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Proposition Let $F: \operatorname{\mathcal{C}}\rightarrow \operatorname{\mathcal{D}}$ be a functor between categories, and suppose that $F$ admits either a left or a right adjoint. Then the induced map $\operatorname{N}_{\bullet }(F): \operatorname{N}_{\bullet }(\operatorname{\mathcal{C}}) \rightarrow \operatorname{N}_{\bullet }(\operatorname{\mathcal{D}})$ is a homotopy equivalence of simplicial sets.

Proof. Without loss of generality, we may assume that $F$ admits a right adjoint $G: \operatorname{\mathcal{D}}\rightarrow \operatorname{\mathcal{C}}$. Then there exist natural transformations $u: \operatorname{id}_{\operatorname{\mathcal{C}}} \rightarrow G \circ F$ and $v: F \circ G \rightarrow \operatorname{id}_{\operatorname{\mathcal{D}}}$ witnessing an adjunction between $F$ and $G$, so that $\operatorname{N}_{\bullet }(F)$ is a simplicial homotopy inverse of $\operatorname{N}_{\bullet }(G)$ by virtue of Example $\square$