Simon Fraser University

Abstract: Let s(n) denote the sum of the proper divisors of n, so, e.g., s(4)=1+2=3. A natural number n is called *perfect* if s(n)=n and *amicable* if s(n) =/= n but s(s(n))=n. For example, 6 is a perfect number, and 220 is an amicable number...

Abstract: Graphs and co-graphs (their matroid duals) dominate the structure of Totally Unimodular Matrices, real matrices whose subdeterminants lie in {0, +1, -1}. Thus some results about graph colorings and flows have common generalizations...

Abstract: Given a binary matroid $M$ represented by a binary matrix $A$ we can consider the binary matroid represented by $A$ plus an extra binary row$\\Sigma$. We call this a signed matroid and say that $(M,\\Sigma)$ is arepresentation of the signed...

Abstract: Aquantum walk is a quantum process on graph. It is proposed by Emms, Hancock, Severini and Wilson in 2006, that the spectrum of a matrix based on theamplitudes of walks in the quantum walk, distinguishes strongly regular graphs. We will try...

Abstract: Given a set of directions S \\subseteq {0,1,-1}^2 \\setminus {(0,0)}, we wish to count the number of lattice walks of length n on S restricted to the quarter plane. For most sets S, this amountsto a full generation of all walks of length n...

Abstract: It is a long standing open problem in algebraic combinatorics to compute the Kronecker coefficients of the symmetric group using a combinatorial rule. In this talk I will discuss explicit combinatorial formulae (for 5 new cases) for...