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An Arad and Fisman’s theorem on products of conjugacy classes revisited. (English) Zbl 07609413

The Arad-Fisman theorem [Z. Arad and E. Fisman, Proc. Edinb. Math. Soc., II. Ser. 30, 7–22 (1987; Zbl 0592.20006)] says that, if \(A\) and \(B\) are conjugacy classes of a non-abelian finite simple group, then \(A\cup B\ne AB\ne A^{-1}\cup B\).
The authors generalise this result and prove (in particular) that for any conjugacy classes \(A\) and \(B\) of a finite group,
if \(AB=A\cup B\), then \(\langle A\rangle=\langle B\rangle\) is solvable;
if \(AB=A^{-1}\cup B\) with \(A\ne A^{-1}\), then \(A=B\) and \(\langle A\rangle\) is solvable;
if \(AA^{-1}=\{1\}\cup A\cup A^{-1}\), then \(A=AA^{-1}\) is elementary abelian.

MSC:

20E45 Conjugacy classes for groups
20D15 Finite nilpotent groups, \(p\)-groups

Software:

GAP

References:

[1] Arad, Z.; Fisman, E., An analogy between products of two conjugacy classes and products of two irreducible characters in finite groups, Proc. Edinb. Math. Soc., 30, 7-22 (1987) · Zbl 0592.20006 · doi:10.1017/S0013091500017922
[2] Arad, Z.; Fisman, E.; Muzychuk, M., Order evaluation of products of subsets in finite groups and its applications. I, J. Algebra, 182, 3, 577-603 (1996) · Zbl 0862.20017 · doi:10.1006/jabr.1996.0191
[3] Arad, Z.; Muzychuk, M., Order evaluation of products of subsets in finite groups and its applications. II, Trans. Am. Math. Soc., 349, 11, 4401-4414 (1997) · Zbl 0895.20022 · doi:10.1090/S0002-9947-97-01866-7
[4] Beltrán, A.; Camina, RD; Felipe, MJ; Melchor, C., Powers of conjugacy classes in a finite group, Ann. Mat. Pura Appl., 199, 2, 409-424 (2020) · Zbl 1471.20022 · doi:10.1007/s10231-019-00885-2
[5] Beltrán, A.; Felipe, MJ; Melchor, C., Multiplying a conjugacy class by its inverse in a finite group, Isr. J. Math., 227, 2, 811-825 (2018) · Zbl 1499.20034 · doi:10.1007/s11856-018-1742-9
[6] Beltrán, A.; Felipe, MJ; Melchor, C., Squares of real conjugacy classes in finite groups, Ann. Mat. Pura Appl., 197, 2, 317-328 (2018) · Zbl 1468.20059 · doi:10.1007/s10231-017-0681-0
[7] Camina, RD, Applying combinatorial results to products of conjugacy classes, J. Group Theory, 23, 5, 917-923 (2020) · Zbl 1476.20032 · doi:10.1515/jgth-2020-0036
[8] Guralnick, RM; Navarro, G., Squaring a conjugacy class and cosets of normal subgroups, Proc. Am. Math. Soc., 144, 5, 1939-1945 (2016) · Zbl 1346.20037 · doi:10.1090/proc/12874
[9] Huppert, B., Character Theory of Finite Groups (1998), Berlin: Walter de Gruyter, Berlin · Zbl 0932.20007 · doi:10.1515/9783110809237
[10] The GAP Group, GAP-Groups, Algorithms and Programming, Vers. 4.7.7 (2015). http://ww.gap-system.org
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