140 lines
6 KiB
Text
140 lines
6 KiB
Text
/-
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Copyright (c) 2024 Joseph Tooby-Smith. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Joseph Tooby-Smith
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-/
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import HepLean.Meta.Informal
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/-!
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# Weyl fermions
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-/
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/-!
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## The definition of Weyl fermion vector spaces.
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We define the vector spaces corresponding to different types of Weyl fermions.
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Note: We should prevent casting between these vector spaces.
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-/
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namespace Fermion
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informal_definition leftHandedWeyl where
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math :≈ "The vector space ℂ^2 carrying the fundamental representation of SL(2,C)."
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physics :≈ "A Weyl fermion with indices ψ_a."
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ref :≈ "https://particle.physics.ucdavis.edu/modernsusy/slides/slideimages/spinorfeynrules.pdf"
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informal_definition rightHandedWeyl where
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math :≈ "The vector space ℂ^2 carrying the conjguate representation of SL(2,C)."
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physics :≈ "A Weyl fermion with indices ψ_{dot a}."
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ref :≈ "https://particle.physics.ucdavis.edu/modernsusy/slides/slideimages/spinorfeynrules.pdf"
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informal_definition altLeftHandedWeyl where
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math :≈ "The vector space ℂ^2 carrying the representation of SL(2,C) given by
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M → (M⁻¹)ᵀ."
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physics :≈ "A Weyl fermion with indices ψ^a."
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ref :≈ "https://particle.physics.ucdavis.edu/modernsusy/slides/slideimages/spinorfeynrules.pdf"
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informal_definition altRightHandedWeyl where
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math :≈ "The vector space ℂ^2 carrying the representation of SL(2,C) given by
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M → (M⁻¹)^†."
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physics :≈ "A Weyl fermion with indices ψ^{dot a}."
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ref :≈ "https://particle.physics.ucdavis.edu/modernsusy/slides/slideimages/spinorfeynrules.pdf"
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/-!
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## Equivalences between Weyl fermion vector spaces.
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-/
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informal_definition leftHandedWeylAltEquiv where
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math :≈ "The linear equiv between leftHandedWeyl and altLeftHandedWeyl given
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by multiplying an element of rightHandedWeyl by the matrix `εᵃ⁰ᵃ¹ = !![0, 1; -1, 0]]`."
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deps :≈ [``leftHandedWeyl, ``altLeftHandedWeyl]
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informal_lemma leftHandedWeylAltEquiv_equivariant where
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math :≈ "The linear equiv leftHandedWeylAltEquiv is equivariant with respect to the
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action of SL(2,C) on leftHandedWeyl and altLeftHandedWeyl."
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deps :≈ [``leftHandedWeylAltEquiv]
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informal_definition rightHandedWeylAltEquiv where
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math :≈ "The linear equiv between rightHandedWeyl and altRightHandedWeyl given
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by multiplying an element of rightHandedWeyl by the matrix `εᵃ⁰ᵃ¹ = !![0, 1; -1, 0]]`"
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deps :≈ [``rightHandedWeyl, ``altRightHandedWeyl]
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informal_lemma rightHandedWeylAltEquiv_equivariant where
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math :≈ "The linear equiv rightHandedWeylAltEquiv is equivariant with respect to the
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action of SL(2,C) on rightHandedWeyl and altRightHandedWeyl."
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deps :≈ [``rightHandedWeylAltEquiv]
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/-!
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## Contraction of Weyl fermions.
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-/
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informal_definition leftAltWeylContraction where
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math :≈ "The linear map from leftHandedWeyl ⊗ altLeftHandedWeyl to ℂ given by
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summing over components of leftHandedWeyl and altLeftHandedWeyl in the
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standard basis (i.e. the dot product)."
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physics :≈ "The contraction of a left-handed Weyl fermion with a right-handed Weyl fermion.
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In index notation this is ψ_a φ^a."
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deps :≈ [``leftHandedWeyl, ``altLeftHandedWeyl]
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informal_lemma leftAltWeylContraction_invariant where
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math :≈ "The contraction leftAltWeylContraction is invariant with respect to
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the action of SL(2,C) on leftHandedWeyl and altLeftHandedWeyl."
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deps :≈ [``leftAltWeylContraction]
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informal_definition altLeftWeylContraction where
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math :≈ "The linear map from altLeftHandedWeyl ⊗ leftHandedWeyl to ℂ given by
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summing over components of altLeftHandedWeyl and leftHandedWeyl in the
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standard basis (i.e. the dot product)."
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physics :≈ "The contraction of a left-handed Weyl fermion with a right-handed Weyl fermion.
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In index notation this is φ^a ψ_a ."
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deps :≈ [``leftHandedWeyl, ``altLeftHandedWeyl]
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informal_lemma leftAltWeylContraction_symm_altLeftWeylContraction where
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math :≈ "The linear map altLeftWeylContraction is leftAltWeylContraction composed
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with the braiding of the tensor product."
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deps :≈ [``leftAltWeylContraction, ``altLeftWeylContraction]
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informal_lemma altLeftWeylContraction_invariant where
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math :≈ "The contraction altLeftWeylContraction is invariant with respect to
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the action of SL(2,C) on leftHandedWeyl and altLeftHandedWeyl."
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deps :≈ [``altLeftWeylContraction]
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informal_definition rightAltWeylContraction where
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math :≈ "The linear map from rightHandedWeyl ⊗ altRightHandedWeyl to ℂ given by
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summing over components of rightHandedWeyl and altRightHandedWeyl in the
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standard basis (i.e. the dot product)."
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physics :≈ "The contraction of a right-handed Weyl fermion with a left-handed Weyl fermion.
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In index notation this is ψ_{dot a} φ^{dot a}."
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deps :≈ [``rightHandedWeyl, ``altRightHandedWeyl]
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informal_lemma rightAltWeylContraction_invariant where
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math :≈ "The contraction rightAltWeylContraction is invariant with respect to
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the action of SL(2,C) on rightHandedWeyl and altRightHandedWeyl."
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deps :≈ [``rightAltWeylContraction]
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informal_definition altRightWeylContraction where
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math :≈ "The linear map from altRightHandedWeyl ⊗ rightHandedWeyl to ℂ given by
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summing over components of altRightHandedWeyl and rightHandedWeyl in the
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standard basis (i.e. the dot product)."
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physics :≈ "The contraction of a right-handed Weyl fermion with a left-handed Weyl fermion.
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In index notation this is φ^{dot a} ψ_{dot a}."
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deps :≈ [``rightHandedWeyl, ``altRightHandedWeyl]
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informal_lemma rightAltWeylContraction_symm_altRightWeylContraction where
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math :≈ "The linear map altRightWeylContraction is rightAltWeylContraction composed
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with the braiding of the tensor product."
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deps :≈ [``rightAltWeylContraction, ``altRightWeylContraction]
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informal_lemma altRightWeylContraction_invariant where
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math :≈ "The contraction altRightWeylContraction is invariant with respect to
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the action of SL(2,C) on rightHandedWeyl and altRightHandedWeyl."
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deps :≈ [``altRightWeylContraction]
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end Fermion
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