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Search options not deleted user 120914
7 votes
0 answers
177 views

Completeness of automorphism groups of free metabelian groups

I am not very familiar with free metabelian groups, so I apologise in advance if this is trivial. A group $G$ is said to be complete if every automorphism of $G$ is inner. In this case, $\operatorname …
Carl-Fredrik Nyberg Brodda's user avatar
3 votes

Embedding of Baumslag-Solitar group into a certain group

A few minutes of running GAP shows that the group has order $6751269$. Hence, as the final edit of the accepted answer points out, the group is finite, and no Baumslag-Solitar group embeds in it.
Carl-Fredrik Nyberg Brodda's user avatar
5 votes
2 answers
425 views

Centre of group with deficiency at least two (Progress on Murasugi's conjecture)

In 1965, Murasugi [1] conjectured that any finitely presented group with deficiency at least two has trivial centre. The year before, he had proved it true for one-relator groups, and in [1] he proved …
Carl-Fredrik Nyberg Brodda's user avatar
6 votes
0 answers
623 views

Minimum Simple Burger-Mozes Type Group

Burger and Mozes constructed (Burger and Mozes - Lattices in products of trees) infinite, finitely presented, torsion-free simple groups which split as amalgams of two finitely generated free groups o …
Carl-Fredrik Nyberg Brodda's user avatar
12 votes
1 answer
406 views

Commutator problem vs conjugacy/word problem

For a finitely presented group $G$, generated by a finite set $A$, the commutator problem is the decision problem: given a word $w$ over the alphabet $A \cup A^{-1}$, can one decide if $w$ is a commut …
Carl-Fredrik Nyberg Brodda's user avatar
7 votes
0 answers
285 views

Uniform word problem in finitely presented simple groups

The following question arose in the comments on this question, and it seems like a reasonable question to ask in its own right. I've added some additional details. The word problem in any fixed finite …
Carl-Fredrik Nyberg Brodda's user avatar
7 votes

Subgroup membership problem in simple groups

After some digging, I was able to find that the answer to my question exists: the problem can be undecidable. Rattaggi, in an unpublished manuscript (available here), proved that there exists a finite …
Carl-Fredrik Nyberg Brodda's user avatar
8 votes
2 answers
480 views

Subgroup membership problem in simple groups

Let $G$ be a finitely presented simple group. By Kuznetsov (1958), $G$ has decidable word problem. However, by Scott [1], $G$ may have undecidable conjugacy problem. Is anything known about other deci …
Carl-Fredrik Nyberg Brodda's user avatar
8 votes
0 answers
121 views

The conjugacy problem for two-relator groups

Is the conjugacy problem for two-relator groups known to be undecidable? The word problem for two-relator groups is a famous open problem (appearing e.g. as Question 9.29 in the Kourovka notebook), an …
Carl-Fredrik Nyberg Brodda's user avatar
7 votes
1 answer
216 views

Howson property of automorphism group of $F_2$ and of $F_3$

Is the intersection of any two finitely generated subgroups of $\operatorname{Aut}(F_2)$ (resp. $\operatorname{Aut}(F_3)$) again finitely generated? That is, does $\operatorname{Aut}(F_2)$ (resp. $\o …
Carl-Fredrik Nyberg Brodda's user avatar
11 votes
Accepted

Reference request: Recent progress on the conjugacy problem for torsion-free one-relator gro...

As mentioned in the comments, this is still considered an open problem. I thought I'd flesh out a few aspects. A solution was claimed in 1992 by Juhasz, but it seems to have failed to convince experts …
Carl-Fredrik Nyberg Brodda's user avatar
18 votes
1 answer
750 views

Is solvability semi-decidable?

Let $G = \langle A \mid R \rangle$ be a finitely presented group, given by a finite presentation. If $G$ is abelian, then we can verify this fact: simply verify the fact that $[a, b] = 1$ for all gene …
Carl-Fredrik Nyberg Brodda's user avatar
3 votes

Which groups are LERF?

Polycyclic groups are LERF, by Mal'cev 1948. In particular, all nilpotent and all abelian groups are LERF. As mentioned in the comments, as not all one-relator groups are residually finite, not all on …
Carl-Fredrik Nyberg Brodda's user avatar
8 votes
1 answer
348 views

Finite two-relator groups and quotients of knot groups

Let $G$ be a one-relator group $\langle A \mid R = 1 \rangle$. Then clearly $G$ is finite if and only if it is cyclic of finite order, i.e. can be given by a presentation $\langle a \mid a^n = 1 \rang …
Carl-Fredrik Nyberg Brodda's user avatar