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# Communications in Number Theory and Physics

## Volume 12 (2018)

### Number 2

### 51 constructions of the Moonshine module

Pages: 305 – 334

DOI: http://dx.doi.org/10.4310/CNTP.2018.v12.n2.a3

#### Author

#### Abstract

We show using Borcherds products that for any fixed-point free automorphism of the Leech lattice satisfying a “no massless states” condition, the corresponding cyclic orbifold of the Leech lattice vertex operator algebra is isomorphic to the Monster vertex operator algebra. This induces an “orbifold duality” bijection between algebraic conjugacy classes of fixed-point free automorphisms of the Leech lattice satisfying this condition and algebraic conjugacy classes of non-Fricke elements in the Monster. We use the duality to show that non-Fricke Monstrous Lie algebras are Borcherds–Kac–Moody Lie algebras, and prove a refinement of Norton’s Generalized Moonshine conjecture: the ambiguous constants relating generalized moonshine Hauptmoduln under conjugation and modular transformations are necessarily roots of unity.We also describe a class of rank $2$ Borcherds–Kac–Moody Lie algebras attached to the Conway group.

Received 18 July 2017

Accepted 28 February 2018