Lattice-integrality of certain group-invariant integral forms in vertex   operator algebras
  Certain vertex operator algebras have integral forms (integral spans of bases which are closed under the countable set of products). It is unclear when they (or integral multiples of them) are integral as lattices under the natural bilinear form on the VOA. We show that lattice-integrality may be arranged under some hypotheses, including cases of integral forms invariant by finite groups. In particular, there exists a lattice-integral Monster-invariant integral form in the Moonshine VOA. 
Chongying Dong and Robert L. Griess Jr
math.GR math.RT