The Stacks project

Comments 861 to 880 out of 9050 in reverse chronological order.

\begin{equation*} \DeclareMathOperator\Coim{Coim} \DeclareMathOperator\Coker{Coker} \DeclareMathOperator\Ext{Ext} \DeclareMathOperator\Hom{Hom} \DeclareMathOperator\Im{Im} \DeclareMathOperator\Ker{Ker} \DeclareMathOperator\Mor{Mor} \DeclareMathOperator\Ob{Ob} \DeclareMathOperator\Sh{Sh} \DeclareMathOperator\SheafExt{\mathcal{E}\mathit{xt}} \DeclareMathOperator\SheafHom{\mathcal{H}\mathit{om}} \DeclareMathOperator\Spec{Spec} \newcommand\colim{\mathop{\mathrm{colim}}\nolimits} \newcommand\lim{\mathop{\mathrm{lim}}\nolimits} \newcommand\Qcoh{\mathit{Qcoh}} \newcommand\Sch{\mathit{Sch}} \newcommand\QCohstack{\mathcal{QC}\!\mathit{oh}} \newcommand\Cohstack{\mathcal{C}\!\mathit{oh}} \newcommand\Spacesstack{\mathcal{S}\!\mathit{paces}} \newcommand\Quotfunctor{\mathrm{Quot}} \newcommand\Hilbfunctor{\mathrm{Hilb}} \newcommand\Curvesstack{\mathcal{C}\!\mathit{urves}} \newcommand\Polarizedstack{\mathcal{P}\!\mathit{olarized}} \newcommand\Complexesstack{\mathcal{C}\!\mathit{omplexes}} \newcommand\Pic{\mathop{\mathrm{Pic}}\nolimits} \newcommand\Picardstack{\mathcal{P}\!\mathit{ic}} \newcommand\Picardfunctor{\mathrm{Pic}} \newcommand\Deformationcategory{\mathcal{D}\!\mathit{ef}} \end{equation*}

On Wataru left comment #8850 on Lemma 61.8.7 in Pro-étale Cohomology

There's a typo in the following part of the proof of Lemma 097X, where should be with a prime ' (there, the ring has not been defined yet):

"the map is surjective too."


On Wataru left comment #8849 on Section 61.8 in Pro-étale Cohomology

There's a typo in the proof of Lemma 097U, where the last prime ' should be deleted:

"By Algebra, Lemma 04D1 we can write for some étale ring map "

There are other B' later in the proof, which are fine.


On Et left comment #8848 on Lemma 10.106.2 in Commutative Algebra

Proposed simpler proof: by lemma 00IP, hence the map is an inclusion. By lemma 00NO is an integral domain, and hence so is .


On Simon Vortkamp left comment #8847 on Section 80.6 in Bootstrap

Typo in Theorem 03Y3 assumption (b): It should be 'representable by algebraic spaces' instead of 'representable by algebraic paces'.


On Sean left comment #8846 on Section 27.8 in Constructions of Schemes

In 01M9, I believe that is nonzero but the ring of global sections is zero.


On Ignazio Longhi left comment #8845 on Section 10.3 in Commutative Algebra

I am afraid there is an ambiguity in (46) and (47). Listing them as two different items suggests that they denote different notions. However, in Definition 0518 they are explained to have the same meaning.


On Z. He left comment #8844 on Lemma 13.4.22 in Derived Categories

I think should be additive, since Definition 12.12.1 requires the cohomological -functors to be additive.


On Yassin Mousa left comment #8843 on Section 33.6 in Varieties

It might by helpfull to clearify that denotes a separable algebraic closure of in 33.6.4. At leat this is the notation that is used in 33.8.8. Of course this is equivalent to the fact that the base change to an algebraic closure is reduced. Maybe one could use the common notation instead.


On ZL left comment #8842 on Lemma 67.30.7 in Morphisms of Algebraic Spaces

In the fifth line of the proof, surjects to instead of ""


On ZL left comment #8841 on Section 35.33 in Descent

I am wondering about the title of this section. Is the word étale missing in the title (étale local on source-and-target)?


On Yunchi Zheng left comment #8840 on Section 34.13 in Topologies on Schemes

In the first example, is there a typo that should be ?


On ZL left comment #8839 on Lemma 67.31.1 in Morphisms of Algebraic Spaces

Typo: In the last three lines, is written as for twice.


On Marco Giustetto left comment #8838 on Section 29.11 in Morphisms of Schemes

8808 It is defined in the proof of Lemma 01SD, it is the fibred product of and along the maps (given by the restriction of ) and (the restriction of ).

About the argument in Lemma 01SD: you have the following commutative cube The front, left and right faces are pullbacks by construction. By the pasting law for pullbacks, therefore, so is the back one, which tells you that . And the latter is affine by Lemma https://stacks.math.columbia.edu/tag/01JQ . (Might it be worth adding the above explanation in Lemma 01SD?)


On Felix Janda left comment #8837 on Section 109.23 in Moduli of Curves

It appears that the proof of uniqueness of the contraction in Lemma 0E8A uses Lemma 0E89 instead of Lemma 0E7C.


On Ben Moonen left comment #8836 on Section 43.15 in Intersection Theory

Something's wrong with the phrasing of Definition 43.15.1 (tag 0AZV). I think this needs to be rewritten along the following lines: 'In the situation above, [...] if d > dim(Supp(M)), and equal to d! times [...] if d = dim(Supp(M)). For d = dim(Supp(M)) we therefore have [...]'


On yujitomo left comment #8835 on Section 101.33 in Morphisms of Algebraic Stacks

Is this a typo?? (the sentence after the statement of Lemma 0DLS)

This holds even if is not smooth over ! (←??)


On Rankeya left comment #8834 on Lemma 42.10.1 in Chow Homology and Chern Classes

In the statement of (3) should be ?


On Eduardo left comment #8833 on Section 15.78 in More on Algebra

Hello, I do not really understand why Lemma 15.78.2 implies that factors through . (Prove of Compact implies Perfect)


On Josh Lam left comment #8831 on Section 50.12 in de Rham Cohomology

Is there a reference for the claim (in Remark 0FMN) that the de Rham cohomology sheaves are locally free? Thanks!


On Wataru left comment #8830 on Lemma 15.89.3 in More on Algebra

In the following sentence, the last should be an :

"If is -power torsion, then the image of any map factors through "