Day convolution on Type-valued functor categories #
Mathlib equips the type synonym C ⊛⥤ V (MonoidalCategory.DayFunctor)
with the Day-convolution monoidal structure, subject to instance
hypotheses: existence of the relevant pointwise left Kan extensions and
preservation of colimits of the relevant costructured-arrow shapes by
tensorLeft/tensorRight in V. For V := Type v and C a small
monoidal category all of these hold via instances that Mathlib already
provides (Type v is monoidal closed and braided, so both tensoring
functors are left adjoints and preserve all colimits, and Type v has
all small colimits); the imports of Closed.Types and Closed.Braided
above are exactly what makes them synthesise.
What Mathlib does not provide is a braided (or symmetric) structure
on C ⊛⥤ V: Mathlib.CategoryTheory.Monoidal.DayConvolution.Braided
constructs the braiding and proves the hexagons at the level of
individual DayConvolution structures on plain functors, but never
assembles them into a BraidedCategory (C ⊛⥤ V) instance. This file
performs that assembly, at the same generality as Mathlib's
MonoidalCategory (C ⊛⥤ V) instance, and records the acceptance tests
for V := Type v at the bottom.
The Mathlib imports above are deliberate exceptions to the
RS.Common.MathlibDeps funnel: the Day-convolution modules are not
reachable from it.
The underlying functor of a tensor product in C ⊛⥤ V is a Day
convolution of the underlying functors. Local instance: Mathlib advises
against registering DayConvolution instances globally.
Equations
Instances For
Right-nested triple Day convolutions, phrased so that instance search
finds them behind the ⊛ notation.
Equations
Instances For
Left-nested triple Day convolutions, phrased so that instance search
finds them behind the ⊛ notation.
Equations
Instances For
The underlying natural transformation of a tensor product of
morphisms of C ⊛⥤ V is the induced morphism of Day convolutions.
Left whiskering in C ⊛⥤ V, read off on underlying natural
transformations.
Right whiskering in C ⊛⥤ V, read off on underlying natural
transformations.
The associator of C ⊛⥤ V, read off on underlying natural
transformations.
Inverse form of RS.natTrans_associator.
The braiding on C ⊛⥤ V, inherited from the Day-convolution
braiding of the underlying functors.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The Day-convolution monoidal structure on C ⊛⥤ V is braided when
C and V are. This discharges, for the type synonym, what
Mathlib.CategoryTheory.Monoidal.DayConvolution.Braided proves at the
level of individual convolutions.
Equations
- RS.dayFunctorBraided = { braiding := RS.dayFunctorBraiding, braiding_naturality_right := ⋯, braiding_naturality_left := ⋯, hexagon_forward := ⋯, hexagon_reverse := ⋯ }
The Day-convolution monoidal structure on C ⊛⥤ V is symmetric when
C and V are, via DayConvolution.symmetry.
Equations
- RS.dayFunctorSymmetric = { toBraidedCategory := inferInstance, symmetry := ⋯ }