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Atlas VII definitions: SmoothBranch

Definition
Atlas_EinsteinMaxwell_ES5_KerrSchild_SmoothBranch

by He Wang · Nov 4, 2026 · Mathlib 0df444a (Lean v4.33.1)

einstein-maxwellexact-spacetime-atlas-viiexact-vacuum-atlasfive-dimensional-gravitygeneral-relativitykerr-schild

Definitions of the Atlas VII module Atlas.EinsteinMaxwell.ES5.KerrSchild.SmoothBranch (kept exactly as in the accepted source, skeleton subtraction).

VII-05 (F2c2): independent smooth extensions at inverse radius zero

The VII-04 pullbacks pull s f x = f(s + x⁻¹), pullM s m x = x · m(s + x⁻¹) are total functions, and Lean's 0⁻¹ = 0 gives the literal value pullM s m 0 = 0 (literal_pullM_zero). A smooth branch at x = 0 with b(0) = 1 therefore can not be phrased with the literal pullM (literal_pullM_not_branch).

SmoothBranch I s ε f m a F b A instead records independent real functions F b A, C^∞ on U = (-ε, ε), equal to the pullbacks only on (0, ε), with the three leading values F(0) = b(0) = 1, A(0) = 0 and the chart tail (s + ε⁻¹, ∞) ⊆ I. This is an additional regularity assumption at infinity (a selected smooth branch); it is not derived from PaperData at finite radii or from bare asymptotic flatness. The structure contains no field equation, no PaperBVP/FactorizedN, no G condition, no Taylor coefficient beyond the three leading values, and no residual, Γ or J/Q condition. The labels M = -F'(0), c = A'(0) are definitions, not hypotheses.

On the open set (0, ε) the matching transfers values, first and second derivatives (Set.EqOn.deriv), hence the four real compactified residuals and realGamma (realP*_congr, realGamma_congr). Nothing is transferred at the single point x = 0.

Constants in this bundle: magneticLabel, massLabel.

Registered B3 definition layer (Mathlib at the pinned revision has no Lorentzian metric / Ricci API): mission/PHYSICS_BOUNDARY.md, Atlas VII sections P–XVII.

Definition code
-- Generated by scripts/vii24r/publish/gen_platform_tree_unitA.py (Atlas VII Unit A; copy of the RELEASE06 generator, header only) by skeleton subtraction from Atlas/EinsteinMaxwell/ES5/KerrSchild/SmoothBranch.lean
-- definition bundle: kept ExactVacuumAtlas.EinsteinMaxwell.ES5.KerrSchild.SmoothExt.magneticLabel, ExactVacuumAtlas.EinsteinMaxwell.ES5.KerrSchild.SmoothExt.massLabel
import Mathlib
import Definitions.Def_Atlas_Core_Basic
import Definitions.Def_Atlas_EinsteinMaxwell_Basic
import Definitions.Def_Atlas_EinsteinMaxwell_D_Basic
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_Defs
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_Generic_Cert
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_Generic_Data
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_Generic_Reduced
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_Generic_Tables
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_CompactifiedBridge
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_CompactifiedResiduals
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_PaperGauge
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_PolynomialJet
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_RadialBVP
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_RadialBVPEquivalence
import Definitions.Def_Atlas_EinsteinMaxwell_ES5_KerrSchild_ScalarCertificate

/-! # VII-05 (F2c2): independent smooth extensions at inverse radius zero

The VII-04 pullbacks `pull s f x = f(s + x⁻¹)`, `pullM s m x = x · m(s + x⁻¹)` are total
functions, and Lean's `0⁻¹ = 0` gives the literal value `pullM s m 0 = 0`
(`literal_pullM_zero`). A smooth branch at `x = 0` with `b(0) = 1` therefore can **not** be
phrased with the literal `pullM` (`literal_pullM_not_branch`).

`SmoothBranch I s ε f m a F b A` instead records *independent* real functions `F b A`, `C^∞` on
`U = (-ε, ε)`, equal to the pullbacks **only on `(0, ε)`**, with the three leading values
`F(0) = b(0) = 1`, `A(0) = 0` and the chart tail `(s + ε⁻¹, ∞) ⊆ I`. This is an *additional*
regularity assumption at infinity (a selected smooth branch); it is not derived from
`PaperData` at finite radii or from bare asymptotic flatness. The structure contains no field
equation, no `PaperBVP`/`FactorizedN`, no `G` condition, no Taylor coefficient beyond the three
leading values, and no residual, Γ or `J`/`Q` condition. The labels `M = -F'(0)`, `c = A'(0)`
are definitions, not hypotheses.

On the open set `(0, ε)` the matching transfers values, first and second derivatives
(`Set.EqOn.deriv`), hence the four real compactified residuals and `realGamma`
(`realP*_congr`, `realGamma_congr`). Nothing is transferred at the single point `x = 0`. -/

open scoped ContDiff

namespace ExactVacuumAtlas.EinsteinMaxwell.ES5.KerrSchild.SmoothExt

open ExactVacuumAtlas.EinsteinMaxwell.ES5.KerrSchild.Compact

/-- Mass label `M = -F'(0)` (a definition, not an extra hypothesis). -/
noncomputable def massLabel (F : ℝ → ℝ) : ℝ := -deriv F 0
/-- Magnetic label `c = A'(0)` (a definition, not an extra hypothesis). -/
noncomputable def magneticLabel (A : ℝ → ℝ) : ℝ := deriv A 0

/-! ## The literal totalized pullback at zero -/

/-! ## Chart membership and positive-side transfer -/

section Transfer

variable {V : Set ℝ} (hV : IsOpen V) {F b A F' b' A' : ℝ → ℝ}
  (hF : Set.EqOn F F' V) (hb : Set.EqOn b b' V) (hA : Set.EqOn A A' V) {x : ℝ} (hx : x ∈ V)
include hV hF hb hA hx

end Transfer

end ExactVacuumAtlas.EinsteinMaxwell.ES5.KerrSchild.SmoothExt
Source
He Wang, Exact Spacetime Atlas VII, Unit A (restricted Kerr–Schild obstruction on the actual asymptotic branch, VII17). Local source, no public repository; commit f64ba9c823ec; Atlas/EinsteinMaxwell/ES5/KerrSchild/SmoothBranch.lean; SHA-256 e37d72518dd6b9f7f135d01adde6be17c1703eb5149865e02988004c1a466b02. Registered definitions: mission/PHYSICS_BOUNDARY.md (Atlas VII sections P–XVII). Physical Kerr–Schild obstruction: Fröb–Khavkine–Málek–Pravda, Eur. Phys. J. C 82 (2022) 215, arXiv:2112.13266 (Eqs. 23–25, 33, 59–60).

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