As we know,a fine sheaf is also soft.So,I need some examples of the sheaves that are soft but not fine.Can the holomorphic sheaf $\mathcal O(X)$ be one?Any help and comments are accepted.Thanks a lot!
2026-03-27 16:54:00.1774630440
some examples of the Soft sheaves but not fine
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No, the sheaf of holomorphic maps can be not soft!
Example. Let $\displaystyle X=\left\{z\in\mathbb{C}:|z|\leq\frac{1}{2}\right\}$ be the "half unitary disk"; the holomorphic maps \begin{equation*} f(z)=\sum_{n=0}^{+\infty}z^n,\,g(z)=\sum_{n=1}^{+\infty}z^{n!} \end{equation*} can not be extendend to the whole of $\mathbb{C}$, so $\mathcal{O}_{\mathbb{C}}$ is neither soft nor fine. $\triangle$
Considering the constant sheaf $\mathcal{F}$ to $\mathbb{Z}$ on $\mathbb{A}^1_{\mathbb{C}}$ with Zariski topology; $\mathcal{F}$ is flabby but not fine (of course), so it is soft not fine.