Products of hopfian manifolds and codimension-2 fibrators
نویسندگان
چکیده
منابع مشابه
Necessary and Sufficient Conditions for S-hopfian Manifolds to Be Codimension-2 Fibrators
Fibrators help detect approximate fibrations. A closed, connected n-manifold N is called a codimension-2 fibrator if each map p : M → B defined on an (n + 2)-manifold M such that all fibre p−1(b), b ∈ B, are shape equivalent to N is an approximate fibration. The most natural objects N to study are s-Hopfian manifolds. In this note we give some necessary and sufficient conditions for s-Hopfian m...
متن کاملHopfian and strongly hopfian manifolds
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.
متن کاملHopfian and co-hopfian subsemigroups and extensions
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...
متن کاملCodimension 2 Cycles on Products of Projective Homogeneous Surfaces
In the present paper, we provide general bounds for the torsion in the codimension 2 Chow groups of the products of projective homogeneous surfaces. In particular, we determine the torsion for the product of four Pfister quadric surfaces and the maximal torsion for the product of three Severi-Brauer surfaces. We also find an upper bound for the torsion of the product of three quadric surfaces w...
متن کاملGeneralizations of Hopfian and co-Hopfian modules
In this paper, all rings are associative with identity and all modules are unital left modules unless otherwise specified. Let R be a ring and M a module. N ≤M will mean N is a submodule of M. A submodule E of M is called essential in M (notation E ≤e M) if E∩A = 0 for any nonzero submodule A of M. Dually, a submodule S of M is called small in M (notation S M) if M = S+T for any proper submodul...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Topology and its Applications
سال: 2000
ISSN: 0166-8641
DOI: 10.1016/s0166-8641(99)00008-5