Algebraic Combinatorics Seminar - Nadia Lafrenière

Title: The spectrum of the random-to-below Markov chain

Abstract:

The random-to-below shuffle of a deck of cards consists of removing any card randomly (with uniform probability), and inserting it anywhere below (with uniform probability). When looking at the eigenvalues of its transition matrix, they all seem to be rational and positive. This is surprising for a non-symmetric matrix, and suggests some combinatorial interpretation. We give a recursive explanation that involves standard Young tableaux and makes connection with the well studied top-to-random shuffle.