# Article

 Title: Cyclic and dihedral constructions of even order (English) Author: Drápal, Aleš Language: English Journal: Commentationes Mathematicae Universitatis Carolinae ISSN: 0010-2628 (print) ISSN: 1213-7243 (online) Volume: 44 Issue: 4 Year: 2003 Pages: 593-614 . Category: math . Summary: Let $G(\circ)$ and $G(*)$ be two groups of finite order $n$, and suppose that they share a normal subgroup $S$ such that $u\circ v = u *v$ if $u \in S$ or $v \in S$. Cases when $G/S$ is cyclic or dihedral and when $u \circ v \ne u*v$ for exactly $n^2/4$ pairs $(u,v) \in G\times G$ have been shown to be of crucial importance when studying pairs of 2-groups with the latter property. In such cases one can describe two general constructions how to get all possible $G(*)$ from a given $G = G(\circ)$. The constructions, denoted by $G[\alpha,h]$ and $G[\beta,\gamma,h]$, respectively, depend on a coset $\alpha$ (or two cosets $\beta$ and $\gamma$) modulo $S$, and on an element $h \in S$ (certain additional properties must be satisfied as well). The purpose of the paper is to expose various aspects of these constructions, with a stress on conditions that allow to establish an isomorphism between $G$ and $G[\alpha,h]$ (or $G[\beta,\gamma,h]$). (English) Keyword: cyclic construction Keyword: dihedral construction Keyword: quarter distance MSC: 05B15 MSC: 20D15 MSC: 20D60 idZBL: Zbl 1101.20014 idMR: MR2062876 . Date available: 2009-01-08T19:31:29Z Last updated: 2012-04-30 Stable URL: http://hdl.handle.net/10338.dmlcz/119414 . Reference: [1] Bálek M., Drápal A., Zhukavets N.: The neighbourhood of dihedral $2$-groups.submitted. Reference: [2] Donovan D., Oates-Williams S., Praeger C.E.: On the distance of distinct Latin squares.J. Combin. Des. 5 (1997), 235-248. MR 1451283 Reference: [3] Drápal A.: Non-isomorphic $2$-groups coincide at most in three quarters of their multiplication tables.European J. Combin. 21 (2000), 301-321. MR 1750166 Reference: [4] Drápal A.: On groups that differ in one of four squares.European J. Combin. 23 (2002), 899-918. Zbl 1044.20009, MR 1938347 Reference: [5] Drápal A.: On distances of $2$-groups and $3$-groups.Proceedings of Groups St. Andrews 2001 in Oxford, to appear. MR 2051524 Reference: [6] Drápal A., Zhukavets N.: On multiplication tables of groups that agree on half of columns and half of rows.Glasgow Math. J. 45 (2003), 293-308. MR 1997707 Reference: [7] Zhukavets N.: On small distances of small $2$-groups.Comment. Math. Univ. Carolinae 42 (2001), 247-257. Zbl 1057.20018, MR 1832144 .

## Files

Files Size Format View
CommentatMathUnivCarolRetro_44-2003-4_4.pdf 324.1Kb application/pdf View/Open

Partner of