A random walk on the indecomposable summands of tensor products of modular representations of $\mathrm{SL}_2(\mathbb{F}_p)$

Abstract: In this paper we introduce a novel family of Markov chains on the simple representations of $\mathrm{SL}_2(\mathbb{F}_p)$ in defining characteristic, defined by tensoring with a fixed simple module and choosing an indecomposable non-projective summand. We show these chains are reversible and find their connected components and their stationary distributions. We draw connections between the properties of the chain and the representation theory of $\mathrm{SL}_2(\mathbb{F}_p)$, emphasising symmetries of the tensor product. We also provide an elementary proof of the decomposition of tensor products of simple $\mathrm{SL}_2(\mathbb{F}_p)$-representations.