  The leitmotif of these Notes is the idea of a vertex operator algebra (VOA)
and the relationship between VOAs and elliptic functions and modular forms.
This is to some extent analogous to the relationship between a finite group and
its irreducible characters; the algebraic structure determines a set of
numerical invariants, and arithmetic properties of the invariants provides
feedback in the form of restrictions on the algebraic structure. One of the
main points of these Notes is to explain how this works, and to give some
reasonably interesting examples.
