Questions tagged [profunctors]
The profunctors tag has no usage guidance.
24
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Is there a name for this variant of the category of elements of a profunctor?
Let $\mathsf{C}$ be a category and let $P : \mathsf{C}^{\text{op}} \times \mathsf{C} \to \mathsf{Set}$ be a functor.
Let $\mathsf{E}$ be the category whose:
objects are pairs $(X,x)$, where $X$ is an ...
- 411
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votes
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Strictness of two operations on proarrow equipments
There are several equivalent definitions of a profunctor between categories $C$ and $D$. I'm interested in the following two:
A functor $C\times D^o \to \text{Set}$
A co-continuous functor between ...
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4
votes
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Adjunctions with respect to profunctors
Let $P : W° \times Y \to \mathbf{Set}$ and $Q : X° \times V \to \mathbf{Set}$ be profunctors, and let $L : X \to W$ and $R : Y \to V$ be functors. Suppose that $$P(Lx, y) \cong Q(x, Ry)$$ natural in $...
- 6,106
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Michel Thiébaud's thesis ("Self-Dual Structure-Semantics and Algebraic Categories")
I am looking for a copy of Michel Thiébaud's 1971 thesis Self-Dual Structure-Semantics and Algebraic Categories, which appears to be an early reference for the relationship between the Kleisli ...
- 6,106
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3
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Prof and the completion of Cat under right adjoints
In Bénabou's Les distributeurs, in which the bicategory of profunctors is introduced, Bénabou remarks (page 17, quoted below) that $\mathbf{Prof}$ may be viewed as the construction of a bicategory ...
- 6,106
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0
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134
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Promonoidal categories as $S$-algebras
A promonoidal category is a pseudomonoid in the monoidal bicategory $\bf Prof$, where the monoidal structure is given (on objects) by the product of categories.
I would like to show that promonoidal ...
- 12.1k
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2
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Profunctors as a Kleisli bicategory
There is some discussion on the nLab on seeing the free cocompletion $\mathbf{Psh}(\mathbf{A}) = [\mathbf{A}^{op}, \mathbf{Sets}]$, as a pseudomonad. The Yoneda embedding $よ \colon \mathbf{A} \to \...
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A multicategory is a ... with one object?
We all know that
A monoidal category is a bicategory with one object.
How do we fill in the blank in the following sentence?
A multicategory is a ... with one object.
The answer is fairly ...
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Is the category of profunctors $Prof(A,B)$ equivalent to $Prof(B,A)^{op}$?
$\def\Prof{\mathsf{Prof}}\def\Set{\mathsf{Set}}\def\tobar{\mathrel{\mkern3mu \vcenter{\hbox{$\scriptscriptstyle+$}}\mkern-12mu{\to}}}$Let $A$ and $B$ be categories. Define a profunctor $A\tobar B$ to ...
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Exponentials of profunctors
Suppose $f:B\to A$ is an exponentiable functor, so that pullback $f^\ast$ has a right adjoint $\Pi_f$. Then $f\times \mathbf{2} : B\times \mathbf{2} \to A\times \mathbf{2}$ is also exponentiable, and ...
- 62.4k
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The $\mathfrak L$ functor on $\textsf{Prof}$
$\def\L{\mathfrak{L}}\def\Prof{\mathsf{Prof}}$ Recall that Isbell duality $\text{Spec}\dashv {\cal O} : {\cal V}^{A^°} \leftrightarrows \big({\cal V}^A\big)^°$ allows us to define the functor
$$
\L : \...
- 12.1k
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Isbell duality for profunctors
$\def\L{\mathfrak{L}}\def\Prof{\mathsf{Prof}}$Let $A,B$ be two $\cal V$-categories, and define the functor
$$
\L : \Prof(A,B) \to \Prof(B,A)
$$
sending $K : A^° \times B \to \cal V$ into $\L(K) : (b,a)...
- 12.1k
4
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1
answer
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Does $\bf Prof$ admit all pseudolimits?
Does the bicategory $\bf Prof$ of categories, profunctors and natural transformations admit all pseudolimits?
By [Kel89, Prop. 5.1] it is enough to show that $\bf Prof$ admits products, cotensors, ...
- 12.1k
1
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1
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Profunctors and multicategories
I've been told that there is a way to link profunctors and multicategories, probably obtaining a multicategory from $\bf Prof$; I feel I didn't understand the meaning of this claim.
Can you provide ...
- 12.1k
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The Kan construction, profunctors, and Kan extensions
It's been a long time since I tried to understand the deep meaning of the "Kan construction", or "nerve-realization" adjunction
$$
\text{Lan}_y F \dashv N_F = \hom(F,1)
$$
that exists among the left ...
- 12.1k
5
votes
1
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Enriched Cauchy completions and underlying categories
The ordinary Cauchy completion $\overline{C}$ of a small category $C$ satisfies a number of conditions: Every idempotent in $\overline{C}$ splits, there's an equivalence of categories $[C^{op}, Set] \...
- 407
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Comparing right and left quasi-representable bimodules
Let $\mathcal V$ be your favourite (closed, symmetric) monoidal model category. To fix ideas, set $\mathcal V = \mathrm{Ch}(k)$, the category of chain complexes over a fixed commutative ring. Given a $...
- 2,009
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Ends and coends – analogues for higher arity – Horn Filling
Consider the setting of categories enriched over a suitable monoidal category $\mathbb V$.
We define $$\mathrm{Dist}(X,Y):=\mathbb V−\mathrm{Cat}(X^ \mathrm{op}⊗Y,\mathbb V).$$
Recall the definition ...
- 3,083
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grothendieck construction for profunctors
Given categories $X$ and $Y$ and a strong functor
$$D:X^{op}\times Y\to Cat$$
we can of course build the oplax colimit
$$\mathrm{colim}^{oplax}_{X^{op}\times Y}D$$
via the usual (covariant) ...
- 3,083
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Composition of Cat-valued distributors - compatible with grothendieck construction?
Let $C$ be a category and $F\in[C^{op}, Cat]$ be a strong functor.
(1) There are functors
$$hom_C(c',c)\times F(c)\to F(c').$$
(2) The grothendieck construction gives a 2-equvalence
$$\int_C: [C^{...
- 3,083
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Ends as a "cotrace" operation on profunctors
As mentioned here, there is a trace operation on the monoidal category of profunctors given by taking coends: for any profunctor $F : A\times X \nrightarrow B \times X$, there is a profunctor $Tr^X(F) ...
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References to using profunctors in program analysis?
Profunctors from a category to itself seem like they'd be useful in representing the result of a program analysis; I can imagine a profunctor that given some information about a function it tells you ...
- 1,490
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In what sense do the categorical trace and coend count fixed points?
According to the nlab, the categorical trace of a 1-endomorphism $F:C\to C$ in a 2-category is the set hom$(1_C, F)$ of global elements of $F$. If $F$ is a functor in the 2-category Cat, the ...
- 1,490
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Co-ends as a trace operation on profunctors
The n-lab site on profunctors (http://ncatlab.org/nlab/show/profunctor) describes profunctor composition as using a co-end to "trace out" the connecting variable:
$F\circ G := \int^{d\in D} F(-, d) \...
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