The fake monster formal group
  The main result of this paper is the construction of ``good'' integral forms for the universal enveloping algebras of the fake monster Lie algebra and the Virasoro algebra. As an application we construct formal group laws over the integers for these Lie algebras. We also prove a form of the no-ghost theorem over the integers, and use this to verify an assumption used in the proof of the modular moonshine conjectures. 
Richard E. Borcherds