Dirichlet L-function

Definition

A Dirichlet L-function is a meromorphic function obtained as the analytic continuation of the Dirichlet series of the Dirichlet character.

The corresponding Dirichlet series is termed a Dirichlet L-series, and the Dirichlet L-series as well as the function are denoted $L(\chi ,s)$ where $\chi$ is the character and $s$ is the argument.

$L(\chi ,s):=\sum _{n\in \mathbb {N} }{\frac {\chi (n)}{n^{s}}}=\prod _{p\in \mathbb {P} }{\frac {1}{1-\chi (p)p^{-s}}}$,

where $\mathbb {P}$ is the set of all prime numbers. The equality follows from the Euler product formula.