Bounding the degree of generic sharp transitivity

TL;DR

This paper establishes an upper bound on the degree of generic sharp transitivity for permutation groups of finite Morley rank, advancing the Borovik-Cherlin conjecture under specific stabilizer conditions.

Contribution

It proves that such groups satisfy t ≤ r+2 when stabilizers are L-groups, providing progress on classifying highly transitive groups of finite Morley rank.

Findings

Bound t ≤ r+2 for generic sharp t-transitivity under stabilizer conditions

Progress on Borovik-Cherlin conjecture for finite Morley rank groups

Analysis of actions of alternating groups and simple groups of rank 6

Abstract

We show that a generically sharply $t$-transitive permutation group of finite Morley rank on a set of rank $r$ satisfies $t\le r+2$ provided the pointwise stabilizer of a generic $(t-1)$-tuple is an $L$-group, which holds, for example, when this stabilizer is solvable or when $r\le 5$. This makes progress on the Borovik-Cherlin conjecture that every generically $(r+2)$-transitive permutation group of finite Morley rank on a set of rank $r$ is of the form $\operatorname{PGL}_{r+1}(F)$ acting naturally on $\mathbb{P}^r(F)$. Our proof is assembled from three key ingredients that are independent of the main theorem - these address actions of $\operatorname{Alt}(n)$ on $L$-groups of finite Morley rank, generically $2$-transitive actions with abelian point stabilizers, and simple groups of rank $6$.