PhysLean Documentation

PhysLean.QFT.PerturbationTheory.FieldSpecification.TimeOrder

Time ordering of states #

Time ordering for states #

Given a list φ :: φs of states, the (zero-based) position of the state which is of maximum time. For example

  • for the list [φ1(t = 4), φ2(t = 5), φ3(t = 3), φ4(t = 5)] this would return 1. This is defined for a list φ :: φs instead of φs to ensure that such a position exists.
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    Given a list φ :: φs of states, the left-most state of maximum time, if there are more. As an example:

    • for the list [φ1(t = 4), φ2(t = 5), φ3(t = 3), φ4(t = 5)] this would return φ2(t = 5). It is the state at the position maxTimeFieldPos φ φs.
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      Given a list φ :: φs of states, the list with the left-most state of maximum time removed. As an example:

      • for the list [φ1(t = 4), φ2(t = 5), φ3(t = 3), φ4(t = 5)] this would return [φ1(t = 4), φ3(t = 3), φ4(t = 5)].
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        Given a list φ :: φs of states, the position of the left-most state of maximum time as an element of Fin (eraseMaxTimeField φ φs).length.succ. As an example:

        • for the list [φ1(t = 4), φ2(t = 5), φ3(t = 3), φ4(t = 5)] this would return ⟨1,...⟩.
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          The sign associated with putting a list of states into time order (with the state of greatest time to the left). We pick up a minus sign for every fermion paired crossed.

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            The time ordering of a list of states. A schematic example is:

            • normalOrderList [φ1(t = 4), φ2(t = 5), φ3(t = 3), φ4(t = 5)] is equal to [φ2(t = 5), φ4(t = 5), φ1(t = 4), φ3(t = 3)]
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              Time ordering for CrAnFieldOp #

              timeOrderRel #

              For a field specification 𝓕, 𝓕.crAnTimeOrderRel is a relation on 𝓕.CrAnFieldOp representing time ordering. It is defined such that 𝓕.crAnTimeOrderRel φ₀ φ₁ is true if and only if one of the following holds

              • φ₀ is an outgoing asymptotic operator
              • φ₁ is an incoming asymptotic field operator
              • φ₀ and φ₁ are both position field operators where the SpaceTime point of φ₀ has a time greater than or equal to that of φ₁.

              Thus, colloquially 𝓕.crAnTimeOrderRel φ₀ φ₁ if φ₀ has time greater than or equal to φ₁. The use of greater than rather then less than is because on ordering lists of operators it is needed that the operator with the greatest time is to the left.

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                For a field specification 𝓕, and a list φs of 𝓕.CrAnFieldOp, 𝓕.crAnTimeOrderSign φs is the sign corresponding to the number of ferimionic-fermionic exchanges undertaken to time-order (i.e. order with respect to 𝓕.crAnTimeOrderRel) φs using the insertion sort algorithm.

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                  theorem FieldSpecification.crAnTimeOrderSign_swap_eq_time {𝓕 : FieldSpecification} {φ ψ : 𝓕.CrAnFieldOp} (h1 : crAnTimeOrderRel φ ψ) (h2 : crAnTimeOrderRel ψ φ) (φs φs' : List 𝓕.CrAnFieldOp) :
                  crAnTimeOrderSign (φs ++ φ :: ψ :: φs') = crAnTimeOrderSign (φs ++ ψ :: φ :: φs')

                  For a field specification 𝓕, and a list φs of 𝓕.CrAnFieldOp, 𝓕.crAnTimeOrderList φs is the list φs time-ordered using the insertion sort algorithm.

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                    theorem FieldSpecification.orderedInsert_in_swap_eq_time {𝓕 : FieldSpecification} {φ ψ φ' : 𝓕.CrAnFieldOp} (h1 : crAnTimeOrderRel φ ψ) (h2 : crAnTimeOrderRel ψ φ) (φs φs' : List 𝓕.CrAnFieldOp) :
                    ∃ (l1 : List 𝓕.CrAnFieldOp) (l2 : List 𝓕.CrAnFieldOp), List.orderedInsert crAnTimeOrderRel φ' (φs ++ φ :: ψ :: φs') = l1 ++ φ :: ψ :: l2 List.orderedInsert crAnTimeOrderRel φ' (φs ++ ψ :: φ :: φs') = l1 ++ ψ :: φ :: l2
                    theorem FieldSpecification.crAnTimeOrderList_swap_eq_time {𝓕 : FieldSpecification} {φ ψ : 𝓕.CrAnFieldOp} (h1 : crAnTimeOrderRel φ ψ) (h2 : crAnTimeOrderRel ψ φ) (φs φs' : List 𝓕.CrAnFieldOp) :
                    ∃ (l1 : List 𝓕.CrAnFieldOp) (l2 : List 𝓕.CrAnFieldOp), crAnTimeOrderList (φs ++ φ :: ψ :: φs') = l1 ++ φ :: ψ :: l2 crAnTimeOrderList (φs ++ ψ :: φ :: φs') = l1 ++ ψ :: φ :: l2

                    Relationship to sections #

                    Time ordering of sections of a list of states.

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                      theorem FieldSpecification.orderedInsert_crAnTimeOrderRel_injective {𝓕 : FieldSpecification} {ψ ψ' : 𝓕.CrAnFieldOp} (h : ψ.fst = ψ'.fst) {φs : List 𝓕.FieldOp} (ψs ψs' : CrAnSection φs) (ho : List.orderedInsert crAnTimeOrderRel ψ ψs = List.orderedInsert crAnTimeOrderRel ψ' ψs') :
                      ψ = ψ' ψs = ψs'

                      normTimeOrderRel #

                      The time ordering relation on CrAnFieldOp such that if two CrAnFieldOp have the same time, we normal order them.

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                        The relation normTimeOrderRel is decidable, but not computable so due to Real.decidableLE.

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                        The sign associated with putting a list of CrAnFieldOp into normal-time order (with the state of greatest time to the left). We pick up a minus sign for every fermion paired crossed.

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