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For questions about sheaves on a topological space.

9 votes

Understanding the definition of stacks

What categories fibered in groupoids over $\mathcal{C}$ corresponds to stacks? A category fibered in groupoids over $\mathcal{C}$ is given by a functor $p_{\mathcal{F}}:\mathcal{F}\rightarrow \ma …
Praphulla Koushik's user avatar
9 votes
1 answer
442 views

Results in “generalised smooth spaces” that did not hold in the case of smooth manifolds

Consider the category of smooth manifolds $\text{Man}$. I quote from n-lab page: Manifolds are fantastic spaces. It’s a pity that there aren’t more of them. I understand that this category $\text{Ma …
Praphulla Koushik's user avatar
7 votes
3 answers
950 views

Encounters with partitions of unity

Not sure how this would be received here. This question is about smooth partitions of unity. Let $M$ be a manifold. Consider an open cover $\{U_\alpha\}_{\alpha\in \Lambda}$ of $M$. A collection o …
Praphulla Koushik's user avatar
3 votes
1 answer
745 views

Are cohomology functors sheaves?

Question is the following: Is the functor $H^n_{dR}:\text{Man}\rightarrow \text{Set}$ a sheaf with respect to open cover topology on $\text{Man}$? More generally, are cohomology functors sheaves in …
Praphulla Koushik's user avatar
1 vote
0 answers
625 views

Sheafification map is surjective

This is not a research level problem for sure. But, similar question was asked by some one else $2$ years back on Stack exchange has not received any attention. So, I thought it does not suit there …
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