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3
votes
1answer
257 views

Group ring and left zero divisor II

Let $K$ be a finite field and $G$ be a discrete group. Is it true that for every $a=e+a_1+\ldots+a_n,b=e+b_1+\ldots+b_m\in K[G]$ with $b_i\neq e,a_j\neq e$ the condition $ab=0$ implies $ba=0$? ...
5
votes
0answers
309 views

Zipper action of a discrete group.

A discrete group $\Gamma$ has zipper action if there is a set $X$ and an action of $\Gamma$ on $X$ (say left-action) and a subset $Z\subseteq X$ such that for every $g \in \Gamma$: $|gZ\Delta ...
18
votes
2answers
2k views

Properties of a non-sofic group

This question is, essentially, a comment of Mark Sapir. I think it deserves to be a question. A countable, discrete group $\Gamma$ is $sofic$ if for every $\epsilon>0$ and finite subset $F$ of ...