OAI.StandardMapEntropy.exists_critical_scale_sequence: intermediate lemma from OpenAI, Positive Metric Entropy for the Standard Map at Large Parameters

Proved

OAI.StandardMapEntropy.exists_critical_scale_sequence

by dbenbenn · Oct 26, 2026 · Mathlib 0df444a (Lean v4.33.1)

openai-math

An intermediate lemma of the split of OpenAI's proof of OAI.StandardMapEntropy.main_entropy, carved from OpenAI's openai/math development for this platform. The statement and its proof are OpenAI's (OpenAI, Positive Metric Entropy for the Standard Map at Large Parameters, OpenAI Math Release, September 23, 2026, result family 146, github.com/openai/math, Apache License 2.0); in Lean it is the declaration OAI.StandardMapEntropy.exists_critical_scale_sequence of lean/OAI/Dynamics/StandardMap/StandardMap/CriticalSequence.lean at commit adc7f12, ported to Lean 4.33.1 and Mathlib 0df444a.

The statement, as published (namespace OAI.StandardMapEntropy, with open MeasureTheory Set, open scoped ENNReal BigOperators, open MeasureTheory Filter Set, open scoped Topology Classical):

lemma exists_critical_scale_sequence (η : ℝ) (hη : 0<η)
    (hbad : ∀ K : ℝ, ∃ k : ℝ, K≤k ∧ BadGrowth η k) : Nonempty CriticalScaleSequence

Definitions. The statement is written with OAI.StandardMapEntropy.BadGrowth and OAI.StandardMapEntropy.CriticalScaleSequence (definitions bundle OAIQ2St000 of this split).

Used by. The proof of OAI.StandardMapEntropy.eventually_meanDeficit_small of this split imports it.

Preamble

import Mathlib
import Definitions.Def_OAIQ2St000

Formal statement

section

attribute [-instance] _root_.OAI.StandardMapEntropy.CriticalScaleSequence.instRegularNonAffineArrayMulti _root_.OAI.StandardMapEntropy.CriticalScaleSequence.instRegularNonAffineArrayTerminal _root_.OAI.StandardMapEntropy.CriticalScaleSequence.multi_dilate_local _root_.OAI.StandardMapEntropy.CriticalScaleSequence.multi_terminal_local
set_option linter.all false
set_option linter.unusedVariables false
set_option linter.unusedTactic false
set_option linter.unreachableTactic false

namespace OAI

open MeasureTheory Set
open scoped ENNReal BigOperators

open MeasureTheory Filter Set
open scoped Topology Classical
namespace StandardMapEntropy
lemma exists_critical_scale_sequence (η : ℝ) (hη : 0<η)
    (hbad : ∀ K : ℝ, ∃ k : ℝ, K≤k ∧ BadGrowth η k) : Nonempty CriticalScaleSequence := by
  sorry
end StandardMapEntropy

end OAI
end

Source

OpenAI, Positive Metric Entropy for the Standard Map at Large Parameters, OpenAI Math Release, September 23, 2026, https://github.com/openai/math (result family 146; paper: https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/preprints/Positive-Metric-Entropy-for-the-Standard-Map-at-Large-Parameters-September-23-2026/paper.pdf; Apache License 2.0); Lean: https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/OAI/Dynamics/StandardMap/StandardMap/CriticalSequence.lean (declaration OAI.StandardMapEntropy.exists_critical_scale_sequence)

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