Asymptotic second moment of Dirichlet $L$-functions along a thin coset

Fuente: arXiv
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Autori principali: Garcia, Bradford, Young, Matthew P.
Natura: Preprint
Pubblicazione: 2023
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author Garcia, Bradford
Young, Matthew P.
author_facet Garcia, Bradford
Young, Matthew P.
contents We prove an asymptotic formula for the second moment of central values of Dirichlet $L$-functions restricted to a coset. More specifically, consider a coset of the subgroup of characters modulo $d$ inside the full group of characters modulo $q$. Suppose that $ν_p(d) \geq ν_p(q)/2$ for all primes $p$ dividing $q$. In this range, we obtain an asymptotic formula with a power-saving error term; curiously, there is a secondary main term of rough size $q^{1/2}$ here which is not predicted by the integral moments conjecture of Conrey, Farmer, Keating, Rubinstein, and Snaith. The lower-order main term does not appear in the second moment of the Riemann zeta function, so this feature is not anticipated from the analogous archimedean moment problem. We also obtain an asymptotic result for smaller $d$, with $ν_p(q)/3 \leq ν_p(d) \leq ν_p(q)/2$, with a power-saving error term for $d$ larger than $q^{2/5}$. In this more difficult range, the secondary main term somewhat changes its form and may have size roughly $d$, which is only slightly smaller than the diagonal main term.
format Preprint
id arxiv_https___arxiv_org_abs_2312_08482
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Asymptotic second moment of Dirichlet $L$-functions along a thin coset
Garcia, Bradford
Young, Matthew P.
Number Theory
11M06
We prove an asymptotic formula for the second moment of central values of Dirichlet $L$-functions restricted to a coset. More specifically, consider a coset of the subgroup of characters modulo $d$ inside the full group of characters modulo $q$. Suppose that $ν_p(d) \geq ν_p(q)/2$ for all primes $p$ dividing $q$. In this range, we obtain an asymptotic formula with a power-saving error term; curiously, there is a secondary main term of rough size $q^{1/2}$ here which is not predicted by the integral moments conjecture of Conrey, Farmer, Keating, Rubinstein, and Snaith. The lower-order main term does not appear in the second moment of the Riemann zeta function, so this feature is not anticipated from the analogous archimedean moment problem. We also obtain an asymptotic result for smaller $d$, with $ν_p(q)/3 \leq ν_p(d) \leq ν_p(q)/2$, with a power-saving error term for $d$ larger than $q^{2/5}$. In this more difficult range, the secondary main term somewhat changes its form and may have size roughly $d$, which is only slightly smaller than the diagonal main term.
title Asymptotic second moment of Dirichlet $L$-functions along a thin coset
topic Number Theory
11M06
url https://arxiv.org/abs/2312.08482