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230 space groups: the exact 230, 219, and 65 counts

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LeanEval.Geometry.SpaceGroupsProblem.space_groups

by xuanji · Sep 6, 2026 · Mathlib 0df444a (Lean v4.33.1)

discrete-geometrygroup-theory

Consider all subgroups of the affine isometry group of R3\mathbb R^3R3 satisfying the finite-displacement discreteness condition and containing translations by three linearly independent vectors, as specified in the accompanying definitions. Write COP(3)C_{\mathrm{OP}}(3)COP​(3) for their number of classes under conjugation by affine maps of positive linear determinant, C(3)C(3)C(3) for the number under arbitrary invertible affine conjugacy, and COP,only(3)C_{\mathrm{OP,only}}(3)COP,only​(3) for the number under the first relation after restricting to groups whose every isometry has positive linear determinant. Then the single goal is the conjunction

COP(3)=230∧C(3)=219∧COP,only(3)=65.C_{\mathrm{OP}}(3)=230\quad\land\quad C(3)=219\quad\land\quad C_{\mathrm{OP,only}}(3)=65.COP​(3)=230∧C(3)=219∧COP,only​(3)=65.

The third number counts the Sohncke subfamily. All three numbers are cardinalities in the extended natural numbers of sets of class subsets, so the equalities assert finiteness as well as exact values. This is the unchanged LeanEval benchmark assertion, not just the length of a list of named space groups.

Formalization Note. The imported definition bundle preserves the source declarations verbatim. The declaration is an unproved statement placeholder, not a submitted proof. It is the sole theorem item; there are no milestones or auxiliary theorem items.

Preamble
import Mathlib
import Definitions.Def_LeanEval_SpaceGroups_Definitions
Formal statement
namespace LeanEval
namespace Geometry
namespace SpaceGroupsProblem

theorem space_groups :
    crystallographicCountOP 3 = 230 ∧
      crystallographicCount 3 = 219 ∧
        crystallographicCountOPOnly 3 = 65 := by
  sorry

end SpaceGroupsProblem
end Geometry
end LeanEval
Source
LeanEval v1, statement revision 1, problem space_groups_230; LeanEval/Geometry/SpaceGroups.lean, LeanEval.Geometry.SpaceGroupsProblem.space_groups, repository commit 296b7491ec989d21bcf8636a9a69231a1e5d1d25: https://github.com/leanprover/lean-eval/blob/296b7491ec989d21bcf8636a9a69231a1e5d1d25/LeanEval/Geometry/SpaceGroups.lean . Metadata: manifests/problems/space_groups_230.toml at the same commit. Background: Oliver Knill, Some Fundamental Theorems in Mathematics, section 94 (Crystallography), printed p. 41, version last updated June 25, 2023, https://people.math.harvard.edu/~knill/graphgeometry/papers/fundamental.pdf . The exact LeanEval definitions, not the background prose alone, govern this target.
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What the Lean code literally says, in plain math · gpt-6-astra

In Euclidean space R3\mathbb{R}^3R3, let C\mathcal CC be the collection of subgroups GGG of the group of bijective affine isometries satisfying both of these conditions: for every x∈R3x\in\mathbb{R}^3x∈R3 and every real ε>0\varepsilon>0ε>0, the set {g∈G:dist⁡(g(x),x)≤ε}\{g\in G:\operatorname{dist}(g(x),x)\leq\varepsilon\}{g∈G:dist(g(x),x)≤ε} is finite; and there exist three linearly independent vectors v1,v2,v3v_1,v_2,v_3v1​,v2​,v3​ such that, for each iii, some g∈Gg\in Gg∈G satisfies g(x)=x+vig(x)=x+v_ig(x)=x+vi​ for every x∈R3x\in\mathbb{R}^3x∈R3. For G,H∈CG,H\in\mathcal CG,H∈C, write G∼HG\sim HG∼H when there exists an invertible affine map φ:R3→R3\varphi:\mathbb{R}^3\to\mathbb{R}^3φ:R3→R3 such that {φ∘g∘φ−1:g∈G}=H\{\varphi\circ g\circ\varphi^{-1}:g\in G\}=H{φ∘g∘φ−1:g∈G}=H, viewing both sides as sets of affine maps, and write G∼+HG\sim_+HG∼+​H when such a φ\varphiφ can be chosen with strictly positive determinant of its linear part. Let C+\mathcal C_+C+​ consist of those G∈CG\in\mathcal CG∈C for which every g∈Gg\in Gg∈G has strictly positive determinant of its linear part. The theorem asserts simultaneously that the collection of distinct subsets {{H∈C:G∼+H}:G∈C}\{\{H\in\mathcal C:G\sim_+H\}:G\in\mathcal C\}{{H∈C:G∼+​H}:G∈C} has cardinality 230230230, the collection {{H∈C:G∼H}:G∈C}\{\{H\in\mathcal C:G\sim H\}:G\in\mathcal C\}{{H∈C:G∼H}:G∈C} has cardinality 219219219, and the collection {{H∈C+:G∼+H}:G∈C+}\{\{H\in\mathcal C_+:G\sim_+H\}:G\in\mathcal C_+\}{{H∈C+​:G∼+​H}:G∈C+​} has cardinality 656565, where each cardinality is taken in the extended natural numbers, with every infinite set assigned cardinality ∞\infty∞.

Human review
  • Endorsed by Shuze Chen · Sep 6, 2026

  • Endorsed by xuanji · Sep 6, 2026

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

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