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Higher moments of arithmetic functions in short intervals: a geometric perspective. (English) Zbl 1472.11255

Summary: We study the geometry associated to the distribution of certain arithmetic functions, including the von Mangoldt function and the Möbius function, in short intervals of polynomials over a finite field \(\mathbb{F}_q\). Using the Grothendieck-Lefschetz trace formula, we reinterpret each moment of these distributions as a point-counting problem on a highly singular complete intersection variety. We compute part of the \(\ell\)-adic cohomology of these varieties, corresponding to an asymptotic bound on each moment for fixed degree \(n\) in the limit as \(q \to \infty \). The results of this paper can be viewed as a geometric explanation for asymptotic results that can be proved using analytic number theory over function fields.

MSC:

11N37 Asymptotic results on arithmetic functions
11R58 Arithmetic theory of algebraic function fields
14F20 Étale and other Grothendieck topologies and (co)homologies
11T55 Arithmetic theory of polynomial rings over finite fields