Example 26.23.10. The morphism $\mathop{\mathrm{Spec}}(\mathbf{Q}) \to \mathop{\mathrm{Spec}}(\mathbf{Z})$ is a monomorphism. This is true because $\mathbf{Q} \otimes _{\mathbf{Z}} \mathbf{Q} = \mathbf{Q}$. More generally, for any scheme $S$ and any point $s \in S$ the canonical morphism

$\mathop{\mathrm{Spec}}(\mathcal{O}_{S, s}) \longrightarrow S$

is a monomorphism.

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