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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.

5 votes

Spectrum of the Grothendieck ring of varieties

This ring is very important for motivic integration; so it might be useful for you to read surveys on this subject. Yet I would say that this ring is too large and complicated. A reasonable factor-rin …
Martin Sleziak's user avatar
3 votes
1 answer
174 views

Are "strongly finite dimensional" homotopy invariant sheaves with transfers (locally) constant?

Moreover, I am actually interested in the extension of $S$ to pro-smooth (say, affine) $k$-schemes; and my finite dimensionality assumption corresponds to the finite dimensionality of $S(\operatorname{ …
0 votes
Accepted

Are "strongly finite dimensional" homotopy invariant sheaves with transfers (locally) constant?

I have proved this statement as Lemma 5.1.3 at Bondarko and Sosnilo - On Chow-weight homology of geometric motives. Comments are very welcome!
LSpice's user avatar
  • 12.9k
4 votes
1 answer
228 views

Which valuations of a field yield codimension $1$ subschemes of their 'models'

For a field $F$ (for example, a one generated by a finite number of its elements) there is a directed set of its 'models' (in this case those are 'arithmetic' schemes whose fraction field is $F$). …
5 votes
1 answer
681 views

For a morphism f from a regular scheme, should there exist an open subscheme U of the target...

All schemes are excellent. If the answer is 'yes', then: could one choose such an $U$ such that the preimage of any regular subscheme of $U$ is regular? Are these conditions on $U$ equivalent? …
2 votes
0 answers
175 views

Regular subscheme of a projective limit of schemes

I am actually only interested in equicharacteristic schemes, and the connecting morphisms are affine and dominant. …
4 votes
1 answer
525 views

Which schemes can be presented as limits of smooth varieties?

In this text I only treat schemes that are excellent separated of finite Krull dimension. So, I have the following questions. … Is there an interesting subclass in the class of all limit schemes of this sort? I don't want to restrict myself to affine schemes. …
0 votes
0 answers
256 views

How would you call a subscheme of a smooth $S$-scheme?

In my preprint I propose to call $X/S$ quasi-smooth if $X$ can be embedded into a smooth $X'/S$. Does this sound fine? Upd. So, smoothly embeddable is better? Is it ok to call a morphism smoothly emb …
6 votes
0 answers
222 views

If $X,Y$ are regular and of finite type over $S$, can $X\times _S Y$ be embedded into a regu...

Now, I am interested in the following setting: $X,Y$ are regular schemes of finite type over $S$; $S$ is separated excellent noetherian of finite Krull dimension (and one may assume that $X$ and $Y$ are …
2 votes
1 answer
1k views

Is every regular (excellent) scheme separated?

I need schemes that are regular, excellent and separated. Are these three conditions independent? …
2 votes
0 answers
368 views

Can any radiciel morphism be presented as the composition of a universal homeomorphism with ...

As in my previous questions, I am interested in excellent schemes of finite Krull dimension. …
4 votes
2 answers
331 views

Is the pre-image of a regular subscheme with respect to a universal homeomorphism of regular...

Let $f:X\to Y$ be a universal homeomorphism of regular (excellent finite-dimensional) schemes, $Z\subset Y$ be a regular subscheme. Is $f^{-1}(Z)$ necessarily regular? …
6 votes
1 answer
814 views

More on universal homeomorphisms

Is a universal homeomorphism of connected regular (excellent finite dimensional) schemes an isomorphism if these schemes are not positive characterstic ones? … Suppose that a finite morphism $f:X\to Y$ of connected regular (excellent finite dimensional) schemes is generically purely inseparable. …
2 votes
0 answers
215 views

When inverse image is conservative; a reference or a generalization?

I am interested in the following question: for $f$ being a morphism of schemes, which conditions ensure that $Rf^*_{et}$ is conservative? …
5 votes
0 answers
734 views

Do all the main properties of constructible and perverse sheaves (in an 'arithmetic' situati...

This question is a continuation of Bad behaviour of perverse sheaves over 'general' bases? Let $S$ (for example) be a finite type separated scheme over $\mathbb{Z}$. I would like: (1) to define the p …

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