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10 votes

Example of a smooth morphism where you can't lift a map from a nilpotent thickening?

Let $Y=\operatorname{Spec} k$ and let $X=\mathbb{P}^1_k$, viewed as $\operatorname{Spec} k[t]$ glued to $\operatorname{Spec} k[t^{-1}]$. Let $T = \operatorname{\bf Spec}(\mathcal{O}_X + \mathcal{O}_X( …
Bjorn Poonen's user avatar
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24 votes
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Example of a smooth morphism where you can't lift a map from a nilpotent thickening?

By wicked smoothness, $x_0$ lifts to some $x_T \in X(T)$. …
Bjorn Poonen's user avatar
  • 23.8k