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2 votes
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Significance of some expected results when defining Grothendieck topology

Let $\mathcal{C}$ be a category. Fixing an object $U$ of $\mathcal{C}$, there are some obvious functors we can associate to it, for example: $h_U:\mathcal{C}^{op}\rightarrow \text{Set}$ given by $V\ …
Praphulla Koushik's user avatar
0 votes

Grothendieck topology for a non-small category

Over a large site there is in general no sheafification functor https://ncatlab.org/nlab/show/sheafification. For how to get around this, the keyword is dense subsite https://ncatlab.org/nlab …
2 votes
1 answer
663 views

Why care about Grothendieck topology? [closed]

Noah Schweber said here the following: Why would you want a notion of sheaf theory for objects more general than topological spaces? Well, the original motivation (to my understanding) was to …
Praphulla Koushik's user avatar
2 votes
1 answer
540 views

Stack associated to Groupoid object in category $\text{Sch}/S$

Consider the category of manifolds $\text{Man}$. A groupoid object in the category of manifolds is called a Lie groupoid, denoted by $\mathcal{G}$. There is a way to associate a stack (over the cate …
Praphulla Koushik's user avatar
0 votes

What is the geometric description of the set of isomorphism class of $G$-torsors over a site...

This is not a complete answer, too long for a comment. If we start with an arbitrary site $\mathcal{C}$ and if we want to define the notion of a $G$-torsor over $\mathcal{C}$, then $G$ is not expecte …
Praphulla Koushik's user avatar