منابع مشابه
On Kernels of Cellular Covers
In the present paper we continue to examine cellular covers of groups, focusing on the cardinality and the structure of the kernel K of the cellular map G → M . We show that in general a torsion free reduced abelian group M may have a proper class of non-isomorphic cellular covers. In other words, the cardinality of the kernels is unbounded. In the opposite direction we show that if the kernel ...
متن کاملFinite Covers with Nite Kernels
We are concerned with the following problem. Suppose ? and are closed permutation groups on innnite sets C and W and : ? ?! is a non-split, continuous epimorphism with nite kernel. Describe (for xed) the possibilities for. Here, we consider the case where arises from a nite cover : C ?! W. We give reasonably general conditions on the permutation structure hW; i which allow us to prove that thes...
متن کاملOn X Free Covers
For an arbitrary graph G = (V,E), let X be a graphical property that can be possessed, or satisfied by the subsets of V . For example, being a clique (maximal complete subgraph), a maximal independent set, an edge, a closed neighborhood, a minimal dominating set, etc. Let CX ={A|A ⊆ V , |A| > 1, and A possesses or satisfies property X}. A set S is an X cover (or X free) if A ∩ S (or A ∩ (V − S)...
متن کاملAlmost-free finite covers
Let W be a first-order structure and ρ be an Aut(W )-congruence on W . In this paper we define the almost-free finite covers of W with respect to ρ, and we show how to construct them. These are a generalization of free finite covers. A consequence of a result of [5] is that any finite cover of W with binding groups all equal to a simple non-abelian permutation group is almostfree with respect t...
متن کاملCellular Covers of Local Groups
We prove that, in the category of groups, the composition of a cellularization and a localization functor need not be idempotent. This provides a negative answer to a question of Emmanuel Dror Farjoun.
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ژورنال
عنوان ژورنال: Mediterranean Journal of Mathematics
سال: 2010
ISSN: 1660-5446,1660-5454
DOI: 10.1007/s00009-010-0109-1