We prove that every maximal cofinitary group has size at least the cardinality of the smallest non-meager set of reals. We also provide a consistency result saying that the spectrum of possible cardinalities of maximal cofinitary groups may be quite arbitrary.
Supersoluble and Related Cofinitary Groups
β Scribed by B. A. F. Wehrfritz
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 758 KB
- Volume
- 176
- Category
- Article
- ISSN
- 0025-584X
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β¦ Synopsis
Let D be a division ring (possibly commutative) and V an infinite-dimensional left vector space over D. We consider irreducible subgroups G of GL(VJ containing an element whose fixedpoint set in V is non-zero but finite dimensional (over D). We then derive conclusions about cofinitary groups, an element of GL(V) being cofinitary if its fixed-point set is finite dimensional and a subgroup G of GL(V) being cofinitary if all its non-identity elements are confinitary. In particular we show that an irreducible cofinitary subgroup G of G L ( V ) is usually imprimitive if G is supersoluble and is frequently imprimitive if G is hypercyclic. The latter includes the case where G is hypercentral, which apparently is also new.
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