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Claude/axioms review tiers bie66 - #119

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Jan 15, 2026
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claude added 13 commits January 15, 2026 11:50
INCREMENT 1: Basic bounds using Mathlib's ExponentialBounds module

Proven theorems:
- exp_one_gt: 2.7 < e (from Real.exp_one_gt_d9)
- exp_one_lt: e < 2.72 (from Real.exp_one_lt_d9)
- sqrt5_gt_two: 2 < sqrt(5)
- sqrt5_lt_three: sqrt(5) < 3
- sqrt5_bounds_tight: 2.236 < sqrt(5) < 2.237
- sqrt5_bounds_4dec: 2.2360 < sqrt(5) < 2.2361

All proofs are axiom-free, using:
- Mathlib's certified decimal bounds for exp(1)
- Squaring inequalities for sqrt(5)

This is the first step toward replacing the 7 numerical axioms
in DimensionalGap.lean and GoldenRatioPowers.lean.
INCREMENT 2+3: Golden ratio bounds from sqrt(5) bounds

Proven theorems:
- phi_gt_1618: 1.618 < phi
- phi_lt_16185: phi < 1.6185
- phi_pos, phi_gt_one, phi_lt_two, phi_ne_zero
- phi_inv_sq_eq: phi^(-2) = 2 - phi (algebraic identity)
- phi_inv_sq_pos: 0 < phi^(-2)
- phi_inv_sq_lt_0383: phi^(-2) < 0.383
- phi_inv_sq_gt_0381: 0.381 < phi^(-2)
- phi_inv_sq_lt_one: phi^(-2) < 1

All proofs axiom-free using:
- sqrt(5) bounds from Section 2
- phi^2 = phi + 1 identity from GoldenRatio.lean

These bounds are key for proving phi^(-54) < 10^(-10).
INCREMENT 4: Logarithm bounds using Mathlib's Real.log_two_*_d9

Proven theorems:
- log_two_gt/lt: 0.693 < log(2) < 0.694
- log_four_eq/bounds: log(4) = 2*log(2), with bounds
- log_eight_eq: log(8) = 3*log(2)
- log_five_gt/lt: 1.386 < log(5) < 2.082
- log_ten_eq: log(10) = log(2) + log(5)
- log_ten_gt/lt_loose: 2.079 < log(10) < 2.776

Note: The loose log(10) bounds (2.079-2.776) are not tight enough
for cohom_suppression_magnitude which needs 2.302 < log(10) < 2.303.

Documented remaining bounds that require interval arithmetic
(not available in Mathlib4) as justified axioms.
Replace axioms with abbrevs pointing to proven theorems:
- exp_one_gt: now PROVEN from Real.exp_one_gt_d9
- exp_one_lt: now PROVEN from Real.exp_one_lt_d9

Remaining axioms (5, down from 7):
- cohom_suppression_magnitude (needs tight log(10) bounds)
- log_phi_bounds (needs exp at rational points)
- phi_inv_54_very_small (needs 0.383^27 computation)
- rpow_27_1618_gt_206 (needs rpow evaluation)
- rpow_27_16185_lt_208 (needs rpow evaluation)

These require interval arithmetic not available in Mathlib4.
- phi_inv_sq_eq: Restructure calc proof to avoid field_simp goal mismatch
- log_four_eq, log_eight_eq: Add norm_cast to handle ↑n * log 2 coercion
…ructure

Phase 1 progress toward proving log(phi) bounds:

Section 6 - log(3) bounds:
- log_three_gt: 0.693 < log(3) (from monotonicity)
- log_three_lt: log(3) < 1.388 (from log(4))
- log_three_gt_one: 1 < log(3) (from exp(1) < 3)

Section 8 - log(1+sqrt5) bounds:
- one_plus_sqrt5_gt/lt: 3.236 < 1+sqrt(5) < 3.237
- log_one_plus_sqrt5_gt: 1 < log(1+sqrt(5))
- log_one_plus_sqrt5_lt: log(1+sqrt(5)) < 1.388

Section 9 - log(phi) foundations:
- log_phi_eq: log(phi) = log(1+sqrt(5)) - log(2)
- log_phi_pos: 0 < log(phi)
- log_phi_lt_one: log(phi) < 1

Current bounds: 0.306 < log(phi) < 0.695 (loose)
Target bounds: 0.48 < log(phi) < 0.49 (tight)

Next step: Tighten log(1+sqrt5) lower bound to ~1.17
MAJOR ACHIEVEMENT: log_phi_bounds is now PROVEN (was axiom)!

Using Mathlib's Real.exp_bound and Real.sum_le_exp_of_nonneg:

exp(0.48) upper bound:
- 5-term Taylor sum = 1.615844
- Error bound < 0.0003
- exp(0.48) < 1.6161 < 1.617 < 1.618 < phi

exp(0.49) lower bound:
- 5-term Taylor sum = 1.632
- exp(x) >= partial sum for x >= 0
- exp(0.49) > 1.631 > 1.6185 > phi

New proven theorems:
- exp_048_lt: exp(0.48) < 1.617
- exp_049_gt: 1.631 < exp(0.49)
- log_phi_gt_048: 0.48 < log(phi)
- log_phi_lt_049: log(phi) < 0.49
- log_phi_bounds: 0.48 < log(phi) < 0.49

Tier 1 axioms: 5 -> 4 (one more eliminated!)
- Add exp_log conversion in log_three_gt_one proof
- Use Real.log_pos instead of log_pos_iff for log_phi_pos
- Rewrite Taylor sum proofs to properly expand factorials via simp
- Add exp_log phi_pos to log_phi_gt_048 and log_phi_lt_049
- Use Nat.factorial_* lemmas for simp instead of raw norm_num on sums
- Use Nat.factorial directly (not Nat.factorial_three/four/five which don't exist)
- Expand sum to explicit terms and prove equality via ring
- Use abs_sub_le_iff.mp and linarith [h.1] for upper bound
- Compute error term explicitly via simp and ring
- Final bound verified with norm_num on explicit expression
- Use ↑(m.factorial) consistently to match Real.exp_bound type
- Simplify herr_eq proof using norm_num directly
- Separate hupper step for cleaner type inference
- Remove unused simp arguments (Nat.cast_ofNat, abs_of_nonneg)
## Summary
New NumericalBounds.lean module provides axiom-free proofs of transcendental
bounds using Mathlib's Taylor series lemmas. Key result: log(φ) ∈ (0.48, 0.49)
is now PROVEN.

## Changes
- CHANGELOG.md: Add v3.3.5 release notes
- CLAUDE.md: Add lessons learned (§24-28) for Taylor series proofs
- docs/USAGE.md: Update to v3.3.5, add NumericalBounds examples
- README.md: Bump version to v3.3.5
- gift_core/_version.py: Bump to 3.3.5

## Axiom Reduction
- Tier 1 (Numerical): 7 → 4 axioms
- Proven: exp_one_gt, exp_one_lt, log_phi_bounds
Replace axiom with abbrev pointing to the Taylor-series-proven theorem.
Reduces Tier 1 axioms from 5 to 4.
@gift-framework
gift-framework merged commit a2f4714 into main Jan 15, 2026
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@gift-framework
gift-framework deleted the claude/axioms-review-tiers-Bie66 branch January 15, 2026 15:18
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