Carsten Feldkamp

activity

20202022

collaborators

3 papers

math.GR2022

On upper bounds for the first $ℓ^{2}$ -Betti number

Carsten Feldkamp, Steffen Kionke

This article presents a method for proving upper bounds for the first $ℓ^{2}$ -Betti number of groups using only the geometry of the Cayley graph. As an application we prove that B…

math.GR2021

Freiheitssatz for amalgamated products of free groups over maximal cyclic subgroups

Carsten Feldkamp

In 1930, Wilhelm Magnus introduced the so-called Freiheitssatz: Let $F$ be a free group with basis $X$ and let $r$ be a cyclically reduced element of $F$ which contains a…

math.GR2020

A Magnus extension for locally indicable groups

Carsten Feldkamp

A group $G$ possesses the Magnus property if for every two elements $u$ , $v \in G$ with the same normal closure, $u$ is conjugate to $v$ or $v^{- 1}$ . O. Bogopolski and J. Howie pro…

On upper bounds for the first ℓ2-Betti number

Freiheitssatz for amalgamated products of free groups over maximal cyclic subgroups

A Magnus extension for locally indicable groups

On upper bounds for the first $ℓ^{2}$ -Betti number