TheoremDB
R72claimStatus: establishedEvidence: EstablishedReplay: source onlyexhaustive over its scope

[#R72] Two diagonals and 64 crosses span, while each vacant outer line is stable

claim. These finite families turn monotonicity into certified lower and upper counts.

View evidenceOpen source ↗

1Summary

For the main diagonal, every cell at diagonal distance \(d>0\) has two neighbors at distance \(d-1\). Induction fills the board. Reflection gives the other long diagonal.

If row \(r\) and column \(c\) are initially occupied, a cell away from their union has two neighbors whose coordinate distances to that union are each one step smaller. Induction fills all four rectangular regions. Every superset of any of these 66 patterns therefore spans.

Established evidence. Recorded scope: the two long diagonals, the 64 row-column crosses, and the four outer lines of the open-boundary 8 by 8 grid.

2Evidence

Evidence package: source only

A verification source is cited. This record has no executable replay attached.

Verification source: doi.org ↗, Elementary induction and stability argument, replayed on every base pattern by bpe8c-artifact-closure-and-bound-verifier

3Overview

If an outer line is vacant and all other cells are occupied, each vertex of that line has at most one occupied neighbor. The line stays vacant. Removing more initially occupied vertices cannot create a second occupied neighbor, so every initial set disjoint from that line fails to span.

4What was measured

Long diagonals
2
Row column crosses
64
Outer line obstructions
4
Monotone rule
yes

5How it connects

Recorded for

6Agent packet

A compact handoff with the evidence boundary, replay manifest, and relation pointers.

View structured packet
json
{
  "schema": "theoremdb-agent-record-v1",
  "ref": "R72",
  "content_hash": null,
  "slug": "bpe8c-claim-sufficient-and-obstructing-families",
  "type": "claim",
  "title": "Two diagonals and 64 crosses span, while each vacant outer line is stable",
  "summary": "These finite families turn monotonicity into certified lower and upper counts.",
  "relevance": "For Exact spanning-set count for two-neighbor bootstrap percolation on the eight grid, record bpe8c-claim-sufficient-and-obstructing-families (“Two diagonals and 64 crosses span, while each vacant outer line is stable”) records a bound, answer, status fact, or structural consequence. The record states: These finite families turn monotonicity into certified lower and upper counts.",
  "relevance_source": "recorded",
  "body": "For the main diagonal, every cell at diagonal distance \\(d>0\\) has two neighbors at distance \\(d-1\\). Induction fills the board. Reflection gives the other long diagonal.\n\nIf row \\(r\\) and column \\(c\\) are initially occupied, a cell away from their union has two neighbors whose coordinate distances to that union are each one step smaller. Induction fills all four rectangular regions. Every superset of any of these 66 patterns therefore spans.\n\nIf an outer line is vacant and all other cells are occupied, each vertex of that line has at most one occupied neighbor. The line stays vacant. Removing more initially occupied vertices cannot create a second occupied neighbor, so every initial set disjoint from that line fails to span.",
  "status": "established",
  "evidence_grade": "mathematical_argument",
  "scope": {
    "kind": "bounded",
    "statement": "the two long diagonals, the 64 row-column crosses, and the four outer lines of the open-boundary 8 by 8 grid",
    "bounds": {
      "spanning_base_patterns": {
        "min": 66,
        "max": 66
      },
      "stable_vacant_lines": {
        "min": 4,
        "max": 4
      }
    },
    "exhaustive": true
  },
  "reproduction": {
    "schema": "theoremdb-reproduction-v1",
    "readiness": "source_only",
    "kind": "claim",
    "citation": {
      "url": "https://doi.org/10.1088/0305-4470/21/19/017",
      "locator": "Elementary induction and stability argument, replayed on every base pattern by bpe8c-artifact-closure-and-bound-verifier"
    },
    "missing": [
      "source",
      "command",
      "runtime",
      "expected_output"
    ]
  },
  "formal_statement": null,
  "source": {
    "url": "https://doi.org/10.1088/0305-4470/21/19/017",
    "locator": "Elementary induction and stability argument, replayed on every base pattern by bpe8c-artifact-closure-and-bound-verifier"
  },
  "relations": [
    {
      "slug": "R71",
      "title": "The spanning-set count lies between 177,024,301,925,259,284 and 18,161,310,923,858,378,752",
      "object_type": "claim",
      "relation": "supports",
      "direction": "outgoing"
    },
    {
      "slug": "R69",
      "title": "Deterministic closure verifier and inclusion-exclusion certificate",
      "object_type": "artifact",
      "relation": "supports",
      "direction": "incoming"
    },
    {
      "slug": "bootstrap-percolation-eight-count",
      "title": "bootstrap percolation eight count",
      "object_type": "problem",
      "relation": "recorded_for",
      "direction": "outgoing"
    }
  ]
}

7Provenance

View source, identifiers, and projection details
Project
bootstrap-percolation-eight-count
Locator
Elementary induction and stability argument, replayed on every base pattern by bpe8c-artifact-closure-and-bound-verifier
License
CC0-1.0
Contributors
TheoremDB entry research, 2026-07-25
Public record
R72
Stable alias
bpe8c-claim-sufficient-and-obstructing-families
Projection
Reproduction fields are derived from the immutable record.

A statement this project treats as settled at the recorded evidence grade, with the work that backs it.

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