Donghi Lee

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20152020

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math.GR2019

Non-residually finite groups hyperbolic relative to residually finite subgroups

Jan Kim, Donghi Lee

Let $m$ and $k$ be integers such that $∣ m ∣, ∣ k ∣ > 1$ and $g cd (m, k) = 1$ . We show that all Baumslag-Solitar groups $B S (m, mk)$ are non-residually finite groups hyperbolic relative…

math.GR2015

Simple loops on 2-bridge spheres in Heckoid orbifolds for the trivial knot

Donghi Lee, Makoto Sakuma

In this paper, we give a necessary and sufficient condition for an essential simple loop on a $2$ -bridge sphere in an even Heckoid orbifold for the trivial knot to be null-homotopi…