6 papers
Non-residually finite groups hyperbolic relative to residually finite subgroups
Jan Kim, Donghi Lee
Let and be integers such that and . We show that all Baumslag-Solitar groups are non-residually finite groups hyperbolic relative…
A family of two generator non-Hopfian groups
Donghi Lee, Makoto Sakuma
We construct -generator non-Hopfian groups , where each has a specific presentation $G_m=\langle a, b \, | \, u_{r_{m,0}}=u_{r_{m,1}}=u_{r_{m,2}}= \…
Simple loops on 2-bridge spheres in Heckoid orbifolds for 2-bridge links
Donghi Lee, Makoto Sakuma
Following Riley's work, for each 2-bridge link of slope $r\in\QQ$ and an integer or a half-integer greater than 1, we introduce the {\it Heckoid orbifold $\orbs(r;n)$} a…
Epimorphisms from 2-bridge link groups onto Heckoid groups (II)
Donghi Lee, Makoto Sakuma
In Part I of this series of papers, we made Riley's definition of Heckoid groups for 2-bridge links explicit, and gave a systematic construction of epimorphisms from 2-bridge link…
Epimorphisms from 2-bridge link groups onto Heckoid groups (I)
Donghi Lee, Makoto Sakuma
Riley "defined" the Heckoid groups for 2-bridge links as Kleinian groups, with nontrivial torsion, generated by two parabolic transformations, and he constructed an infinite family…
A new proof for small cancellation conditions of 2-bridge link groups
Daewa Kim, Donghi Lee
In this paper, we give a simple proof for the small cancellation conditions of the upper presentations of 2-bridge link groups, which holds the key to the proof of the main result…