The group of the Mondello BLT-sets

Abstract

A BLT-set is a set of (q+1) points of a Q(4,q) parabolic quadric with a collinearity condition. There are many infinite families of BLT-sets, all of which have had their stabilizers computed except for the Mondello BLT-sets of Penttila. Following an introduction to, and survey of BLT-sets and their related geometries, we compute the group stabilizing the Mondello BLT-sets.