Rowmotion Markov chains

Abstract

Rowmotion is a certain well-studied bijective operator on the distributive lattice $J\left(P\right)$ of order ideals of a finite poset P. We introduce the rowmotion Markov chain $M_{J\left(P\right)}$ by assigning a probability $p_x$ to each $x\in P$ and using these probabilities to insert randomness into the original definition of rowmotion. More generally, we introduce a very broad family of toggle Markov chains inspired by Striker's notion of generalized toggling. We characterize when toggle Markov chains are irreducible, and we show that each toggle Markov chain has a remarkably simple stationary distribution.

We also provide a second generalization of rowmotion Markov chains to the context of semidistrim lattices. Given a semidistrim lattice L, we assign a probability $p_j$ to each join-irreducible element j of L and use these probabilities to construct a rowmotion Markov chain $M_L$. Under the assumption that each probability $p_j$ is strictly between 0 and 1, we prove that $M_L$ is irreducible. We also compute the stationary distribution of the rowmotion Markov chain of a lattice obtained by adding a minimal element and a maximal element to a disjoint union of two chains.

We bound the mixing time of $M_L$ for an arbitrary semidistrim lattice L. In the special case when L is a Boolean lattice, we use spectral methods to obtain much stronger estimates on the mixing time, showing that rowmotion Markov chains of Boolean lattices exhibit the cutoff phenomenon.