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Let $k$ be a field and let $A$ be a (commutative) $k$-algebra. Assume that for every maximal ideal $P \subseteq A$ the residue class field $A/P$ has finite dimension as a $k$-vector space.

Is there a name for $k$-algebras like that?

Clearly, finitely generated $k$-algebras $A$ satisfy this property, but what about the case $A$ not finitely generated over $k$?

Examples of such algebras can easily be obtained by localizing finitely generated $k$-algebras:

For instance let $\mathcal{O} = k[x]_{(x)}$ be the localization of the finite $k$-algebra $k[x]$ by the maximal ideal generated by $x$. Then $\mathcal{O}$ is a local ring with maximal ideal $P$ generated by $x$ which is a non finitely generated $k$-algebra. But it has a finite dimensional residue class field $\mathcal{O}/P \cong k$.

I was thinking about this since I am working with schemes over $k$ that do not need to be of finite type over $k$ but have finite dimensional residue class fields as above. I haven't encountered a definition or naming of this.

I am grateful for any kind of input. I posted this question also on math.stackexchange, but did not receive any answer or input.

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  • $\begingroup$ At least essentially finitely generated algebras (a localization of a finitely generated algebra) have this property. This condition arises frequently. $\endgroup$
    – Leo Alonso
    Commented Jun 8, 2020 at 10:52
  • $\begingroup$ I would very much like to say "residually finite", but that's already taken by group theory :-) $\endgroup$
    – M.G.
    Commented Jun 8, 2020 at 11:31
  • $\begingroup$ @LeoAlonso Essentially finite type includes localizations at arbitrary multiplicatively closed subsets, but the property desired by the OP is satisfied only if you semilocalize at maximal ideals. $\endgroup$
    – Mohan
    Commented Jun 8, 2020 at 14:38
  • $\begingroup$ There are also the completions of such local $k$-algebras, like $k[[x]]$, and any $k$-algebra in between. $\endgroup$ Commented Jun 9, 2020 at 10:14

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