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Errata and Addenda for Algebraic Geometry I (Edition 1) Show errata for edition 2

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840 errata listed.

PageDescriptionSubmitted byEd.
p. 0 - V,
Contents of chapter 2
The page's number of section "Excursion: Sheaves" of chapter 2 should be 47, not 46. Ehsan Shahoseini 1
p. 0 - VII,
Contents of Chapter 16
The page numbers given for the last 3 sections of Chapter 16 should be increased by one. p.528 should be p.529, p.532 should be p.533, p.539 should be p.540. F. Ebert 1
p. 1,
Line 10
The condition "If the polynomials f_i are linear" should be replaced by "linear with constant term $0$" (or the solution set is only an affine subspace, in general). Mahdi Majidi-Zolbanin 1
p. 1,
Line -16
The term "affine variety" is undefined at this point. Mahdi Majidi-Zolbanin 1
p. 2,
Line -8
Replace 1994 by 1995. J. Hilgert 1
p. 2,
Line 6
In "asserts that this equations has no solutions" the word "equations" should be replaced with "equation". Mahdi Majidi-Zolbanin 1
p. 5,
Line 12
then $X$ inherits many properties of $X'$ (rather than: of $X$) P. Barik 1
p. 7,
Figure 1
Replace $T_2^2-T_1^2(T_1+1)$ by $T_2^2-T_1^2(T_1+1)=0$. A. B. Nguyen 1
p. 7,
Example 1.1, first paragraph
Exercise 1.8 should be replaced by, or extended by, an example where the real-valued points are not connected with respect to the analytic topology, to illustrate the point "and sometime the visualizations obtained in this way may be deceptive, see Exercise 1.8." Mahdi Majidi-Zolbanin 1
p. 7,
Line 9
Replace "guide line" by "guideline". Mahdi Majidi-Zolbanin 1
p. 8,
16
Replace "field" by "fields". A. Graf 1 2
p. 10,
Theorem 1.8
Add the assumption that $A\ne 0$. D. Gerigk 1
p. 10,
Line -17
Omit ``We will not use this characterization for the proof of the Nullstellensatz.''. A simple form of it is used in the beginning of the proof of Lemma~1.9. J. Hilgert 1
p. 10,
Line 17
The definition of finite ring homomorphism is messed up. Replace it by: A homomorphism $R \rightarrow R'$ of rings is finite, if it is integral and $R'$ is generated as an $R$-algebra by finitely many elements. K. Mohri, C. Frank 1
p. 10,
Line -3
Replace $\beta_{n-1}+\beta_{n-2}a+\cdots +a^{n-1}$ by $-(\beta_{n-1}+\beta_{n-2}a+\cdots +\beta_0 a^{n-1})$. P. Zsifkovits 1
p. 11,
Line -6
The period at the end of the displayed formula and the space at the beginning of the next line should be removed. 1 2
p. 11,
Line 13 (in the Proof of Theorem 1.7)
The sentence "Then A[x^(-1)] is a finitely generated K-Algebra not equal to 0" is true for all nonzero x. The proof then shows that there exists a maximal ideal of A not containing x. So there is no need to use proof by contradiction. Mahdi Majidi-Zolbanin 1
p. 12,
Line 5
The space at the beginning should be removed. 1 2
p. 13,
Line -7
After ``hence'', add ``if $Z \cap U \ne \emptyset$''. U. Görtz 1
p. 13,
Line 15
Replace nonconnected by non-connected. P. Zsifkovits 1
p. 13,
Line 16
Replace "subset" by "open subset". A. Graf 1 2
p. 14,
Lemma 1.19 (2)
The statement remains true without the assumption that $I$ be finite: Let $\emptyset\ne V\subseteq X$ be open. It is enough to show that $V\cap U_i\ne\emptyset$ for all $i$, because this implies that the closure of $V$ in $X$ contains $U_i$, hence that $V$ is dense in $X$.
Let $I_1 = \{ i\in I;\ V\cap U_i=\emptyset\}$, $I_2=I\setminus I_1$. Then $X = \bigcup_{i\in I_1} U_i\cup \bigcup_{i\in I_2} U_i$, and this union is disjoint. In fact, assume $U_{i_1}\cap U_{i_2}\ne \emptyset$, $i_\nu\in I_\nu$. Since $V\cap U_{i_2}\ne \emptyset$ and any two non-empty opens in the irreducible space $U_{i_2}$ intersect, we find $U_{i_1}\cap U_{i_2}\cap V \ne \emptyset$, a contradiction to $i_1\in I_1$. Since $X$ is connected, $I_1$ must be empty.		 M. Schaller 1 2
p. 14,
3
In order to apply Zorn's Lemma here, one should note that every non-empty topological space $X$ indeed contains some irreducible subset, e.g., any singleton. L. Prader 1
p. 14,
Line 14
Replace ``than'' by ``then'' and omit ``be''. P. Zsifkovits 1
p. 14,
Line 10
Replace ``$\emptyset \ne J \subset I$'' by ``$\emptyset \ne J \subsetneq I$''. J. Buck 1
p. 14,
Lemma 1.19 (2)
Add the assumption that $X\ne\emptyset$. Ulrich Görtz 1
p. 14,
Proof of second part of Lemma 1.19
It would be helpful to explain better why $X$ has only finitely many irreducible components. Mahdi Majidi-Zolbanin 1
p. 15,
Line 14
Replace ``Every open subset'' by ``Every subspace''. T. Wedhorn 1
p. 15,
Line 15
Replace ``Every closed subset'' by ``Every subspace''. T. Wedhorn 1
p. 15,
Line -15
Replace "there existed" with "there would exist". F. Gispert Sánchez 1
p. 15,
Second sentence of the proof of Lemma 1.25(3)
It should say "there would exist a minimal element $Z \in \mathscr M$". Javier de la Bodega 1 2
p. 15,
Line -15
Replace $\mathscr M$ by $\mathcal M$. I. Tselepidis 1 2
p. 16,
Line -16
Replace $T_2-T_1^2$ by $T_1-T_2^2$. P. Zsifkovits 1
p. 16,
Line -13
Omit superfluous (. P. Zsifkovits 1
p. 17,
Line 20
Replace "function" by "functions". Ehsan Shahoseini 1 2
p. 19,
Line 9
In the diagram exchange $m$ and $n$. J. Buck 1
p. 19,
Line 12
Replace "obtain the desired inverse homomorphism" by "obtain the desired inverse map", as Hom(X,Y) is just a set. Mahdi Majidi-Zolbanin 1
p. 19,
Line -15
Replace ``Proposition 1.20'' by ``Proposition 1.32''. P. Zsifkovits 1
p. 19,
Line 11
In the definition of $f$ add the missing bracket at the end. T. Przezdziecki 1
p. 19,
Line 18
Add "contravariant" (or "opposite category of ..."). Denis Vogel 1 2
p. 19,
Line 14
Insert ``$A$'' after ``$k$-algebra''. J. Buck 1
p. 20,
Line -15
Replace ``set morphisms'' by ``set of morphisms''. P. Zsifkovits 1
p. 20,
Sentence after Def. 1.35
Replace "spaces with function over $K$" by "spaces with functions over $K$". Elias Gee 1 2
p. 20,
Line -4 (Proof of Lemma 1.38)
The proof can be simplified: The closed subset $V(f_1g_2 - f_2g_1)$ contains the dense subset $U$, hence equals $X$, and that implies $f_1g_2 - f_2g_1 = 0$, as desired. Mahdi Majidi-Zolbanin 1
p. 21,
Line 12
Require $V$ to be non-empty. Ulrich Görtz 1
p. 21,
Definition 1.39
An exception needs to be made if $U$ is the empty set. Nick Mertes 1
p. 21,
Line 8
Remove "of" in the sentence "how to identify elements of $f \in \mathscr O_X(U)$ with ..." Mahdi Majidi-Zolbanin 1
p. 22,
Line -14
Replace $g\circ f$ with $g\circ f_{|f^{-1}(U)}$. A.Graf 1
p. 23,
Line 15 (Def. 1.46 (2))
Replace ``finite covering'' by ``finite open covering''. F. Gispert Sánchez 1
p. 23,
Line 6
Replace ``manifolds'' by ``manifold''. J. Buck 1
p. 23,
Line -14
1.47 (i), "opposed category" should be "opposite category". Peng Du 1
p. 23,
Prop. 1.48
Add the assumption that $X\ne \emptyset$ (or put this into the definition of prevariety?). Ulrich Görtz 1
p. 23,
Cor. 1.47 (i)
Exclude the zero $k$-algebra. Ulrich Görtz 1
p. 24,
Proof of Lemma 1.50
The reduction step in the first paragraph is superfluous because the rest of the proof shows that $D(f)$ and $Y$ are isomorphic spaces of functions. Menachem Dov Mostowicz 1
p. 25,
Prop. 1.54
All the open subsets considered here, i.e., also $U'$ and $U$, $V$ in the final sentence, should be assumed to be non-empty. Ulrich Görtz 1
p. 25,
Proposition 1.54
Replace $\mathscr O(U) \to \mathscr O(U')$ by $\mathscr O_X(U) \to \mathscr O_X(U')$. Tien Nguyen Thanh 1 2
p. 26,
Prop. 1.56
Add that the inclusion $Z\to X$ is a morphism of prevarieties. Ulrich Görtz 1
p. 26,
Line -13
Replace $k$ by $R$. D. Gerigk 1
p. 27,
Line 5
Replace $R_n$ by $X_n$. Peng Du 1
p. 28,
Displayed equation in prop. 1.59
Replace ``exist'' by ``$\exists$''. P. Zsifkovits 1
p. 28,
Line 13
The reason provided after the "as ..." is not related to this definition giving a topology (you will not need this in a verification of the axioms for a toplogy; it is the final topology wr.t. the inclusion maps for the U_i). Instead, it is the reason that the U_i are open in this topology. Denis Vogel 1 2
p. 28,
Line 7
Replace "space with function" with "space with functions". F. Ebert 1
p. 29,
Line 2
Replace "space with function" with "space with functions". F. Gispert Sánchez 1
p. 29,
Line 8
Replace ``is then given by'' by ``is given abstractly by''. Furthermore, the map $K(U_i) \rightarrow K(U_j)$ maps $\frac{X_\ell}{X_i} \mapsto \frac{X_\ell}{X_j}\frac{X_j}{X_i} = \frac{X_\ell}{X_i}$. (I.e., as subfields of $K(X_0, \dots, X_n)$, the $K(U_i)$ all coincide, and coincide with $K(\mathbb P^n(k))$, and the isomorphism induced by our identifications is the identity map.) M. Kaneda 1
p. 29,
Proof of Corollary 1.60
For the proof of the second assertion, i.e. $\mathbb{P}^n$ is a prevariety, one needs to show the connectedness of $\mathbb{P}^n$. But the book use part (2) of Lemma 1.19 (to show irreduciblity) which itself needs the connectedness! If connectedness is trivial, the second assertion of the Corollary 1.60 is proved and there is no need to speak about Lemma 1.19 and irreduciblity; and if connectedness is not trivial, then one cannot use the Lemma 1.19. To resolve this, one should make the reference to Lemma 1.19 more precise: Use part (1) to show that $\mathbb P^n(k)$ is connected (from the construction and previous discussion it is clear that any two of the standard charts have non-empty intersection.). Then irreducibility follows from part (2) (which needs the connectedness), but that was already noted as a general fact in Proposition 1.48. Ehsan Shahoseini 1 2
p. 29,
Line 7
Add $g \ne 0$ in the description of the function field of $K({\mathbb P}^n(k))$. T. Wedhorn 1
p. 30,
Line -15
After "are again in a", add reference to Exercise 1.20 (b). Ehsan Shahoseini 1 2
p. 30,
Line -6
Replace $f_m$ by $f_r$ at the end of the line. Ehsan Shahoseini 1 2
p. 33,
Proof of Prop. 1.65
Some further explanations should be added, why the restrictions $h^{-1}(U_j)\to \mathbb A^m(k)$ are morphisms.
To be able to apply Proposition 1.59, we first consider the case $Y = \mathbb P^n(k)$. We now apply Exercise 1.14 which says that ${\rm Hom}(h^{-1}(U_j), \mathbb A^m(k)) = \mathscr{O}_{\mathbb P^n(k)}(h^{-1}(U_j))^m$. Since $h^{-1}(U_j)=D_+(f_j)$, the claim follows.
(Alternatively: The open subsets $D_+(f_j)$ actually are affine (as can be shown using the Veronese embedding, Exercise 1.30); using this one can avoid the use of Exercise 1.14.)
To handle the case of a general $Y$ note that ($Y$ being open in a closed subprevariety of projective space) $h^{-1}(U_j) = D_+(f_j)\cap Y$ is open in a closed subprevariety of $D_+(f_j)$. The map we are interested in is the composition of the natural inclusion of $D_+(f_j)\cap Y$ into $D_+(f_j)$ (a morphism by Propositions 1.51 and 1.56) and the map considered in the first step (where it was shown to be a morphism).		 Oria Frenkel 1 2
p. 33,
Lines 4 and 6
Replace $\mathbb P^n$ with $\mathbb P^m$ and $\mathbb A^n$ with $\mathbb A^m$. Safak Ozden 1
p. 33,
Line 21 and 22
Replace $\mathbb{P}_k^n$ by $\mathbb{P}^n(k)$. E. Hong 1 2
p. 34,
Line -5
Replace "function field" with "function fields". Ehsan Shahoseini 1 2
p. 34,
Line -12 (Cor. 1.71)
Insert "be" before "quadrics". Peng Du 1
p. 35,
Figure 1.2
Replace $X^2+Y^2-1$ by $X^2+Y^2=1$ and $XY-1$ by $XY=1$. A. B. Nguyen 1
p. 35,
Line 12
Replace "it" by ", the quadric of rank 3". Ehsan Shahoseini 1 2
p. 35,
Last displayed equation of proof of Cor. 1.71
Replace Quot by Frac (twice). Javier de la Bodega 1 2
p. 35,
Line 4
$r \gt 2$ (rather than: $r \gt 1$) P. Barik 1
p. 36,
Exercise 1.8
The statement of the exercise is correct as it stands, but it does not illustrate the phenomenon that connectedness for the Zariski topology does not imply connectedness for the analytic topology. It should be replaced by:
Show that the affine algebraic set $V(Y^2-X^3+X)\subset \mathbb A^2(k)$ is irreducible and in particular connected. Sketch the set $\{ (x, y)\in\mathbb R^2;\ y^2 = x^3-x\}$ and show that it is not connected with respect to the analytic topology on $\mathbb R^2$.		 Torsten Wedhorn/Alexey Beshenov 1
p. 38,
Exercise 1.20 (a)
$x_1, \dots , x_n \in k$ should be $x_1, \dots, x_n \in K$. Steven Jin 1 2
p. 38,
Exercise 1.21 (3)
Remove "in" in "The set of closed affine cones in $C\subseteq \mathbb A^{n+1}(k)$". Menachem D. Mostowicz 1
p. 40,
9
Replace "of functions" by "with functions". Peng Du 1
p. 40,
Line 15
"third point" should really say "second point" S. Jin 1 2
p. 41,
7
Replace "with the category" by "to the category". Peng Du 1
p. 44,
Proposition 2.10
Replace ``Let $A$ be a ring.'' by ``Let $\varphi\colon A\rightarrow B$ be a ring homomorphism.''. U. Görtz 1
p. 46,
Example 2.16
Replace Quot by Frac (twice). Javier de la Bodega 1 2
p. 46,
Line -7
Replace "$R$-module" by "an $R$-module". A. Graf 1 2
p. 46,
Line -14
It should say "non-equivalent"; i.e. the hyphen is missing. Javier de la Bodega 1 2
p. 48,
Line 9
Add the ``category of abelian groups'' as the first example. A. Kaučikas 1
p. 48,
Line -3 (def. 2.18.Sh2)
Replace "by (a)" with "by (Sh1)". F. Gispert Sánchez 1
p. 49,
Line -8
Replace "on an arbitrary open" by "on an arbitrary open subset $V$". Yuhao Cheng 1 2
p. 50,
Section 2.6 Line 3
Maybe replace ``containment'' by ``reverse containment'' or state explicitly in which direction the order goes. 1
p. 50,
Prop. 2.20
The basis B has to be closed under finite intersections for the (Sh) condition to be well-defined. (In Lemma 1.31 the notion of basis of topology is "defined", in passing, by requiring also that it is stable under finite intersections; but this appears to be non-standard terminology, so both places should be fixed.) Florian Ebert 1
p. 51,
Line 12
Replace ``if and only of'' by ``if and only if''. J. Watterlond 1
p. 51,
Line 8
$\mathscr O(U)$ should be $\mathscr O_{\mathbb C}(U)$ Ehsan Shahoseini 1 2
p. 51,
Line $-2$
Replace $s^x$ by ${s^x}_{|V_x}$. A. Graf 1
p. 53,
Line -2
Since $f^{-1}$ includes sheafification by definition, the restriction $\mathscr G_{|X}$ to an open subspace in this sense coincides with Example 2.19 (1) only if $\mathscr G$ is a sheaf. E. Viehmann 1
p. 54,
(2.8.2) and (2.8.3)
In the book, (2.8.3) is deduced from (2.8.2). However, it is not clear, how (2.8.2) can be proved without using either (2.8.3) or Proposition 2.27, so either the order should be changed, or further details on the proof of (2.8.2) should be added. Indeed, (2.8.3) can be proved without using (2.8.2) by noting that
$(f^{-1}\mathcal{G})_x \cong (f^+ \mathcal{G})_x = \varinjlim_{x \in V} (f^+ \mathcal{G})(V) = \varinjlim_{x \in V} \varinjlim_{f(V) \subseteq U} \mathcal{G}(U) = \varinjlim_{f(x) \in U} \mathcal{G}(U) = \mathcal{G}_{f(x)},$
where the first isomorphism is due to Proposition 2.24(1). Given the above, we can deduce (2.8.2) from (2.8.3): First note that it suffices to prove that $f^{-1}(g^+ \mathcal{H}) \cong f^{-1}(g^{-1} \mathcal{H})$, then observe that the induced stalk maps are isomorphisms by (2.8.3) and Proposition 2.24(1), thus (2.8.2) follows from Proposition 2.23(2). (See also Math StackExchange.)		 A. Graf / L. P. 1
p. 54,
Line 3
Replace ``$f(V)$'' by ``$f(U)$''. K. Mohri 1
p. 54,
Line -9
Replace ``sheaves'' by ``presheaves''. J. Watterlond 1
p. 54,
Line 2
Replace ``$X$'' by ``$Y$''. K. Mohri 1
p. 54,
Proof of Prop. 2.27
Introducing the element $t$ could be avoided. E. Viehmann 1
p. 55,
Line 11
Replace ``statements'' by ``statement''. D. Gerigk 1
p. 55,
9
Replace "limit" by "inductive limit". Peng Du 1
p. 55,
Line 2 (Remark 2.28)
The assumption on $\psi$ should be that it is a morphism of presheaves. L. P. 1
p. 55,
Line -13
Insert "$U$" after "open subset". F. Ebert 1
p. 58,
Proof of Thm. 2.33
In the proof, you write: ``As $D(f)$ is quasi-compact, we can assume that $I$ is finite.'' Indeed, this works for condition (1); however, it is less trivial for (2). Of course, the strategy of proof (i.e., reducing to the case of finite $I$) is successful, but I do think that this deserves an explanation. The key step is to note that any finite subcovering $D(f) = \bigcup_{i \in I} D(f_i) = \bigcup_{j=1}^k D(f_{i_j})$ (where $I$ is possibly infinite) gives rise to a finite subcovering $D(f_l) = \bigcup_{j=1}^k D(f_{i_j}) \cap D(f_l) = \bigcup_{j=1}^k D(f_{i_j} \cdot f_l)$ for every $l \in I$, and then to apply (1). L. P. 1
p. 58,
Line -2
The third sum should be over the index set $I$ instead of $J$. Sebastian Schlegel Mejia 1
p. 59,
Def. 2.34
Replace "A locally ringed space $(X, \mathscr O_X)$ is called affine scheme" with "... is called an affine scheme". Elias Gee 1 2
p. 60,
Line -9
Replace "$f\in A$" by "$f\in A\setminus \{0\}$". Harmeet Singh 1 2
p. 60,
Line -9
Exclude $f=0$ here. Philipp Reichenbach 1 2
p. 61,
Line 8
Replace $i^\flat_x$ by $i^\sharp_x$. A. Graf 1 2
p. 61,
Lines -3, -2
Replace ``$\mathfrak a$'' by ``$\mathfrak a_1$'' and ``$\mathfrak b$'' by ``$\mathfrak a_2$''. P. Zsifkovits 1
p. 62,
Exercise 2.6
Replace "if and only if it the complement ..." by "if and only if it is the complement ...". Long-Ping Li 1 2
p. 62,
Line -18
Insert "is" before "the complement". Philipp Reichenbach 1 2
p. 62,
Exercise 2.3 line 2
Change "every open subset" to "every non empty open subset" Vishal Gupta 1
p. 63,
Exercise 2.9 (b), line 1
Make it clearer that the reference points to Section (B.13), not to Def. B.13. Viktor Tabakov 1
p. 63,
Exercise 2.13
In property (i), add the requirement that $\mathscr F(\emptyset)$ is a set with one element. Louis Martini 1
p. 63,
Line 8 (ex. 2.9 (d))
Replace "elements of $u \in A$" with "elements $u \in R$". F. Gispert Sánchez 1
p. 63,
Exer. 2.13 (b)
The assumption that $X$ be connected can be omitted. A. Beshenov 1
p. 64,
Exer. 2.15
The assumption that $X$ be locally compact is superfluous. V. Paškūnas 1 2
p. 64,
Ex.~2.14 (c)
The condition that $Z$ is locally connected is not sufficient. It should be replaced by the condition that every point in the closure of $Z$ has a fundamental system of open neighborhoods which intersect $Z$ in a connected set. J. Calabrese 1
p. 64,
Line 19 (Exercise 2.16)
Replace "show an analogous results" by "show that an analogous result holds". 1
p. 65,
Line -6
Replace "equivalence " by "anti-equivalence ". Yuhao Cheng 1 2
p. 65,
Line -14
Replace "subset" by "open subset". A. Graf 1 2
p. 67,
Prop.+Def. 3.2 (2)
Note that the affine open subschemes are not closed under finite intersections. This is inconsistent with the notion of a basis of a topology "defined" in Lemma 1.31. F. Ebert 1
p. 67,
Line -6
Replace ``constitute homomorphism'' by ``constitute a homomorphism''. D. Gerigk 1
p. 68,
Use consistent terminology: ``principal open'' or ``principally open'' subset. E. Viehmann 1
p. 69,
10
Replace "(or more" by ". More". Peng Du 1
p. 70,
Line -5
Replace "with an open subscheme of $T_i$" by "with an open subscheme $T_i$ of $T$". E. Hong 1 2
p. 70,
Prop. 3.8
Add a reference to Exer. 2.18. A. Graf 1 2
p. 70,
Prop. 3.10
Add a reference to Exer. 2.16. (And/or odd a reference to Prop. 3.10 to the exercise.) A. Graf 1 2
p. 71,
Line 18
$U \subseteq \psi_i(U_i) \cap \psi_j(U_j)$ (rather than: $U \subseteq U_i \cap U_j$) P. Barik 1
p. 71,
Example 3.12
Replace ``$\prod_{i=1}^n A_i$'' by ``$\mathop{\rm Spec}\prod_{i=1}^n A_i$''. P. Zsifkovits 1
p. 71,
Last line of the proof
Replace ``$X = \bigcup U_i$'' by ``$X = \bigcup_{i \in I} \psi_i(U_i)$''. L. P. 1
p. 71,
3rd paragraph in the proof
$\mathcal{O}_{U_{ij}}(U)$ is not well--defined. Instead, one could write: ``$\ldots$ then we identify $$\mathcal{O}_{U_i}(\psi_i^{-1}(U)) = \mathcal{O}_{U_{ij}}(\psi_i^{-1}(U)) \cong (\varphi_{ij})_*\mathcal{O}_{U_{ji}}(\psi_i^{-1}(U)) = \mathcal{O}_{U_{ji}}(\varphi_{ij}^{-1}\psi_i^{-1}(U))) $$ $$ = \mathcal{O}_{U_{ji}}(\psi_j^{-1}(U)) = \mathcal{O}_{U_j}(\psi_j^{-1}(U))$$ via $\varphi_{ij}$.'' L. P. 1
p. 72,
Line -9
Exchange the indices $\frac{X_i}{X_j}$ and $\frac{X_j}{X_i}$, and reverse the direction of the arrow. F. Grelak, A. Elashry 1
p. 73,
15
Replace ``subset'' by ``a subset''. E. Viehmann 1
p. 74,
Line 7
Replace the reference to Section (4.14) by a reference to Section (4.13). N.T. 1 2
p. 76,
Line 20
Replace ``ideals'' by ``ideal''. D. Gerigk 1
p. 77,
Proof of Prop. 3.27 (2)
At this point in the proof, $X$ is not yet assumed to be affine. But $V(f)$ has only been defined in the affine setting until this point in the book. So it might be worth noting that $V(f)$ denotes the set of $x\in X$ where $f(x)=0$ in the sense of the penultimate paragraph of p.57. This is a closed subset of $X$ by Ex. 2.19. (Later in the book, $X_f$ is reintroduced after Def. 7.15, without reference to Ex. 2.19). Denis Vogel 1 2
p. 77,
Line 12
Replace ``scheme'' by ``non-empty scheme''. M. Jarden 1
p. 78,
Prop. 3.29(2)
The "$V$" appearing in the statement of (2) is not related to the "$V$" introduced in the proof of (2). L. P. 1
p. 78,
End of proof of Prop. 3.29(3)
It might be worthwile to spell out the argument of Example 2.37 more explicitly. E. Viehmann 1
p. 78,
Prop. 3.29 (3)
Add the assumption that all $U_i$ are non-empty. D. Gerigk 1
p. 79,
Proof of Prop. 3.33
Replace the beginning of the first sentence by "If $x\in X$ and if $U={\rm Spec} A$ is an affine open neighborhood of $x$, then $x$ is closed in $U$ and corresponds to ..." A. Graf 1 2
p. 79,
Proof of Lemma 3.32, second paragraph
Replace "the $f_i$ generated the" by "the $f_i$ generate the". L. P. 1
p. 79,
Line 14
Replace ``locally finite type'' by ``locally of finite type''. J. Watterlond 1
p. 79,
Proposition 3.33
It might be worthwile to aim for a consistent notation for algebraically closed vs. not necessarily algebraically closed fields (e.g., $k$ versus $K$). V. Gupta 1
p. 79,
Line -1 (Proof of Prop 3.33)
Replace "(1)" with "(i)" , "(2)" with "(ii)" and "(3)" with "(iii)". R.Ishizuka 1
p. 79,
Line 12
Replace "if follows" with "it follows". F. Gispert Sánchez 1
p. 80,
Corollary 3.36
Make it more explicit that $k=\kappa(x)$ means that the natural homomorphism $k\rightarrow\kappa(x)$ is an isomorphism (rather than just the existence of any isomorphism between these two fields). V Gupta 1
p. 81,
10
Replace "opposed category" by "opposite category". Peng Du 1
p. 81,
Proof of Thm. 3.37
The point that $X(k)$ is connected should be addressed explicitly. A. Graf 1 2
p. 81,
Line 7
Add reference to Proposition 3.27(2) for proving the equivalence of (i) and (ii). Yuhao Cheng 1 2
p. 81,
Line 11, line 21
"Definition 1.15" should be replaced with "Definition 1.46". In line 21, replace "is the sense" by "in the sense". Alexander Isaev 1
p. 82,
Line -21
Add index $i$ to the second intersection. A. Graf 1 2
p. 82,
Line 13
Replace ``points'' by ``type''. D. Gerigk 1
p. 83,
The line after the title: (3.14) Open Immersions
3.2 should be Section (3.2) Yuhao Cheng 1 2
p. 83,
Line -8
Replace "$j_*\mathscr O_Y$" by "$(j_*\mathscr O_Y)_{|U}$". Peng Du 1
p. 84,
Def. 3.41 (1)
The definition of closed subscheme is not ideal, because it does not become sufficiently clear when two closed subschemes are equal. It would be better to say that a closed subscheme is given by a closed subset $Z\subseteq X$ together with an ideal sheaf $\mathscr J\subseteq \mathscr O_X$ such that certain properties hold. Ulrich Görtz 1
p. 85,
Line 14
Replace "$\varphi(g)|U$" with "$\varphi(g)_{|U}$". F. Gispert Sánchez 1
p. 85,
Proof of Thm. 3.42, Condition (2)
Omit ``and $x \not\in U_i$ for all $i$'' (this is neither (a priori) possible in general, e.g. if $X$ is irreducible and $x$ its generic point, nor necessary in the sequel of the proof). B. Heintz 1
p. 85,
Line -17
Replace ``biggest'' by ``largest''. P. Johnson 1
p. 86,
Line -2
Replace "Remark 3.45" by "Example 3.45". Peng Du 1
p. 88,
Line -7
Replace "ordered set" by "partially ordered set". Peng Du 1
p. 88,
3rd line of the proof of Prop. 3.52
Replace "on" by "in" in the sentence "[...] $Z$ is closed on $U$". 1
p. 90,
Line 21
Replace "component" by "components". A. Graf 1 2
p. 90,
Ex. 3.14
Add the assumption that the maximal ideal of $A$ is the union of all prime ideals properly contained in it. See Knaf's answer to this question on MathOverflow. B. Heintz 1
p. 90,
Exercise 3.19
Replace ${\rm Hom}({\rm Spec}(R), \mathbb P^n_R)$ by ${\rm Hom}_{R}({\rm Spec}(R), \mathbb P^n_R)$ to make explicit that we only consider $R$-morphisms here. A. Graf 1 2
p. 90,
Ex. 3.19
The set $(R^{n+1}\setminus\{0\})/R^\times$ must be replaced by the set $M/R^\times$, where $M\subset R^{n+1}$ denotes the subset of all tuples which have at least one entry in $R^\times$. B. Heintz 1
p. 90,
Exercise 3.13
$X$ should be nonempty. 1
p. 91,
Exercise 3.25 (2)
Replace "factors through the surjective homomorphism $\mathscr O_Y\twoheadrightarrow i_*\mathscr O_Z$" by "factors through the homomorphism $\mathscr O_Y\to i_*\mathscr O_Z$". Yijiu Li 1 2
p. 91,
Exercise 3.26(a)
The statement is true for $V = X$, but not in general. (E.g., take $Y= \mathbb A^1_k$, $U=\mathbb A^1_k\setminus \{0\}$, $I=\{1, 2\}$, $i=1$, $V=U_2\subseteq X$.) Paulo Lima-Filho 1 2
p. 92,
Line -5
Replace ``shows'' by ``show''. P. Zsifkovits 1
p. 93,
Line -9
Insert "=" before $f_m(x)$. Peng Du 1
p. 94,
Example 4.4
Conflict of notation: $T$. E. Viehmann 1
p. 94,
Example 4.5
Insert: ``Let $\pi\colon R[T_1,\dots, T_n]\rightarrow R$ be the projection mapping each $T_i$ to $0$.'' after the definition of the $a_i$. P. Zsifkovits/F. Gispert Sánchez 1
p. 94,
Line -3 (ex. 4.5)
Replace "Equivalent" with "Equivalently". F. Gispert Sánchez 1
p. 95,
Corollary 4.7
Replace "$S$-morphism of schemes" by "morphism of $S$-schemes", the notion of $S$-morphism is only introduced later on. (Or define $S$-morphisms in (3.1).) Lam Pham 1
p. 95,
Line 7
Replace "objects" with "object". F. Gispert Sánchez 1
p. 95,
Line 12
Replace "for all objects Y we are given an in $Y$ functorial map" by "for all objects $Y$ we are given a map [...] functorial in $Y$"? Lam Pham 1
p. 96,
Remark 4.9
In the displayed line, it should say "$x \mapsto x^r$". Javier de la Bodega 1 2
p. 97,
Definition 4.10
Add the condition that $f \circ p = g \circ q$. C. Frei 1
p. 100,
-9
"are morphisms" should be replaced by "be morphisms". Kuo Tzu-Ang 1
p. 100,
Last sentence of part (i) in the proof of Theorem 4.18
It should say "$f = p \circ h$ and $g = q \circ h$"; i.e. it should be = instead of := Javier de la Bodega 1 2
p. 101,
Prop. 4.20, Condition (I)
Replace ``affine neighborhood $U'$ of $x'$'' by ``affine neighborhood $U'$ of $f(x')$''. B. Heintz 1
p. 101,
Prop. 4.20, condition (I)
The proof of the proposition when condition (I) holds uses the fact that all the assertions can be checked locally. However, to pass to the affine situation, one also needs to know that for every open neighborhood $U''$ of $f(x')$ contained in $U'$, $f^{-1}(U'')$ is also quasi-compact. This is true (Prop. 10.1) but had not been stated at this point. F. Gispert Sánchez 1
p. 101,
Line -7
In the statement of Prop. 4.20, maybe it should be made clearer that the assumptions (I) and (II) should refer to each factor of $f$, namely if $f=f_r\cdots f_1$, then each $f_i$ should satisfy one of the assumptions (I) and (II) (not $f$ itself). Peng Du 1
p. 102,
Proof of Prop. 4.20, Case (II)
To see that $(p^{-1}(f(X')), \mathscr O_{Z|p^{-1}(f(X'))})$ is a fiber product in the category of schemes, one needs to know that the fiber product of schemes taken in the category of locally ringed spaces exists and is a scheme. This stronger version of Thm. 4.18 should have been stated and proved before. It is proved similarly as Thm. 4.18; for the affine case use Proposition 3.4 in the form given (but not proved) in the book. O. Körner 1
p. 102,
Line -10
Replace "homomorphisms" by "homomorphism" (... "is injective"). F. Gispert Sánchez 1
p. 104,
Line -13
The numbering "Frobenius morphism 4.24" here is a bit inconsistent, and confusing when referred to later - better replace by "Definition 4.24 (The Frobenius morphism)". Ulrich Görtz 1
p. 104,
4.24 (Frobenius morphism)
Conflict of notation: There are too many $f$'s here, $f\in \Gamma(U, \mathscr O_S)$ in line 2, the morphism $f\colon X\to S$, the polynomial $f$ in (1). U. Görtz 1 2
p. 104,
Line -3
Replace ``be'' by ``by''. U. Görtz 1
p. 104,
Line 13
Add "Let" before "$X$ and $Y$ be". F. Gispert Sánchez 1
p. 105,
Line 2 ff.
Rename the variables as $T_i$ since the symbol $X$ is in use already. Peng Du 1
p. 105,
Eqn. (4.7.1)
The label of the lower arrow should be $(t, h)_S$. Peng Du 1
p. 105,
Line -6
Insert ``be'' before ``the first projection''. P. Zsifkovits 1
p. 106,
Line 4
Replace ``(applied to $X, S, X' = \mathop{\rm Spec} \kappa(s), Y=S$)'' by ``(applied to $S, X = S, X' = \mathop{\rm Spec} \kappa(s), Y=X$)''. P. Zsifkovits 1
p. 106,
Line -2
Add missing parenthesis. P. Zsifkovits 1
p. 107,
Line 20 (proof of prop. 4.30)
Replace "$(f \times_S id_Y)\circ (id_X \times_S g)$" with "$(f \times_S id_Y)\circ (id_{X'} \times_S g)$". F. Gispert Sánchez 1
p. 107,
Line -10 (def. 4.31)
Replace "morphism of $f\colon X\rightarrow S$ of $S$-schemes" by "morphism $f\colon X\rightarrow S$ of schemes". F. Gispert Sánchez 1
p. 108,
Line -6 (prop. 4.34)
Replace "immersion" with "immersions". F. Gispert Sánchez 1
p. 108,
Line -14
Replace "locally" by "local". F. Gispert Sánchez 1
p. 108,
Proof of Prop. 4.32
Replace second sentence by: ``Proposition 4.20 shows that the properties immersion, open immersion and closed immersion are stable under base change (see the discussion at the beginning of (4.11)).'' P. Zsifkovits 1
p. 109,
-14
Strictly speaking, $f^{–1}(Z)$ should be $f^{–1}(i(Z))$. Jan Willing 1
p. 111,
Line -10
Replace ``$g(a)$'' by ``$g(a)=0$''. P. Zsifkovits 1
p. 111,
Line -7
It might be worthwile to add a few words on the construction of $f$ as a morphism of schemes. (Formally, one has to cover $Z$ by affine charts, and glue the morphisms obtained on these charts. At this point in the book, it might be asking too much from the reader to skip this point.) Ulrich Görtz 1
p. 111,
Line -4
The fiber product of the two projective spaces should be $\times_R$ instead of $\times_S$. Jingyi Xu 1 2
p. 112,
Line -4
Add parentheses around $U_i\times_R W_j$. Peng Du 1
p. 113,
Line -4
Replace "as $S$-scheme" by "as an $S$-scheme". A. Graf 1 2
p. 113,
(4.15.1)
The top morphism of the commutative diagram in the middle should be "${\rm id}_G \times_S e$" instead of "$({\rm id}, e)_S$". Jan Willing 1 2
p. 113,
Line -8
Add reference to Cor. 4.7. A. Graf 1 2
p. 117,
Line 15 (Exercise 4.21)
The first line "... let $f\colon \mathbb A^1_k \to k$ the structure morphism." should read "... let $f\colon\mathbb A^1_k \to k$ be the structure morphism." Thomas Brazelton 1
p. 118,
Line 11
Replace "arbitrary morphism" with "arbitrary morphisms". F. Gispert Sánchez 1
p. 120,
l. 9
Replace "Corollary 3.33" by "Proposition 3.33". M. Pereira 1
p. 121,
Line 9
Replace $\mathfrak p_0$ by $\mathfrak p_0 A[T]$, and correspondingly for $\mathfrak p_r$. P. Zsifkovits 1
p. 123,
Proposition 5.11 (i)
Add '.' at the end. 1 2
p. 124,
Line -9
Add "the" before "following". Ulrich Görtz 1
p. 124,
Line 18 (Proof of Lemma 5.14)
Replace "finite-dimension" by "finite-dimensional". Peng Du 1
p. 124,
Lines -3, -2 (Remark 5.16 (3))
It should be made clear that we are talking about the numbers $h(i)$ of the previous theorem here, for the chain of ideals given by the $Z_i$. (At least, rename the $\mathfrak p_i$ as $\mathfrak a_i$; or state the relationship more explicitly). Ulrich Görtz 1
p. 125,
Thm. 5.19 (2)
Change (a) to (1). Peng Du 1
p. 125,
Line 21
Replace "completed to maximal chain" by "completed to a maximal chain". Ulrich Görtz 1
p. 126,
Theorem 5.22
Replace "of finite type" with "locally of finite type". (This slightly more general statement is used in the proof of Proposition 5.26, for example.) Note that the proof does not use the finiteness of the affine open cover. F. Gispert Sánchez 1
p. 126,
Proof of Prop. 5.20
Replace the last sentence by: Corollary 5.17 shows that the structure morphism $X\rightarrow \mathop{\rm Spec} k$ corresponds to a finite homomorphism $k\rightarrow A$. P. Hartwig 1
p. 126,
Prop. 5.22 (4)
It would be enough to assume that $X$ and $Y$ are locally of finite type over $k$. A. Graf 1 2
p. 127,
Line -3
Replace "$\sup_{Z\in I} (Z\cap U)$" with "$\sup_{Z\in I} \dim(Z\cap U)$" F. Gispert Sánchez 1
p. 128,
Line -12
Since $d$ is never refered to, its definition in the statement of Prop. 5.30 should be removed. A. Graf 1 2
p. 129,
Proposition 5.31
The converse direction should include the additional assumption that $f$ is a non-unit. Zhi-Lin Zhang 1 2
p. 130,
Proof of Cor. 5.33
Since the formulation "vanishes identically" has not been formally defined, it would be clearer to replace "in which case" by "i.e.,". A. Graf 1 2
p. 130,
Line 4
The notion of finite scheme morphism is not defined at this point, one should talk about the corresponding ring homomorphism instead. Ulrich Görtz 1
p. 130,
Line -14
Replace "$f_1\in A$" by "$0\neq f_1\in A$". Yuhao Cheng 1 2
p. 133,
Line 15
Better: "... where $S$ is the spectrum of a field $k$ and $X$ is of finite type over $k$." A. Graf 1 2
p. 133,
Cor. 5.45
Add the hypothesis that $Y$ be non-empty. 1
p. 134,
Line -15
It might be clearer to move this remark up so that it comes directly after the proof of Corollary 5.45. A. Graf 1 2
p. 134,
Line -4
It should be explained why $\bar{x}$ is closed in $X_K$. The point $\bar{x}$ is a point of the fiber $p^{-1}(x) = \mathop{\rm Spec} \kappa(x)\otimes_k K$. We now use Proposition 3.33. Since the extension $\kappa(x)/k$ is finite, $\kappa(x)\otimes_k K$ is a finite-dimensional $K$-vector space. This implies that the residue class field of $\bar{x}$ (which is a quotient of this tensor product) is finite over $K$. Hence $\bar{x}$ is a closed point of $X_K$. (A variant of the argument: Since $\kappa(x)\otimes_k K$ is finite over $K$, it is an Artin ring, hence the fiber $p^{-1}(x)$ has dimension $0$. Therefore $\bar{x}$ is a closed point of the fiber. Since $x$ is closed in $X$, $p^{-1}(x)$ is closed in $X_K$. Altogether we see that $\bar{x}$ is closed in $X_K$.) A. Graf 1 2
p. 134,
Line 18
Replace ``$X=\mathop{\rm Spec} B$'' by ``$Y=\mathop{\rm Spec} B$''. K. Kidwell 1
p. 134,
Proof of Cor. 5.47
Note that the first statement in the proof holds by Cor. 5.23. K. Kidwell 1
p. 135,
Line -2
The reference to Proposition B.97 is not required at this point and should be omitted (our definition of separability B.91 (6) is exactly what is needed here). Jinyong / U.G. 1 2
p. 136,
Prop. 5.50
In the proof of Prop 5.50, we may avoid using the difficult fact that the projection $p$ is open: Since $p$ is faithfully flat, for any $x=p(y)$, every generalization of $x$ admits a preimage that is a generalization of $y$. Hence every irreducible component of $X \times Z$ has non-empty intersection with the generic fiber of $p$. By Exercise 3.17, $X \times Z$ is irreducible if and only if the generic fiber of $p$ is irreducible. Yijiu Li 1 2
p. 137,
Proof of Prop. 5.53
In the proof of (iv) $\Rightarrow$ (iii), further details should be added about the construction of the scheme $Y'$.
To define $Y'$, one applies gluing of schemes (Prop. 3.10) to the family of schemes $U_i := {\rm Spec} (A_i\otimes k')/(f_{ij})$ (this is a different $U_i$ than in the proof of 5.53; I use $U_i$ here to indicate how Prop. 3.10 is applied), and $U_{ij} = U_i \cap {\rm Spec} (A_j \otimes k')$ (scheme-theoretic intersection inside $X\otimes k'$).
To construct a complete gluing datum, one has to show that $U_{ij} = U_{ji}$ as closed subschemes of ${\rm Spec} (A_i\otimes k') \cap {\rm Spec} (A_j\otimes k')$. (Since these identifications are (basically) equalities, it is clear that the cocycle condition of a gluing datum is satisfied, so that Prop. 3.10 can be applied.)
By construction, it is clear that the desired equality holds after base change to $\Omega$, i.e., that $U_{ij}\otimes_{k'}\Omega = U_{ji}\otimes_{k'}\Omega$. It therefore suffices to prove the following general statement:
Let $Z$ be a scheme over a field $k'$, let $\Omega / k'$ be a field extension and let $Z_1, Z_2$ be closed subschemes of $Z$ such that $Z_1 \otimes_{k'} \Omega = Z_2 \otimes_{k'} \Omega$ (as closed subschemes of $Z\otimes \Omega$). Then $Z_1 = Z_2$.
To prove this statement, it is enough to show that $Z_1\subseteq Z_2$ and that $Z_2\subseteq Z_1$, or in other words that the inclusions $Z_1\cap Z_2 \subseteq Z_i$ (for $i=1,2$) are equalities. With this observation, one easily reduces to the case that $Z_2 \subseteq Z_1$ (replace $Z_2$ by $Z_1\cap Z_2$, and apply the statement again with the roles of $Z_1$ and $Z_2$ reversed). Furthermore, one may work locally on $Z$, so that we may assume that $Z$ is affine, say $Z = {\rm Spec} A$.
Then the closed subschemes correspond to ideals $\mathfrak a_1 \subseteq \mathfrak a_2 \subseteq A$ such that $\mathfrak a_1 \otimes \Omega = \mathfrak a_2 \otimes \Omega$ (inside $A\otimes \Omega$). This implies that $(\mathfrak a_2 / \mathfrak a_2) \otimes \Omega = 0$, so $\mathfrak a_2 / \mathfrak a_1 = 0$ (base change by a field extension preserves the vector space dimension), and we get $\mathfrak a_1 = \mathfrak a_2$, as desired.
 Jin Yong / U.G. 1 2
p. 137,
Cor. 5.56 (2), (3)
Insert "then" before $X_K$ (twice). Peng Du 1
p. 138,
Line 5
Replace "roughly spoken" by "roughly speaking". Peng Du 1
p. 140,
Line -13
Replace $\bigoplus$ by $\bigoplus_d$. A. Graf 1 2
p. 140,
Line 15
It is clearer to write $A\otimes_kK = \Gamma(C_K\cap D_K, \mathscr O_{C_K\cap D_K})$ (so to make use of the calculation in the previous line). A. Graf 1 2
p. 140,
Line 7
Replace $af+bg$ by $af+bg=0$. Peng Du 1
p. 140,
Proof of Lemma 5.62
It would be helpful to add a reference to equation (4.12.4). A. Graf 1 2
p. 142,
Exer. 5.8 (b)
Replace $\mathop{\rm codim}(Y, X)$ by $\mathop{\rm codim}\nolimits_X(Y)$ etc. Peng Du 1
p. 142,
Exercise 5.7
Before the first ``Show'', add ``Let $X=\mathop{\rm Spec} A[T]$.'' A. Steinbach 1
p. 142,
Exer. 5.6
The assumption that $f$ is closed is required only for part (a). Ulrich Görtz 1
p. 142,
Line -14 (ex. 5.11)
In the definition of the special orthogonal group scheme SO, the condition that the determinant must be +1 is missing. F. Gispert Sánchez 1
p. 143,
Line -6 (ex. 5.20)
Replace "$x\in X_{\Omega}$" with "$x' \in X_{\Omega}$" F. Gispert Sánchez 1
p. 144,
Line 10 (ex. 5.21)
Replace "intgral" with "integral". F. Gispert Sánchez 1
p. 146,
l. $-8$
Replace ``heuristics'' by ``heuristic''. P. Johnson 1
p. 147,
Line 13
It would be more precise to say "cardinality of any minimal generating set" (rather than "... a minimal ..."). Ulrich Görtz 1
p. 147,
Example 6.3 (3)
Maybe explain that the finiteness conditions are imposed to ensure that the construction (and passing to the dual vector space, resp.) is compatible with the tensor product. Also, the condition that $T_{f(x)}Y$ be finite-dimensional over $\kappa(f(x))$ is imposed twice. A. Graf 1 2
p. 147,
Line -4
Add subscript $k$ (twice). A. Graf 1 2
p. 148,
Line 10
Replace "homomorphisms" by "local homomorphisms". A. Graf 1 2
p. 148,
Example 6.5
It is important that $x$ is a $k$-valued point, not just a closed point. In general, the tangent space is not the kernel of the Jacobian matrix. For example, consider the purely inseparable extension $X={\rm Spec}(\mathbb F_p(T)) \to {\rm Spec}(\mathbb F_p(T^p))={\rm Spec}(k)$ as in Example 6.34, the Jacobian matrix is the zero matrix. The kernel of the Jacobian has dimension 1, but clearly the tangent space of ${\rm Spec}(\mathbb F_p(T))$ is 0. Yijiu Li 1 2
p. 148,
Line -10
$D(g_1 \cdots g_s)$ should instead read $D(g_1 \cdots g_r)$. Nathan Pflueger 1
p. 148,
Line 14
Label the final arrow with $df_x$. A. Graf 1 2
p. 149,
Line 13
Replace "projection $X(k[\varepsilon])\to X(k)$" by "map $X(k[\varepsilon])\to X(k)$ induced by the projection $k[\varepsilon]\to k$, $\varepsilon\mapsto 0$. A. Graf 1 2
p. 149,
Lines -8, -7
Remove "is in $T_x X$". F. Gispert Sánchez 1
p. 150,
Line -1
Replace the reference to Section (4.14) by a reference to Section (4.13). Dominik Briganti 1 2
p. 150,
Prop. 6.10 (1)
One should choose a representative $x = (x_0,\dots, x_n)\in \mathbb A^{n+1}_k(k)$ of the point of interest to start with in order to obtain a natural isomorphism between the two sides, because the isomorphism will depend on this choice. See also Section (8.9) (and Section (17.7) in Volume II for a relative version). U. Görtz 1 2
p. 152,
Line 22
Replace "isoomorphism" by "isomorphism". Ulrich Görtz 1
p. 152,
Line 15
Replace "$k$-scheme" by "$K$-scheme". Dominik Briganti 1 2
p. 152,
Lines 1, 2
It should be added that here ${\rm Spec}(K[\varepsilon])$ is considered as an $S$-scheme via the composition ${\rm Spec}(K[\varepsilon])\to{\rm Spec}(K)\to S$, where the first morphism is the one coresponding to the inclusion $K\subset K[\varepsilon]$. Ho Hai Phung 1 2
p. 153,
Def. 6.14 (1)
It might be helpful to add that requiring that $j$ is a morphism of $R$-schemes amounts to saying that the composition of $j$ with the projection to $\mathop{\rm Spec}(R)$ is $f$. Peng Du 1
p. 153,
Def. 6.14 (1)
Conflict of notation: $j$ is used for the map and as an index. Ulrich Görtz 1
p. 153,
Def. 6.14 (2)
Replace ``in all points'' by ``at all points''. P. Johnson 1
p. 154,
Line -17
Replace "a $r\times r$ minor" by "an $(n-d)\times (n-d)$ minor" as $r$ is not defined in Definition 6.14. Jan Willing 1 2
p. 154,
Line 8
Replace "for $X$" by "for $f$". Ulrich Görtz 1
p. 155,
Part (3) (Line 8)
Add the condition that $k$ has characteristic $\ne 2$. Peng Du 1
p. 155,
Prop. 6.18
Add that $g$ is monic. Peng Du 1
p. 155,
Example 6.16 (3)
Add the condition that $n\geq 2$. Yuhao Cheng 1 2
p. 155,
Part (4) (Line 10)
Add the condition that $k$ has characteristic $\ne 2$. Also, to see that for $f$ with multiple zeros the given scheme is not smooth, it seems that one wants to invoke (the relevant part of) Theorem 6.28. Ulrich Görtz 1
p. 156,
Prop. 6.21, end of proof
The second half of the proof (starting from "Replacing $X$ by $U$ ...") should be replaced by the following (in the current "proof", evaluating $g$ at $T_i=0$ ($i=1, \dots, d$) might not produce a separable polynomial; also, after applying Prop. 6.18, since this gives only an isomorphism between dense opens, it is not enough to show that $\Sigma$ is non-empty):
As $X$ is geometrically reduced, its function field is a separable extension of $k$ (Proposition 5.49). By Proposition 6.18 we may assume that $X={\rm Spec}(B)$, where $B=k[T_1, \dots, T_{d+1}]/(g)$ for a separable monic irreducible polynomial $g\in k(T_1, \dots, T_d)[T_{d+1}]$ with coefficients in $k[T_1,\dots, T_d]$.
We have a finite morphism ${\rm Spec}(B) \to \mathbb A^d_k = {\rm Spec}(k[T_1, \dots, T_d])$. The subset of points $z\in\mathbb A^d_k$ such that the image $\overline{g}$ of $g$ in $\kappa(z)[T_{d+1}]$ is non-separable is the vanishing locus of the discriminant of the polynomial $g$, hence a Zariski closed subset. Since $g$ is separable over $k(T_1, \dots, T_d)$ it does not contain the generic point, so its complement $V$ is open and dense. Whenever $z\in U$, the fiber of the above morphism over $z$ is ${\rm Spec}(\kappa(z)[T_{d+1}]/(\overline{g}))$, a product of separable extensions of $k$ (since $\overline{g}$ might not be irreducible over $\kappa(z)$, we might have more than one factor).
(It might be useful to add a few more words about the discriminant, maybe in App. B.)		 Peng Du 1
p. 156,
Proof of Thm. 6.19
The final part of the proof can be simplified: The polynomial $g$ being a $p$-th power is already a contradiction to the irreducibility as a polynomial in $T_{d+1}$. Alternatively, and this seems even simpler, it is enough to consider $\partial g/\partial T_{d+1}$ rather than all the partial derivatives. Ulrich Görtz 1
p. 157,
Proof of Prop. 6.23
Instead of ``renumbering the $f_i$'', we need to renumber the $T_i$ such that the $(r \times r)$ minor given by the first $r$ columns of $J$ does not vanish at $x$. B. Smithling 1
p. 157,
Statement of Lemma 6.22
Replace $\partial\varphi(Y_j)$ by $\partial\varphi(Y_i)$ and $\partial X_i$ by $\partial X_j$. B. Smithling 1
p. 159,
Line 12
Replace $T_{\mathbb A^n_k, y}$ by $T_{\mathbb A^n_k, y}^*$. F. Gispert Sánchez 1
p. 159,
Proof of Lemma 6.26
Replace ``By Example 6.5'' by ``By the argument in Example 6.5'' and/or add explanation why we obtain the desired linear independence over $\kappa(y)$ even though $y$ might not be a $k$-valued point. P. Johnson 1
p. 159,
Proof of Lemma 6.27
In the second line of the proof, replace ``columns'' by ``rows''. B. Smithling 1
p. 160,
Line 9
Replace "point of $x$" with "point of $X$". F. Gispert Sánchez 1
p. 160,
Corollary 6.29
Replace ``of finite type'' by ``locally of finite type''. (Theorem 5.22 requires only ``locally of finite type'' as noted in a previous erratum.) Fabian Roll 1
p. 161,
Line 3 of Example 6.34
Change $\cdots Spec(\mathbb{F}_p(T)\otimes_{\mathbb{F}_p[T^p]} \mathbb{F}_p(T))$ to $\cdots Spec(\mathbb{F}_p(T)\otimes_{\mathbb{F}_p(T^p)} \mathbb{F}_p(T))$. Shaopeng Z 1
p. 161,
Lines 4, 5 (cor. 6.31)
The two ranks in the statement of the corollary should be of the Jacobian matrix evaluated at $x$: replace "$\partial g_i / \partial T_j$" by "$\frac{\partial g_i}{\partial T_j}(x)$" (twice). F. Gispert Sánchez 1
p. 162,
Last sentence of the proof of Lemma 6.38
It should say "every non-empty closed subset". Javier de la Bodega 1 2
p. 162,
Remark 6.37
Replace the final sentence of the remark by: If a point in an arbitrary scheme lies on more than one irreducible component, then its local ring will have more than one minimal prime ideal and hence cannot be an integral domain. In particular, such a point is not normal. U. Hartl/B. Smithling 1
p. 163,
Line -6
Replace "Exercise 6.19" by Exercise "6.18". Peng Du 1
p. 163,
Line 17
Replace ``$\dim {\mathscr O}_{X,x} = 2$'' by ``$\dim {\mathscr O}_{X,x} \geq 2$''. T. Wedhorn 1
p. 165,
Line 21 (Exer. 6.4)
Replace $df$ by $df_e$. Jan Willing 1
p. 165,
Line 17 (ex. 6.4)
Replace "$df_{(e,e)}$" with "$dm_{(e,e)}$". F. Gispert Sánchez 1
p. 166,
Line 7
Insert "be" before "the set". Peng Du 1
p. 166,
Exercise 6.12 (b) (iii)
Condition (iii) should be changed to: "$X \cong \coprod_i {\rm Spec}(K_i)$, where $K_i$ are finite separable field extensions of $k$." (Alternatively, add the assumption that $X$ is quasi-compact in the beginning.) Rafael M. Saavedra 1 2
p. 167,
Exercise 6.19 (iii)
It might be more stringent to replace "Inseparable" by "purely inseparable". Yuhao Cheng 1 2
p. 169,
Lines 7, 14
Wrong quotation marks around "globalizations" and "sheaf version". Zhaodong Cai 1
p. 170,
Line -12
Somewhere (maybe after Example 7.2) add a sentence like "If $\mathscr A$ is a presheaf of rings and $\mathscr F$ is a presheaf of abelian groups with an $\mathscr A$-module structure (as presheaves), then the sheafification of $\mathscr F$ is a sheaf of modules over the sheafification of $\mathscr A$, because sheafification is compatible with products. A. Graf 1 2
p. 170,
Equation (7.1.1)
Add the notation $\mathscr F(x)$ and $s(x)$ to the Index of Symbols in the end. Philipp Reichenbach 1 2
p. 170,
Line 15
Replace "for all $s,s' \in \mathscr{F}(U)$" by "for all $s,s' \in \mathscr{F}_1(U)$". Yubo Zhou 1 2
p. 171,
Line 4
Replace "homomorphism" with "homomorphisms". F. Gispert Sánchez 1
p. 171,
Line 4
Replace $\mathscr O$ by $\mathscr O_X$. Peng Du 1
p. 171,
Line 14
Replace "of an $\mathscr O_X$-module" by "of an $\mathscr O_X$-module $\mathscr F$". A. Graf 1 2
p. 171,
Line -3
Wrong quotation marks around "surjective". Zhaodong Cai 1
p. 175,
Line 3
Add period at the end of the sentence. A. Graf 1 2
p. 175,
Around line -7
Add that the tensor product is associative (up to canonical isomorphism) and that one can similarly form tensor products of more than two factors (with the same result as taking successive tensor products). A. Graf 1 2
p. 175,
Line -5
In addition to $s^{\otimes n}$, the notation $s\otimes t$ should also be defined (a couple of lines above). Peng Du 1
p. 175,
Line -3
Maybe the tensor symbols $\otimes$ should be accompanied by O_X(U) as a subscript. Victor Zhang 1
p. 176,
Line 4
A more appropriate reference than (7.1) is Section (7.3), specifically the comment after equation (7.3.6). Philipp Reichenbach 1 2
p. 177,
Line -11
Replace "$\mathscr{F}_{|U} \otimes_{\mathscr{O}_U} \mathscr{H}_{|U}$" by "$\mathscr{G}_{|U} \otimes_{\mathscr{O}_U} \mathscr{H}_{|U}$". F. Gispert Sánchez 1
p. 177,
Line 9ff
In this general setting some stalks of $\mathcal{O}_X$ might be zero. But in order to read off the rank at $x$ from the local rank you need that $\mathcal{O}_{X,x}$ is a nonzero ring. Denis Vogel 1 2
p. 178,
Line 19
The morphism "$\iota$" has not been defined; it should be (7.5.7). F. Gispert Sánchez 1
p. 179,
Line 6
Add "for all open $U\subseteq X$" at the end of the line. A. Graf 1 2
p. 181,
Line -7
Replace "and" by "an". F. Gispert Sánchez 1
p. 181,
Line 12
Replace "(2.27)" by "Proposition 2.27". Peng Du 1
p. 182,
Line 6
Replace "with respect" by "with respect to". U. Görtz 1 2
p. 182,
Line 16
Replace "localization in the prime ideal" by "localization at the prime ideal". A. Graf 1 2
p. 184,
Line 18
Replace "identity" by "identity morphism of". Peng Du 1
p. 185,
Corollary 7.19. (4)
Define $\mathscr{F}$ and $\mathscr{G}$ to be quasi-coherent $\mathscr{O}_X$-modules. F. Ebert 1
p. 185,
Proof of corollary 7.19 (4)
Maybe replace the final sentence by the following, to make this clearer: These isomorphisms show that the presheaf $\mathscr H$ on the basis of the topology given by the $D(f)$ is actually a sheaf, and therefore yield the desired isomorphism (7.10.3). Caiyong Qiu 1 2
p. 186,
Line 18
Replace "(7.4)" by "(7.5)". (Invertible $\mathscr{O}_X$-modules are explained at the end of section (7.5).) F. Gispert Sánchez 1
p. 187,
Theorem 7.22
Replace $X_s$ by $X_s(\mathscr L)$ in the statement (and in the proof before the reduction to $\mathscr L \cong \mathscr O$. A. Graf 1 2
p. 188,
-11
Add reference to Corollary 3.22 (open subschemes of noetherian schemes are noetherian). A. Graf 1 2
p. 188,
Line -14
Replace "of Dedekind schemes" with "by Dedekind schemes". Peng Du 1
p. 189,
Line -13
Replace "$\mathscr{L}_{|U_x}$" by "$\mathscr{L}_{D|U_x}$" F. Gispert Sánchez 1
p. 189,
Line -16
Replace "$y\in U_x\cap X_0$" by "$y\in (U_x\cap X_0)\setminus\{x\}$". Peng Du 1
p. 190,
Line 23
In general, there are $\mathscr O_X$-modules of finite type that are not of finite presentation even over Noetherian schemes (take a quotient of $\mathscr O_X$ by a non-quasi-coherent sheaf of ideals) . (It is true that a quasi-coherent $\mathscr O_X$-modules of finite type over a Noetherian scheme is of finite presentation.) H. Iriarte 1
p. 190,
Line -15
Add "be" before "extended". F. Gispert Sánchez 1
p. 191,
Line -2
Replace "$X''$" by "$U''$". F. Gispert Sánchez 1
p. 191,
Line -1
Replace "generated" by "generate". F. Gispert Sánchez 1
p. 191,
Commutative diagram
In the right-most column, replace $n$ by $m$ in both rows. P. Carlucci 1
p. 192,
Line 3
Replace "as" by "as an". A. Graf 1 2
p. 194,
Line 8
Replace $\mathop{\rm Spec} A$ by $\mathop{\rm Spec} B$. Longxi Hu 1
p. 194,
Line -9
Replace "analogue" by "analogous". Peng Du 1
p. 194,
(7.18.1)
Here $\mathscr{F}$ needs to be flat over Y (before, it was only assumed to be $f$-flat in a point $x$). Longxi Hu 1
p. 195,
Proof of Lemma 7.42
`The corresponding homomorphism $A'^n \to M'$` should be `The corresponding homomorphism $A'^r → M'$`; similarly, `an isomorphism $A^r_s \to M^r_s$' should be `an isomorphism $A^r_s \to M_s$'. Kannappan Sampath 1
p. 195,
Remark 7.43
It might be worth adding a reference to arxiv:1011.0038 and/or the Stacks project (058B, 05A5). Ulrich Görtz 1
p. 196,
Line -2
Use a different letter for the submodule $N$, since the letter $N$ is used before and afterwards for stating the universal property. Jan Willing 1
p. 197,
Line 15
Replace "holds of" by "holds for". Peng Du 1
p. 199,
Exer. 7.4
Add a comma before $s_r(x)$ in both (a) and (b). A. Graf 1 2
p. 200,
Exer. 7.10 (a)
Replace the first occurrence of "polynomials" by "polynomial". A. Graf 1 2
p. 200,
Exercise 7.7 (b)
The exercise is not correct as written. Instead, one could say that there is a natural surjective $\mathscr O_X$-module homomorphism $\mathscr F^\eta\to \mathscr F^x$ and its kernel $\mathscr G$ has the property that $\mathscr G_{|U}$ is not globally generated for any open neighborhood $U$ of $x$. Mathis Birken 1 2
p. 201,
Exercise 7.16
Replace $\mathscr F$ by $\mathscr E$ (four times). Jan Willing 1 2
p. 201,
Exercise 7.17
(a) Replace "There exists $u$-stable" by "There exists a $u$-stable"
(c) The identities to be proved are $(f*\mathscr{E})_{nil}(f*u)=f*(\mathscr{E}_{nil}(u))$ and $(f*\mathscr{E})_{iso}(f*u)=f*(\mathscr{E}_{iso}(u))$.		 Yuhao Cheng 1 2
p. 202,
Exer. 7.18
Add the condition $\mathscr I \ne 0$. Peng Du 1
p. 202,
Exercise 7.18
Add the assumption that $X$ is connected. (Alternatively, assume that $\mathscr{I}_x\neq 0$ for all $x\in X$.) Yuhao Cheng 1 2
p. 202,
Exercise 7.20
Replace ${\mathscr F}$ by ${\mathscr G}$. J. Calabrese 1
p. 203,
Exercise 7.30
The $\mathcal{O}_X$-modules should be finite locally free, as the determinant was defined in that setting. 1
p. 204,
Line 4 (ex. 7.32)
Replace "send" with "sent". F. Gispert Sánchez 1
p. 206,
Statement of Proposition 8.4
Replace “Then the locus, where $v$ is surjective, is open” with “Then the locus where $v$ is surjective is open”. Owen Colman 1
p. 206,
Prop. 8.4
It might be helpful to add a Remark after the Proposition pointing out that as a formal consequence one gets the following: Let $S$ be a scheme, let $X$ be an $S$-scheme, and let $v$ be a homomorphism of quasi-coherent $\mathscr{O}_X$-modules. Then the functor $F'$ on $S$-schemes with $F'(T) = \{ f\in \mathop{\rm Hom}_S(T,X);\ f^*(v)\ \text{surjective} \}$ is representable by an open subscheme of $X$. (Apply the original proposition to $X$, $v$ to obtain an open subscheme $U$ of $X$, and observe that the $S$-scheme $U$ represents the functor $F'$. This is how the Proposition is often used later, e.g., in the proof of Lemma 8.13. (Likewise for part (2) of the proposition and other similar statements, like Theorem 11.17.) F. Gispert Sánchez 1
p. 206,
Prop. 8.4
It would be helpful to point out explicitly that for an $S$-Scheme $T$ the set ${\rm Hom}_S(T, S)$ is a singleton set (and that therefore in both (1) and (2) of Prop. 8.4 the set $F(T)$ has at most one element). A. Graf 1 2
p. 207,
Proof of Prop. 8.4
For part (1), one could add a reference to Exer. 7.2 (c). For part (2), maybe the argument in the last sentence should be expanded a little bit (one could say that $f^*(\tilde{v}) = 0$ if and only if the ideal generated by $\mathscr I$ in $\mathscr O_T$ is zero, which happens if and only if $f$ factors through $V(\mathscr I)$. Peng Du 1
p. 209,
Lines -14, -13
Replace all $S$ by $T$. Peng Du 1
p. 209,
Line 15
The second subscript $F$ is missing in the fiber product $F_i \times_F F_j\times F_k$. Shahram Mohsenipour 1
p. 209,
Line 10
Change the first "and" to "by". 1
p. 209,
Equation (8.3.1)
Replace $U_{ij}\cap U_{jk}$ by $U_{ij}\cap U_{ik}$. 1
p. 209,
Line 12
Replace "all $S$" by "all $T$". Peng Du 1
p. 211,
Line -7
Add "of" between "homomorphism" and "$\mathscr{O}_S$-modules". F. Gispert Sánchez 1
p. 211,
Line -16
Replace $\mathscr O_S /U$ by $\mathscr O_S^n/U$. Yingying 1 2
p. 211,
Line 9
Replace ``bijective'' by ``an isomorphism''. Ulrich Görtz 1
p. 212,
Line -19
Replace "therefore" by "therefore we get". Peng Du 1
p. 212,
Line -16
Insert ``and is'' before ``also''. D. Gerigk 1
p. 212,
Line -5
Replace "subvector space of $K^n$" by "subvector space $U$ of $K^n$". F. Gispert Sánchez 1
p. 214,
Proof of Proposition 8.17
It would be useful to explain in greater detail how to apply Proposition 8.4 (2). Maybe something along the lines of "Let $h: X \to S$ be an $S$-scheme. Given $X \to {\rm Grass}^e(\mathcal{E}_1)$, let $\mathcal{V}_X$ be the corresponding element of ${\rm Grass}^e(\mathcal{E}_1)(X)$, and apply Proposition 8.4 (2) to the composite $\ker(h^*(v)) \to h^*(\mathscr E_1)/\mathcal{V}_X$." Owen Colman 1
p. 214,
Line -4, (8.7.1)
Maybe replace $u^*\mathrm{Grass}^e(\mathscr{E})$ by $\mathrm{Grass}^e(\mathscr{E})\times_SS'$ here to emphasize that the Yoneda lemma is used in order to obtain an isomorphism of schemes. The corresponding identification of functors is already obtained in the displayed line above. Xiaolong Liu 1 2
p. 214,
Line 11
Replace "$S$ scheme" by "$S$-scheme". Peng Du 1
p. 216,
Line 4
Replace "of $\mathscr{O}_S$-module" by "of $\mathscr{O}_S$-modules". F. Gispert Sánchez 1
p. 216,
Line 6
Replace $q'$ by $q''$. Xiaolong Liu 1 2
p. 216,
Line -7
Replace "disjoint sum" with "disjoint union". F. Gispert Sánchez 1
p. 217,
Line -2
Replace ${\rm Grass}^1(\bigwedge^d\mathscr{O}_{Spec(\mathbb{Z})})$ by ${\rm Grass}^{\binom{n}{d}-1}(\bigwedge^d\mathscr{O}_{Spec(\mathbb{Z})})$. Xiaolong Liu 1 2
p. 217,
Line -2
Replace ${\rm Grass}_1$ by ${\rm Grass}^1$. Peng Du 1
p. 218,
Line 10
Rephrase as "... we have a bijection, functorial in $S$,". Peng Du 1
p. 219,
Line -7
Replace "Corollary 5.45" by "Proposition 5.51". Peng Du 1
p. 219,
Line -11, Def. 8.25
Insert "$X$" after "$k$-scheme". D. Gerigk/Peng Du 1
p. 219,
Line -13
Replace $k$ by $\mathbb C$. Peng Du 1
p. 219,
Line 10
Replace "the kernel of $\bigwedge^e \mathscr E\dots$" by "the kernel of $\bigwedge^e f^*\mathscr E\dots$. (And maybe also, in the same line, $\mathbb P(\bigwedge^e \mathscr E)$ by $\mathbb P(\bigwedge^e \mathscr E)(T)$.) Peng Du 1
p. 220,
Line 4
Replace "$(v,u)$" by "$(v,s)$". F. Gispert Sánchez 1
p. 220,
Line 19 (Proof of Proposition 8.26)
Replace $M_{1 \times n}$ by $M_{1\times n}(R)$. Sz-Sheng Wang 1 2
p. 221,
Line -13
Insert "points" between "$R$-valued" and "of". F. Gispert Sánchez 1
p. 221,
Line -13
Add subscript $k$ to $\otimes$. Peng Du 1
p. 221,
Line -16
Replace "(v)" by "(iv)". 1
p. 223,
Exercise 8.7
Replace `$\mathscr N_n$ is the called ...' by `The scheme $\mathscr N_n$ is called'. Akash N 1 2
p. 224,
Exercise 8.11
Repace ${\mathscr G}$ by $f^*{\mathscr G}$, and the map $f^*{\mathscr G} \to f^*{\mathscr E}$ will not be injective in general. L. Galinat 1
p. 226,
Lines 10/12
Replace ``$\{(x,f(x)) ; x \in X\}$ is closed in $X\times Y$'' by ``$\{(y,f(y)); y \in Y\}$ is closed in $Y\times X$'' in (ii), and replace ``$\{x \in X; f(x) = g(x)\}$ is closed in $X$'' by ``$\{y \in Y; f(y) = g(y)\}$ is closed in $Y$'' in (iii). O. Das 1
p. 226,
Line 20
Replace ``separable'' by ``separated''. T. Wedhorn 1
p. 227,
Line 19
Replace "an $S$-objects" by "an $S$-object". F. Gispert Sánchez 1
p. 228,
Statement of Prop. 9.3 (3)
Replace $f$ by $u$ everywhere (i.e., in 3 places). K. Kidwell 1
p. 229,
Line 13
Replace "$p\colon X\times_S Y$" by "$p\colon X\times_S Y \to X$". F. Gispert Sánchez 1
p. 230,
Lines 16, 17
Replace $X\rightarrow X_{\rm red}$ by $X_{\rm red}\rightarrow X$, and likewise for $Y$, and replace $f_{\rm red}\circ i_Y$ by $i_Y\circ f_{\rm red}$. P. Barik/U. Hartl 1
p. 232,
Lines 6-9
Replace "Grass$_{n,n-e}$" with "Grass$_{n-e,n}$" (4 times) to keep the same notation as in chapter 8. F. Gispert Sánchez 1
p. 233,
Prop. 9.19 (iii)
$f$ and $g$ should be $S$-morphisms. K. Kidwell 1
p. 233,
Def. 9.21
Replace ``$\mathfrak p_x$'' by ``$\mathfrak m_x$''. A. Isaev 1
p. 234,
Line 30 (Remark 9.25)
Replace $U\subseteq S$ by $U\subseteq X$. P. Barik 1
p. 234,
Line 28 (Remark 9.25)
Replace ``can checked'' by ``can be checked''. L. Galinat 1
p. 234,
Lines -3, -1
Replace "$\mathcal R$" by "$\mathcal R(X, Y)$" (twice). Peng Du 1
p. 235,
Def. 9.26
Our definition of rational map is different from that in other places in the literature. Notably, in EGA I (new ed.) 8.1, it is not required that the open subset $U$ be schematically dense. Cf. however the notion of pseudo-morphism introduced in EGA IV, 20.2. P. Hartwig 1
p. 235,
Line 9
The claimed injectivity does not hold in general. It does hold if $Y$ is separated over $S$ (by Prop. 9.19). K. Kidwell 1
p. 236,
Line -3
Replace "$K$" with "$K(X)$". F. Gispert Sánchez 1
p. 236,
Line 5
Replace "$(\lambda,\mu)$" with "$(\lambda : \mu)$". F. Gispert Sánchez 1
p. 236,
Second equation in Example 9.30
It should say "$(x,y) \mapsto \dots$" rather than "$(x,y)\to\dots$". Javier de la Bodega 1 2
p. 237,
Line 24 (Remark 9.34)
Replace $f\colon - - \rightarrow Y$ by $f\colon X - - \rightarrow Y$. P. Barik 1
p. 237,
Proposition 9.35
Add a period at the end of the statement of (2) 1 2
p. 237,
Line -16
Replace "tape" with "type". F. Gispert Sánchez 1
p. 238,
Line 17 (Exercise 9.2)
Replace ``$X \times_S Y \to X \times_S Y$'' by ``$X \times_S Y \to X \times_T Y$'' L. Galinat 1
p. 238,
Line 3
Delete the second $X$. Peng Du 1
p. 241,
Paragraph 2, Line -4
Replace "this" by "these". Jenna Nieminen 1 2
p. 241,
Line -16
Replace "among" by "along". Peng Du 1
p. 241,
8
Replace "roughly spoken" by "roughly speaking". Peng Du 1
p. 242,
Rmk. 10.2 (4)
At the end, replace ``if $Y$ not separated'' by ``if $Y$ is not separated''. U. Hartl 1
p. 242,
Line -1
Maybe add Remark 10.2(2) for reference. Yuhao Cheng 1 2
p. 243,
Proof of Prop./Def. 10.5
The proof could be streamlined a bit more, replacing the final paragraph and the previous invocation of Lemma 3.32 by just one invocation of that lemma. U. Görtz 1 2
p. 248,
Line 9
Replace ``ad'' by ``and''. U. Hartl 1
p. 248,
Line -14
Replace "on" with "an". F. Gispert Sánchez 1
p. 249,
Line 1
Replace "$\mathscr{O}_{Y,f(y)}$" with "$\mathscr{O}_{Y,f(x)}$" F. Gispert Sánchez 1
p. 250,
Line -3
Replace $f^{\flat}_V$ by $f^{\flat}_Y$. Lei Yu 1 2
p. 251,
Lines 29, 31 (Proof of Prop. 10.30)
Replace $i\colon Z\rightarrow X$ by $i\colon Z\rightarrow Y$ and $i^\flat$ by $i^\flat \colon \mathscr O_Y \rightarrow i^* \mathscr O_Z$. P. Barik 1
p. 251,
Line 20
Replace "Its sum" by "The sum". Peng Du 1
p. 253,
Remark 10.40 (3)
Add the assumption that $X$ has a basis of retro-compact open subsets. A. Gross 1
p. 253, 282,
Remark 10.40, Exercise 10.28

In the two mentioned places it is claimed that "In every quasi-compact topological space the notions of global and local constructibility coincide". It seems that a stronger assumption is needed for this to be true.

It is true in the case of quasi-separated quasi-compact schemes (for instance Stacks Project 054E). EGA I Proposition 0.2.3.11 proves it under the assumption that $X$ has a basis of retrocompact opens. See also MO 499696.

 Branislav Sobot / Yuhao Cheng 1 2
p. 254,
Line 3
Replace "Definition 10.5" by "Definition 10.12". Peng Du 1
p. 254,
Line -12, -11
Replace 'constructible' by 'globally constructible' twice. Xiaolong Liu 1 2
p. 255,
Line 4
Replace $Z$ by $C$. P. Barik 1
p. 256,
Line 18 (Cor. 10.49)
In the conclusion of the corollary, add that $\mathscr{F}$ is also quasi-coherent. F. Gispert Sánchez 1
p. 256,
Line -2
Replace $\mathscr{F}$ by $\mathscr{G}$. Yuhao Cheng 1 2
p. 256,
Line 8
The implicit definition of the $U^i$ is a bit confusing. It might be clearer to write "The set $\mathcal U = \dots$ is totally ordered by inclusion. We define $U^i$ by $\mathcal U = \{ U_0, \dots, U^n\}$ and $U^0\subsetneq U^1\subsetneq\cdots\subsetneq U^n$, so $U^0 = U_0=U$, $U^n = X$. Jan Willing 1 2
p. 257,
Line 7
Replace "an" with "a". F. Gispert Sánchez 1
p. 259,
Line 16
Replace "inductive limit" by "inductive limits". Peng Du 1
p. 261,
Line 17
Replace "inverse images under continuous maps" by "inverse images under morphisms". Peng Du 1
p. 261,
Proposition 10.56 (i); Theorem 10.57 (1), (2), (3)
For each line, add a period at the end. Yuhao Cheng 1 2
p. 262,
Line -12
Replace "is it" by "it is". Yuhao Cheng 1 2
p. 263,
Line 4
Replace $v_{0\lambda}^{-1}$ by $x_{0\lambda}^{-1}$. Peng Du 1
p. 264,
Corollary 10.64
The assumption that $Y_0$ is qcqs should be added. Yuhao Cheng 1 2
p. 264,
Line 2
Replace "1., 3., 5." with "1.-3., 5.". F. Gispert Sánchez 1
p. 265,
Line -15 (cor. 10.67)
Add "of" between "morphism" and "$S$-schemes". F. Gispert Sánchez 1
p. 265,
l. $-2$
Replace ``$R$-scheme'' by ``of $R$-schemes''. U. Hartl 1
p. 267,
Line -10 (prop. 10.75)
Replace "$f$" with "$f_0$". F. Gispert Sánchez 1
p. 267,
Line -8
Add "or" after property (1). Peng Du 1
p. 268,
l. $-7$
Insert ``if'' after ``In fact,''. U. Hartl 1
p. 268,
Theorem 10.76
It is not true in general that $B$ is the inductive limit of its smooth $A$-sub-algebras. All one can say in general is that $B$ is isomorphic to a filtered inductive limit of smooth $A$-algebras. See the discussion in Spivakovsky's paper [Sp] (Problem 1.3; Section 10). M. Hoyois, S. Kelly 1
p. 268,
l $-2$
Remove one ``that'' and replace ``morphism'' by ``morphisms''. U. Hartl 1
p. 268,
Line 22
Replace "morphism" with "morphisms". F. Gispert Sánchez 1
p. 270,
Line 17
Remove "it". F. Gispert Sánchez 1
p. 270,
(10.22.2)
$M_i$ is not a submodule of $M$, so in the expression $M/M_i$, replace $M_i$ with $\sum_{j=0}^ix^jN$, or replace $M$ by $M/N$. Matthew Snodgrass 1 2
p. 272,
Line 3
Replace "theorem" by "proposition". Yuhao Cheng 1 2
p. 272,
Line 12
Replace "subscheme) structure" with "subscheme structure)". F. Gispert Sánchez 1
p. 273,
Line 4
Add "holds" in the definition of $E_0$ Yuhao Cheng 1 2
p. 273,
Line -14
Add "is" before "constructible". F. Gispert Sánchez 1
p. 273,
Line -22
Replace "Frobenius (4.24)" by "Frobenius morphism (Definition 4.24)". (Cf. this erratum.) Peng Du 1
p. 273,
Line 3
Define $S_0 = {\rm Spec}(A_0)$. Yuhao Cheng 1 2
p. 274,
Line 9
Replace "$E\subseteq \pi^{-1}(\mathcal{P})$" with "$\overline{E}\supseteq \pi^{-1}(\mathcal{P})$". (If $\pi(\mathfrak{p})=p$ with $p\in\mathcal{P}$, then $\pi(\mathfrak{m})=p$ for all closed points $\mathfrak{m}$ which are specializations of $\mathfrak{p}$, as $\pi$ is continuous. Since all such closed points belong to $E$ and $R$ is a finitely-generated $\mathbb{Z}$-algebra and, in particular, Jacobson, we conclude that $\mathfrak{p}\in\overline{E}$.) F. Gispert Sánchez 1
p. 274,
Line 4
Replace ``suffice'' by ``suffices''. U. Görtz 1
p. 275,
Line 21
Replace "Corollary 10.85" with "Theorem 10.84" (we want to apply it to $\mathscr{H}$, not to $\mathscr{O}_X$). F. Gispert Sánchez 1
p. 276,
Line -8
Replace "$D(t)_s$ is dense $X_s$" by "$D(t)_s$ is dense in $X_s$". Yuhao Cheng 1 2
p. 276,
Line 14
Replace $M$ by $M_\eta$ (twice). Yuhao Cheng 1 2
p. 276,
Line 12
$\Gamma(\mathscr{F},X)$ should be $\Gamma(X,\mathscr{F})$. Yuhao Cheng 1 2
p. 276,
Line 20
Add "of" between "is" and "finite type". F. Gispert Sánchez 1
p. 277,
Line 10
Replace "Corollary 5.12" with "Corollary 5.17". F. Gispert Sánchez 1
p. 277,
Line 21
Add that $S$ is noetherian. F. Gispert Sánchez 1
p. 278,
Line 17
$f(X_i\cap Y)$ should be $f(X_i)$. Yuhao Cheng 1 2
p. 278,
Lines 21-26 (last paragraph of the proof of thm. 10.97)
Replace "$X_\xi$" with "$X_\eta$" (three times). Moreover, if $U$ is the non-empty open subset of $S$ which we are considering, the last equation holds for $v\in V=Y\cap f^{-1}(U)$ (not all $Y$). F. Gispert Sánchez 1
p. 279,
Line -8
Replace "a $R$-subalgebra" by "an $R$-subalgebra". Yuhao Cheng 1 2
p. 280,
Line 20
It would look better to replace $N>1$ by $N\ge 1$ (as in the following line). Peter Johnson 1
p. 281,
Line 9
Replace the final part of the sentence by "and $\kappa(x)$ is a finite extension of $\kappa(f(x))$.". Peng Du 1
p. 281,
Line 25 (ex. 10.22)
Replace "is" with "be its". F. Gispert Sánchez 1
p. 282,
Exercise 10.30(b)
$(u-t,t^2-t)$ should be replaced by $(t^2-t,u+t)$. (The original definition is not a well defined map from ${\rm Spec}(B)$ to ${\rm Spec}(A)$.) Yuhao Cheng 1 2
p. 283,
Line -14 (ex. 10.34)
Replace "inductive limit" with "inductive system". F. Gispert Sánchez 1
p. 283,
Exercise 10.37(a)
"Lemma 10.81" should be "Lemma 10.82". Yuhao Cheng 1 2
p. 284,
Line 20
Replace "generic" by "generically". Peng Du 1
p. 286,
Line 11
Replace "between to ..." by "between two ...". Peng Du 1
p. 286,
Line 5
Delete "Line bundles and". Peng Du 1
p. 286,
Line -9
Replace "roughly spoken" by "roughly speaking". 1
p. 287,
Line 3
Replace "$S$" by "$X$". F. Gispert Sánchez 1
p. 288,
Line 2
Replace "$\binom{r+n-1}{r}$" with "$\binom{r+n-1}{n}$" (or "$\binom{r+n-1}{r-1}$"). F. Gispert Sánchez 1
p. 288,
2 lines above equation (11.1.6)
Replace $f\colon X\rightarrow Y$ by $f\colon Y\rightarrow X$. Zhaodong Cai 1
p. 288,
Last line of the statement of Proposition 11.1
$({\rm Sch})^{\rm opp}$ should be $({\rm Sch}/X)^{\rm opp}$. 1
p. 289,
Prop. 11.3
In the statement of the proposition (and in its proof), one should add parentheses in order to emphasize that the target of the isomorphism is $\Gamma(T, (h^* \mathscr E)^\vee)$. P. Hartwig 1
p. 291,
Line 9
Remove the extra parenthesis in "$\mathscr{S}(V/X))$". F. Gispert Sánchez 1
p. 292,
-14
Replace "is the group $G$ itself" by "is the sheaf of groups $G$ itself" Félix Baril Boudreau 1
p. 292,
Line 18
Write morphism instead of morphisms. Saskia Kern 1 2
p. 293,
Lines 5-7
Define $\theta$ and $\theta'$ as $\theta := (g_{ij})_{i,j}$ and $\theta' := (g_{ij}')_{i, j}$, respectively. Maybe replace "for all $i$" with "for all $i \in I$". Mention explicitly that the equation (in line 7) holds on $U_i \cap U_j$. N. T. 1 2
p. 293,
Line -14
Replace "1-cocycle" with "1-cocycles". F. Gispert Sánchez 1
p. 293,
Line 18
Replace "straight forward" by "straightforward". Ulrich Görtz 1
p. 293,
Line 9
Replace "1-cocycle" with "1-cocycles". F. Gispert Sánchez 1
p. 294,
Line -2
Replace $\check{H}^1(X, G)$ by $\check{H}^1(X, G')$. Saskia Kern 1 2
p. 295,
Line 5
Add somewhere that $\varphi$ is the map $G'\to G$ in the short exact sequence (11.5.5). F. Gispert Sánchez 1
p. 295,
Lines -2, -3, -5
Replace $\mathscr Isom(\mathscr E, \mathscr O_X^n)$ by $\mathscr Isom(\mathscr O_X^n, \mathscr E)$. A. Schiller 1
p. 296,
Line -3
The discussion in Example 11.42 only considers the noetherian case. (The result is true in general, see e.g. Stacks project 0BCH.)
Also, add "ring" after "factorial" (alternatively, remove "a" before).		 F. Gispert Sánchez 1
p. 298,
Line 6
We can only conclude that the immersion is locally of finite presentation. F. Gispert Sánchez 1
p. 299,
Line 6
The sheaf $\mathscr{R}_X$ has not been defined (it is the sheaf given by $U\mapsto R(U)$), and maybe should not a priori be called a ``constant sheaf'' here. F. Gispert Sánchez 1
p. 299,
6th line after Definition 11.19
TeX: $\mathop{\rm Div}(X)$ should be upright 1
p. 299,
Line 14
Maybe add remark on neutral element and inverses in the group of Cartier divisors. woo 1 2
p. 300,
Line 3
The mapping $U\mapsto {\rm Frac}(\Gamma(U,\mathscr O_X))$ is not a presheaf in general (rather, one should consider the localization with respect to elements which are non-zero divisors in every stalk). See Kleiman, Misconceptions about $K_X$. Enseign. Math. (2) 25 (1979), no. 3-4, 203--206 (1980), for a detailed discussion. P. Hartwig 1
p. 303,
Line 3
Replace ``detailed'' by ``detail''. J. Calabrese 1
p. 304,
Line 1
Delete the second $U$. Peng Du 1
p. 305,
Line 27
Replace "$\mathscr{O}$" with "$\mathscr{O}_X$". F. Gispert Sánchez 1
p. 305,
Line -8 (Lemma 11.33)
The notation for the codimension is different from the notation used in chapter 5. F. Gispert Sánchez 1
p. 305,
Line 19 (displayed bijection)
Replace "cartier" with "Cartier". F. Gispert Sánchez 1
p. 305,
Prop. 11.32
Replace the definition of ``regular'' given in parentheses by ``i.e., the associated homomorphism $\mathscr O_X \rightarrow \mathscr L$ is injective''. K. Kidwell 1
p. 305,
Line -13
Replace "isomorphism" by "isomorphisms". Ulrich Görtz 1
p. 305,
Line -3
Replace ``for every maximal point of ${\rm Supp} D$'' by ``for every maximal point $\eta$ of ${\rm Supp} D$''. T. Wedhorn 1
p. 306,
Lemma 11.35
The hypothesis of A being local is not needed. In fact, Corollary B.64 doesn't have to be invoked: Let $a$ be a regular element. By a slightly different version of Krull's principal ideal theorem (e.g. Corollary 11.17 in [AM]), every minimal prime ideal over $a$ has height 1. In particular, for every such prime $P$, $\dim(A/P) \leq \dim(A)-{\rm ht}(P) = 1-1 = 0$, and hence $\dim(A/P) = 0$. Moreover, if $a$ is not a unit, then $\dim(A/(a)) = 0$. Therefore, $A/(a)$ is an Artinian ring for every regular elements $a$. Now the proof continues with no further changes. Javier de la Bodega 1 2
p. 306,
Line 7
Replace $\mathop{\rm codim}(Z, X)$ by $\mathop{\rm codim}\nolimits_X(Z)$ (twice). U. Görtz 1
p. 306,
Line -16
Replace "$\mathscr{O}_{X,c}$" with "$\mathscr{O}_{X,C}$". F. Gispert Sánchez 1
p. 307,
Line -6
Replace (B.75) by B.75. Peng Du 1
p. 308,
First paragraph of the proof of Theorem 11.38
Replace Quot by Frac. Javier de la Bodega 1 2
p. 308,
Prop. 11.40
The proposition is not true as it stands (a counterexample is given by $X$ the plane with a fattened origin, and $Z$ the origin). It is correct with the additional assumption that $U$ be schematically dense in $X$ (use the characterization in Lemma 9.23 (ii) to conclude that the exactness at $Z^1(X)$ of the corresponding sequence of groups of cycles yields the exactness at ${\rm Cl}(X)$ of the sequence in the proposition). B. Smithling 1
p. 308,
Line 13
Replace $U$ by $U_i$ (twice). B. Smithling 1
p. 309,
Line -4ff
Replace ``as product $f_1f_2\dots f_r$, where $f_i \in S$ are irreducible homogeneous polynomials'' by ``as product $f_1^{d_1}f_2^{d_2}\dots f_r^{d_r}$, where $f_i \in S$ are irreducible homogeneous polynomials and $d_i \in {\mathbb Z}$'' and replace ``$Z\colon {\mathcal R} \to Z^1({\mathbb P}^n_k), f \mapsto \sum_i [V_+(f_i)]$'' by ``$Z\colon {\mathcal R} \to Z^1({\mathbb P}^n_k), f \mapsto \sum_i d_i[V_+(f_i)]$''. T. Wedhorn 1
p. 309,
Lines -4, -1
The expression for $f$ in line 8 (ed. 1: line -4) ignores that there may be denominators. A homogeneous polynomial may be expressed as stated and for those $f$ the expression in line 11 (ed. 1: line -1) is correct. In general, we express an element of $\mathcal R$ as a fraction and extend the map $Z$ in the obvious way so that it becomes a group homomorphism. J.-C. Syu 1 2
p. 309,
Line 11
Replace $\mathop{\rm codim}(Z, X)$ by $\mathop{\rm codim}\nolimits_X(Z)$. Peng Du 1
p. 310,
Line 15
The symbol $D(f)$ is not defined, and should be defined explicitly as the Cartier divisor $(D_+(T_i), f/T_i^d)_i$. Peng Du 1
p. 311,
Line 17
Replace "Example 7.13" by "(7.13)". Peng Du 1
p. 313,
Line -6
Replace ``set'' by ``sets''. P. Johnson 1
p. 313,
Line 1
The morphism $\phi$ is not necessarily flat: See mathoverflow.net/questions/65267/global-sections-of-flat-scheme-also-flat. The statement of the proposition is true, though: One should first remark that one can work locally on target and source and hence can assume that everything is affine. Hernan I. 1
p. 314,
Lemma 11.50

The given proof of the lemma is erroneous, because the reduction to the $2\times 2$-case does not work as asserted. The following is one possibility to fix this.

(1) Bring the given matrix in upper triangular form (11.17.2) with powers of $T$ on the diagonal, as described in loc.~cit. Multiplying the matrix with a suitable power of $T$, we may assume that all entries of the matrix are in $R^+$. (Multiplying all entries by $T$ commutes with all the operations below, so we may revert this after we have put the matrix into diagonal form.)

(2) Our next goal is to bring the matrix into the form (11.17.2) with the additional requirement that $d_1 \ge d_2 \ge \cdots \ge d_n$ (of course, the exponents $d_i$ may change). Note that once this is achieved, we can bring the matrix into diagonal form with powers of $T$ on the diagonal by using row/column operations to subtract suitable $R^+$- or $R^-$-multiples of the diagonal entries from the entries above the diagonal.

To obtain an upper triangular matrix where the $T$-exponents on the diagonal are in descending order, we apply the following lemma $n-1$ times, first for $i=1$, then for $i=2$, etc.

Lemma. Let $1\le i \le n$. Given a matrix $A$ in the form (11.17.2) with all entries in $R^+$, we may multiply $A$ by some matrix in $GL_n(R^+)$ on the left and by some matrix in $GL_n(R^-)$ on the right to obtain an upper triangular matrix $A'$ with all entries in $R^+$ and diagonal entries $T^{d_1'}, \dots, T^{d_n'}$ such that in addition

  • $d_i' = \max(d_i', d_{i+1}', \dots, d_n')\le \max(d_i, \dots, d_n)$,
  • the rows $1, \dots, i-1$ are the same in $A$ and $A'$.

Proof. To simplify the notation we write out the case $i=1$. It will be clear from the proof that the general case works in the same way, because (with a general $i$) only row/column operations for rows and columns with index $\ge i$ are required.

Given an upper triangular matrix $B$ with entries in $R^+$ and powers $T^{b_1}, \dots, T^{b_n}$ on the diagonal, we define the following quantities:

  • ``maximum exponent on diagonal'' $m(B) = \max(b_1, \dots, b_n)$,
  • ``number of max entries'' $n(B) = \# \left\{ j; b_j = m(B) \right\}$,
  • ``position of left-most max entry'' $p(B) = \min \left\{ j;\ b_j = m(B) \right\}$.

We go from $A$ to the desired $A'$ step by step. The procedure described below will ensure that at each step, transforming $B$ to $B'$, say, at least one of the following happens:

  • (I) $m(B') < m(B)$,
  • (II) $m(B') = m(B)$ and $n(B') < n(B)$,
  • (III) $m(B') \le m(B)$ and $p(B') < p(B)$.

We stop the procedure when $p(B') = 1$; then the conditions in the statement of the lemma are all satisfied for $B'$. Note that this has to happen after finitely many steps. In fact, $m(B) \ge 0$ for all matrices $B$ involved, so (I) can only happen finitely many times, and thus after finitely many steps we must reach a situation where (I) does not happen again. But then (II) can happen only finitely many times since $n(B) \ge 1$, so we must at some point reach a situation where neither (I) nor (II) can happen again. But that leaves only (III) and we must eventually reach $p(B')=1$.

It remains to describe the step transforming a given $B$ to $B'$ such that one of (I), (II), (III) happens.

Let $j = p(B) > 1$, so $b_{j-1}< b_j$.

Case 1. The entry $b_{j-1,j}$ of $B$ in row $j-1$, column $j$ is $=0$. Then we may swap the $(j-1)$-th and $j$-th rows, and the $(j-1)$-th and $j$-th columns by multiplying by a suitable permutation matrix on the left and on the right. This gives us an upper triangular matrix $B'$ where the diagonal entries at index $j-1$ and $j$ are exchanged, so $p(B') < p(B)$, i.e., (III) happens.

Case 2. We have $b_{j-1,j} \ne 0$ and $b_{j-1} = b_j - 1$ (as before the $b_i$ are the exponents of $T$ in the diagonal entries). In this case we may achieve $b_{j-1,j} =0$ by suitable row and column operations which leave the diagonal entries unchanged, and continue as in Case 1.

Case 3. Finally, consider the case $b_{j-1,j} \ne 0$ and $b_{j-1} < b_j - 1$. We then apply the reasoning for $GL_2$ described in loc.~cit. This shows that either we can reach Case 1 without changing the diagonal entries, or there exists $v$ with $b_{j-1} < v < b_j$ and row/column transformations such that the diagonal entries $T^{b_{j-1}}$, $T^{b_j}$ of the given matrix are replaced by $T^v$, $T^{b_{j-1}+b_j-v}$. (We only do this step once, there is no need for an additional induction now and we do not care whether the entry at $(j-1, j)$ in the new matrix is $=0$.) Then \( \max(v, b_{j-1}+b_j-v) < b_j. \) In fact, $v < b_j$ by the choice of $v$ we made; and similarly $b_{j-1}+b_j -v < b_j$ follows from $v > b_{j-1}$. From this we see that either (I) or (II) must happen.

Typos: The definition of the subgroup $G_\alpha$ is not correct (it should have possibly non-trivial entries at positions $(i_0, i_0)$, $(i_0, j_0)$, $(j_0, i_0)$, $(j_0, j_0)$. In the last line of the proof, the middle term of the expression should be $d+e-2v$.

There are several other known proofs for this fact in elementary terms, e.g. [Hazewinkel, Martin, A short elementary proof of Grothendieck's theorem on algebraic vector bundles over the projective line, J. Pure Appl. Algebra 25 (2), 1982, 207--211], [Clancey, Gohberg, Factorization of Matrix Functions and Singular Integral Operators, Springer, 1981] Theorem 2.1.

 Matthias Schempp / Giulia Messineo / UG 1 2
p. 315,
Line -2
The notion of being "of pure dimension 1" has not been defined. It is defined in brackets in Proposition 15.1. The easiest fix here might be to replace it by ``equidimensional of dimension 1''. F. Gispert Sánchez 1
p. 315,
Line -13
Replace $d$ by $d_i$ in the definition of $\mathscr E^\lambda$ (twice). Peng Du 1
p. 316,
Exercise 11.1 (a)
Add "quasi-coherent" before $\mathscr O_X$-algebras. Yuhao Cheng / YUBO ZHOU / Jan Willing 1 2
p. 318,
Exercise 11.18 (a)
Replace '$Z^1({\rm Spec}\ A)\cong\mathbb{Z}^r$' by '$Z^1({\rm Spec}\ A)\cong\mathbb{Z}$'. Xiaolong Liu 1 2
p. 319,
Line -13 (ex. 11.22 (a))
Replace "an" with "a". F. Gispert Sánchez 1
p. 321,
Line -16
Replace "a affine scheme" with "an affine scheme". F. Gispert Sánchez 1
p. 321,
Line 24
Replace ``affine over $X$'' by ``affine over $Y$''. P. Barik 1
p. 323,
Line 17
Replace $\otimes_{(A'\otimes_A B})\otimes$ by $\otimes_{(A'\otimes_A B)}$. P. Barik 1
p. 323,
Line 12
Replace $X' = \mathop{\rm Spec} B' \otimes_{B} A$ by $X' = \mathop{\rm Spec}(B \otimes_A A')$. P. Barik 1
p. 323,
Line -9
The (finite) covering $(U_i)_i$ of $X$ should be an affine open covering. F. Gispert Sánchez 1
p. 323,
Line 8
In the last expression of 12.2.3 replace $Y'$ by $X'$. P. Barik 1
p. 323,
Line 12
Replace "and hence $X' = {\rm Spec}(B' \otimes_B A)$" by "and hence $X' = {\rm Spec}(A' \otimes_A B)$". Akash N 1 2
p. 324,
Line -17
Remove ``a'' at the end of the line. K. Kidwell 1
p. 324,
Line 2
Replace "$\mathscr{F}(X)$" with "$\mathscr{F}(U_i)$" F. Gispert Sánchez 1
p. 324,
The commutative diagram
In the lower right corner, the index "$ij$" of the direct sum should be "$i,j$". Yuhao Cheng 1 2
p. 325,
Line -3
``Corollary 5.12'' should be ``Proposition 5.12''. U. Hartl 1
p. 328,
Prop. 12.18
The first formula is false (almost always, e.g. if $Y=\mathop{\rm Spec} \mathbb F_p$, $X=\mathop{\rm Spec} \mathbb F_{p^2}$, $X'=\mathop{\rm Spec} \mathbb F_{p^2}$). Yehao Zhou 1
p. 329,
Line 4
In addition to the notion of degree of $f$, add the notion of rank of $f$ with the same meaning. Nevertheless, we will try to stick to the term degree (change this on p. 331, l. 3, l. 15; p. 479, l. 1). Peng Du / Ulrich Görtz 1
p. 329,
Line -7
Switch the order in all pairs $z/x, \dots$ in this line. Peng Du 1
p. 329,
Line 18
Replace "be" with "by". F. Gispert Sánchez 1
p. 330,
Line 2
Switch the order in all pairs $z/x, \dots$ in this line. Peng Du 1
p. 332,
Lines 2 and 22
Both in the statement (twice) and in the proof (once) of Proposition 12.27, "$\mathscr{O}$" is used to denote "$\mathscr{O}_X$". F. Gispert Sánchez 1
p. 332,
Line -15
Replace ``Corollary 5.12'' by ``Proposition 5.12''. S. Köbele 1
p. 333,
Line -14
Replace $a_0$ by $a_n$. S. Köbele 1
p. 333,
Example 12.29
In several places, replace $t$ by $t'$. S. Köbele 1
p. 335,
Theorem 12.35
The assumption that $X$ be quasi-separated is superfluous. This is currently used to invoke Theorem 7.22 in the proof of (ii) $\Rightarrow$ (i), but it follows from (ii) since $X_{f_i}\cap X_{f_j}$ is a principal open subset of the affine scheme $X_{f_i}$. Alternatively, one could prove (ii) $\Rightarrow$ (i) by saying that for all $i$, the morphism $X_{f_i}\to D(f_i)$ is affine (since $X_{f_i}$ is affine), so that by Prop. 12.1 the morphism $X\to {\rm Spec}(A)$ is affine. U. Görtz 1 2
p. 335,
Equation (12.8.1)
The middle term should be $\frac{f_j^{k+\ell}x_{\mathbf i}}{f_{\mathbf i}^k}$ instead of $\frac{f_j^{k+\ell}x_{\mathbf i}}{f_{\mathbf i}^r}$. P. Barik 1
p. 338,
Line 8
Add "be" between "let $\eta$" and "its generic point". F. Gispert Sánchez 1
p. 338,
Line 6
Replace "$H^1(\mathscr{O}_Y,\mathscr{F})$" with "$H^1(Y,\mathscr{F})$". F. Gispert Sánchez 1
p. 339,
Line -13
Replace $L$ by $L_X$. Peng Du 1
p. 339,
Section (12.10)
Is it not clear that the presheaf $\mathscr A'$ is a sheaf, and it should instead be defined locally (as in the Stacks project), asking that $\mathscr A'(U)$ consists of all $b$ such that the stalk of $b$ at $x$ is integral over $\mathscr O_{X,x}$ for all $x \in U$. Then it is obviously a sheaf, and it also agrees with your definition if $U$ is affine. Florian Herzig 1 2
p. 341,
Line 11
Add "be" before "its normalization". F. Gispert Sánchez 1
p. 342,
Line -6
Remove the second "C" in this line. Yuhao Cheng 1 2
p. 342,
Line -12 (prop. 12.53)
Add that $X$ is integral. F. Gispert Sánchez 1
p. 344,
Line -11
Replace $f^{-1}(U)\subseteq V$ by $f^{-1}(V)\subseteq U$. P. Barik 1
p. 345,
Line 17
Replace "proposition" by "theorem". Yuhao Cheng 1 2
p. 346,
Line -4
Replace "$\mathscr{O}_X$-module" with "$\mathscr{O}_X$-modules". F. Gispert Sánchez 1
p. 347,
Line 7
Add "is" before "not irreducible". F. Gispert Sánchez 1
p. 348,
Line -14
Replace "Remark 12.10 (2)" by "Remark 12.10 (3)". Peng Du 1
p. 348,
Line -10
Add "be" before "its Stein factorization". F. Gispert Sánchez 1
p. 351,
Line -9
Replace "$\varphi$" by "$\varphi\colon A\to B$". Peng Du 1
p. 352,
Line 18
Replace ``finite'' by ``integral'': We do not know whether $A'$ is finite over $A$, but it being integral is enough for the following argument. Yugo Takanashi 1
p. 352,
Line -12
Replace ``relation'' by ``relations''. U. Görtz 1
p. 353,
Proof of Prop. 12.76
In the beginning of the proof, it would be useful to note that the inclusion $\mathop{\rm Isol}(B/A) \supseteq \mathop{\rm LocIsom}(B/\overline{A})$ follows easily from Lemma 12.75 (1) and going up for integral extensions, so that only the opposite inclusion is considered in the following.
In the second step, to see that $\mathfrak q'\in \mathop{\rm Isol(A'/A)}$, note that the existence of $U'$ shows that $\mathfrak q'$ is open in its fiber over $\mathop{\rm Spec} A$. By Lemma 12.72 it is therefore isolated, because the fiber is of finite type over $\kappa(\mathfrak q)$.		 F. Gispert Sánchez 1
p. 354,
Line 1
Replace $a_0+a_1y+\dots a_my^m$ by $a_0+a_1y+\dots+ a_my^m$. Yuhao Cheng 1 2
p. 356,
line -8
Replace "this is implies" by "this implies". Shahram Mohsenipour 1
p. 356,
Lines 6 to 8
Replace "$W'$" with "$W$" and "$X'$" with "$X$" (three times altogether). Replace $f\mathscr O_Y$ by $\mathscr O_Y$ (twice). F. Gispert Sánchez 1
p. 357,
Line 2
A reference to Equation (11.2.4) is more precise than Proposition 11.1. Yuhao Cheng 1 2
p. 357,
Proof of Thm. 12.73
In general, it is not true that $f'$ as defined in the book is of finite type; hence Cor. 12.78 cannot be applied directly. Instead, one can proceed as follows: Start the proof as in the book: the restriction of $c$ to ${\rm Isol}(c)$ is an open immersion, hence $h$ is an open immersion. Now approximate $X'$ by $X'_\mu$ which are affine of finite type over $Y$ (analogously to approximating $Z$ by $Z_\lambda$). Using Lemma 12.84, we may assume that $V'\rightarrow X'_\mu$ is an open immersion (for some fixed large $\mu$). Now replace $X'$ by $X'_\mu$ and continue as in the book: Define $Z$, apply 12.78 (which is now justified), observe that $V' \subseteq {\rm Isol}(X'/Z)$, and apply Lemma 12.84 again to approximations of $Z$. Yehao Zhou 1
p. 360,
Line 21
Replace "$\mathscr B_y/\mathfrak m_s \mathscr O_{Y,y}$" by $\mathscr B_y/m_s\mathscr B_y$". Yubo Zhou 1 2
p. 361,
Line 6
Replace "my" by "may". Peng Du 1
p. 361,
Ex. 12.6
Replace isomporphism by isomorphism. T. Keller 1
p. 363,
Line -22, Exer. 12.21
Insert "be" before "Dedekind rings". Peng Du 1
p. 363,
Exercise 12.21
Add the definition $K= {\rm Frac}(A)$. In Part (b), replace "Form now" by "From now". Jan Willing 1 2
p. 365,
Exercise 12.29
The morphism $f$ should be assumed to be dominant to have a field extension $K(Y) \to K(Y)$. Javier de la Bodega 1 2
p. 367,
Line -6
With the terminology introduced before, the definition of homegeneous ideal should read "A homogeneous ideal I of A is a homogeneous submodule of A." (But maybe the term graded submodule, with the same meaning as homgeneous submodule, should also be introduced.) Johann Birnick 1 2
p. 367,
Line 20
Replace $\sum_{d\ge 0}$ by $\sum_d$ (to also cover the case of graded modules). Peng Du 1
p. 368,
Line -6
Replace ``ideal'' by ``ideals''. U. Görtz 1
p. 368,
Line -20
The element $f$ should be homogeneous. U. Görtz 1
p. 368,
Prop. 13.2 (2)
The set of ideals disjoint from $S$ may be empty. A corrected version of (2) is: "Let $S\subset A_+$ be a non-empty subset such that $s,t\in S$ implies $st\in S$ (hence $S\cup\{1\}$ is a multiplicative subset). Suppose that there exists a homogeneous ideal $I\subsetneq A_+$ such that $S\cap I = \emptyset$. Then every ideal maximal among the set of homogeneous ideals $I$ satisfying $I\subsetneq A_+$ and $S\cap I=\emptyset$ is of the form $\mathfrak{p}_+$ for a relevant prime ideal $\mathfrak{p}$." Maybe also include justification in the proof of (3) why the set of ideals with those properties for $S=\{f,f^2,\dots\}$ is non-empty: "Conversely, if $f\notin\text{rad}(I)$, then let $S=\{f,f^2,\dots\}$ and note $I\cap S=\emptyset$ and $I\subsetneq A_+$. Hence there is a relevant prime ideal disjoint from $S$ by (2), so $f$ is not contained in the intersection of all relevant prime ideals." Matthew Snodgrass 1 2
p. 368,
Proof of Prop 13.2 (3)
To apply (2), $f$ must be in $A_+$. The current argument is sufficient to show (3) (together with a direct proof that the ideal $\operatorname{rad}(I)$ is homogeneous) but not for the statement in the first line of the proof. 1 2
p. 368,
Equation (13.1.1)
Replace $\mod f-1$ by $\mod (f-1)$ A. Kaučikas 1
p. 368,
Prop. 13.2 (3)
Replace ``with all relevant prime ideals'' by ``with the intersection of all relevant prime ideals''. K. Kidwell 1
p. 368,
Statement of Prop. 13.2 (2)
We must assume that $0\notin S$ and that $S$ contains an element of $A_+$. K. Kidwell 1
p. 368,
Line 10
Replace "graded ideal" by "homogeneous ideal". Peng Du 1
p. 369,
Line 21
We defined $V_+(\mathfrak a)$ only for homogeneous ideals contained in $A_+$. Therefore $V(\mathfrak a^h)$ should be replaced by $V(\mathfrak a^h\cap A_+)$. Note that for $\mathfrak p\in {\rm Proj}(A)$, we have \(\mathfrak a\subseteq \mathfrak p \Leftrightarrow \mathfrak a^h\subseteq\mathfrak p\Leftrightarrow \mathfrak a^h\cap A_+\subseteq\mathfrak p.\) (Alternatively we could define $V_+(-)$ for all homogeneous ideals (or even all subsets of $A$) and explain why this doesn't make a difference.) Dominik Briganti 1 2
p. 370,
Line 10
$f \in {\rm rad}(g)_+$ should read $g \in {\rm rad}(f)_+$. F. Gispert Sánchez/N. Pflueger 1
p. 371,
Line -18
Remove "be" and replace "$R$-algebras" by "$R$-schemes". Peng Du 1
p. 371,
Line -19
Insert "be" before "a graded". Peng Du 1
p. 371,
Line 4 (Remark 13.7)
In the last line of the remark, it should read $A_{(f)}=A'_{(f^{k\delta})}$. Jesús Martín O. 1
p. 373,
Line -9
It is not true in general that the functor considered here commutes with tensor products, see Stacks Project01ML. But this does hold if $A$ is generated by $A_1$ as an $A_0$-algebra. D. Vogel 1 2
p. 375,
Line -3
Replace definition of $\sigma$ by ``$\sigma(t'):= t / f^n \in \Gamma_*(\mathscr F)_{(f)}$''. P. Johnson 1
p. 376,
Line 5
Replace '$(M_{(f)})_n$' by '$(M_f)_n$'. Xiaolong Liu 1 2
p. 376,
Line -15
Insert "$M$" after "module". Peng Du 1
p. 376,
Line -10 (thm. 13.20, displayed equation, under the arrow)
Replace "$\mathscr{F}\leftarrow\!\shortmid \Gamma_{*}(\mathscr{F})$" with "$\Gamma_{*}(\mathscr{F}) \leftarrow\!\shortmid\mathscr{F}$". F. Gispert Sánchez 1
p. 377,
Prop. 13.24
The subscheme $Z$ should be assumed to be non-empty, to ensure we can find $I$ as in the proposition which does not contain $A_+$. U. Görtz 1 2
p. 377,
Line 15
Replace ``$n \ge 0$'' by ``$n\ge n_0$''. P. Johnson 1
p. 377,
Proposition 13.22 (statement and proof)
The symbol $n$ is used for two different things: the number of generators of $A_+$ and as an index for $\mathscr{F}(n)$. F. Gispert Sánchez 1
p. 377,
Line 7
Remove a ")" at the end. 1 2
p. 378,
Line 12
Insert "the" before "saturation". Peng Du 1
p. 378,
Line 18
Replace "Corollary 13.24" by "Proposition 13.24". Peng Du 1
p. 378,
line 2
Replace "on" with "one." N. Pflueger 1
p. 379,
Lines -14, -13
The notation $-\otimes_{\mathscr O_S}\mathscr O_{S'}$ (used twice) is a bit sloppy. Maybe the $\otimes$ should be replaced by $\boxtimes$, or the tensor product could be replaced by $g'^*$, where $g'$ is the base change of $g$ (which would have to be defined). Peng Du 1
p. 379,
Prop. 13.28
In the first line of the statement of the proposition, replace ``modules'' by ``module''. P. Johnson 1
p. 379,
Line -2
Replace "$\varphi$" with "$\varphi_i$". F. Gispert Sánchez 1
p. 379,
Line -1
The domain and codomain of $g_i$ are swapped: switch $\mathscr{A}_i$ and $\mathscr{A}'_i$. F. Gispert Sánchez 1
p. 379,
Line -9
The meaning of the symbol $\pi$ should be stated again. Both in the statement of proposition 13.28 and at the end of the proof (in the next page), I would write "$g^*_{\mathscr{L}}(\mathscr{O}_X(n)\otimes\pi^*(\mathscr{L}^{\otimes n}))$" with the extra parentheses (or, alternatively, replace "$\pi$" with "$\pi'$"). F. Gispert Sánchez 1
p. 380,
Line 6
Add "be" before "the structure morphism". F. Gispert Sánchez 1
p. 380,
Line 8
Replace "$\mathscr{O}(n)$" with "$\mathscr{O}_X(n)$". F. Gispert Sánchez 1
p. 380,
Line 17
Add "be" before "the structure morphism". F. Gispert Sánchez 1
p. 380,
Line 11
Replace "by" with "given by". Peng Du 1
p. 380,
Line 3
Replace "$f_j^{-1}$" with "$f_j^{-n}$". F. Gispert Sánchez 1
p. 382,
Line 21
Replace "$\mathscr{O}^{n+1}$" with "$\mathscr{O}^{n+1}_X$". F. Gispert Sánchez 1
p. 382,
Line 18
Replace '$\mathbb{P}^{n+1}=\mathbb{P}(\mathscr{O}_S^{n+1})$' by '$\mathbb{P}_S^{n}=\mathbb{P}(\mathscr{O}_S^{n+1})$'. Xiaolong Liu 1 2
p. 382,
Lines 15, 18
Replace $\mathbb P^{n+1}$ by $\mathbb P^n$ (three times). K. Kidwell 1
p. 382,
Line -12
Replace $\alpha_i$ by $\alpha_j$. T. Keller 1
p. 383,
Line 10
Replace "$R$-modules" with "$R$-module". F. Gispert Sánchez 1
p. 384,
Line -4
Insert the condition $x\ne x'$. Peng Du 1
p. 384,
line -16
Replace "Corollary 13.24" with "Proposition 13.24". N. T. 1
p. 384,
Line 16
Replace "$\mathscr O_S$-module" by "$\mathscr O_S$-module $\mathscr E$". Peng Du 1
p. 387,
Line 8
Replace "$f$ is invertible in $x$" by "$f(x) \ne 0$ in the fiber $\mathscr L(x)$". Ulrich Görtz 1
p. 388,
Line -6, Line -3
Add that $f$ is homogeneous. F. Gispert Sánchez 1
p. 389,
Line -17
Replace "relevant prime ideals ... of $A_+$" by "relevant prime ideals ... of $A$". Peng Du 1
p. 390,
Line -9
Replace "$(i\times \id_{S'}) \mathscr{O}_{P'}(1)$" with "$(i\times \id_{S'})^* \mathscr{O}_{P'}(1)$". F. Gispert Sánchez 1
p. 390,
Line -16
Omit the statement in parentheses. It is not true that the existence of an ample line bundle implies properness. P. Hartwig 1
p. 391,
Line 2
Replace "(the globalization) of" with "(the globalization of)". F. Gispert Sánchez 1
p. 392,
Prop. 13.56 (iii)
As explained in the beginning of the proof, the word "quasi-compact" may be omitted in the statement of (iii) since it is automatic (and should be omitted to be consistent with how the proofs of (ii) $\Rightarrow$ (iii) and (iii) $\Rightarrow$ (iv) are written). U. Görtz 1 2
p. 392,
Line -17
Remove "be". F. Gispert Sánchez 1
p. 393,
Line -15
Replace "$i'\colon X \hookrightarrow P'$" with "$i'\colon X \to P'$" (as $i'$ is not necessarily an immersion, only $i$ is). F. Gispert Sánchez 1
p. 393,
Line 8
Replace "send" with "sent". F. Gispert Sánchez 1
p. 393,
Proof of Prop. 13.57 (1)
Maybe a few details should be added on why it follows, at the end of the proof, that $\mathscr L\otimes \mathscr L'$ is very ample: Since $S$ is affine, we find a surjection $\mathscr O_S^n \to \mathscr E\otimes \mathscr E'$ for some $n$, and from this obtain an immersion $X\to \mathbb P^{n-1}_S$ of $S$-schemes under which $\mathscr O(1)$ pulls back to $\mathscr L\otimes \mathscr L'$. Jin Yong / U.G. 1 2
p. 393,
Lines -8 and -7
Replace "(2)" with "(1)" (twice). F. Gispert Sánchez 1
p. 394,
Line -15
Replace "$n\geq n_0+m_0$" with "$n\geq d+m_0$". F. Gispert Sánchez 1
p. 394,
Line 20
Add that "$S={\rm Spec}\ R$" somewhere ($R$ has not been defined). F. Gispert Sánchez 1
p. 394, 395,
(13.13)
In line $-8$, replace ``non-zero'' by ``regular''. At the end of that paragraph, add a reference to Prop. 11.32 (in addition to Cor. 11.28). At the beginning of page 395, add the assumption that $X$ be integral (to ensure that all non-zero global sections of a line bundle are regular). K. Kidwell 1
p. 395,
Def. 13.60
Insert $\mathscr L$ after $\mathscr O_X$-module. P. Johnson 1
p. 396,
Line -1
Add the missing closing parenthesis at the end. F. Gispert Sánchez 1
p. 396,
Line -6
Replace "$g^{-1}(X_s)$" with "$(g')^{-1}(X_s)$". F. Gispert Sánchez 1
p. 397,
Line 10
Replace "be" by "by". Peng Du 1
p. 398,
Line -9
Replace $Y\backslash \varepsilon(S)$ by $C\backslash \varepsilon(S)$. U. Görtz 1
p. 398,
Lines -6 & -2 (def./prop. 13.68)
Replace "a quasi-coherent $\mathscr{O}_X$-module $\mathscr{E}$" with "a quasi-coherent $\mathscr{O}_S$-module $\mathscr{E}$" (twice). F. Gispert Sánchez 1
p. 401,
Proof of Prop. 13.76 (2)
For "the converse'' note that we already know by Part (1) that $Y$ is quasi-projective and thus in particular separated, so that the assumptions of Prop. 12.59 are satisfied. LY 1 2
p. 404,
Line -3 (the diagram)
Add label $r$ to the right hand arrow. Peng Du 1
p. 404,
Line 19
Replace "by Corollary 13.42" with "by Example 13.69". F. Gispert Sánchez 1
p. 405,
Line 19
Replace '$X$' by '$Z$'. Xiaolong Liu 1 2
p. 405,
Line 22
It should be stated that, in the definition of $H_m$, we set $m = e+1 (={\rm rk}\ \mathscr F)$. Peng Du 1
p. 408,
Line 11
Replace '$A^x=k[x,y,\mu]/(\mu x=y)$' by '$A^x=k[x,y,\mu]/(\mu x-y)$'. Xiaolong Liu 1 2
p. 408,
Line 5
Replace $\mathbb{A}^2\setminus \{0\}$ by $\mathbb{A}^2(k)\setminus \{0\}$. Yuhao Cheng 1 2
p. 409,
Prop. 13.91
Replace "let $Z$ be a closed subscheme of $X$" by "let $Z$ be a closed subscheme of $X$ with corresponding ideal sheaf $\mathscr I$". Peng Du 1
p. 409,
Line 14
Replace "Cartier-divisor" by "Cartier divisor". Yuhao Cheng 1 2
p. 409,
Diagram (13.19.1)
In the top right corner, replace $\mathop{\rm Bl}\nolimits_X(Z)$ by $\mathop{\rm Bl}\nolimits_Z(X)$. J. Watterlond 1
p. 410,
Line 21 (the 2nd displayed eqn.)
The identification $A[I f^{-1}] = A[(T_\alpha)_\alpha] / (f T_\alpha - x_\alpha)_\alpha$ is not true in general and should be replaced by $A[I f^{-1}] = (A[(T_\alpha)_\alpha] / (f T_\alpha - x_\alpha)_\alpha)/(f-{\rm torsion})$, i.e., replace the right hand side by its quotient by the ideal of all elements annihilated by a power of $f$. Owen Colman 1
p. 410,
Line 21 (the 2nd displayed eqn.)
Replace the second $=$ by $-$. Peng Du 1
p. 410,
Example 13.93
The letter "$n$" is used in both the affine space $\mathbb{A}_R^n$ and the index $B=\bigoplus B_n$ for different meanings. Yuhao Cheng 1 2
p. 410,
Line -6
Delete "of". Peng Du 1
p. 410,
Lines -5, -3
Replace $=$ by $-$ (one in each line). Peng Du 1
p. 411,
Line -2 (Proof of Prop. 13.96)
Replace $(I \oplus J)/J$ by $(I+J)/J$. Peng Du / Matthieu Romagny 1
p. 412,
Line 20
Replace "roughly spoken" by "roughly speaking". Peng Du 1
p. 416,
Line 19
Replace "morphisms" with "morphism". F. Gispert Sánchez 1
p. 417,
Line -20
Switch the exponents $d+1$ and $d$. Peng Du 1
p. 417,
Line -6
Replace "particular" by "particularly". Peng Du 1
p. 418,
Line -6 (ex. 13.2 (a))
Replace "(resp. bijective)" with "(resp. surjective)". F. Gispert Sánchez 1
p. 418,
Exercise 13.2(c)
The forward implication may not hold without further assumptions on $A$, e.g., $A_+$ finitely generated (EGA II (2.7.3)). In fact, take $A = k[x_1,x_2, ...]$, $I = (x_1, x_2^2,x_3^3,...)$, $M = A/I$. Then ${\rm supp}(M) = V(I)$, but every prime ideal containing $I$ is irrelevant, thus ${\rm supp}(\tilde{M})$ is empty. Vishal Kannan 1 2
p. 419,
Line 1 (ex. 13.3)
Replace "$A$-modules" with "$A$-module". F. Gispert Sánchez 1
p. 420,
Exer. 13.13
Replace "inductive limits of schemes" by "inductive limits of rings". Peng Du 1
p. 421,
Exercise 13.19 (e), Remark
The remark, at the time of writing, was too optimistic, but see A. Langer, Ample vector bundles on non-proper schemes, arxiv:2608.29320. A. Langer 1 2
p. 422,
Line -18
Remove one ":" between $j_{\mathscr{E}}$ and $V$. Yuhao Cheng 1 2
p. 422,
Line 17
Insert "be" before "its structure morphism". Peng Du 1
p. 423,
Line 11
Replace ``morphisms'' by ``morphism''. K. Kidwell 1
p. 424,
Line -7
Replace "let be $f:X\to Y$" by "let $f:X\to Y$ be". Yuhao Cheng 1 2
p. 424,
Prop. 14.3. (1)
Replace $\mathop{\rm Spec} A \rightarrow \mathop{\rm Spec} B$ by $\mathop{\rm Spec} B \rightarrow \mathop{\rm Spec} A$. F. Ebert 1
p. 426,
Line 16 (cor. 14.12)
Replace "a morphism" with "morphisms". F. Gispert Sánchez 1
p. 426,
Line -2
Replace ``$\mathop{\rm Spec} R$'' by ``$Y$''. T. Wedhorn 1
p. 427,
Proof of prop. 14.16
In the proof, $X$ is replaced by $\mathop{\rm Spec} \mathscr{O}_{X,x}$ and $f$ is replaced by the composition of $f$ with the canonical morphism $\mathop{\rm Spec} \mathscr{O}_{X,x} \to X$ without saying so. It would be useful to state this explicitly. F. Gispert Sánchez 1
p. 427,
Proposition 14.14 (ii)
Replace "schematic closure of the generic fiber $f^{-1}(\eta)$ in X" by "schematic image of the canonical morphism $f^{-1}(\eta) \rightarrow X$". In 10.31, schematic closure is defined only for quasi-compact immersion but the morphism above may not be an immersion. An example: $X=Y=Spec\mathbb{Z}$. Then $\{ 0 \}$ is not a subscheme in the sense of 3.43. 1 2
p. 427,
Prop. 14.16
The term "special point" which is used here was not defined before. Define it (and maybe also "special fiber") before the proposition. Peng Du 1
p. 427,
Line 11
Replace "und" by "and". Yuhao Cheng 1 2
p. 428,
Proof of prop. 14.17
Here, Proposition B.70 (6) is not enough because $X$ is not assumed to be locally noetherian. Thus, we need a slightly different result: If $f$ is flat, then it is even faithfully flat (since it is closed and dominant). Now use that if $A\subseteq B$ are domains with the same field of fractions and $B$ is faithfully flat over $A$, then $A=B$. (Say $\frac as\in B$ for $a, s\in A$. Then $a\in sB\cap A = sA$ by Matsumura, Commutative Ring Theory, Thm. 7.5 (ii), so $\frac as\in A$.) F. Gispert Sánchez 1
p. 428,
Proposition 14.20, Lemma 14.21
The lemma is incorrect as stated, because the reduction to the local case does not work as claimed. It should be replaced by the following: (1) Let $A$ be a noetherian ring, let $B$ be a noetherian $A$-algebra, and let $M$ be a $B$-module of finite type which is flat over $A$. Let $f\in B$ such that for every maximal ideal $\mathfrak M\subset B$, multiplication by $f$ is an injection $M/(\mathfrak M\cap A) \rightarrow M/(\mathfrak M\cap A)$. Then $M/fM$ is flat over $A$. (2) With the techniques of Chapter 10 the hypothesis ``noetherian'' can be replaced by suitable conditions like ``finite presentation''. See also MathOverflow and Matsumura, Commutative Ring Theory, Thm. 22.6.
To avoid the additional difficulty for non-noetherian rings, in the statement of the proposition the assumption that $S$ and $X$ be noetherian should be added. Assuming that $S=\mathop{\rm Spec} A$, $X = \mathop{\rm Spec B}$, the injectivity assertion means that for all maximal ideals $\mathfrak m\subset A$, $f\not\in \mathfrak mB$; it follows that $f\not\in (\mathfrak M \cap A)B$ for all maximal ideals $\mathfrak M\subset B$, so that the lemma (statement (1) of the previous paragraph) can be applied.
In the proof of Theorem 14.22 (in the non-noetherian case) a version of the Lemma as alluded to in (2) above is required.		 U. Görtz 1
p. 428,
Lemma 14.19
Replace ``such'' by ``such that''. U. Görtz 1
p. 430,
Line 8
Replace '$h=g\circ f$' by '$g=h\circ f$'. Xiaolong Liu 1 2
p. 434,
Line -14
Add "the" between "If $y$ is not" and "closed point". F. Gispert Sánchez 1
p. 435,
Line -17
Replace "morphism" with "morphisms". F. Gispert Sánchez 1
p. 440,
Line 8
Replace $N' = {\rm Ker}(A')^n \to M'$ by $N' = {\rm Ker}({A'}^n \to M')$. 1 2
p. 440,
Line 3
Replace $a_{ij}\in A$ by $a_{ij} \in A'$. 1 2
p. 442,
Proposition 14.51 (4)
Add a comma at the end of the line. Yuhao Cheng 1 2
p. 443,
Line -16
Add "a" between "Let $\mathbf{P}$ be" and "property". F. Gispert Sánchez 1
p. 443,
Line 3
Replace "a open immersion" with "an open immersion". F. Gispert Sánchez 1
p. 443,
Line -9
Replace "morphism" with "morphisms". L. Potter 1 2
p. 446,
Line -10
Replace "heuristics" with "heuristic". L. Potter 1 2
p. 447,
Line 10
Replace $\mathscr G$ by $\mathscr G'$. K. Kidwell 1
p. 447,
Line 10
Replace "$(\mathscr{G},\psi)$" with "$(\mathscr{G}',\psi)$". F. Gispert Sánchez 1
p. 449,
Line -9
Replace the second $\to$ by $\mapsto$. Yuhao Cheng 1 2
p. 449,
Line -10
Replace $\varphi$ by $\varphi'$ (twice). Peng DU 1 2
p. 449,
Line 5
Replace "$q=p_1\circ p=p_2\circ p$" with "$q=p\circ p_1=p\circ p_2$". F. Gispert Sánchez 1
p. 450,
Prop. 14.65
The lower right triangle of the diagram constructed at the end of the proof is not commutative in general, therefore the proof is not valid as given here. Furthermore, in Step (i) of the proof of Theorem 14.66 (ed. 1) / Theorem 14.68 (ed. 2), a morphism $f': T'\rightarrow S'$ is considered where $T'$ is a finite disjoint union of affine open subschemes of $S'$ covering $S'$. If $S'$ is not quasi-separated, then it is not possible to find a quasi-compact such $f'$. Therefore, it seems better to handle individually the two cases of this proposition that are needed in the proof of the theorem: The case where $T'$ is a finite disjoint union of open subschemes of $S'$, and the case where $f' : T'=S \rightarrow S'$ is a section of $p: S' \rightarrow S$. Both cases are easy to deal with (the first one because it is clear that morphisms of this kind satisfy descent). A posteriori, the theorem implies that the proposition is actually true in the form stated. M. Bruneaux, P. Godfard 1 2
p. 452,
Line -10
Replace "homomorphism" with "homomorphisms". F. Gispert Sánchez 1
p. 453,
Line 14
The reference to Theorem 14.17 is wrong. It should refer to Theorem 14.70. F. Gispert Sánchez 1
p. 454,
Line 2
Replace "or fppf-sheaves of sheaves" with "or fppf-sheaves or sheaves". F. Gispert Sánchez 1
p. 454,
Line -17
Replace "an morphism" with "a morphism". F. Gispert Sánchez 1
p. 455,
Line -10
Replace "$G_{S'}$" with "$G_{|S'}$". F. Gispert Sánchez 1
p. 457,
Proof of Thm. 14.83
It should maybe be stated that for the last assertion of the theorem (taking invariants is a quasi-inverse), it is enough to show - given that we have proved that base change is an equivalence of the two categories - that $(V\otimes k')^\Gamma = V$, which is clear. U. Görtz/T. Wedhorn 1
p. 457,
Line 3
Replace "$\gamma(a_\delta)$" with "$\gamma(b_\delta)$". F. Gispert Sánchez 1
p. 458,
Line 9
Replace $\mathscr{O}_S’$ by $\mathscr{O}_{S’}$. Yuhao Cheng 1 2
p. 458,
Line -10
Replace "straight forward" by "straightforward". Peng Du 1
p. 458,
Line -3
Replace $X$ by $X’$. Yuhao Cheng 1 2
p. 460,
Diagram (14.22.1), definition of $c(\gamma)$
It looks like if we want $c$ to be 1-cocycle, then $c(\gamma)$ should be $\gamma_Y\circ\gamma^{-1}$ instead of $\gamma^{-1}\circ\gamma_Y$ as you defined using the diagram. Han Zhou 1
p. 461,
Proof of Prop. 14.90
Replace "Corollary 5.45" by "Corollary 5.54" and "Theorem 6.28" by "Corollary 6.32". Peng Du 1
p. 461,
Proof of Theorem 14.91
For $n=1$ the proof needs to be modified slightly (this case is easier, but the exception should be stated explicitly).
Furthermore, in the second part of the proof it might be appropriate to give a few more details, see here.		 J.-C. Syu / U. Görtz 1 2
p. 461,
Line 11
Replace "Remark 11.13" by "Proposition 11.13". (For Vol I: Proposition 11.12.) 1 2
p. 461,
Theorem 14.91
Replace (1),(2) by (i),(ii) respectively. Yuhao Cheng 1 2
p. 461,
Line 8
Define the symbol $X^{\rm sep}$ as $X\otimes_k k^{\rm sep}$. Peng Du 1
p. 462,
Line 9
Replace the second $=$ by $-$. Peng Du 1
p. 464,
Line 4
Insert "Proposition" before "5.30 (2)". Peng Du 1
p. 465,
Line 6
Replace $\mathfrak q$ by $\mathfrak q'$. 1 2
p. 467,
Line 11
Replace $\mathrm{trdeg}_{\mathscr O_{Y,y}}B$ by $\mathrm{trdeg}_{\mathrm{Frac}(\mathscr O_{Y,y})}\mathrm{Frac}(B)$. Yuhao Cheng 1 2
p. 467,
Line -9
Replace $n$ by another letter. Yuhao Cheng 1 2
p. 468,
Lemma 14.109
It is enough to assume that $f$ is locally of finite type (and in fact in the proof of the following theorem the lemma is applied with that weaker assumption). The same proof works in the general case. Jin yong An 1 2
p. 468,
Line -11
Replace ``Lemma 14.106 2'' by ``Lemma 14.106 (2)''. U. Görtz 1
p. 468,
Line 9
Remove "a" between "is" and "constructible". Yuhao Cheng 1 2
p. 469,
Line 23
Conflict of notation: Replace the subscript $n$ of $X_n$ with another letter. xq 1 2
p. 470,
Line 12
The correct formula is $\mathop{\rm dim} X = \mathop{\rm dim} Y + \mathop{\rm dim} f^{-1}(y)$, i.e., $X$ and $Y$ must be exchanged. Yong Hu 1
p. 471,
Cor. 14.116
In part (1), we only obtain $\mathop{\rm dim} f^{-1}(V) = \mathop{\rm dim} f^{-1}(y) + \mathop{\rm dim}(V)$. (In fact, just take $X=Y=\mathop{\rm Spec} R$, where $R$ is a (universally catenary) discrete valuation ring, and $f$ the identity morphism. Then the original statement holds for $V=Y$, but is false for $V$ consisting only of the generic point of $Y$.) In the proof of part (2), it would be easier to appeal to Lemma 14.109, than to invoke Theorem 14.110. (And note that the statement is void for the empty fibers, anyway.) Yong Hu 1
p. 471,
Line 4
Replace "und" by "and". Yuhao Cheng 1 2
p. 471,
Line 14
In the expression $\dim \mathscr O_{X',x}$, the $\mathscr O$ is missing. 1 2
p. 472,
Proof of Cor. 14.119
It is not clear from Prop. 14.107 (1) and Cor. 14.118 why the fibers over the maximal points of $Y$ are non-empty, so it seems better to invoke Cor. 14.116 (and Prop. 14.102) instead. Peng Du / G. Dill 1
p. 473,
Proof of Prop. 14.124 (2)
It is not clear why ${\rm depth}(A/\mathfrak p) = {\rm depth}(A)$, and it would be better to argue instead with the chain $\dim(A/\mathfrak p) \ge {\rm depth}(A) = \dim(A) \ge \dim(A/\mathfrak p)$ which shows that $\mathfrak p$ is a minimal prime ideal. The first inequality follows from [Mat] Theorem 17.2. Alternatively, we can invoke Proposition B.84 (=[Mat] Theorem 17.3) directly. Runze Meng 1 2
p. 475,
Corollary 14.127
Add the assumption that $X$ (and hence $Y$) is connected, or equivalently, integral. (An example showing the necessity of this is the morphism ${\rm Spec}(k[X]\times k)\to {\rm Spec}(k[X])$ for a field $k$ which is not flat.) Branislav Sobot 1 2
p. 475,
Proof of Cor. 14.127
It might be helpful to add a reference to Thm. B.54 (4) for the equality of the dimensions of the local rings of $x$ and $y$. Peng Du 1
p. 477,
Line 19
Delete the comma after "means". Peng Du 1
p. 478,
Line -11/Page 583, Line 2
The reference [AK] should point to the following article: Altman, Allen B.; Kleiman, Steven L. Compactifying the Picard scheme. Adv. in Math. 35 (1980), no. 1, 50-112. P. Hartwig 1
p. 481,
Exercise 14.8
Replace $X$ by $Y'$. 1 2
p. 483,
Exercise 14.21, line 3
Delete $f$. The letter $f$ is already taken in the first line of the exercise. Erhard Neher 1 2
p. 483,
Exercise 14.20 (b)
replace "if flat." with "is flat". L. Potter 1 2
p. 483,
Exercise 14.20
The condition in line 4 should be that $A_{ij}$ is a free $R'_i$-module (instead of a free $R$-module).
 Erhard Neher 1 2
p. 484,
Exercise 14.26
Replace $F(\mathrm{Spec} K)\to F(\mathrm{Spec} R)$ by $F(\mathrm{Spec} R)\to F(\mathrm{Spec} K)$. Yuhao Cheng 1 2
p. 485,
Prop. 15.1 (ii)
Add ``and none of the $X_i$ consists of only one point''. U. Görtz 1
p. 487,
Line 11
Replace the title of the segment by ``Morphisms from spectra of valuation rings to schemes''. U. Görtz 1
p. 488,
Line 11
Replace ``we can in addition assume that the ring $A$ is noetherian'' by ``then the ring $A$ is noetherian''. U. Görtz 1
p. 488,
Prop. 15.7
Rephrase the statement of the Proposition to indicate that the equality $g(\eta) = y$ can/should be understood in the schematic sense, i.e., that $g$ extends the morphism $\mathop{\rm Spec} K \rightarrow Y$ coming from the inclusion $\kappa(y)\subseteq K$. U. Görtz 1
p. 488,
Line -6
It is claimed that the implication “(i) ⇒ (ii)” of Theorem 15.8 is proved in Lemma 12.61, but the lemma only claims and shows that universal closedness implies the existence of a lift, not the quasi-compactness. The quasi-compactness does hold, though, as e.g. shown by Bjorn Poonen in this answer on MathOverflow. Bianca Fürstenau 1 2
p. 490,
Line 22
Replace "Theorem 15.8" by "Theorem 15.9". Peng Du 1
p. 490,
Line 20
Replace "integers" by "be integers". Peng Du 1
p. 491,
Line 7
Switch ${\rm Spec}\ K$ and ${\rm Spec}\ R$. Peng Du 1
p. 492,
Line -4
Replace "$\mathrm{id}_X$" by "the canonical morphism $\mathbb{P}_X^1\to X$". Yuhao Cheng 1 2
p. 494,
Proof of Lemma 15.19
In the first paragraph, one needs to argue more carefully in order to conclude that the homomorphisms $f_x^\sharp$ are bijective. (It is not enough to assume that $f$ is dominant and locally on $X$ an immersion, and $Y$ is reduced.) Note that the morphisms $U_i\to Y$ are dominant since $U_i\subseteq X$ is dense and $f$ is dominant. Thus they are dominant immersions, and $Y$ being reduced are open immersions. From this it is clear that the $f_x^\sharp$ are isomorphisms. J. Ehrhard 1 2
p. 494,
Proof of Theorem 15.21
At a period at the end of the proof. 1 2
p. 495,
Line 19
The term "complete" (= proper over $k$) has not been defined. Peng Du 1
p. 495,
Line -9
Replace "two sets" by "three sets". Peng Du 1
p. 496,
Proposition 15.26 and its proof
The curve should consistently be called $C$ (while currently it is called sometimes $C$ and sometimes $X$). Christian Dahlhausen 1 2
p. 497,
Line 13
Replace ``If $C$ is a separated curve over a field,'' by ``If $C$ is a separated curve over a field and $U$ is chosen affine,''. T. Wedhorn 1
p. 499,
Line -12
Replace "over a field" by "over a field $k$". Peng Du 1
p. 499,
First line after Definition 15.33
Replace left by right. 1
p. 501,
Exercise 15.4
The condition should be "every discrete valuation ring of $K(X)$ that dominates a local ring of $Y$ dominates a *unique* local ring of $X$". (If one does not require uniqueness, $f$ is not necessarily separated. A counterexample: Let $Y$ be the affine line and $X$ be an affine line with doubled origin, and $f$ be the canonical morphism.) Yuhao Cheng 1 2
p. 501,
Line 13
Replace "discrete valuation" by "discrete valuation ring". Peng Du 1
p. 501,
Exercise 15.9
Add the assumption that $k$ has characteristic $\ne 2$. V. Paškūnas 1 2
p. 501,
Line 9
Replace ``morpism'' by ``morphism''. J. Scarfy 1
p. 503,
Line 12
Replace "roughly spoken" by "roughly speaking". Peng Du 1
p. 504,
Line before Remark 16.3
Add a period at the end. U. Görtz 1 2
p. 505,
Line 5/6
Replace the period at the end of the displayed formula by a comma and remove the space at the beginning of the following line. Yuhao Cheng 1 2
p. 506,
Line -6
Replace $\mathbb P^{nm}_R$ by $\mathbb P^{nm-1}_R$. Peng Du 1
p. 507,
Lines 17, -3
Replace $v_n$ by $v_m$ and $w_m$ by $w_n$ (with indices as given, the identifications of Hom spaces and spaces of matrices do not hold as stated). Correspondingly, in Line -3, change $k^n$ to $k^m$. Peng Du 1
p. 507,
Line -9
Replace $\times_k$ by $\times$. Peng Du 1
p. 507,
Line 6
Replace "geometrically integral" by "is geometrically integral". Peng Du 1
p. 508,
Line 3
Change $k^n$ to $k^m$ (cf. the corresponding erratum on page 507). Peng Du 1
p. 508,
Second line in the proof of Prop. 16.11
Add "open subset" after dense. Andreas Blatter 1 2
p. 508,
Line 5
Delete "the same argument and". Peng Du 1
p. 510,
Second line of Lemma 16.17
Replace "$M$ is free of $m$" by "$M$ is free of rank $m$". Yuhao Cheng 1 2
p. 511,
Line 3
Replace $\otimes_k R$ by $\otimes_R k$. Peng Du 1
p. 512,
Line 21 (Proof of Lemma 16.20)
Replace $k[T_{ij}]$ by $R[T_{ij}]$. Peng Du 1
p. 512,
Line 14
Replace $\underline{\rm Hom}_{\mathscr G, \mathscr H}$ by $\underline{\rm Hom}(\mathscr G, \mathscr H)$ Peng Du 1
p. 513,
Line 13 (the diagram), Line -10
Replace $\pi_{\mathscr F}$ by $\pi_{\mathscr V}$. Peng Du 1
p. 514,
Line 3
Remove "below". Peng Du 1
p. 514,
Line -7
Replace ``$Y = \mathop{\rm Spec} B[1/d_{I,J}]$'' by ``$Y_{I,J} = \mathop{\rm Spec} B[1/d_{I,J}]$''. T. Wedhorn 1
p. 516,
Proof of Lemma 16.28
The definition of $g'$ should be replaced by $g'(e_j') = \sum_{i=1}^n b_{ij}e_i$, $j=1, \dots, n'$. Then $B=(b_{ij})$ is in $M_{n\times n'}(R)$. Then $v(a, b) = (Aa+Bb, b)$, so viewing the direct sums in the source and target of $v$ as column vectors, the matrix $C$ is $C=\left(\begin{array}{cc}A & B \\ 0 & I_{n'}\end{array}\right)$. Finally, in the end we want to consider $(n-r+1)$-minors of $A$ and $(n+n'-r+1)$-minors of $C$. Peng Du 1
p. 516,
Line 6
Delete "an". Ulrich Görtz 1
p. 517,
Line -14
Delete "the spectrum of". Peng Du 1
p. 519,
Line 17
Add period at the end of the sentence. Peng Du 1
p. 521,
Line 8
In the expression for $g$, in the third parenthesis there should be $(X_2-1)^2$ instead of $(X_2^2-1)^2$. Alejandro Vargas and Tim Seynnaeve 1 2
p. 524,
Line -7
Replace $(\beta, \alpha)$ by $(\beta : \alpha)$. Peng Du 1
p. 528,
Line -18
Replace $T_2T_3^3$ by $T_2T_3^2$. U. Görtz 1
p. 528,
Line 14
Replace ``$V_+(p)\in\mathbb P^3_k$'' by ``$V_+(p)\subset\mathbb P^3_k$''. U. Görtz 1
p. 529,
Caption of Figure 16.2
Add $=0$ in the end. Peng Du 1
p. 530,
Line -14
It should say "the singularities of $Z={\rm Spec}\ k[S,T,U]/(U^3-ST)$", i.e. the base field $k$ is missing. Javier de la Bodega 1 2
p. 530,
Line 14
Add "Spec" before $k[X,Y]/(XY-u,X^3-t,Y^3-s)$. Yuhao Cheng 1 2
p. 531,
Proposition 16.46
Replace $n$ by $r$ in both statement and proof. Javier de la Bodega 1 2
p. 531,
Line -14
Replace "Remark (12.31)" by "Remark 12.31". Peng Du 1
p. 531,
Line 19
It should say "If $p(x,y) \in Z(k)$ is a singular point". Javier de la Bodega 1 2
p. 532,
Line 5
To emphasize that the minus signs are not a typo, maybe replace "continued fraction" by "negative regular continued fraction". Peng Du 1
p. 534,
Line -8
Replace $f(a_1 a_2)f(a_1)^{-1}f(a_2)^{-1}$ by $f(a_1 a_2)f(a_2)^{-1}f(a_1)^{-1}$. Philipp Reichenbach 1
p. 534,
Prop. 16.45, statement + Line 18, Proof of Prop. 16.45
In the statement of the proposition, $Y$ must be assumed to be integral rather than just reduced (to ensure that the $V$ in the proof is dense in $Y$, hence $X\times V$ dense in $X\times Y$).
In the proof (line 18 of the page), replace "Proposition 12.67" by "Corollary 12.67". This result is applied to the morphism $X\otimes\kappa(y')\to U\otimes\kappa(y')$ whence $Y$ in this line must be replaced by $U\otimes_k\kappa(y')$.		 Peng Du 1
p. 534,
Line 20
Replace "Proposition 5.51" by "Proposition 5.49". Peng Du 1
p. 534,
Line -8
The correct formula is $f(a_1a_2)f(a_2)^{-1}f(a_1)^{-1}$. Peng Du 1
p. 534,
Line 11
Replace the definition of $g$ by ``$g := f \circ (x \times \mathop{\rm id}\nolimits_Y) \circ p_2$''. K. Kidwell 1
p. 534,
Line 5 of the Proof of Proposition 16.54
$p^{-1}(y)$ should be $p_2^{-1}(y)$. 1
p. 534,
Line 6 of the Proof of Proposition 16.54
"nieghborhood" should be "neighborhood" 1
p. 536,
Line 17
Replace "Example 16.18" by "Example (16.18)". Peng Du 1
p. 537,
Line -8
Add "if" after "only". U. Görtz 1 2
p. 539,
Caption of Figure 16.3
Add $=0$ at the end of the first line. Maybe it would look nicer to replace $0.1$ by $\frac{1}{10}$. Peng Du 1
p. 540,
Exercise 16.7
As a connected component $G'$ has not necessarily a rational point, it is not geometrically connected in general (and in particular not geometrically irreducible). The exercise should be reformulated as follows: Let $k$ be a field and let $G$ be a $k$-group schemes locally of finite type. Show that every connected component $G'$ of $G$ is irreducible and of finite type. Show that the geometric number of connected components of $G'$ is equal to the geometric number of irreducible components of $G'$. For $k = {\mathbb Q}$ and $G = \mu_p$ (Exercise 16.6) for a prime number $p$ show that $G$ has two connected components and that the geometric number of connected components of $G$ is $p$. B. Conrad 1
p. 540,
Line -6
Replace "is no divisor of" by "does not divide". Peng Du 1
p. 540,
Line 18
Add space between the comma and the citation. Ulrich Görtz 1
p. 545,
Line -14, -7
Better to switch the definition of the zero object with the remark, i.e., define the zero object as an initial and final object (the correct definition fo arbitrary categories), and remark that in an additive category it suffices to check one of the two properties. Peng Du 1
p. 545,
Line 6
Replace x_i by x. Jan Willing 1 2
p. 546,
Line -10/-9
Replace ``left'' by ``right'' and ``right'' by ``left''. D. Heiss 1
p. 549,
Line -2
The rank of a free module over the zero ring is not uniquely determined, so this case should be excluded. P. Hartwig 1
p. 550,
Line 2
It should say "An $A$-module", instead of "Am $A$-module". Javier de la Bodega 1 2
p. 551,
Example A.5.(3)
The category of sets should also be in the list. Andreas Blatter 1 2
p. 552,
Line 7 (ex. B.17)
Replace "$\mathfrak{m}M\neq M$" with "$\mathfrak{m}M=M$". F. Gispert Sánchez 1
p. 554,
Line -2
It might be worth adding a reference to arxiv:1011.0038 and/or the Stacks project (058B, 05A5). (Cf. also the Erratum for Remark 7.43, p. 195). Ulrich Görtz 1
p. 554,
Line -1
Add the assumption that $A$ is a domain here (since this is when $M_{\rm tors}$ was defined). Same for p. 555, Prop. B.28. Peng Du 1
p. 558,
Line -3
Replace "$A$-modules" by "abelian groups". Peng Du 1
p. 558,
Line -16
Replace "$\dots, \mathfrak a_n)$" by "$\dots, a_n)$". Peng Du 1
p. 559,
Theorem B.48
Replace "$A/\mathfrak a$ module" by "$A/\mathfrak a$-module" (twice). U. Görtz 1 2
p. 559,
Line -16
Replace $\mathfrak I^n$ by $\mathfrak I_n$ (and similarly for $n+1$; four changes altogether). Peng Du 1
p. 560,
The line after (B.10.1)
Replace “a $A$-subalgebra” by “an $A$-subalgebra”. Yuhao Cheng 1 2
p. 560,
Line 2
Replace "form" by "forms". Ulrich Görtz 1
p. 560,
Prop. B.55
Add the hypothesis that $A$ is noetherian (cf. [Atiyah-Macdonald], Prop. 5.17). Akira Masuoka 1
p. 561,
Definition B.58
In the second line of the definition, $r$ should be replaced by $n$. P. Hartwig 1
p. 562,
Line -19
Add "be" between the first "$B$" and "local rings". Yuhao Cheng 1 2
p. 562,
Line 1
Remove the space at the beginning of the line. Yuhao Cheng 1 2
p. 563,
Line 15
Replace "as in (iv)" by "as in (v)". Peng Du 1
p. 563,
Prop. B69 (2)
The assumption that the extension be algebraic is not required, see [BouAC] VI § 1.2 Cor. to Thm. 2. Akira Masuoka 1
p. 564,
Proposition B.70 (6)
What is true (and proved in Matsumura's book) is: If $B$ is normal, then $A$ is normal. If $A$ and $B\otimes_A\kappa(\mathfrak p)$ are normal for all $\mathfrak p\in {\rm Spec}(A)$, then $B$ is normal.
It is not true that normality of $B$ implies normality of the fibers. Consider for instance a discrete valuation ring $A$ with uniformizer $t$ and $B=A[X,Y]/(XY-t)$. Then $B$ is regular and in particular normal, but the special fiber $(A/t)[X, Y]/(XY)$ is not normal.		 M. Kerz 1 2
p. 564,
Prop. B.72 (3)
Replace "be a noetherian" by "be noetherian". Peng Du 1
p. 565,
Remark B.75 (2)
Replace the reference to B.70 (2) by B.70 (3). Akira Masuoka 1
p. 565,
Proposition B.80
"all minimal prime ideals of $A$ containing $\mathfrak a$" should read "all preimages in $A$ of associated prime ideals of $A / \mathfrak a$", as stated in the reference (Matsumura, 17.6). For example $A = k[x,y] / (x^2,xy)$ is not Cohen-Macaulay, but satisfies the condition with "minimal prime ideals...". F. Heß, K. Meiwald 1 2
p. 566,
Def./Prop. B.84
Add the equivalent term "Dedekind ring", and also change the index to reflect that "Dedekind ring = Dedekind domain". Peng Du / Ulrich Görtz 1
p. 566,
Prop. B.81 (2), Prop. B.82
In both cases $\mathop{\rm depth}\nolimits_A(\mathfrak a)$ needs to be replaced by $\mathop{\rm depth}(\mathfrak a, A)$ (the length of a maximal $A$-regular sequence of elements in $\mathfrak a$, and this symbol needs to be defined). Akira Masuoka 1
p. 568,
Def. B.95
Since some of its terms are used before, Def. B.95 and the paragraph preceding it should be moved to right after Def. B.88. Peng Du 1
p. 569,
Def. B.95 (3)
Rephrase as "every extension $K\to \Omega$" with $\Omega$ algebraically closed" to avoid the condition being misread as "$K$ being algebraically closed in $\Omega$". Peng Du 1
p. 571,
Line 12
Replace $b_{i0}$ by $b_{0i‎}$. Yuhao Cheng 1 2
p. 571,
Line -9
Add "theorem" after "ideal". Yuhao Cheng 1 2
p. 574, 575,
Add (IND) for faithfully flat and surjective (cf. EGA IV 8.10.5 (vi)). Y. Zaehringer 1
p. 576,
Line 12
Replace "universal homomorphism" by "universal homeomorphism". Yun Hao 1
p. 576,
Line 16
Replace "Converse" by "Conversely". Peng Du 1
p. 576,
Line 5
Replace "as usually" by "as usual". Ulrich Görtz 1
p. 578,
Final sentence of (2)
Replace "constructible" by "ind-constructible’’. Yuhao Cheng 1 2
p. 583,
Line 4 (Reference [AK])
The reference (from p. 478) should instead point to A. Altman, S. Kleiman, Compactifying the Picard scheme, Adv. Math. 35 (1980), 50--112. Ulrich Görtz 1
p. 598,
Left col., lines 3, 4
The symbols for direct sum and product should be exchanged. J.-C. Syu 1 2
p. 600,
2nd column, line 8
Replace $P^n(k)$ by $\mathbb P^n(k)$. Ulrich Görtz 1
p. 603,
Line 17
Replace ``Brauer-Severy'' by ``Brauer-Severi''. J. Calabrese 1
p. 612,
1st column, Line -11, -9
The entries for quasi-finite morphism (of schemes) should be combined. Ulrich Görtz 1
p. 624,
Second line of the on large paragraph of text
The most minor of typos, but in a somewhat prominent place: On the back of the book, “Grothendieck‘s” should be “Grothendieck’s” (i.e., there should be an apostrophe, not a single opening quotation mark). Bianca Fürstenau 1