PhysLean Documentation

PhysLean.QFT.PerturbationTheory.FieldOpAlgebra.Basic

Field operator algebra #

The set contains the super-commutators equal to zero in the operator algebra. This contains e.g. the super-commutator of two creation operators.

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    For a field specification 𝓕, the algebra 𝓕.FieldOpAlgebra is defined as the quotient of the free algebra 𝓕.FieldOpFreeAlgebra by the ideal generated by

    • [ofCrAnOpF φc, ofCrAnOpF φc']ₛF for φc and φc' field creation operators. This corresponds to the condition that two creation operators always super-commute.
    • [ofCrAnOpF φa, ofCrAnOpF φa']ₛF for φa and φa' field annihilation operators. This corresponds to the condition that two annihilation operators always super-commute.
    • [ofCrAnOpF φ, ofCrAnOpF φ']ₛF for φ and φ' operators with different statistics. This corresponds to the condition that two operators with different statistics always super-commute. In other words, fermions and bosons always super-commute.
    • [ofCrAnOpF φ1, [ofCrAnOpF φ2, ofCrAnOpF φ3]ₛF]ₛF. This corresponds to the condition, when combined with the conditions above, that the super-commutator is in the center of the algebra.
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      For a field specification 𝓕, ι is defined as the projection

      𝓕.FieldOpFreeAlgebra →ₐ[ℂ] 𝓕.FieldOpAlgebra

      taking each element of 𝓕.FieldOpFreeAlgebra to its equivalence class in FieldOpAlgebra 𝓕.

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        Super-commutes are in the center #

        The kernel of ι #

        Constructors #

        For a field specification 𝓕 and an element φ of 𝓕.FieldOp, ofFieldOp φ is defined as the element of 𝓕.FieldOpAlgebra given by ι (ofFieldOpF φ).

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          For a field specification 𝓕 and a list φs of 𝓕.FieldOp, ofFieldOpList φs is defined as the element of 𝓕.FieldOpAlgebra given by ι (ofFieldOpListF φ).

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            For a field specification 𝓕 and an element φ of 𝓕.CrAnFieldOp, ofCrAnOp φ is defined as the element of 𝓕.FieldOpAlgebra given by ι (ofCrAnOpF φ).

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              For a field specification 𝓕 and a list φs of 𝓕.CrAnFieldOp, ofCrAnList φs is defined as the element of 𝓕.FieldOpAlgebra given by ι (ofCrAnListF φ).

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                For a field specification 𝓕, and an element φ of 𝓕.FieldOp, the annihilation part of 𝓕.FieldOp as an element of 𝓕.FieldOpAlgebra. Thus for φ

                • an incoming asymptotic state this is 0.
                • a position based state this is ofCrAnOp ⟨φ, .create⟩.
                • an outgoing asymptotic state this is ofCrAnOp ⟨φ, ()⟩.
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                  For a field specification 𝓕, and an element φ of 𝓕.FieldOp, the creation part of 𝓕.FieldOp as an element of 𝓕.FieldOpAlgebra. Thus for φ

                  • an incoming asymptotic state this is ofCrAnOp ⟨φ, ()⟩.
                  • a position based state this is ofCrAnOp ⟨φ, .create⟩.
                  • an outgoing asymptotic state this is 0.
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                    For field specification 𝓕, and an element φ of 𝓕.FieldOp the following relation holds:

                    ofFieldOp φ = crPart φ + anPart φ

                    That is, every field operator splits into its creation part plus its annihilation part.