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Feb 26 at 22:52 comment added Alex Kruckman @DonuArapura That's right, no negations.
Feb 26 at 22:24 comment added Donu Arapura @AlexKruckman OK, thanks for the comment. I hadn't realized that there was a strong statement. I assume "positive" means no negations.
Feb 26 at 16:16 comment added Alex Kruckman @DonuArapura That's true, but the model-theoretic proof uses a refinement of the idea of quantifier elimination, namely that if a formula is preserved by all homomorphisms from subrings to algebraically closed fields (rather than all embeddings from subrings to algebraically closed) then it is equivalent to a positive quantifier-free formula, and as a consequence, it defines a Zariski-closed set, rather than just a constructible set.
Feb 21 at 14:54 history edited Alex Kruckman CC BY-SA 4.0
fixed a crucial typo in the last line
Feb 21 at 14:49 history edited Alex Kruckman CC BY-SA 4.0
cleaned up post, fixed typos, added a link to the paper, etc.
Feb 21 at 14:48 comment added Donu Arapura I admit that I haven't had the time or energy to read your question carefully. But probably yes: elimination of quantifiers for algebraically closed fields on the model theory side is equivalent in algebraic geometry to the fact the class of constructible sets is stable under projections.
Feb 21 at 12:56 history asked George CC BY-SA 4.0