Published online by Cambridge University Press: 20 November 2018
We define a notion of $p$ -adic measure on Artin
$n$ -stacks that are of strongly finite type over the ring of
$p$ -adic integers.
$p$ -adic measure on schemes can be evaluated by counting points on the reduction of the scheme modulo
${{p}^{n}}$ . We show that an analogous construction works in the case of Artin stacks as well if we count the points using the counting measure defined by Toën. As a consequence, we obtain the result that the Poincaré and Serre series of such stacks are rational functions, thus extending Denef's result for varieties. Finally, using motivic integration we show that as
$p$ varies, the rationality of the Serre series of an Artin stack defined over the integers is uniform with respect to
$p$ .