# Kerodon

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Proposition 7.1.3.9. Let $F: \operatorname{\mathcal{C}}\rightarrow \operatorname{\mathcal{D}}$ be an equivalence of $\infty$-categories and let $K$ be a simplicial set. Then:

$(1)$

A morphism $\overline{u}: K^{\triangleleft } \rightarrow \operatorname{\mathcal{C}}$ is a limit diagram if and only if the composition $F \circ \overline{u}$ is a limit diagram in $\operatorname{\mathcal{D}}$.

$(2)$

A morphism $\overline{u}: K^{\triangleright } \rightarrow \operatorname{\mathcal{C}}$ is a colimit diagram if and only if the composition $F \circ \overline{u}$ is a colimit diagram in $\operatorname{\mathcal{D}}$.

In particular, the equivalence $F$ preserves $K$-indexed limits and colimits.

Proof. We will prove $(1)$; the proof of $(2)$ is similar. Let $\overline{u}: K^{\triangleleft } \rightarrow \operatorname{\mathcal{C}}$ be a diagram and set $u = \overline{u}|_{K}$. We then have a commutative diagram of $\infty$-categories

$\xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}_{ / \overline{u} } \ar [r] \ar [d] & \operatorname{\mathcal{D}}_{ / (F \circ \overline{u} )} \ar [d] \\ \operatorname{\mathcal{C}}_{/u} \ar [r] & \operatorname{\mathcal{D}}_{ / (F \circ u )}. }$

Since $F$ is an equivalence of $\infty$-categories, the horizontal maps in this diagram are also equivalences of $\infty$-categories (Corollary 4.6.4.19). It follows that the left vertical map is an equivalence of $\infty$-categories if and only if the right vertical map is an equivalence of $\infty$-categories. The desired result now follows from the criterion of Proposition 7.1.2.12. $\square$