Generalised nice sets

Abstract

A new combinatorial object, called generalised nice set, is classified up to collineations of the Fano plane. This classification is necessary to find the graded contractions of all the exceptional complex Lie algebras of dimension at least 52, endowed with ${\mathbb{Z}}_2^3$-gradings coming from the octonions. Our classification is of purely combinatorial nature.

41 pages