Covering the symmetric groups with proper subgroups
نویسنده
چکیده
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−1, while for alternating groups we find σ(An) ≥ 2n−2 unless n = 7 or 9. An application of this result is also given.
منابع مشابه
On the covering number of small symmetric groups and some sporadic simple groups
A set of proper subgroups is a covering for a group if its union is the whole group. The minimal number of subgroups needed to cover G is called the covering number of G, denoted by σ(G). Determining σ(G) is an open problem for many nonsolvable groups. For symmetric groups Sn, Maróti determined σ(Sn) for odd n with the exception of n = 9 and gave estimates for n even. In this paper we determine...
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عنوان ژورنال:
- J. Comb. Theory, Ser. A
دوره 110 شماره
صفحات -
تاریخ انتشار 2005