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Numina/aqft in lean - #38

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KellyJDavis merged 8 commits into
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numina/aqft-in-lean
Sep 30, 2026
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Added geodesics

KellyJDavis and others added 8 commits September 30, 2026 07:30
…spacetime model

Stage 1 of notes/agents/plan-levi-civita-geodesics: new §10.4 nodes for a
pseudo-Riemannian metric, metric-compatible and Levi-Civita connections, the
Koszul formula and existence/uniqueness, the chart-free geodesic definition
(affinely parametrised, imposed at interior parameters), and the Minkowski and
isometry lemmas. def:trip and def:causal-trip now cite def:geodesic. Not yet
formalized.

Spacetime gains the instance field boundaryless : model.Boundaryless, which
the new layer relies on (open chart targets).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
New Physicslib4/Geometry/PseudoRiemannian/{Basic,LeviCivita}.lean:
PseudoRiemannianMetric and the spacetime instance, metric compatibility and
Levi-Civita connections on Mathlib's CovariantDerivative, with the musical
isomorphism, Koszul formula, uniqueness and existence stated as sorry'd
theorems, and leviCivita chosen from existence. Blueprint links recorded.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Stage 3 of the Levi-Civita plan: bijective_val, IsLeviCivitaFor.koszul and
IsLeviCivitaFor.uniqueness, following Mathlib's Riemannian proofs with the
nondegenerate metric in place of the inner product.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
…metric

Completes stage 3: the Koszul connection (koszulAux, flatEquiv, leviCivitaAux,
koszulConnection) is a covariant derivative, compatible with g and
torsion-free, so exists_isLeviCivitaFor holds without sorry.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
New Physicslib4/Spacetime/AlongPath.lean: derivatives of functions vanishing
along a path, locality of covariant derivatives along a path, globalising local
vector fields, a local left inverse of a smooth path, and extension of a path's
velocity to a smooth vector field. These make the chart-free geodesic
definition well defined and non-vacuous.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
IsGeodesic is now the chart-free condition: at every interior parameter, the
Levi-Civita derivative of any smooth extension of the velocity along itself
vanishes. The five proofs that relied on the placeholder are repaired:
- Minkowski straight segments are geodesics (new Geometry/PseudoRiemannian/
  Flat.lean: the flat connection is Levi-Civita for a constant metric;
  standardMinkowski_isGeodesic_iff characterises geodesics by zero acceleration);
- Lorentz transformations, isometries and cross-metric isometries map geodesics
  to geodesics (Koszul-formula naturality of the Levi-Civita connection).
The Restriction on IsGeodesic is removed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
…stage 5)

Drop the 57 formalization notes and the placeholder remark after
def:causal-trip, which described IsGeodesic := True, and update the stale
docstrings. Rewrite the blueprint's isometry lemmas to the Koszul-invariance
route used in Lean, replacing the pullback-connection nodes by
lmm:isometry-pullback-metric, -metric-derivative and -lie-bracket.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Adds the 24 new §10.4 entries (Lemma 311 not formalised), removes the
geodesic-placeholder caveat, and renumbers items and pages for the 322-page
build (597 declarations, 595 formalised).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
@KellyJDavis
KellyJDavis merged commit 0cf1f85 into main Sep 30, 2026
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