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Question 10536: Finite-Tail Success Does Not Certify General Convergence

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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R0020-10536 · q-20261013-advance-20261023-r04-metric-convergence-0036

Original question and givens

Use the complete qualified finite metric table=[[0, 11, 23, 36], [11, 0, 12, 25], [23, 12, 0, 13], [36, 25, 13, 0]] on Fin(4)={0,…,3}. Preserve the convergence quantifiers: for every positive epsilon there exists N such that every n≥N satisfies d(x_n,candidate)<epsilon. A finite recorded tail alone does not certify this infinite statement. recorded finite sequence=[3, 2, 1, 1], candidate=1, positive epsilon=1/1, cutoff N=2 may equal the recorded length. Give (sequence,candidate,epsilon,N,every [index,state,distance,status] row,all recorded indices at least N are inside?,general convergence certified?,boundary label). Status is prefix below N, otherwise inside or outside using the strict bound; general convergence is always No and the boundary label is finite-tail-insufficient-for-general-convergence.

  • G001 — Use the complete qualified finite metric table=[[0, 11, 23, 36], [11, 0, 12, 25], [23, 12, 0, 13], [36, 25, 13, 0]] on Fin(4)={0,…,3}. Preserve the convergence quantifiers: for every positive epsilon there exists N such that every n≥N satisfies d(x_n,candidate)<epsilon. A finite recorded tail alone does not certify this infinite statement. recorded finite sequence=[3, 2, 1, 1], candidate=1, positive epsilon=1/1, cutoff N=2 may equal the recorded length. Give (sequence,candidate,epsilon,N,every [index,state,distance,status] row,all recorded indices at least N are inside?,general convergence certified?,boundary label). Status is prefix below N, otherwise inside or outside using the strict bound; general convergence is always No and the boundary label is finite-tail-insufficient-for-general-convergence.

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

carrier Fin(4);complete distance table=[[0, 11, 23, 36], [11, 0, 12, 25], [23, 12, 0, 13], [36, 25, 13, 0]]

After

nonnegative typed entries=Yes;zero iff equal=Yes;symmetric=Yes;all triangle tests=Yes

Conditions: none

Qualify the whole metric table,not only queried cells.Labels are not distances:diagonal zero,positive separation,symmetry and every triangle condition are premises for later reasoning.

Step identifiers and dependencies

Rule: whole_qualified_finite_metric · Uses: G001

S002 · implies

Before

raw epsilon=[1, 1]

After

normalized positive epsilon=1

Conditions: none

The original denominator is nonzero and normalized epsilon must be positive.A negative original denominator may normalize legitimately;do not bypass the guard by totalized machine division.

Step identifiers and dependencies

Rule: metric_positive_epsilon_original_denominator · Uses: G001, S001

S003 · implies

Before

original index=0;state=3;candidate=1;distance=25;cutoff=2

After

recorded status=prefix

Conditions: none

Keep original sequence positions.List prefix distances,but test strict inside/outside only at indices≥N.

Step identifiers and dependencies

Rule: finite_recorded_tail_row_roles · Uses: G001, S002

S004 · implies

Before

original index=1;state=2;candidate=1;distance=12;cutoff=2

After

recorded status=prefix

Conditions: none

Keep original sequence positions.List prefix distances,but test strict inside/outside only at indices≥N.

Step identifiers and dependencies

Rule: finite_recorded_tail_row_roles · Uses: G001, S003

S005 · calculation

Before

recorded index2 distance times epsilon denominator := mul(0, 1)

After

recorded index2 distance times epsilon denominator = 0

Conditions: none

Compute exactly with this step's original roles and operands,without floating approximation or reordering source data.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

recorded index2:distance=0;epsilon=1;positive denominator=1

After

cross product=0;strictly below numerator=Yes

Conditions: none

Cross-multiply by the positive denominator and retain strict inequality.Equality with epsilon is outside the open ball.

Step identifiers and dependencies

Rule: strict_metric_distance_comparison · Uses: G001, S005

S007 · implies

Before

original index=2;state=1;candidate=1;distance=0;cutoff=2

After

recorded status=inside

Conditions: none

Keep original sequence positions.List prefix distances,but test strict inside/outside only at indices≥N.

Step identifiers and dependencies

Rule: finite_recorded_tail_row_roles · Uses: G001, S006

S008 · calculation

Before

recorded index3 distance times epsilon denominator := mul(0, 1)

After

recorded index3 distance times epsilon denominator = 0

Conditions: none

Compute exactly with this step's original roles and operands,without floating approximation or reordering source data.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · implies

Before

recorded index3:distance=0;epsilon=1;positive denominator=1

After

cross product=0;strictly below numerator=Yes

Conditions: none

Cross-multiply by the positive denominator and retain strict inequality.Equality with epsilon is outside the open ball.

Step identifiers and dependencies

Rule: strict_metric_distance_comparison · Uses: G001, S008

S010 · implies

Before

original index=3;state=1;candidate=1;distance=0;cutoff=2

After

recorded status=inside

Conditions: none

Keep original sequence positions.List prefix distances,but test strict inside/outside only at indices≥N.

Step identifiers and dependencies

Rule: finite_recorded_tail_row_roles · Uses: G001, S009

S011 · implies

Before

recorded rows=[[0, 3, 25, prefix], [1, 2, 12, prefix], [2, 1, 0, inside], [3, 1, 0, inside]];recorded tail starts at=2

After

bounded recorded tail passes=Yes;general convergence certified=No

Conditions: none

N may equal the recorded length,so an empty recorded tail passes vacuously.Finite records do not supply the infinite all-n≥N tail and do not certify general convergence.

Step identifiers and dependencies

Rule: finite_tail_not_infinite_convergence · Uses: G001, S010

Reverse checks

  • S011 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • 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 — Recompute recorded index3 distance times epsilon denominator with exact rational arithmetic, not rounded decimals.
  • 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 — Recompute recorded index2 distance times epsilon denominator with exact rational arithmetic, not rounded decimals.
  • 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

([3, 2, 1, 1], 1, 1, 2, [[0, 3, 25, prefix], [1, 2, 12, prefix], [2, 1, 0, inside], [3, 1, 0, inside]], Yes, No, finite-tail-insufficient-for-general-convergence)

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: d2244d63dfb3af8062225c8c73160d66594e1767efbdfcd15cb25c99186c49ff
  • candidate record SHA-256: e99b298462e16306f76159b52272260b3645d99e1f6caa7cc785176bafa425c0
  • semantic review receipt SHA-256: b4c47938fd38085d44967226cfa8337d61334455472e7307c60d3a488cef598f
  • question-first witness SHA-256: 3c23baa97a5933bc07b44f2257017ef4e845bf1429bd6f5381410681c43b97e4
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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