On hopfian groups
نویسندگان
چکیده
منابع مشابه
On co-Hopfian nilpotent groups
We characterize co-Hopfian finitely generated torsion free nilpotent groups in terms of their Lie algebra automorphisms, and construct many examples of such groups.
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Let p : M → B be a proper surjective map defined on an (n+ 2)-manifold such that each point-preimage is a copy of a hopfian n-manifold. Then we show that p is an approximate fibration over some dense open subset O of the mod 2 continuity set C′ and C′ \O is locally finite. As an application, we show that a hopfian n-manifold N is a codimension-2 fibrator if χ(N) 6= 0 or H1(N) ∼= Z2.
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This paper investigates the preservation of hopficity and co-hopficity on passing to finite-index subsemigroups and extensions. It was already known that hopficity is not preserved on passing to finite Rees index subsemigroups, even in the finitely generated case. We give a stronger example to show that it is not preserved even in the finitely presented case. It was also known that hopficity is...
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ژورنال
عنوان ژورنال: Pacific Journal of Mathematics
سال: 1970
ISSN: 0030-8730,0030-8730
DOI: 10.2140/pjm.1970.32.753