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Backlund's explicit bound for N(T)N(T)N(T), T>2T>2T>2

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RiemannVonMangoldt.backlund_bound

by Lucas · Oct 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

analytic-number-theoryriemann-zetazeros-of-zeta

Write N(T)N(T)N(T) for the number of zeros ρ\rhoρ of the Riemann zeta function ζ(s)\zeta(s)ζ(s) with 0<Re⁡ρ<10<\operatorname{Re}\rho<10<Reρ<1 and 0<Im⁡ρ≤T0<\operatorname{Im}\rho\le T0<Imρ≤T, counted with multiplicity. Backlund's explicit bound states that for every real T>2T>2T>2,

∣N(T)−(T2πlog⁡T2π−T2π+78)∣<0.137log⁡T+0.443log⁡log⁡T+4.350.\left|N(T)-\left(\frac{T}{2\pi}\log\frac{T}{2\pi}-\frac{T}{2\pi}+\frac78\right)\right|<0.137\log T+0.443\log\log T+4.350 .​N(T)−(2πT​log2πT​−2πT​+87​)​<0.137logT+0.443loglogT+4.350.

This makes the error term in the Riemann–von Mangoldt formula fully explicit, with numerical constants, and in particular implies the formula itself.

Formalization Note The source PDF prints the constant inside the bracket as −78-\tfrac78−87​. Backlund's theorem and the standard literature (e.g. Titchmarsh, Ch. 9, and Hasanalizade–Shen–Wong 2022) have +78+\tfrac78+87​, matching the expansion N(T)=T2πlog⁡T2π−T2π+78+S(T)+O(1/T)N(T)=\frac{T}{2\pi}\log\frac{T}{2\pi}-\frac{T}{2\pi}+\frac78+S(T)+O(1/T)N(T)=2πT​log2πT​−2πT​+87​+S(T)+O(1/T); this draft uses +78+\tfrac78+87​. The decimal constants are exact rationals (0.137 = 137/1000, etc.). N(T)N(T)N(T) is zetaZeroCount T.

Preamble
import Mathlib
import Definitions.Def_RiemannVonMangoldt_ZeroCounts

open Filter Asymptotics Real
Formal statement
namespace RiemannVonMangoldt

theorem backlund_bound (T : ℝ) (hT : 2 < T) :
    |zetaZeroCount T - (T / (2 * π) * Real.log (T / (2 * π)) - T / (2 * π) + 7 / 8)| <
      0.137 * Real.log T + 0.443 * Real.log (Real.log T) + 4.350 := by sorry

end RiemannVonMangoldt
Source
Wikipedia, "Riemann–von Mangoldt formula", revision oldid=1362774495 (https://en.wikipedia.org/w/index.php?title=Riemann–von_Mangoldt_formula&oldid=1362774495), displayed formula after "Backlund gives an explicit form of the error for all T > 2" (sign of 7/8 corrected to +7/8). R. J. Backlund, Über die Nullstellen der Riemannschen Zetafunktion, Acta Math. 41 (1918) 345–375.
Human review
  • Endorsed by Shuze Chen · Oct 13, 2026

    Confirmed by the moderator at approval.

  • Endorsed by Lucas · Oct 13, 2026

    Confirmed by the mission captain (proposal self-audit).

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