Lorentzian Kac-Moody algebras with Weyl groups of 2-reflections

Valery Gritsenko, Viacheslav V. Nikulin

We describe a new large class of Lorentzian Kac--Moody algebras. For all ranks, we classify 2-reflective hyperbolic lattices S with the group of 2-reflections of finite volume and…