Abstract
A universal algebra is called Hopfian if any of its surjective endomorphisms is an automorphism, and co-Hopfian if injective endomorphisms are automorphisms. In this paper, necessary and sufficient conditions are found for Hopfianity and co-Hopfianity of unitary acts over groups. It is proved that a coproduct of finitely many acts (not necessarily unitary) over a group is Hopfian if and only if every factor is Hopfian.
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Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 23, No. 3, pp. 131–139, 2020.
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Kozhukhov, I.B., Kolesnikova, K.A. On Hopfianity and Co-Hopfianity of Acts Over Groups. J Math Sci 269, 356–361 (2023). https://doi.org/10.1007/s10958-023-06286-4
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DOI: https://doi.org/10.1007/s10958-023-06286-4