The Epstein zeta function for a matrix
of a positive definite real quadratic form and
a complex variable with
(where
denotes the real part) is
defined by
(1)
|
where the sum is over all column vectors with integer coordinates and the prime means the summation excludes the origin (Terras 1973). Epstein (1903) derived the analytic continuation, functional equation, and so-called Kronecker limit formula for this function.
Epstein (1903) defined this function in the course of an effort to find the most general possible function satisfying a functional
equation similar to that satisfied by the Riemann
zeta function
(Glasser and Zucker 1980, p. 68).
A slightly different notation is used in theoretical chemistry, where the Epstein zeta function arises in connection with lattice sums.
Let
be a positive definite quadratic form
(2)
|
where
with
,
...
is a symmetric matrix. Then the Epstein zeta function can be defined as
(3)
|
where
and
are arbitrary vectors, the sum
runs over a
-dimensional
lattice, and
is omitted if
is a lattice vector (Glasser and
Zucker 1980, p. 69).