Search Results
Search type | Search syntax |
---|---|
Tags | [tag] |
Exact | "words here" |
Author |
user:1234 user:me (yours) |
Score |
score:3 (3+) score:0 (none) |
Answers |
answers:3 (3+) answers:0 (none) isaccepted:yes hasaccepted:no inquestion:1234 |
Views | views:250 |
Code | code:"if (foo != bar)" |
Sections |
title:apples body:"apples oranges" |
URL | url:"*.example.com" |
Saves | in:saves |
Status |
closed:yes duplicate:no migrated:no wiki:no |
Types |
is:question is:answer |
Exclude |
-[tag] -apples |
For more details on advanced search visit our help page |
For questions about groups whose elements commute.
24
votes
The existence of non-trivial homomorphisms $\prod_{n=1}^{\infty}\mathbb{Z}/\bigoplus_{n=1}^{...
Here's an elementary proof that doesn't require ultrafilters, but uses axiom of choice.
The group
\begin{equation*}
\prod_{n=1}^\infty \mathbb{Z} / \bigoplus_{n=1}^\infty \mathbb{Z}
\end{equation*}
…
1
vote
Accepted
Example involving partially ordered Abelian groups
Let $G=\mathbb{R}^2$ with order defined by
$(a_1,a_2)\leq (b_1,b_2) \iff a_1\leq b_1$ and $a_2\leq b_2$.
Let $u=(1,1)$ and let $g_0=(1,2)$.
Then $p(g_0)=1$ and $r(g_0)=2$.