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Results tagged with sheaf-theory
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user 5513
For questions about sheaves on a topological space.
7
votes
Accepted
Describing global sections of sheafifications
The following is a counterexample for $\mathcal{F}$ a presheaf of abelian groups (or sets, if you like).
Let $X=\lbrace a,b,c,d\rbrace$ with nontrival opens given by $\lbrace a \rbrace,\lbrace b \rbr …
- 4,790
19
votes
Accepted
The single-plus construction is not the left adjoint of the inclusion of separated presheaves?
If $(-)^+$ were left adjoint to $\iota$, we would have $(-)^+\circ\iota=id.$, but this is impossible since $(-)^+$ applied to a separated presheaf gives its sheafification.
- 4,790