Transport of tensor powers and the permutation action along #
C ⥤ Ind C
The embedding RS.indOf : C ⥤ Ind C is monoidal up to isomorphism
(RS.indOfTensorIso, RS.Classical.Deligne.IndTensorExact). This
file upgrades that comparison to the full coherent package needed to
transport the symmetric-group action on tensor powers
(RS.Novel.Envelope.SymPerm) across the embedding:
RS.dayCoyonedaIso_hom_braidingandRS.dayCoyonedaIso_hom_associator— the co-Yoneda identifications ofRS.dayCoyonedaIsointertwine the Day braiding and the Day associator with the braiding and associator of the base, with Yoneda formsRS.dayYonedaIso_hom_braidingandRS.dayYonedaIso_hom_associator;RS.indOfUnitIso— the unit ofInd Cis the embedded unit;RS.indOfTensorIso_hom_braidingandRS.indOfTensorIso_hom_associator— the embedding-tensor comparison is compatible with braiding and associator:indOfwithindOfTensorIsois a braided monoidal functor up to isomorphism;RS.indOfPowIso— the tensor powers of an embedded object are the embedded tensor powers, with recursion lemmasRS.indOfPowIso_zero/RS.indOfPowIso_succ;RS.indOfPowIso_swapTop/RS.indOfPowIso_insertTop/RS.indOfPowIso_permMor— the permutation action on the tensor powers ofindOf.obj Xis conjugate, underindOfPowIso, to the embedded permutation action;RS.permMor_indOf_eq_zero_iffandRS.schurKilled_iff_indOf_map_permAlg_eq_zero— vanishing of the action transports faithfully across the embedding.
The Mathlib pin has Preadditive (Ind C) (for C preadditive with
finite colimits) but no Linear ℂ (Ind C) instance, so Ind C
carries no permAlg, so Schur vanishing cannot be stated on
Ind C; the lemmas above are the permMor-level substrate, which is
what the group-algebra layer would rest on were Linear ℂ (Ind C)
available.
The single-element method used throughout the Day-level proofs: a
morphism out of a (possibly iterated) Day tensor of corepresentables
is classified, through the Kan-extension universal property and the
Yoneda lemma, by one element — its value on the canonical element
RS.dayCoyonedaUnitElt assembled from identities. All coherence
comparisons are decided by evaluating both sides there.
The Day-convolution structure of a plain presheaf pair, read
through the synonym: makes the DayConvolution API available on
underlying functors of the Day category.
Equations
- RS.dayConvPlain F G = RS.dayConv { functor := F } { functor := G }
Instances For
The canonical element of the Day tensor of two corepresentables: the Kan-extension unit evaluated on the pair of identities.
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The canonical element of a left-nested triple Day tensor of corepresentables.
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The canonical element of a right-nested triple Day tensor of corepresentables.
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The left-nested triple Day tensor of corepresentables
corepresents evaluation at (a ⊗ b) ⊗ c: iterate the Kan-extension
universal property twice and read off the Yoneda lemma on the
external product of three corepresentables, which is definitionally
the corepresentable of the triple product category.
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Instances For
Evaluation of RS.dayEvaluation on a morphism of the Day
category.
The corepresentability of a Day tensor of two corepresentables classifies a morphism by its value on the canonical element.
The corepresentability of a left-nested triple Day tensor of corepresentables classifies a morphism by its value on the canonical element.
The classification of RS.dayCoyonedaIso under the
corepresentability of the Day tensor of two corepresentables: its
value is the identity of p ⊗ q.
RS.dayCoyonedaIso sends the canonical element to the
identity.
Right-whiskering RS.dayCoyonedaIso sends the left-nested
canonical element to the canonical element at (a ⊗ b, c).
Left-whiskering RS.dayCoyonedaIso sends the right-nested
canonical element to the canonical element at (a, b ⊗ c).
The Day associator carries the left-nested canonical element to the image of the right-nested one under the base associator.
Day convolution of corepresentables intertwines the associator: under the co-Yoneda identifications, the two reassociation routes of a triple Day tensor of corepresentables differ by precomposition with the associator of the base.
Day convolution of corepresentables intertwines the braiding: under the co-Yoneda identifications, the braiding of the Day tensor of two corepresentables is precomposition with the braiding of the base.
The forward and reversed transports along RS.dayMkIso
compose to the identity.
Cancellation form of RS.dayMkIso_hom_symm_hom, stated against
a leading morphism so that no identity is left behind.
Naturality of Coyoneda.objOpOp, forward form, at a general
double-opposite morphism.
The Day tensor of representables intertwines the braiding:
the Yoneda form of RS.dayCoyonedaIso_hom_braiding.
The Day tensor of representables intertwines the associator:
the Yoneda form of RS.dayCoyonedaIso_hom_associator.
The embedding into the Day presheaf category carries the embedding-tensor comparison to the Day-level comparison.
The indization equivalence's forward functor is braided: the
braiding of Ind C is transported across it.
Equations
- One or more equations did not get rendered due to their size.
The embedding into the Day presheaf category is braided.
Equations
- RS.instBraidedIndDayFunctorOppositeTypeIndToDay = { toMonoidal := RS.instMonoidalIndDayFunctorOppositeTypeIndToDay, braided := ⋯ }
The embedding-tensor comparison intertwines the braiding:
indOf with indOfTensorIso is a braided functor up to
isomorphism.
The embedding-tensor comparison intertwines the associator:
the associativity axiom of the monoidal-functor-up-to-isomorphism
structure of indOf.
The tensor powers of an embedded object are the embedded
tensor powers: n = 0 is RS.indOfUnitIso, and each successor
stage tensors the previous one with indOf.obj X and applies the
embedding-tensor comparison.
Equations
- RS.indOfPowIso X 0 = RS.indOfUnitIso
- RS.indOfPowIso X n.succ = CategoryTheory.MonoidalCategory.whiskerRightIso (RS.indOfPowIso X n) (RS.indOf.obj X) ≪≫ RS.indOfTensorIso (RS.tensorPow C X n) X
Instances For
The base case of the power comparison.
The defining recursion of the power comparison.
The embedding-tensor comparison conjugates the braiding block of
swapTop to its embedded form.
Transport of the top braiding: swapTop on the powers of an
embedded object is conjugate to the embedded swapTop.
Whiskering by one more embedded factor preserves the transport relation.
Transport of the insertion cycle: insertTop on the powers
of an embedded object is conjugate to the embedded insertTop.
Transport of the permutation action along the embedding
C ⥤ Ind C: the action of a permutation on the tensor powers of an
embedded object is conjugate, under RS.indOfPowIso, to the
embedded action.
Conjugation form of RS.indOfPowIso_permMor.
The faithfulness bridge: the embedding C ⥤ Ind C reflects
and preserves vanishing of morphisms.
Vanishing of the permutation action on an embedded object is vanishing of the embedded action.
Vanishing of the permutation action transports faithfully
along the embedding C ⥤ Ind C. This is the permMor-level form
of Schur-vanishing transport: the group-algebra form waits on a
Linear ℂ (Ind C) instance, which the Mathlib pin does not
provide.
Schur vanishing, read through the embedding: the shape μ
kills X precisely when the embedded action of its block idempotent
vanishes. Together with RS.permMor_indOf_eq_zero_iff this is the
substrate for transporting RS.SchurKilled to Ind C; phrasing the
Ind C side through permAlg needs Linear ℂ (Ind C), which is a
mainline decision.