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Question 23538: Ambient Hausdorffness and Compactness Are Both Theorem Hypotheses

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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R0046-23538 · q-20261014-advance-20261112-r03-compact-subset-closed-in-hausdorff-0013

Original question and givens

Use complete finite labeled carrier=[a12, b12, c12], topology=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []] in its original supplied open-set order, and compact_subset K=[a12, b12]. Qualify the topology and every Hausdorff distinct-point pair. Finite K is compact; the general theorem still needs both ambient Hausdorffness and compactness. Give (points, compact_subset, pair_separation_rows, Hausdorff, compact, certificate).

  • G001 — Use complete finite labeled carrier=[a12, b12, c12], topology=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []] in its original supplied open-set order, and compact_subset K=[a12, b12]. Qualify the topology and every Hausdorff distinct-point pair. Finite K is compact; the general theorem still needs both ambient Hausdorffness and compactness. Give (points, compact_subset, pair_separation_rows, Hausdorff, compact, certificate).

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

source operation=compactclosed-hypotheses-qualification;original snapshot and mathematics retained

After

explicit ordered source output fields=[points, compact_subset, pair_separation_rows, Hausdorff, compact, certificate]

Conditions: none

Keep the source snapshot while listing ordered fields without JavaScript.Radius uses its original mode to select6 or11 fields without padding;distinguish nonclaims from actual negations.

Step identifiers and dependencies

Rule: source_ordered_interface_explicit_without_javascript · Uses: G001

S002 · implies

Before

ORIGINAL carrier order=[a12, b12, c12];ORIGINAL open-list order=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []];point=a12;ALL given sets containing it have indices=[0, 1, 2, 3]

After

candidate N(a12)=intersection of ALL those sets=[a12];no original open-list reordering

Conditions: none

Intersect every declared neighborhood to form a candidate,without yet assuming a topology.Retain the original open-list order;only set elements use UTF16 sorting.

Step identifiers and dependencies

Rule: compactclosed_ALL_given_neighborhood_intersection_candidates · Uses: G001, S001

S003 · implies

Before

ORIGINAL carrier order=[a12, b12, c12];ORIGINAL open-list order=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []];point=b12;ALL given sets containing it have indices=[0, 1, 4, 5]

After

candidate N(b12)=intersection of ALL those sets=[b12];no original open-list reordering

Conditions: none

Intersect every declared neighborhood to form a candidate,without yet assuming a topology.Retain the original open-list order;only set elements use UTF16 sorting.

Step identifiers and dependencies

Rule: compactclosed_ALL_given_neighborhood_intersection_candidates · Uses: G001, S002

S004 · implies

Before

ORIGINAL carrier order=[a12, b12, c12];ORIGINAL open-list order=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []];point=c12;ALL given sets containing it have indices=[0, 2, 4, 6]

After

candidate N(c12)=intersection of ALL those sets=[c12];no original open-list reordering

Conditions: none

Intersect every declared neighborhood to form a candidate,without yet assuming a topology.Retain the original open-list order;only set elements use UTF16 sorting.

Step identifiers and dependencies

Rule: compactclosed_ALL_given_neighborhood_intersection_candidates · Uses: G001, S003

S005 · implies

Before

ORIGINAL ordered open masks=[7, 3, 5, 1, 6, 2, 4, 0];ALL neighborhood-containment [x,y,N(y)_subset_N(x)] rows=[[a12, a12, Yes], [b12, b12, Yes], [c12, c12, Yes]]

After

ALL carrier masks0..7 audited;EXACT qualifying U with every x in U having N(x) subset U=[0, 1, 2, 3, 4, 5, 6, 7];given family equals this COMPLETE upset family

Conditions: none

In a finite topology,opens are exactly upsets of its minimal neighborhoods.Conversely,after comparing every carrier subset,upsets are closed under arbitrary unions and finite intersections and contain empty/full sets,so this is a topology with open N(x).This covers all closure obligations,not sampled pairs,without printing millions of pairs.

Step identifiers and dependencies

Rule: compactclosed_ALL_carrier_subsets_exact_neighborhood_upsets_topology · Uses: G001, S004

S006 · implies

Before

Compact-closed ORIGINAL pair index0-1:ORIGINAL distinct x=a12,y=b12;N(y)=[b12];open-list order=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []]

After

ALL tested [U_index,U_intersect_N(y),disjoint_V_possible] rows=[[0, [b12], No], [1, [b12], No], [2, [], Yes]];for FIRST possible U,ALL tested [V_index,intersection,disjoint] rows=[[0, [a12, c12], No], [1, [a12], No], [4, [c12], No], [5, [], Yes]];FIRST ORIGINAL witness=[[a12, c12], [b12]]

Conditions: none

If U meets N(y),every open containing y also meets U.If disjoint,N(y) itself is an available open,then search original V order for the first witness.This preserves exactly the original full U/V search result,not an alternate minimal-neighborhood answer.

Step identifiers and dependencies

Rule: compactclosed_FIRST_original_separator_with_complete_neighborhood_screen · Uses: G001, S005

S007 · implies

Before

Compact-closed ORIGINAL pair index0-2:ORIGINAL distinct x=a12,y=c12;N(y)=[c12];open-list order=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []]

After

ALL tested [U_index,U_intersect_N(y),disjoint_V_possible] rows=[[0, [c12], No], [1, [], Yes]];for FIRST possible U,ALL tested [V_index,intersection,disjoint] rows=[[0, [a12, b12], No], [2, [a12], No], [4, [b12], No], [6, [], Yes]];FIRST ORIGINAL witness=[[a12, b12], [c12]]

Conditions: none

If U meets N(y),every open containing y also meets U.If disjoint,N(y) itself is an available open,then search original V order for the first witness.This preserves exactly the original full U/V search result,not an alternate minimal-neighborhood answer.

Step identifiers and dependencies

Rule: compactclosed_FIRST_original_separator_with_complete_neighborhood_screen · Uses: G001, S006

S008 · implies

Before

Compact-closed ORIGINAL pair index1-2:ORIGINAL distinct x=b12,y=c12;N(y)=[c12];open-list order=[[a12, b12, c12], [a12, b12], [a12, c12], [a12], [b12, c12], [b12], [c12], []]

After

ALL tested [U_index,U_intersect_N(y),disjoint_V_possible] rows=[[0, [c12], No], [1, [], Yes]];for FIRST possible U,ALL tested [V_index,intersection,disjoint] rows=[[0, [a12, b12], No], [2, [a12], No], [4, [b12], No], [6, [], Yes]];FIRST ORIGINAL witness=[[a12, b12], [c12]]

Conditions: none

If U meets N(y),every open containing y also meets U.If disjoint,N(y) itself is an available open,then search original V order for the first witness.This preserves exactly the original full U/V search result,not an alternate minimal-neighborhood answer.

Step identifiers and dependencies

Rule: compactclosed_FIRST_original_separator_with_complete_neighborhood_screen · Uses: G001, S007

S009 · implies

Before

ORIGINAL points=[a12, b12, c12];ALL original-index distinct-pair witnesses=[[a12, b12, [[a12, c12], [b12]]], [a12, c12, [[a12, b12], [c12]]], [b12, c12, [[a12, b12], [c12]]]];actual K=[a12, b12]

After

Hausdorff=Yes;K compact=Yes by finiteness:from ANY cover choose one member per K point;empty K needs no members;ambient complement=[c12],closed=Yes

Conditions: none

Finite K compactness does not replace ambient Hausdorffness.An empty pair domain is vacuous.Closedness tests the complement in this same ambient space,not a relative complement.

Step identifiers and dependencies

Rule: compactclosed_ALL_pairs_Hausdorff_and_finite_subset_compact_separate · Uses: G001, S008

S010 · implies

Before

CURRENT ambient Hausdorff=Yes;compact K=[a12, b12];consider ANY exterior x

After

for EACH y in K choose disjoint opens U_y containing x,V_y containing y;the V_y cover K;compactness picks FINITELY MANY indices;their U_y intersection is open,contains x and avoids ALL K,so X minus K is open

Conditions: none

The general theorem uses compactness to select a finite subcover,not numbers from this finite model.Each K point lies in a selected V disjoint from its corresponding U;the finite intersection therefore avoids all K.For empty K,the empty intersection is X.No converse closed-implies-compact is claimed.

Step identifiers and dependencies

Rule: compactclosed_GENERAL_Hausdorff_finite_subcover_intersection_proof · Uses: G001, S009

Reverse checks

  • S010 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S009 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • 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

([a12, b12, c12], [a12, b12], [[a12, b12, [[a12, c12], [b12]]], [a12, c12, [[a12, b12], [c12]]], [b12, c12, [[a12, b12], [c12]]]], Yes, Yes, complete_finite_topology_Hausdorff_and_finite_subset_compact)

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: 15a7a9147c452563ff8620b3bf9053e0e97dc0a16365c7b7971904ffe8f093f1
  • candidate record SHA-256: d892cc880cfcc4c41ba81e8cce27ad4bea6fd4d10561fb9424dae68aaade84cb
  • semantic review receipt SHA-256: a7c0d888ade6d307703c4222c4137c78c0d2448babdcba2fa3446fe6fdd343c1
  • question-first witness SHA-256: c9571f97a37d503ad6a61034cc00108543a05c37ef246d1c4962f55136a3de02
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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