The moduli space of Enriques surfaces and the fake monster Lie superalgebra. 
27 October 1994, corrected 27 January 1995. 

Topology vol. 35 no. 3, 699-710, 1996. 

Richard E. Borcherds,

Mathematics department, Evans Hall #3840, 
University of California at Berkeley, CA 94720-3840 U. S. A. 

MSC numbers: 14J28, 11F55. 

We show that the moduli space of complex Enriques surfaces is an affine 
variety with a copy of the affine line removed. We do this by using the 
denominator function of a generalized Kac-Moody superalgebra (associated 
with superstrings on a 10-dimensional torus) to construct a non-vanishing 
section of an ample line bundle on the moduli space.