For questions about $\theta$ functions (special functions of several complex variables).
In mathematics, $\theta$ functions are special functions of several complex variables. They are important in many areas, including the theories of abelian varieties and moduli spaces, and of quadratic forms. They have also been applied to soliton theory. When generalized to a Grassmann algebra, they also appear in quantum field theory. The most common form of $\theta$ function is that occurring in the theory of elliptic functions.