Toward to a generalization of modular invariance of vertex operator algebras into Hilbert type and Siegel type.

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A concept of vertex operator algebras (VOA shortly) has originated from the moonshine vertex operator algebra, which was constructed in order to explain a mysterious relation (the moonshine conjecture) between Monster simple finite group (the largest sporadic finite simple group) and the classical elliptic modular function. Our purpose of this project is to clarify the modular invariance property of VOAs and extend it in multivarables. (1)We found a new construction of the moonshine vertex operator algebra by using Ising models, which offers a new modular invariance in multivariables. Compared with the original construction, our construction is easy and we can apply our construction for many other VOAs. (2)We have shown that C2-condition is enough to get, a modular invariance. Classically, the rationality (completely reducibility of modules) was considered to be more important than C2-condition, but our research has shown that we don't need rationality. (3)We construct an infinitely many VOAs with Euclidian Jordan Algebras as Griess algebras for any complex central charge c. So we construct a candidate of Siegel modular invariance. (4)We found an order formula to determine the automorphism group of VOAs. In our construction, Miyamoto involution plays an essential role and so we can easily get information about the centralizer of Involution in the full automorphism group. The question is if we can determine the automorphism group from it.