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arXiv · 2511.12871

Classification of Fixed Subgroups of Endomorphisms in Free-abelian Times Surface Groups

Ke Wang·Qiang Zhang·Dongxiao Zhao
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Abstract

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-abelian times hyperbolic groups are Hopfian but not co-Hopfian. Moreover, we give a complete classification of fixed subgroups of endomorphisms in free-abelian times surface groups, which extends that of automorphisms. Finally, we study the endomorphisms of free-abelian times non-elementary torsion-free hyperbolic groups and give an equivalent condition for them to contain, up to isomorphism, finitely many end-fixed subgroups.

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Ke Wang, Qiang Zhang, Dongxiao Zhao. 2025-11-17. Classification of Fixed Subgroups of Endomorphisms in Free-abelian Times Surface Groups. https://arxiv.org/abs/2511.12871

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