Theta function

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.

Quotes

 * Theta functions pervade all of mathematics ranging from the theory of partial differential equations, mathematical physics, to algebraic geometry, number theory and more recently to representation theory.