Tagged Questions

0
votes
0answers
69 views

Is there a better function?

Let $A$ be a finite $n$-element set. Let $\mathbb R^A$ be an $n$-dimensional Euclidean space (with the ordinary Euclidean distance). Let $X$ be an arbitrary topological space. Cons …
0
votes
0answers
87 views

When does the rank of a module behave sub-multiplicatively under tensoring?

Let $\cal{E}$ be a finitely generated projective bimodule over a (noncommutative) algebra $A$. Moreover, let us assume that $\cal{E}$ is of finite rank $n$. The tensor product $ …
16
votes
6answers
1k views

Pathological Examples of Dimension

I am trying to wrap my head around all the different notions of dimension (and their equivalences). To get a sense of this, it would be nice to know the subtle difficulties that ar …
3
votes
2answers
118 views

Hutchinson’s formula for asymptotically homogeneous Cantor sets

As everyone knows, the standard middle-thirds Cantor set is constructed by dividing the interval into three equal parts, removing the middle one, then applying the same procedure t …
2
votes
1answer
108 views

Can the isoperimetric dimension of a d-generated group attain any value?

Background The isoperimetric dimension of a finitely generated group $G$, which we denote by $\dim(G)$, is the largest number $d$ such that any Cayley graph $\Gamma$ of $G$ (const …
5
votes
2answers
385 views

On some finiteness properties for schemes

Consider the following properties of scheme $X$: A: $X$ is of finite type over $\mathbb{Z}$ B: $X$ is Noetherian C: $X$ is of finite Krull dimension What implications are there …
7
votes
4answers
492 views

Tessellating $\mathbb{R}^n$ by bricks.

Let us call the $\ell_1$-product of intervals $[0,k_1]\times...\times [0,k_n]$ a brick of size $k_1+...+k_n$. Consider a tessellation $T$ of $\mathbb{R^n}$ by (shifted) bricks so …
11
votes
3answers
1k views

Krull dimension <= transcendence degree?

Let $k$ be a field, and $A$ a $k$-domain, so that the fraction field of $A$ has transcendence degree $n$ over $k$. If $A$ is finitely-generated over $k$, then $A$ has Krull dimens …
10
votes
5answers
827 views

Is there an axiomatic approach of the notion of dimension ?

There are many notions of dimension : algebraic, topological, Hausdorff, Minkowski... (and others). While the topological one generalize the algebraic one, the last three need not …
14
votes
2answers
2k views

Nonseparable example in dimension theory?

Could you give me an example of a complete metric space with covering dimension $> n$ all of which closed separable subsets have covering dimension $\le n$? The question close …
29
votes
3answers
2k views

What the heck is the Continuum Hypothesis doing in Weibel’s Homological Algebra?

On page 98 of Weibel's An Introduction to Homological Algebra he mentions that the ring $R = \prod_{i=1}^\infty \mathbb{C}$ has global dimension $\geq 2$ with equality iff the cont …
0
votes
0answers
62 views

A question about dense subsets of a Noetherian topological space X of infinite dimension

Can we obtain an example of a Noetherian topological space X of infinite dimension with at least one dense open subset U of finite dimension? If so, please let me know the example …
9
votes
2answers
473 views

infinite dimensional CAT(0) groups

Usually a CAT(0) group is defined to be a group acting properly isometrically and cocompactly on a CAT(0) space, but I would like to consider only those groups that act properly, i …
10
votes
6answers
1k views

Different definitions of the dimension of an algebra

I know of three ways to define the dimension of a finitely-generated commutative algebra A over a field F: The Gelfand-Kirillov (GK) dimension, based on the growth of the Hilbert …
4
votes
3answers
494 views

dimension of a real affine variety

Let $V$ be a real affine variety in $\mathbb R^n$, i.e. the zero set of a real polynomial $p(x_1,\dots,x_n)$. Consider the following three definitions of the dimension of $V$, $dim …

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