The purpose of this note is to give a new upper bound of the shortest string containing all r-permutations. Thus we disprove the conjecture considered in Cl]. The terminology used in this note fullows [I]. Koutas and Nu [I] proposed the foIlowing problem of constructing a shortest string of (1, 2,
On a subgroup contained in some words with a bounded length
β Scribed by Yahya Ould Hamidoune
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 315 KB
- Volume
- 103
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
β¦ Synopsis
Hamidoune, Y.O., On a subgroup contained in some words with a bounded length, Discrete Mathematics 103 (1992) 171-176. Let G be a group and let A and B be two finite nonvoid subsets of G such that 1$ B. Using results of Kemperman, we show that either IA U B U ABl b IAl + IBI or there exists a nonnull subgroup contained in A U B U Al?. As an application we obtain the following result: Let A,, 4, . . , A, be subsets of a finite group G such that 1 $ A,; 2 c i s k and IA,1 + IA,1 + . . + jAkl 3 ICI. The union of sets of the form A,,A,, . . . Aij; 1 s i, <i, <. . . <ii s k must include a nonnull subgroup. In particular if B is a subset of G\l such that k IBI 2 ICI, the set B U /3* U. . . U B* must contain a nonnull subgroup.
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