Selberg zeta function
The Selberg zeta-function was introduced by Atle Selberg (1956). It is analogous to the famous Riemann zeta function ζ ( s ) = ∏ p ∈ P 1 1 − p − s {\displaystyle \zeta (s)=\prod _{p\in \mathbb {P} }{\frac {1}{1-p^{-s}}}} where P {\displaystyle \mathbb {P} } is the set of prime numbers.