Cycle-free cuts of mutual rank probability relations

summary:It is well known that the linear extension majority (LEM) relation of a poset of size $n≥9$ can contain cycles. In this paper we are interested in obtaining minimum cutting levels $\alpha_m$ such that the crisp relation obtained from the mutual rank probability relation by setting to $0$ its elements smaller than or equal to $\alpha_m$, and to $1$ its other elements, is free from cycles of length $m$. In a first part, theoretical upper bounds for $\alpha_m$ are derived using known transitivity properties of the mutual rank probability relation. Next, we experimentally obtain minimum cutting levels for posets of size $n≤13$. We study the posets requiring these cutting levels in order to have a cycle-free strict cut of their mutual rank probability relation. Finally, a lower bound for the minimum cutting level $\alpha_4$ is computed. To accomplish this, a family of posets is used that is inspired by the experimentally obtained $12$-element poset requiring the highest cutting level to avoid cycles of length $4$