Definition:Direct Image of Presheaf/Definition 2

Definition

Let $\mathbf C$ be a category.

Let $T_1 = \struct {S_1, \tau_1}$ and $T_2 = \struct {S_2, \tau_2}$ be topological spaces.

Let $f : T_1 \to T_2$ be continuous.

Let $\FF$ be a $\mathbf C$-valued presheaf on $T_1$.

The direct image of $\FF$ via $f$ is the $\mathbf C$-valued presheaf $f_*\FF$ that is the composition $\FF \circ \map {\operatorname{Open} } f$, where $\operatorname{Open}$ is the open subsets functor.

Also see

• Equivalence of Definitions of Direct Image of Presheaf