Solitons: Differential equations, symmetries, and infinite-dimensional algebras
《Solitons: Differential equations, symmetries, and infinite-dimensional algebras》 · 第 48–49 页 · Section 2.3「Presheaves and sheaves」
The elements of $\mathcal F(U)$ are called sections of $\mathcal F$ over $U$. Very often we will also write $\Gamma(U,\mathcal F)$ instead of $\mathcal F(U)$.