ALL are Welcome ****