PhysLean/HepLean/PerturbationTheory/FieldStruct/Basic.lean

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/-
Copyright (c) 2025 Joseph Tooby-Smith. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Joseph Tooby-Smith
-/
import HepLean.Lorentz.RealVector.Basic
import HepLean.PerturbationTheory.FieldStatistics.ExchangeSign
import HepLean.SpaceTime.Basic
import HepLean.PerturbationTheory.FieldStatistics.OfFinset
/-!
# Field structures
-/
/-- A field structure is a type of fields plus a specification of the
statistics (fermionic or bosonic) of each field. -/
structure FieldStruct where
/-- The type of fields. This also includes anti-states. -/
Fields : Type
/-- The specification if a field is bosonic or fermionic. -/
statistics : 𝓕 → FieldStatistic
namespace FieldStruct
variable (𝓕 : FieldStruct)
/-- Negative asymptotic states are specified by a field and a momentum. -/
def AsymptoticNegTime : Type := 𝓕.Fields × Lorentz.Contr 4
/-- Positive asymptotic states are specified by a field and a momentum. -/
def AsymptoticPosTime : Type := 𝓕.Fields × Lorentz.Contr 4
/-- States specified by a field and a space-time position. -/
def PositionStates : Type := 𝓕.Fields × SpaceTime
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/-- The combination of asymptotic states and position states. -/
inductive States (𝓕 : FieldStruct) where
| negAsymp : 𝓕.AsymptoticNegTime → 𝓕.States
| position : 𝓕.PositionStates → 𝓕.States
| posAsymp : 𝓕.AsymptoticPosTime → 𝓕.States
/-- Taking a state to its underlying field. -/
def statesToField : 𝓕.States → 𝓕.Fields
| States.negAsymp φ => φ.1
| States.position φ => φ.1
| States.posAsymp φ => φ.1
/-- The statistics associated to a state. -/
def statesStatistic : 𝓕.States → FieldStatistic := 𝓕.statistics ∘ 𝓕.statesToField
/-- The field statistics associated with a state. -/
scoped[FieldStruct] notation 𝓕 "|>ₛ" φ => statesStatistic 𝓕 φ
/-- The field statistics associated with a list states. -/
scoped[FieldStruct] notation 𝓕 "|>ₛ" φ => FieldStatistic.ofList
(statesStatistic 𝓕) φ
/-- The field statistic associated with a finite set-/
scoped[FieldStruct] notation 𝓕 "|>ₛ" "⟨" f ","a "⟩"=> FieldStatistic.ofFinset
(statesStatistic 𝓕) f a
end FieldStruct