منابع مشابه
covering monolithic groups with proper subgroups
given a finite non-cyclic group $g$, call $sigma(g)$ the smallest number of proper subgroups of $g$ needed to cover $g$. lucchini and detomi conjectured that if a nonabelian group $g$ is such that $sigma(g) < sigma(g/n)$ for every non-trivial normal subgroup $n$ of $g$ then $g$ is textit{monolithic}, meaning that it admits a unique minimal normal subgroup. in this paper we show how thi...
متن کاملCovering the symmetric groups with proper subgroups
Let G be a group that is a set-theoretic union of finitely many proper subgroups. Cohn defined σ(G) to be the least integer m such that G is the union of m proper subgroups. Tomkinson showed that σ(G) can never be 7, and that it is always of the form q +1 (q a prime power) for solvable groups G. In this paper we give exact or asymptotic formulas for σ(Sn). In particular, we show that σ(Sn) ≤ 2n...
متن کاملCovering Monolithic Groups with Proper Subgroups
Given a finite non-cyclic group G, call σ(G) the smallest number of proper subgroups of G needed to cover G. Lucchini and Detomi conjectured that if a nonabelian group G is such that σ(G) < σ(G/N) for every non-trivial normal subgroup N of G then G is monolithic, meaning that it admits a unique minimal normal subgroup. In this paper we show how this conjecture can be attacked by the direct stud...
متن کاملPOS-groups with some cyclic Sylow subgroups
A finite group G is said to be a POS-group if for each x in G the cardinality of the set {y in G | o(y) = o(x)} is a divisor of the order of G. In this paper we study the structure of POS-groups with some cyclic Sylow subgroups.
متن کاملNilpotent groups with three conjugacy classes of non-normal subgroups
Let $G$ be a finite group and $nu(G)$ denote the number of conjugacy classes of non-normal subgroups of $G$. In this paper, all nilpotent groups $G$ with $nu(G)=3$ are classified.
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ژورنال
عنوان ژورنال: Bulletin of the Australian Mathematical Society
سال: 1997
ISSN: 0004-9727,1755-1633
DOI: 10.1017/s0004972700034109