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The first purpose of schemes theory is the geometrical study of solutions of algebraic systems of equations, not only over the real/complex numbers, but also over integer numbers (and more generally over any commutative ring with 1). It was finalized by Alexandre Grothendieck, during the 1950s and the 1960s.

45 votes
1 answer
2k views

Useful, non-trivial general theorems about morphisms of schemes

I'm trying to compile a list of non-obvious theorems about morphisms of schemes which are useful for general intuition but whose proofs are not easy/technical. … Mnemonic: reasonable schemes have quasi-projective "replacements" and proper schemes have projective "replacements" Hopefully it's clear now what I'm looking for. …
21 votes
1 answer
2k views

Are all formal schemes *really* Ind-schemes?

Denote the subcategory of formal schemes by $\FSch\subset \ALRS$. This raises a problem though. … There's no obvious way to turn a "formal scheme" in this sense into an ind-schemes (which are much more convenient for certain purposes). …
Saal Hardali's user avatar
  • 7,799
9 votes
1 answer
835 views

Algebro-geometric version of {vector fields} $\longleftrightarrow$ {flows} correspondence?

Main Question: What Is the correpondence between flows and vector fields in algebraic geometry? Here is a more precise statement could be an answer If it was true (I have no idea it is): "P …
Saal Hardali's user avatar
  • 7,799
6 votes
2 answers
939 views

An apparent equivalence of the category of affine schemes over $S$ and the category of quasi...

\operatorname{Spec} A \to S$ where $A$ ranges over all possible rings and whose morphisms are morphisms of schemes above $S$. … Being affine schemes over $S$ they can be considered as $\mathcal{O}_S$-algebras. Their intersection is the pullback which corresponds to their tensor product as $\mathcal{O}_S$-algebras. …
Saal Hardali's user avatar
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0 votes

What elementary problems can you solve with schemes?

One can prove this by a clever induction on dimension using punctured spectra of local rings and exact sequences in local cohomology both of which are difficult to deal with without schemes. …