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Enriched categories, topoi, abelian categories, monoidal categories, homological algebra.

1 vote

What are the relative advantages of n-fold categories and n-categories?

I believe is more a matter of tastes, personally I find easier and simpler n-fold categories than categories. For me n-fold categories are more natural and so are easier, for different reasons: for …
Giorgio Mossa's user avatar
5 votes

What is the difference between a function and a morphism?

Another interesting reason why categories cannot be identified always with categories having functions for morphisms is given in this paper, by Peter Freyd in which is proven that there are some categ …
Giorgio Mossa's user avatar
13 votes
Accepted

Categories presented with Arrows only, no objects: partial monoids

Of course you can define a (just-arrow) category $\mathcal C$ like a partial algebra which consist of: a set $\mathcal C$ (namely the set of arrows of your category), a set $D_\mathcal{C} \subseteq \ …
Giorgio Mossa's user avatar
1 vote
Accepted

Relations between ordinary functor categories and higher categories

Maybe this doesn't address completly to the question, but I think it's a start. Functor categories and higher categories are quite different objects, the only relation that I can think of is that usu …
Giorgio Mossa's user avatar
2 votes
Accepted

A notion of limit sketches that makes theories unique up to equivalence

If I understand correctly your question you are looking for some definition of limit-sketches such that if two sketches $\mathcal T$ and $\mathcal T'$ are Morita-equivalent (that is the categories of …
Giorgio Mossa's user avatar
7 votes

Multicategories vs Categories

Is there a way to recapture the additional understanding imparted by multicategories using higher categories? Well I would say so. Multicategories are basically categories whose morphisms have multi …
Giorgio Mossa's user avatar
1 vote
Accepted

Understanding the reason for the particular formulation of the definition of a concrete refl...

I suppose that there are possibly many different answer to this question. Here is the one I got. Being a reflector is equivalent to being an inclusion that has a left adjoint. In general being a co …
Giorgio Mossa's user avatar
6 votes

Category theorists stance on deductive systems

I think the idea should pretty much like this: once you drop the requirement for the deductive system to be freely generated from the axioms by the inference rules (i.e. you accept the existence of no …
Giorgio Mossa's user avatar
2 votes
Accepted

Basic category theory: Universality of adjunction unit is justified by Yoneda Proposition in...

By Yoneda for every natural transformation $\tau \colon \mathbf C(c,-) \to F$, where $F \colon \mathbf C \to \mathbf{Set}$ and $\mathbf C(c,-)$ is the covariant $\hom$-functor, is a family of function …
Giorgio Mossa's user avatar
4 votes
2 answers
646 views

Equivalence in $\infty$-categories

In every $n$-category (weak or strict) can be defined the concept of equivalence via a recursive definition: * an equivalence in a set ($0$-category) is just an identity; * for each $n \in \mathbb N$ …
Giorgio Mossa's user avatar
2 votes
1 answer
440 views

What are $n$-poset?

Yesterday I was wandering for the $n$-lab and I've found the definition of $n$-poset. Following this post it seems that a $n$-poset should be a $(n,n+1)$-category. Now an $(n,r)$-category should be a …
Giorgio Mossa's user avatar
8 votes
3 answers
3k views

What is higher dimensional algebra?

Could anyone explain what higher dimensional algebra is? I tried to look on the web but I couldn't find a satisfactory definition, the ones that I found are too vague. What I'm looking for is a good …
Giorgio Mossa's user avatar
4 votes

Categories First Or Categories Last In Basic Algebra?

A little preliminary: I'm an undergraduate student and I started to study category theory as self-taught at the beginning of second year of university, mostly because of my interest in logic and found …
20 votes
5 answers
3k views

Computations in $\infty$-categories

Direct to the point. Since now I've looked a lot of presentations of $\infty$-categories, but it seems that the only way to do explicit computations on these objects is via model categories. Is that s …
Giorgio Mossa's user avatar
2 votes

comparison between two monadic definitions for an operad

Well the two monads are quite different: in May definition you deal with an actual monad in $\mathbf {Cat}$ (i.e. a strict-$2$-category) while in the second case you work with monads in the bicategory …
Giorgio Mossa's user avatar

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