4 papers
A note on test elements for monomorphisms of free groups
Dongxiao Zhao, Qiang Zhang
A word in a group is called a test element if any endomorphism fixing it is necessarily an automorphism. In this note, we give a sufficient condition in geometry to construct test…
Alternating and Symmetric Separability of Free Products
Dongxiao Zhao, Qiang Zhang
Let be a free product of a free group and a LERF group . In this note, we provide sufficient conditions for a subgroup of to be $\mathcal{A} \cup \…
Classification of Fixed Subgroups of Endomorphisms in Free-abelian Times Surface Groups
Ke Wang, Qiang Zhang, Dongxiao Zhao
In this paper, we first study the endomorphisms of free-abelian times surface groups and give a characterization of when they are injective and surjective. Then, we see that free-a…
Howson groups which are not strongly Howson
Qiang Zhang, Dongxiao Zhao
A group is called a Howson group if the intersection of any two finitely generated subgroups is again finitely generated, and called a strongly Howson group…