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Question 15683: A Nonoptimal Valid Coloring Still Supplies an Upper Bound

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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R0030-15683 · q-20261014-advance-20261031-r05-graph-coloring-0058

Original question and givens

Use the complete finite undirected loop-free simple graph on Fin(6)={0,…,5} with edges=[[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]]. Normalize each edge increasingly, then sort edges lexicographically; reversed duplicates and loops are forbidden. Keep isolated vertices in the carrier. No directed-graph conclusion is inferred. Total vertex colors=[7, 8, 7, 8, 7, 8] are labels, not cardinalities. Only adjacent endpoints must differ; nonadjacent vertices may share a color. A proper k-coloring uses at most k distinct labels, even if their numerical names exceed k−1. One such coloring gives only a chromatic-number upper bound, not optimality or a general greedy guarantee. Proposed k=3. Give (used_count,k,proper?,certificate?,conclusion,upper_bound_not_exact_optimum). A valid certificate yields chromatic_number_at_most_k with the supplied numeric k; otherwise no_upper_bound_from_this_coloring.

  • G001 — Use the complete finite undirected loop-free simple graph on Fin(6)={0,…,5} with edges=[[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]]. Normalize each edge increasingly, then sort edges lexicographically; reversed duplicates and loops are forbidden. Keep isolated vertices in the carrier. No directed-graph conclusion is inferred. Total vertex colors=[7, 8, 7, 8, 7, 8] are labels, not cardinalities. Only adjacent endpoints must differ; nonadjacent vertices may share a color. A proper k-coloring uses at most k distinct labels, even if their numerical names exceed k−1. One such coloring gives only a chromatic-number upper bound, not optimality or a general greedy guarantee. Proposed k=3. Give (used_count,k,proper?,certificate?,conclusion,upper_bound_not_exact_optimum). A valid certificate yields chromatic_number_at_most_k with the supplied numeric k; otherwise no_upper_bound_from_this_coloring.

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

complete undirected vertex carrier Fin(6);original edges=[[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]]

After

normalized sorted simple edges=[[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]];all vertices including isolates=[0, 1, 2, 3, 4, 5]

Conditions: none

Normalize endpoints and then sort edges lexicographically.Reversed duplicates are still duplicates and are rejected,as are loops.The complete carrier includes vertices absent from the edge list.

Step identifiers and dependencies

Rule: graph_complete_simple_carrier_normalized_edge_order · Uses: G001

S002 · implies

Before

colors:normalized edge index=0;edge=[0, 1];endpoint labels=[7, 8]

After

different endpoints=Yes;same-label conflict=No

Conditions: none

Check the endpoints of each actual edge.Reused labels at nonadjacent vertices are not conflicts,and one crossing edge does not certify all other edges.

Step identifiers and dependencies

Rule: graph_every_edge_endpoint_constraint · Uses: G001, S001

S003 · implies

Before

colors:normalized edge index=1;edge=[1, 2];endpoint labels=[8, 7]

After

different endpoints=Yes;same-label conflict=No

Conditions: none

Check the endpoints of each actual edge.Reused labels at nonadjacent vertices are not conflicts,and one crossing edge does not certify all other edges.

Step identifiers and dependencies

Rule: graph_every_edge_endpoint_constraint · Uses: G001, S002

S004 · implies

Before

colors:normalized edge index=2;edge=[2, 3];endpoint labels=[7, 8]

After

different endpoints=Yes;same-label conflict=No

Conditions: none

Check the endpoints of each actual edge.Reused labels at nonadjacent vertices are not conflicts,and one crossing edge does not certify all other edges.

Step identifiers and dependencies

Rule: graph_every_edge_endpoint_constraint · Uses: G001, S003

S005 · implies

Before

colors:normalized edge index=3;edge=[3, 4];endpoint labels=[8, 7]

After

different endpoints=Yes;same-label conflict=No

Conditions: none

Check the endpoints of each actual edge.Reused labels at nonadjacent vertices are not conflicts,and one crossing edge does not certify all other edges.

Step identifiers and dependencies

Rule: graph_every_edge_endpoint_constraint · Uses: G001, S004

S006 · implies

Before

colors:normalized edge index=4;edge=[4, 5];endpoint labels=[7, 8]

After

different endpoints=Yes;same-label conflict=No

Conditions: none

Check the endpoints of each actual edge.Reused labels at nonadjacent vertices are not conflicts,and one crossing edge does not certify all other edges.

Step identifiers and dependencies

Rule: graph_every_edge_endpoint_constraint · Uses: G001, S005

S007 · implies

Before

total original vertex colors=[7, 8, 7, 8, 7, 8];all normalized conflicts=[]

After

increasing distinct used labels=[7, 8];used count=2;all edges proper=Yes

Conditions: none

Colors are names:count distinct used labels rather than maximum label plus1.Only adjacent equal colors conflict;nonadjacent color reuse is allowed.

Step identifiers and dependencies

Rule: coloring_distinct_label_count_not_numeric_magnitude · Uses: G001, S006

S008 · implies

Before

all-edge proper=Yes;distinct used count=2;original k=3

After

at most k=Yes;proper k-coloring certificate=Yes;upper_bound_not_exact_optimum

Conditions: none

Both edge properness and at most k used colors are required for χ(G)≤k.Rename the used labels into a k-color palette if needed;large numeric names do not invalidate it.Without excluding all smaller k,this is not an optimum certificate.

Step identifiers and dependencies

Rule: coloring_k_bound_conjunction_not_minimum_chromatic_number · Uses: G001, S007

Reverse checks

  • 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

(2, 3, Yes, Yes, chromatic_number_at_most_3, upper_bound_not_exact_optimum)

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: 99eb9ae7bfee986c567db6251659ec6c8a41ed2c157412920748457898843793
  • candidate record SHA-256: 2ec261bcffe4ac0222a7a9839918005bc0c17378f855f4e18b013e90c020f82c
  • semantic review receipt SHA-256: 73bc08066ffb1a81eacb2d4e288d03f522aeefd3949fa0d97da41b484ed737bc
  • question-first witness SHA-256: ac120452a208b257b8270f38351a09dcd832cdbc8d9db6b69933f83e43cc9336
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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