Questions tagged [dimension-theory-algebra]
For questions about notions of dimension, rank, or length used in abstract algebra (e.g. Krull dimension, homological dimensions, composition length, Goldie dimension). Questions about dimension of vector spaces, and rank of linear transformations are better placed under the [linear-algebra] tag.
190 questions
2 votes
1 answer
46 views
Contraction of Zero-dimensional Ideal in Finite Extension of Jacobson Ring is Zero-dimensional
Let $R$ be a Jacobson ring, meaning that every prime ideal is an intersection of maximal ideals, and let $S$ be a finitely generated $R$-algebra. I am interested in proving the following. (I sadly ...
1 vote
0 answers
46 views
Minimal Primes of Highest Dimension of a Polynomial Ideal in Noether Position
The following is 2.3 in Krick and Logar (1991). (ISBN: 978-3-540-38436-6) Let $I \leq k[X_1, \dots X_n]$ be of dimension $d$, and w.l.o.g assume that $I \cap k[X_1, \dots, X_d] = (0)$. We say that $...
2 votes
1 answer
116 views
Part of Affine Dimension Theorem
Question Let $k$ be an algebraically closed field, and give $\mathbb{A}^n_k$ the Zariski topology. Let $Y$ be an irreducible closed subset of $\mathbb{A}^n$, and let $Z:=V(F)\subseteq \mathbb{A}^n$ ...
0 votes
1 answer
57 views
Chain of Prime Ideals in Polynomial Ring $R[x]$ ($R$ is commutative) is saturated When Their Intersection Over $R$ is Equal
Let $R$ be a commutative ring, and let $p_0 \subset p_1$ be prime ideals in $R[x]$ such that $p_0 \neq p_1$ and $p_0 \cap R = p_1 \cap R$. Prove that the chain $p_0 \subset p_1$ is saturated. ( A ...
0 votes
1 answer
120 views
Contraction of principal ideal in integral extension
Let $A$ an integrally closed domain and $B$ a commutative ring extension of $A$ that is finitely generated as an $A$-module. For $f\in B$ is it true that there exists $a_f\in A$ s.t. $\sqrt{(f)\cap A}=...
1 vote
1 answer
170 views
Is $\dim (M/xM) = \dim M - 1$ for some $x \in m$ implies $x$ is an $M$-regular element ? where $m$ is the maximal ideal of a local ring $R$.
Let $R$ be a Noetherian local ring with maximal ideal $m$, and let $M$ be a finitely generated $R$-module. It is known that if $x \in m$ is an $M$-regular element, then the dimension of $M/xM$ is ...
3 votes
1 answer
189 views
A prime ideal of height $\geq 2$ in a Noetherian ring contains infinitely many prime ideals of height 1
I am trying to prove this statement by deducing a contradiction to Krull's Principal ideal theorem. Here is my attempt: Denote $R$ and $P$ the ring and the prime ideal under consideration, ...
0 votes
0 answers
87 views
Kodaira dimension
Let $C$ be a smooth projective curve over an algebraic field $k$. I suppose the Kodaira dimension of $C$ is $0$. Why the genus must be $1$? If $C$ is a smooth projective surface, and if I suppose the ...
0 votes
0 answers
61 views
Does the set of antiderivatives of $tan(x)$ have uncountable dimension?
On a connected domain, the set of antiderivatives of a continuous function $f$ is $1$-dimensional. However, for a punctured domain like $\mathbb{R} - \{0\}$, the set of antiderivatives becomes $2$-...
1 vote
0 answers
68 views
How to combine the $4$-dimensions of spacetime into 1 dimension?
I have been thinking about the possibility of representing all points in a $4$-dimensional spacetime coordinate system $\mathbb{R}^{1,4}$, as points on one line $P$ (or axis of a $1$-dimensional ...
2 votes
0 answers
164 views
Confusion about codimension of a subvariety of a scheme
In Eisenbud's and Harris's "3264 & All That", they define the codimension of a subvariety $Y$ of a variety $X$ as $\operatorname{codim}_X(Y)=\dim(X)-\dim(Y)$. This part is fine and also ...
1 vote
1 answer
275 views
dimension of intersection of algebraic variety
I know there are similar questions, but everyone uses different approaches and it's complicated to change proofs. In my algebraic geometry course, we're dealing with algebraic variety (topological ...
2 votes
1 answer
139 views
A semi-algebraic set in $\mathbb{R}^d$ has dimension $d$ if and only if its interior is non empty
I would like to prove the following result : A semi-algebraic set in $\mathbb{R}^d$ has dimension $d$ if and only if its interior is non empty The dimension here has to be understood in the semi ...
2 votes
1 answer
448 views
Computing the height of an ideal...?
I hope I'm not overbearing in this site. Yes, I'm still struggling. If you can, I have a question about primary decomposition that still needs help, you can find it in my page. Now I wanted to find ...
6 votes
0 answers
206 views
Real-valued dimension
Let $\overline{\mathbb{R}}_{\geq 0} = \mathbb{R}_{\geq 0} \cup \{\infty\}$. Given a commutative ring with unity $R$, $R\operatorname{-Mod}$ denotes the category of $R$-modules. Given $R$-modules $A$ ...