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Relabeling a strict Hlawka failure so its total-sum size is largest

Proved
HlawkaSchatten.DiagonalConstruction.exists_failure_total_largest

by savarin · Sep 28, 2026 · Mathlib 0df444a (Lean v4.33.1)

counterexamplehlawka-schattenlp-normnormalizationrelabeling

Let ι\iotaι be a finite index set and, for a real exponent ppp, write ∥v∥p:=(∑i∈ι∣vi∣p)1/p\|v\|_p := \big(\sum_{i\in\iota} |v_i|^p\big)^{1/p}∥v∥p​:=(∑i∈ι​∣vi​∣p)1/p for the coordinate power-sum functional of a real vector v:ι→Rv:\iota\to\mathbb Rv:ι→R, and call ∥v∥p\|v\|_p∥v∥p​ the ppp-size of vvv (it is a norm for p≥1p\ge1p≥1; this argument does not use the triangle inequality). For real vectors x,y,z:ι→Rx,y,z:\iota\to\mathbb Rx,y,z:ι→R and a real constant KKK, put

S=∥x∥p+∥y∥p+∥z∥p,T=∥x+y+z∥p,P=∥x+y∥p+∥x+z∥p+∥y+z∥p,S = \|x\|_p+\|y\|_p+\|z\|_p,\qquad T = \|x+y+z\|_p,\qquad P = \|x+y\|_p+\|x+z\|_p+\|y+z\|_p,S=∥x∥p​+∥y∥p​+∥z∥p​,T=∥x+y+z∥p​,P=∥x+y∥p​+∥x+z∥p​+∥y+z∥p​,

and call (x,y,z)(x,y,z)(x,y,z) a strict Hlawka failure at level KKK when

(2K−1)S+T−KP<0;(2K-1)S+T-KP<0;(2K−1)S+T−KP<0;

equivalently — since this quantity equals K(2S−P)−(S−T)K(2S-P)-(S-T)K(2S−P)−(S−T) — when (x,y,z)(x,y,z)(x,y,z) violates the inequality S−T≤K(2S−P)S-T\le K(2S-P)S−T≤K(2S−P) that the construction seeks to establish.

Given K≥1K\ge 1K≥1 and a strict Hlawka failure (x,y,z)(x,y,z)(x,y,z) at level KKK, this theorem produces a new triple u,v,w:ι→Ru,v,w:\iota\to\mathbb Ru,v,w:ι→R that is again a strict Hlawka failure at level KKK, and for which the total-sum size dominates every individual size:

∥u∥p≤∥u+v+w∥p,∥v∥p≤∥u+v+w∥p,∥w∥p≤∥u+v+w∥p.\|u\|_p\le \|u+v+w\|_p,\qquad \|v\|_p\le \|u+v+w\|_p,\qquad \|w\|_p\le \|u+v+w\|_p.∥u∥p​≤∥u+v+w∥p​,∥v∥p​≤∥u+v+w∥p​,∥w∥p​≤∥u+v+w∥p​.

This is the relabeling step in normalizing a hypothetical counterexample to the diagonal Hlawka bound: among the four sizes ∥x∥p,∥y∥p,∥z∥p,∥−(x+y+z)∥p\|x\|_p,\|y\|_p,\|z\|_p,\|{-(x+y+z)}\|_p∥x∥p​,∥y∥p​,∥z∥p​,∥−(x+y+z)∥p​ associated with the zero-sum quadruple x,y,z,−(x+y+z)x,y,z,-(x+y+z)x,y,z,−(x+y+z), it arranges for the total-sum size ∥u+v+w∥p\|u+v+w\|_p∥u+v+w∥p​ to be at least each of the three retained singleton sizes, while preserving the fact that the relabeled triple is still a strict failure.

Formalization Note No hypothesis constrains the exponent ppp: the argument is a purely algebraic rearrangement of the four sizes and of the deficit quantity above, valid for every real ppp. Accordingly the ppp-size is an arbitrary power-sum functional here, not necessarily a norm.

Preamble
import Definitions.Def_HlawkaSchatten_DiagonalConstruction_Basic
import Definitions.Def_HlawkaSchatten_DiagonalConstruction_Normalization
import Mathlib.Analysis.InnerProductSpace.Basic
import Mathlib.Analysis.InnerProductSpace.Dual
import Mathlib.Analysis.Normed.Lp.PiLp
import Mathlib.Analysis.SpecialFunctions.Pow.Continuity
import Mathlib.Tactic.Abel

/-
Copyright (c) 2026 Ezzeri Esa. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Ezzeri Esa
-/

/-! # Relabeling and normalization of a strict counterexample -/


variable {ι : Type*} [Fintype ι]

open HlawkaSchatten.DiagonalConstruction
Formal statement
theorem HlawkaSchatten.DiagonalConstruction.exists_failure_total_largest {p K : ℝ} (hK : 1 ≤ K)
    (x y z : ι → ℝ) (hfail : hlawkaDeficit p K x y z < 0) :
    ∃ u v w : ι → ℝ, hlawkaDeficit p K u v w < 0 ∧
      lpNorm p u ≤ lpNorm p (u + v + w) ∧
      lpNorm p v ≤ lpNorm p (u + v + w) ∧
      lpNorm p w ≤ lpNorm p (u + v + w) := by sorry
Source
https://github.com/savarin/hlawka-schatten/blob/79aa498bfcf7b22bd91d771fb32ec278e2d4704b/HlawkaSchatten/DiagonalConstruction/Normalization.lean#L49-L81
Human review
  • Endorsed by Shuze Chen · Sep 29, 2026

    Confirmed by the moderator at approval.

  • Endorsed by savarin · Sep 29, 2026

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

  • Endorsed by marwahaha · Sep 30, 2026

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