On Universal Inverse Monoids with the $F$-Inverse Property

Abstract: An inverse monoid $M$ is called $F$-inverse if each $\sigma$-class of $M$, where $\sigma$ is the minimum group congruence of $M$, has a maximum element with respect to the natural order of $M$. Upon Kinyon's observation made in 2018 that $F$-inverse monoids form a variety in the enriched signature involving an additional unary operation mapping each element of $M$ to the maximum element of its $\sigma$-class, a separate theory of $F$-inverse monoids is developing in recent years, greatly aided by a recent solution to the long-standing problem of Henckell and Rhodes on finite $F$-inverse covers of finite inverse monoids. In particular, a description of the universal object $F(G,X)$ in the class of $X$-generated $F$-inverse monoids with a prescribed maximum group image was provided recently. In this paper we introduce yet another object $M_F(G,X)$, the one that is universal for inverse monoids (so, not in the enriched signature) that are $X$-generated with maximum group image a quotient of $G$ and which happen to be $F$-inverse. We obtain presentations and geometric models based on Cayley graphs of groups for such inverse monoids. As an application, we are able to characterise all one-relator special inverse monoids $\mathrm{Inv}\langle{X}\,|\,{w=1}\rangle$ with a cyclically reduced relator word $w$ enjoying the $F$-inverse property.