Skip to main content
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
Results tagged with
Search options not deleted user 7206

Questions about the branch of algebra that deals with groups.

9 votes
3 answers
1k views

First-order axiomatization of free groups

Is there a way to axiomatize [non-abelian] free groups in first-order logic using the language of groups (which contains the binary operation symbol $\cdot$, and the constant symbol $e$)? Is there on …
Asaf Karagila's user avatar
  • 39.8k
7 votes
Accepted

Number of torsion-free abelian groups

You can construct antichains of size $\frak c$ without using choice, you can even have them to be antichains in a stronger sense of the word: i.e. every two have a finite intersection. The one thing …
Asaf Karagila's user avatar
  • 39.8k
82 votes

Results from abstract algebra which look wrong (but are true)

The free group with infinitely many generators is a subgroup of the free group with two generators.
12 votes
Accepted

The Tall Tale of Terminating Transfinite Towers

Here is a relevant paper, Kaplan, Itay; Shelah, Saharon, The automorphism tower of a centerless group without choice, Arch. Math. Logic 48, No. 8, 799-815 (2009). ZBL1192.03026. At least for a c …
Asaf Karagila's user avatar
  • 39.8k