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Question 16152: One Supplied Finite Subcover Is Not the Universal Compactness Definition

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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R0031-16152 · q-20261014-advance-20261101-r03-open-cover-and-subcover-0077

Original question and givens

Use the complete finite topology=[[], [0], [0, 1], [0, 1, 2], [0, 1, 2, 4], [0, 1, 2, 3, 4]] on the same carrier Fin(5)={0,…,4}. Every subset is an increasing duplicate-free carrier list. First check the unique empty/whole opens and all union/intersection closure obligations; finite topology suffices for exhaustive closure checks. Complements refer to this carrier. No metric is silently supplied. Target=[0, 1, 2, 4], ordered original cover family=[[0, 1], [0, 1, 2, 4], [0, 1, 2, 3, 4]]. Every original family member must be open and their union must include the target before a selected subcover is certified. Cover indices begin at 0; selection only uses those original members, sorts indices and rejects duplicates. Keep original family order, including any equal sets at different indices. selected=[1]. Give (selected_indexes,valid_subcover?,proves_compactness?,one_finite_subcover_does_not_prove_compactness).

  • G001 — Use the complete finite topology=[[], [0], [0, 1], [0, 1, 2], [0, 1, 2, 4], [0, 1, 2, 3, 4]] on the same carrier Fin(5)={0,…,4}. Every subset is an increasing duplicate-free carrier list. First check the unique empty/whole opens and all union/intersection closure obligations; finite topology suffices for exhaustive closure checks. Complements refer to this carrier. No metric is silently supplied. Target=[0, 1, 2, 4], ordered original cover family=[[0, 1], [0, 1, 2, 4], [0, 1, 2, 3, 4]]. Every original family member must be open and their union must include the target before a selected subcover is certified. Cover indices begin at 0; selection only uses those original members, sorts indices and rejects duplicates. Keep original family order, including any equal sets at different indices. selected=[1]. Give (selected_indexes,valid_subcover?,proves_compactness?,one_finite_subcover_does_not_prove_compactness).

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

same finite carrier Fin(5);complete original ordered topology=[[], [0], [0, 1], [0, 1, 2], [0, 1, 2, 4], [0, 1, 2, 3, 4]]

After

unique empty and whole opens=Yes;all ordered open pairs=36;first union closure failure=null;first intersection closure failure=null

Conditions: none

Check canonical subsets,empty and whole sets,and union/intersection of every ordered pair.Since the topology family is finite,an arbitrary union involves only finitely many distinct opens and follows by repeated binary unions.Finite intersections follow similarly with the whole set.No metric is supplied or inferred.

Step identifiers and dependencies

Rule: cover_qualified_complete_topology_no_silent_metric · Uses: G001

S002 · implies

Before

original cover family index=0;member=[0, 1];complete same topology=[[], [0], [0, 1], [0, 1, 2], [0, 1, 2, 4], [0, 1, 2, 3, 4]]

After

original member open=Yes

Conditions: none

Check openness at every original index.Equal sets at different indices remain distinct indexed members.Do not deduplicate the input or ignore a nonopen member merely because it is unselected.

Step identifiers and dependencies

Rule: cover_every_original_index_open_including_unused_members · Uses: G001, S001

S003 · implies

Before

original cover family index=1;member=[0, 1, 2, 4];complete same topology=[[], [0], [0, 1], [0, 1, 2], [0, 1, 2, 4], [0, 1, 2, 3, 4]]

After

original member open=Yes

Conditions: none

Check openness at every original index.Equal sets at different indices remain distinct indexed members.Do not deduplicate the input or ignore a nonopen member merely because it is unselected.

Step identifiers and dependencies

Rule: cover_every_original_index_open_including_unused_members · Uses: G001, S002

S004 · implies

Before

original cover family index=2;member=[0, 1, 2, 3, 4];complete same topology=[[], [0], [0, 1], [0, 1, 2], [0, 1, 2, 4], [0, 1, 2, 3, 4]]

After

original member open=Yes

Conditions: none

Check openness at every original index.Equal sets at different indices remain distinct indexed members.Do not deduplicate the input or ignore a nonopen member merely because it is unselected.

Step identifiers and dependencies

Rule: cover_every_original_index_open_including_unused_members · Uses: G001, S003

S005 · implies

Before

same target=[0, 1, 2, 4];union of ALL original members=[0, 1, 2, 3, 4];nonopen original indices=[]

After

covers target=Yes;whole original open cover valid=Yes

Conditions: none

Openness and coverage are separate obligations.The union may exceed the target;containment,not equality,is required.Certify the original cover only when both hold.

Step identifiers and dependencies

Rule: cover_openness_and_target_coverage_separate_conjunction · Uses: G001, S004

S006 · implies

Before

raw selected ORIGINAL indices=[1];normalized duplicate-free indices=[1];selected original sets=[[0, 1, 2, 4]]

After

selected union=[0, 1, 2, 4];selected all open=Yes;selected covers target=Yes;original family qualified=Yes;valid selected subcover=Yes

Conditions: none

Select only original indexed members,sorting indices but rejecting duplicates.Empty selection can qualify for an empty target.This protocol additionally requires the whole original family to qualify;an otherwise good selected subfamily cannot erase an unselected bad original member.

Step identifiers and dependencies

Rule: cover_selected_original_indices_whole_family_premise_retained · Uses: G001, S005

S007 · implies

Before

this one original cover and selected indices=[1];valid subcover=Yes

After

proves compactness from this one check=No;one_finite_subcover_does_not_prove_compactness

Conditions: none

Compactness quantifies over every open cover;checking one finite subcover does not discharge that universal obligation.Finiteness can separately prove this space compact.The No does not declare the finite space noncompact.

Step identifiers and dependencies

Rule: cover_one_instance_not_all_open_covers_or_noncompactness · Uses: G001, S006

Reverse checks

  • S007 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S006 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S005 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S004 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S003 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

([1], Yes, No, one_finite_subcover_does_not_prove_compactness)

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 0e0e3288e67da2c1d59d397acf6847633f7b82065fb37135570f71bab1a4113b
  • candidate record SHA-256: f4813074ca5282f9f68ae381f827bb88272fba5382fe17e703720a8c3b27ee76
  • semantic review receipt SHA-256: 55bb21783e2125ecf1e67e42f83fd25bec0ccd493f911f4bb937a5e9d6f9369a
  • question-first witness SHA-256: 754ddf2a6039c5ef4aae78a538c6e9a1e9a58d4825aee194e869a27b8a4c95bb
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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