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Jan 27, 2022 at 23:48 history edited Karl Schwede CC BY-SA 4.0
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Jan 27, 2022 at 23:42 history edited Karl Schwede CC BY-SA 4.0
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Jan 27, 2022 at 23:27 comment added Karl Schwede You are right, I screwed that up. Sorry. I will fix that.
Jan 26, 2022 at 22:31 comment added R. van Dobben de Bruyn If you ask that $\operatorname{Spec} S \to \operatorname{Spec} R$ induces isomorphisms on residue fields and is universally a homeomorphism, then the criterion is somehow the opposite of what you wrote: $S$ is iteratively generated by adjoining elements $x_i$ such that $x_i^2,x_i^3 \in R[x_1,\ldots,x_{i-1}]$. See Tag 0CND.
Jan 26, 2022 at 20:16 comment added Will Sawin The characterization of subintegral sounds wrong to me. If we take $R = k[x^2, x^3]$ and $S= k[x]$ then the condition in terms of elements is not satisfied but the map is a bijection on prime spectra with the extensions of residue fields all isomorphisms. On the other hand if $R$ and $S$ are fields then the condition in terms of elements is always satisfied but the extension of residue fields is usually not an isomorphism.
Jan 26, 2022 at 20:09 history edited Karl Schwede CC BY-SA 4.0
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Jan 26, 2022 at 19:47 history answered Karl Schwede CC BY-SA 4.0