The Stacks project

Comments 941 to 960 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 Zhenhua Wu left comment #8760 on Lemma 10.50.17 in Commutative Algebra

the zero prime ideal of doesn't correspond to any ideal of because by the definition here we don't allow zero ideal in , unless you allow to be an ideal of .


On Tong Zhou left comment #8759 on Lemma 49.15.1 in Discriminants and Differents

Typo in the statement of 0BUL: in the displayed formula, "" should be "".


On Nico left comment #8758 on Lemma 59.68.2 in Étale Cohomology

Is there a reason that is decorated with ? It is already strictly Henselian (tag 04HX).


On ZL left comment #8755 on Lemma 85.7.2 in Simplicial Spaces

Typo:


On Colin Ni left comment #8754 on Lemma 12.19.10 in Homological Algebra

In the first sentence, I believe the should be


On Maozhou Huang left comment #8753 on Lemma 10.97.1 in Commutative Algebra

In the proof of (3), to apply 0315, we need to show that is finite. This seems true because is a Noetherian module ( is Noetherian). Am I correct?


On Boaz Moerman left comment #8752 on Lemma 10.120.17 in Commutative Algebra

Should (2) not also include the possibility of being a field? In Definition 10.50.13. (tag 00IE) fields are excluded from being DVRs, yet they are Dedekind domains as defined in this section.


On Anonymous left comment #8751 on Definition 10.50.13 in Commutative Algebra

Pedantic point, but do you want to allow fields to be discrete valuation rings? For example, Tag 034X seems to consider fields as discrete valuation rings, but the value group will trivial.


On David R left comment #8750 on Lemma 10.44.2 in Commutative Algebra

I was confused by this too. I believe the following clarifies the argument: given we may choose to be irreducible (for the full polynomial ring) by defining where is the gcd of the coefficients (well-defined because is a UFD). This subsequently shows that the given polynomial for is irreducible and therefore that is separable.


On left comment #8749 on Lemma 31.28.5 in Divisors

Don't we need to assume that is Noetherian?


On Michael left comment #8748 on Section 33.24 in Varieties

Why the image of is in Lemma 04Q0 ?


On Roy Shtoyer left comment #8747 on Lemma 10.9.7 in Commutative Algebra

I beleive the statement is supposed to be and not .

Also, I think it's useful to add an explanation about what does "all the elements of S act as automorphisms on N" mean - with respect to what action? I find it a bit confusing.


On Anonymous left comment #8745 on Lemma 12.5.10 in Homological Algebra

If " is left inverse to " means that is the identity (where means "apply first"), then I think "left" and "right" should be switched in this lemma.


On Matt Broe left comment #8744 on Section 10.126 in Commutative Algebra

Someone pointed out to me that this claim holds in more generality: finitely generated projective modules are dualizable objects in RMod, and tensoring with dualizable objects commutes with limits.


On Zhenhua Wu left comment #8743 on Lemma 30.8.1 in Cohomology of Schemes

I believe the lemma is wrong in the case . Unwrapping the definition we should have , which is compatitable with but not compatitable with when .


On Matt Broe left comment #8742 on Section 10.126 in Commutative Algebra

I have found the criterion given in claim 1 of the following link for commuting tensor with an inverse limit of modules useful, but have not seen it in any reference: https://math.stackexchange.com/a/4577954/304290 Perhaps it would be worth mentioning here, either on this tag or wherever else it would fit.


On Zongzhu Lin left comment #8741 on Section 23.12 in Divided Power Algebra

In the definition of Koszul complex , should the differential be defined by ?


On pkas left comment #8740 on Section 10.160 in Commutative Algebra

In the second part of the proof for 10.160.8 (the case of positive characteristic), the terminology is slightly confusing. I suggest rewording the condition required of to the commutative square , where are the projections and , and is a chosen isomorphism. Moreover, the map to lift using formal smoothness is the composition .

It could also be helpful for readers to mention that this proof shows that the map from Cohen rings (up to isomorphism) to fields (up to isomorphism) is injective.


On Paolo Lammens left comment #8739 on Section 110.9 in Examples

Here what is the ideal that defines the -adic topology/completion?


On Yicheng Zhou left comment #8738 on Lemma 37.46.3 in More on Morphisms

I guess that in the first sentence of the last paragraph should be only "geometrically connected"?