Tchebotarev density theorem
Let be any finite Galois extension of number fields
with Galois group
. For any conjugacy class
, the subset of prime ideals which are unramified in and satisfy the property
has analytic density , where denotes the Artin symbol at .
Note that the conjugacy class of is independent of the choice of prime lying over , since any two such choices of primes are related by a Galois automorphism and their corresponding Artin symbols are conjugate
by this same automorphism.