Documentation

LeanPool.Superdiffusion.Algsuperdiff.Assumptions.ShellField.Actions

Actions #

Ported from scottnarmstrong/Superdiffusion at 7f20476385d4af418f110303085ad0740c9eba46. Module imports, support namespace and local option directives adapted for Lean Pool.

Exact transformations of regular shell fields #

The actions in this module are the literal transformations used in ABK26: amplitude scaling, real spatial translation, spatial scaling, triadic shell scaling, negation, and signed-permutation conjugation. Each transformation acts on the stored first and second derivatives by the exact chain rule.

Instance caches for the derivative carriers #

The derivative carrier Vec d →L[ℝ] Mat d and the Hessian carrier Vec d →L[ℝ] (Vec d →L[ℝ] Mat d) are searched hundreds of times while elaborating this file. Caching the recurring classes once at module level (outside the section, so that every declaration sees them) turns each search into a single step. Every cache below is literally the instance Lean would otherwise rediscover.

Amplitude scaling #

Continuous scalar multiplication of matrix values.

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    Scale the values and both stored derivatives of an ambient shell.

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      @[simp]
      theorem Algsuperdiff.Frozen.Assumptions.ShellField.scale_apply {d : ℕ} (c : ℝ) (j : ShellField d) (x : HCPolySupport.Vec d) :
      (↑(scale c j)).1 x = c • (↑j).1 x

      Real spatial translations #

      Continuous translation of the spatial argument.

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        Translate the values and both stored derivatives of an ambient shell.

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          @[simp]
          @[simp]

          Translation by the zero vector is the identity on shell fields.

          Spatial scaling and triadic shell scaling #

          Continuous dilation of the spatial argument.

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            The second-derivative chain rule for spatial dilation.

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              Dilate a shell's spatial argument with the corresponding derivative factors.

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                Precompose with x ↦ r • x; the derivative carries the chain-rule factor r.

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                  @[simp]
                  theorem Algsuperdiff.Frozen.Assumptions.ShellField.spatialScale_apply {d : ℕ} (r : ℝ) (j : ShellField d) (x : HCPolySupport.Vec d) :
                  (↑(spatialScale r j)).1 x = (↑j).1 (r • x)
                  noncomputable def Algsuperdiff.Frozen.Assumptions.ShellField.triadicScale {d : ℕ} (gamma : ℝ) (k : ℤ) (j : ShellField d) :

                  The literal marginal scaling action 3^(γ k) j(3^(-k) ·).

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                    @[simp]
                    theorem Algsuperdiff.Frozen.Assumptions.ShellField.triadicScale_apply {d : ℕ} (gamma : ℝ) (k : ℤ) (j : ShellField d) (x : HCPolySupport.Vec d) :
                    (↑(triadicScale gamma k j)).1 x = Real.rpow 3 (gamma * ↑k) • (↑j).1 ((3 ^ k)⁻¹ • x)

                    Negation #

                    Value and derivative negation, as required by J3.

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                      @[simp]

                      Signed-permutation conjugation #

                      Matrix multiplication bundled as a continuous linear map on vectors.

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                        The linear map sending a matrix to its conjugate by R.

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                          The exact derivative action D ↦ (M ↦ RᵀMR) ∘ D ∘ (v ↦ Rv).

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                            The exact Hessian action H ↦ (v ↦ w ↦ Rᵀ H (Rv) (Rw) R).

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                              Rotate a shell's argument, values and stored derivatives together.

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                                Compatibility with CoarseGraining regular-field operations #