Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 18702

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

1 vote

Is there a name for (pre)sheaves satisfying this transitivity condition?

I am not well-versed in these matters, but I believe Olivia Caramello uses something like this in her toposical formulation of Galois theory. See her paper and, if you can understand French, this brie …
Yuri Sulyma's user avatar
  • 1,838
13 votes
2 answers
1k views

What is the universal property of the Weyl group?

If $G$ is a group and $H\le G$ a subgroup, let $NH$ denote the normalizer of $H$ in $G$, and let $WH = NH/H$; following May's Concise Course, §3.4 this I call the Weyl group. I have also seen the defi …
Yuri Sulyma's user avatar
  • 1,838
9 votes
2 answers
474 views

Algebras in a bicategory of spans

$ \newcommand{\Span}{\mathbf{Span}} \newcommand{\cE}{\mathcal E} $Given a category $\cE$ with plenty of limits, let $\Span(\cE)$ denote the bicategory of spans in $\cE$. It is known that monads in $\S …
Yuri Sulyma's user avatar
  • 1,838
6 votes

Functor category's objects fail to be a class?

This can be circumvented (to some degree) if we use Grothendieck universes instead of classes. Roughly speaking, a set $\mathcal U$ is a universe if it's closed under all the operations we use in ZF. …
Yuri Sulyma's user avatar
  • 1,838
2 votes
2 answers
264 views

Automorphisms and Bicategories

Sorry if this isn't the right place for this, it hasn't gotten any answers on ME. I'm reading Lang's section on field theory and he stresses that, unlike typical "universal" constructions which are de …
Yuri Sulyma's user avatar
  • 1,838
3 votes
2 answers
741 views

Localization of symmetric monoidal category

Let $\mathcal M$ be a symmetric monoidal category, $S\subset \mathcal M$ a collection of objects and morphisms. I would like to construct the localization $\mathcal M \mathop{\longrightarrow}^T \mathc …
Yuri Sulyma's user avatar
  • 1,838
11 votes
4 answers
2k views

Embedding Theorem for topological spaces, and in general

There are many examples throughout mathematics of abstracting the formal properties of a "familiar" structure, but then having a theorem stating that all models of the abstract axioms embed into one o …
Yuri Sulyma's user avatar
  • 1,838