Factor extraction from splitting data #
The dévissage engine of the trichotomy: from splitting data over
a duality datum, the unit of the splitting algebra is a direct
factor of the base change of the module. The insertion extends
B-linearly to an evaluation on the base change; the copairing
against the dual insertion supplies a coevaluation; the section
identity of the data makes the pair a retract.
The descent condition of the evaluation: an insertion
that is linear over the base through φ coequalizes the two
legs of the base-change tensor.
The evaluation of the insertion on the base change: the
B-linear extension of a base-linear insertion.
Equations
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Instances For
Defining equation of the evaluation.
Defining equation of the evaluation.
A base-linear insertion, bundled as a module morphism into the restricted regular module.
Equations
- RS.insHom A B φ w hw = CategoryTheory.Mod.Hom.mk' w hw
Instances For
The coevaluation core: swap the pair and push the dual factor into the algebra — the module tensor product lands in the base change.
Equations
- RS.splitCoevalCore A B φ w hw = CategoryTheory.CategoryStruct.comp (RS.modTensorSwap A M M') (RS.modTensorMap A (RS.insHom A B φ w hw) (CategoryTheory.CategoryStruct.id M))
Instances For
Defining equation of the coevaluation core.
Defining equation of the coevaluation core.
Evaluating the coevaluation core multiplies the two insertions: the core composite is any descended pair product.
The evaluation is linear over the algebra.
The evaluation is linear over the algebra.
The coevaluation: the copair element with its dual factor pushed into the algebra, multiplied against the algebra.
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Instances For
The coevaluation is linear over the algebra.
The coevaluation is linear over the algebra.
The retract identity (the dévissage step of the trichotomy): over splitting data, the coevaluation followed by the evaluation is the identity — the algebra is a direct factor of the base change of the module.
The evaluation, as a module morphism onto the regular module.
Equations
- RS.splitEvalMod A B φ v hv = CategoryTheory.Mod.Hom.mk' (RS.splitEval A B φ v hv) ⋯
Instances For
The coevaluation, as a module morphism from the regular module.
Equations
- RS.splitCoevalMod A B φ w d hw = CategoryTheory.Mod.Hom.mk' (RS.splitCoeval A B φ w d hw) ⋯