The alternating group of degree 6 in the geometry of the Leech lattice and K3 surfaces

The alternating group A6 plays a very special role in the theory of-nite groups [28]. Indeed, A6 is a simple group which is located at a sort of junction of three series of simple non-commutative groups: simple sporadic groups, alternating groups and simple groups of Lie type. More explicitly, there are distinguishe