Questions tagged [enriched-category-theory]

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Interpreting a diagram in Borceux-Quinteiro's paper on enriched sheaves

I am somewhat new to working with enriched categories, and have a question about how to interpret Definition 1.2 in Borceux-Quinteiro's paper A theory of enriched sheaves. The authors consider a ...
memento morison's user avatar
12 votes
1 answer
177 views

Large V-categories admitting the construction of V-presheaves

By a result of Foltz, and Freyd and Street, a category $C$ is essentially small (i.e. equivalent to a small category) if and only if both $C$ and $[C^{\text{op}}, \mathrm{Set}]$ are locally small. I ...
varkor's user avatar
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3 votes
0 answers
54 views

Self-enrichment for a closed monoidal bicategory

First, there are two possible generalization of the notion of closed category, vertical and horizontal. I'm interested in the vertical one, something saying, I guess, that a monoidal bicategory $\...
Nikio's user avatar
  • 351
5 votes
1 answer
327 views

Day convolution and sheafification

$\DeclareMathOperator\Psh{Psh}\DeclareMathOperator\Sh{Sh}\newcommand\copower{\mathrm{copower}}$I was looking through Bodil Biering's thesis On the Logic of Bunched Implications - and its relation to ...
Anthony D'Arienzo's user avatar
7 votes
1 answer
213 views

Can every weighted colimit in a $\mathbf{Pos}$-enriched category be rephrased as a conical colimit?

For ordinary category theory, we have the following fact. A weighted colimit of a functor can always be equivalently expressed as a colimit of a different functor. Specifically, the weighted colimit ...
Nick Hu's user avatar
  • 161
2 votes
0 answers
127 views

Tensor product of objectwise weak homotopy equivalences of $\mathcal{M}$-spaces

I consider the enriched category $[\mathcal{M}^{op},\mathrm{Top}]$ of enriched functors (I call them $\mathcal{M}$-spaces) from the enriched small category $\mathcal{M}^{op}$ to the enriched category $...
Philippe Gaucher's user avatar
2 votes
0 answers
71 views

Are $\mathscr{V}$-modules uniquely (nicely) enrichable?

$\require{AMScd}\newcommand{\V}{\mathscr{V}}\newcommand{\M}{\mathcal{M}}\newcommand{\hom}{\operatorname{hom}}\newcommand{\op}{{^\mathsf{op}}}$Fix a closed symmetric monoidal category $(\V;\otimes;\...
FShrike's user avatar
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3 votes
1 answer
165 views

Enriched cofibrant replacement in spectrally enriched categories

If $\mathcal{V}$ is a monoidal model category with all objects cofibrant, Theorem 13.5.2. of Categorical Homotopy Theory will guarantee that the functorial cofibrant replacement of a $\mathcal{V}$-...
Connor Malin's user avatar
  • 5,191
0 votes
1 answer
180 views

Free enriched monoidal categories

Suppose $(\mathcal{V},\otimes,1)$ is a symmetric monoidal category and $\mathbb{C}$ is a $\mathcal{V}$-category. I will deliberately avoid usual powerful assumptions (eg completeness/cocompleteness) ...
Morgan Rogers's user avatar
0 votes
0 answers
98 views

Understanding this (standard?) notion of enriched product category

$\newcommand{\V}{\mathscr{V}}\newcommand{\A}{\mathcal{A}}\newcommand{\B}{\mathcal{B}}\newcommand{\C}{\mathcal{C}}$Fix a closed symmetric monoidal category $\V$, writing the product as $\otimes$, the ...
FShrike's user avatar
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7 votes
1 answer
136 views

Preservation of lax limits in categories of functors and lax natural transformations

Let $f:\mathbb{C} \to \mathbb{D}$ be a functor of 2-categories and let $\operatorname{Fun}(\mathbb{C},\operatorname{Cat})^{\operatorname{lax}}$ denote the 2-category of functors and lax natural ...
Abellan's user avatar
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8 votes
2 answers
415 views

Condition for an equivalence of functor categories to imply an equivalence of categories

Given small categories $\mathcal{C}$ and $\mathcal{D}$, we have that $[\mathcal{C}^\text{op},\textbf{Set}]\simeq[\mathcal{D}^\text{op},\textbf{Set}]$ if and only if the Cauchy-completions of $\...
Cameron's user avatar
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2 votes
1 answer
102 views

Can we do away with cotensors when exploring the equivalence between closed $\mathscr{V}$-modules and strongly tensored $\mathscr{V}$-categories?

$\newcommand{\M}{\mathcal{M}}\newcommand{\ML}{\underline{\mathcal{M}}}\newcommand{\N}{\mathcal{N}}\newcommand{\NL}{\underline{\mathcal{N}}}\newcommand{\V}{\mathscr{V}}\newcommand{\VL}{\underline{\...
FShrike's user avatar
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6 votes
1 answer
833 views

Are algebroids "just matrices"?

$\DeclareMathOperator\Vect{Vect}\DeclareMathOperator\Mat{Mat}$This question was originally asked on MSE but may be better here. Algebroids are particularly interesting structures: they are basically ...
Mike Battaglia's user avatar
8 votes
1 answer
383 views

Why are enriched (co)ends defined like that?

I'm mainly following references such as Kelly, Loregian and the nLab, and it seems customary there to generalize (co)ends to the enriched context (over a symmetric monoidal category $\mathcal{V}$) by ...
Nikio's user avatar
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3 votes
0 answers
75 views

Conditions for natural transformations of weights to induce adjunctions of weighted limits

Suppose we have: -) A $2$-category $\mathsf{J}$ -) A natural transformation of $\alpha : M \Longrightarrow W : \mathsf{J} \longrightarrow \mathsf{Cat}$ -) A functor $X:\mathsf{J} \longrightarrow \...
theAdmiral's user avatar
2 votes
1 answer
374 views

Why do we need enriched model categories?

As far as I understand, model categories mainly provide tools for studying the "homotopy theories" (that is, $\infty$-categories) that are ubiquitous in mathematics. From this point of view, ...
Arshak Aivazian's user avatar
1 vote
0 answers
100 views

Finite groups acting on algebraic groups and representations

Let $H$ be a connected algebraic group over an algebraically closed field $k$, and $I$ a finite group which acts on $H$ through group scheme morphisms. Denote by $Rep(H)$ the category of finite ...
SoruMuz's user avatar
  • 11
7 votes
0 answers
476 views

Condensed categories vs categories (co)tensored with condensed sets

I am not sure how to solve set-theoretic issues properly, so let me first ignore them. There are two notions, probably closely related: Condensed categories, i.e. condensed objects in the category of ...
Z. M's user avatar
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2 votes
2 answers
518 views

Can a category be enriched over abelian groups in more than one way?

An $\mathbf{Ab}$-category is a category enriched over the category of abelian groups. What is an example of a category that can be enriched over abelian groups in more than one way? An abelian ...
Didier de Montblazon's user avatar
9 votes
0 answers
99 views

Cocompleteness of enriched categories of algebras

A useful result due to Linton is that for a cocomplete category $C$ and monad $T$ on $C$, if the category of algebras $C^T$ admits reflexive coequalisers, then it is cocomplete (see here for a sketch ...
varkor's user avatar
  • 8,665
10 votes
0 answers
117 views

V-categories enriched in a monoidal V-category

In an email to the categories mailing list dated 21 August 2003, Street writes: Max reminded me of his old result (not in the LaJolla Proceedings, but known soon after) that a monoidal V-category is ...
varkor's user avatar
  • 8,665
2 votes
0 answers
114 views

Are homotopy colimits strict?

Let's say we are working with a fibrant simplicially enriched category $\mathbf{B}$ that has all limits and all homotopy limits, and let $\mathbf{A}$ be a full subcategory that is closed under weak ...
Giulio Lo Monaco's user avatar
2 votes
1 answer
190 views

Strictification of $\mathcal{V}$-pseudofunctors

Let $\mathcal{B}$ be a bicategory. Section 4.10 of Gordon, Power and Street's paper "Coherence for Tricategories" states that there is a bicategory $\textbf{st}\mathcal{B}$ and a ...
Zbyszek's user avatar
  • 23
12 votes
1 answer
354 views

What is the right notion of a functor from an internal topological category to a topologically enriched category?

Let $\mathcal{C}$ be a category internal to (some convenient model for) topological spaces (which I will denote by $\mathsf{Top}$). In the question Greg Arone asks: What is the correct notion of a ...
Niall Taggart's user avatar
3 votes
1 answer
53 views

Reference request for facts about bi(co)descent objects

I know the following facts are true, but I struggle to find adequate references for them: Let $T$ be a pseudo-monad on a bicategory $\mathcal{C}$, and let $A$, $B$ be pseudo-algebras for $T$. Then, ...
JeCl's user avatar
  • 901
1 vote
0 answers
63 views

Tensored and cotensored simplicial comma category

To transfer a tensored and cotensored simplicially enriched structure from a category $\mathcal{C}$ to $(\mathcal{C}\downarrow Z)$, we define $(X\to Z)\otimes K$ by the composite $(X\otimes K \to X \...
Philippe Gaucher's user avatar
5 votes
0 answers
85 views

Constructing lax limits from lax limits

Let $K$ be a 2-category. It's well-known that if $K$ has all PIE limits, then $K$ also has all lax limits. But I don't know a general "limit-decomposition" result which works "...
Tim Campion's user avatar
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6 votes
0 answers
176 views

Examples of nonpointwise Kan extensions that "play a mathematical role"

Most Kan extensions arising in nature are pointwise, and this observation prompts Kelly to write [1]: Our present choice of nomenclature is based on our failure to find a single instance where a [...
varkor's user avatar
  • 8,665
5 votes
1 answer
189 views

Enriched categories over a semi-monoidal category

Let $\mathcal{V}$ be a semi-monoidal category, meaning it satisfies the axioms of a monoidal category except missing a unit and the unit axiom. One could then still go about defining a $\mathcal{V}$-...
Bjorn's user avatar
  • 53
9 votes
1 answer
585 views

What are abelian categories enriched over themselves?

As far as I understand, an arbitrary abelian category is not enriched over itself, for example, $\mathrm{ChainComplex}(\mathrm{Ab})$ is, right? On the other hand, the categories $\mathrm{Mod}(R)$ (in ...
Arshak Aivazian's user avatar
5 votes
0 answers
301 views

$V$-cat and $V$-graph: coequalizers in the category of enriched functors

This question is regarding the 1974 JPAA paper $V$-cat and $V$-graph by Harvey Wolff. To be precise, I don't understand a certain step in the proof of Corollary 2.9, which (the corollary) is crucial ...
Jxt921's user avatar
  • 1,075
8 votes
1 answer
565 views

What is the right notion of a functor from an internal topological category to topological spaces?

Let $\mathcal C=(\mathcal O, \mathcal M)$ be a category internal to topological spaces. Thus $\mathcal O$ and $\mathcal M$ are topological spaces: the space of objects and the space of morphisms ...
Gregory Arone's user avatar
2 votes
0 answers
142 views

When this coend is invariant up to homotopy?

It is a follow-up of my question Calculation of the homotopy colimit of a diagram of spaces which was badly formulated. Consider a fixed diagram $D:I^{op}\to {\rm Top}$ where ${\rm Top}$ is a ...
Philippe Gaucher's user avatar
1 vote
0 answers
125 views

Universal property of the V-Mat construction

Internal categories and enriched categories can both be realised as monads in certain bicategories. If $\mathcal E$ is a category with pullbacks, then a monad in $\mathbf{Span}(\mathcal E)$ is a ...
varkor's user avatar
  • 8,665
2 votes
0 answers
38 views

Determining enriched limit-preserving functors by their global sections

Let $\mathcal{C}$ be a small 1-category and let $\mathcal{M}$ be a category enriched over the presheaf category $\widehat{\mathcal{C}}$ which is complete as $\widehat{\mathcal{C}}$ enriched category. ...
Martin Bidlingmaier's user avatar
5 votes
0 answers
143 views

Are weighted limits terminal in a category of cones?

Consider a Benabou-cosmos $(\mathcal{V},\otimes,J)$, $\mathcal{V}$-categories $\mathcal{I},\mathcal{C}$ and $\mathcal{V}$-functors $\mathcal{W}:\mathcal{I} \rightarrow \mathcal{V}$ and $\mathcal{D}:\...
Jonas Linssen's user avatar
6 votes
0 answers
845 views

Tannaka without Yoneda?

I am studying enriched categories, and as I wrote in my previous question How is the morphism of composition in the enriched category of modules constructed?, this is very difficult because there are ...
Sergei Akbarov's user avatar
5 votes
2 answers
562 views

How is the morphism of composition in the enriched category of modules constructed?

I asked this a week ago at MSE, but without success. I am studying enriched categories and I have a feeling that I am doing something wrong because all the way each step, each elementary proposition, ...
Sergei Akbarov's user avatar
3 votes
1 answer
295 views

When are enriched categories equivalent?

$F : \mathbf{MonCat} \to \mathbf{2Cat}$ is the 2-functor for change of enrichment. What is the maximal subcategory of $\mathbf{MonCat}$ whose arrows $b : V \to W$ each induce an equivalence of ...
Corbin's user avatar
  • 424
5 votes
1 answer
335 views

Does an Ab-enriched category have a unique Ab-enrichment?

I know that the group structure on Hom sets can be recovered from biproducts if they exit. Indeed, if $f, g : A \to B$ are two maps then there is a uniquely defined map $f \oplus g : A \oplus A \to B \...
Ben C's user avatar
  • 3,226
10 votes
1 answer
243 views

Structural properties of $\mathcal{V}$-$\mathsf{Cat}$

In this question $(\mathcal{V}, \otimes, e)$ is a (bi)complete symmetric monoidal category. We have an adjunction $$\mathscr{l}: \mathsf{Cat} \leftrightarrows \mathcal{V}\text{-}\mathsf{Cat} :(-)_0,$$ ...
Ivan Di Liberti's user avatar
11 votes
3 answers
799 views

Relation between Ind-completion and "additive"-ind-completion

Suppose that $\mathcal{C}$ is a skeletally small additive category. To enlarge $\mathcal{C}$ and produce a bigger category whose "small" objects can be identified with those in $\mathcal{C}$,...
3 A's's user avatar
  • 425
3 votes
0 answers
108 views

Density with respect to a family of diagrams, versus a class of weights

In Theorem 5.19 of Kelly's Basic Concepts of Enriched Category Theory, it is proven that a fully faithful functor $K \colon \mathcal A \to \mathcal C$ is dense if and only if $\mathcal C$ is the ...
varkor's user avatar
  • 8,665
12 votes
1 answer
662 views

Yoneda Lemma for monoidal functors

Let $(\mathcal V,\otimes,I)$ be a closed symmetric monoidal category, and let $\mathcal C$ be a $\mathcal V$-enriched category. The (weak) enriched Yoneda Lemma gives us a nice description of the set $...
Alexander Betts's user avatar
6 votes
1 answer
690 views

Examples of (co)ends

I am reading texts about (co)ends, and everywhere I see a lack of examples. I am not an expert in this area, and without examples it is difficult for me to use my intuition to grasp the idea. MacLane ...
Sergei Akbarov's user avatar
4 votes
1 answer
243 views

Explicit description of a pullback of $(2,1)$-categories

In the 1-category of 2-categories, with objects being categories enriched over Cat, and morphisms being 2-functors, is there an explicit way to describe a pullback of two functors $G:E\to D$ and $F:C\...
EBP's user avatar
  • 85
5 votes
0 answers
208 views

Is there a nice way to define discrete enriched categories?

In the setting of classical category theory, one defines the discrete category associated to a set $X$ as the category $X_\mathsf{disc}$ having the elements of $X$ as its objects and only identities ...
Emily's user avatar
  • 10k
4 votes
1 answer
733 views

How to compute Homotopy Pullback

What on Earth is a homotopy pullback of $$A \rightarrow B \leftarrow C \ \ \ \ \ ???$$ Here $A,B,C$ are elements of a category ${\mathcal V}$ enriched in topological spaces (any convenient category ...
Bugs Bunny's user avatar
  • 12.1k
1 vote
0 answers
151 views

Reference request: a class of matrices leading to interesting metric geometry

For $0 \le A \in GL(n,\mathbb{R})$, let $Aw = \Delta(A)$, where $\Delta$ denotes the map taking a matrix to a vector of its diagonal entries and/or forming a diagonal matrix from a vector, according ...
Steve Huntsman's user avatar