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Spin-flip symmetry and the Peierls long-range-order criterion

5 fully proved

A. The global spin flip

DefinitionGlobal spin flip of a configuration#✓fully proved

The global spin flip σ ↦ -σ of an infinite-volume configuration.

def flipConfig (s : ConfigSpace (Site d)) : ConfigSpace (Site d) := fun y => !(s y)
Uses 2 · Used by 1

DefinitionSpin flip inside the box#✓fully proved

The spin flip of a configuration inside the box Λ_n.

def flipInterior {n : ℕ} (τ : {x // x ∈ box d n} → Bool) : {x // x ∈ box d n} → Bool :=
  fun x => !(τ x)
Uses 2 · Used by 2

DefinitionSpin flip inside the box as an involutive equivalence#✓fully proved

The spin flip inside the box as an involutive equivalence.

def flipInteriorEquiv {n : ℕ} :
    ({x // x ∈ box d n} → Bool) ≃ ({x // x ∈ box d n} → Bool) where
  toFun := flipInterior
  invFun := flipInterior
  left_inv := flipInterior_involutive
  right_inv := flipInterior_involutive
Uses 3 · Used by 1

C. Magnetization at the origin

DefinitionFinite-volume magnetization at the origin#✓fully proved

The magnetization ⟨σ_0⟩ at the origin in the finite-volume Ising measure on Λ_n with boundary condition η, bond set B, inverse temperature β and field h.

noncomputable def fvMagOrigin (η : ConfigSpace (Site d)) (n : ℕ)
    (B : Finset (Sym2 (Site d))) (β h : ℝ) : ℝ :=
  ∑ τ : {x // x ∈ box d n} → Bool, fvProb η n B β h τ * spin (glue η τ) (origin d)
Uses 7 · Used by 2

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