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Counterexamples of Friedlander--Iwaniec dual sums conjecture

Number Theory 2026-07-18 v1

Abstract

Let a(n)a(n) and b(n)b(n) be arithmetic sequences, and A(s)=n1a(n)ns,B(s)=n1b(n)ns,A(s)=\sum_{n\ge1}a(n)n^{-s}, \qquad B(s)=\sum_{n\ge1}b(n)n^{-s}, be the two Dirichlet series related by a certain functional equation. Let mm be the \emph{analytic degree} of the functional equation. For x>0x>0 and a positive integer NN, Friedlander and Iwaniec (2005) define the sharply truncated nonlinear dual sum B,D(x,N):=nNnNb(n)nβmcos(2πm(nxD)1/m+π4),\mathcal B_{\ell,D}(x,N) := \sum_{\substack{n\in\mathbb N\\ n\le N}} b(n)n^{-\beta_m} \cos\left( 2\pi m\left(\frac{nx}{D}\right)^{1/m} +\frac{\pi\ell}{4} \right), where D1D\ge1 is the conductor, βm:=m+12m\beta_m:=\frac{m+1}{2m}, and =m32k\ell=m-3-2k is determined by the archimedean weight kk of the functional equation. Their Conjecture 1 predicts that, for every ε>0\varepsilon>0, B,D(x,N)ε,κ(DNx)ε,\mathcal B_{\ell,D}(x,N) \ll_{\varepsilon,\boldsymbol\kappa} (DNx)^\varepsilon, uniformly in the variables xx and NN, with the degree, conductor, and archimedean datum fixed. We give counterexamples to this prediction with A(s)=B(s)=ζ(s)m,  m4A(s)=B(s)=\zeta(s)^m,\; m\geq 4 where ζ(s):=n1ns(Res>1)\zeta(s):=\sum_{n\ge1}n^{-s} \qquad(\operatorname{Re}s>1) is the Riemann zeta function.

Keywords

Cite

@article{arxiv.2607.16695,
  title  = {Counterexamples of Friedlander--Iwaniec dual sums conjecture},
  author = {Khai-Hoan Nguyen-Dang},
  journal= {arXiv preprint arXiv:2607.16695},
  year   = {2026}
}

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