Description
In 1983, Feigold and Frenkel posed a question about possible relations between affine Lie algebras, hyperbolic Kac--Moody algebras and Siegel modular forms. We give an automorphic answer to this question and its generalization. We classify hyperbolic Borcherds--Kac--Moody superalgebras whose super-denominators define reflective automorphic products of singular weight on lattices of type $2U\oplus L$. We prove that there are exactly 81 affine Lie algebras $g$ which have nice extensions to hyperbolic BKM superalgebras for which the leading Fourier--Jacobi coefficients of super-denominators coincide with the denominators of $g$. We find that 69 of them appear in Schellekens’ list of semi-simple $V_1$ structures of holomorphic CFT of central charge 24, while 8 of them correspond to the $N=1$ structures of holomorphic SCFT of central charge 12 composed of 24 chiral fermions. The 4 extra cases are related to the exceptional modular invariants from nontrivial automorphisms of fusion algebras. This is based on a joint work with Haowu Wang and Brandon Williams.
