Complements in the symmetric group

About 20 years ago I was asked a question of Herbert Kociemba, a computer scientist who has one of the best Rubik’s cube solving programs known. Efficient methods of storing permutations in S_E and S_V (the groups of all permutations of the edges E and vertices V, respectively, of the Rubik’s cube) are needed, hence leading naturally to the concept of the complement of S_m in S_n. Specifically, he asked if S_8 has a complement in S_{12} (this terminology is defined below). The answer is,
as we shall see, ”no.” Nonetheless, it turns out to be possible to introduce a slightly more general notion of a “k-tuple of complementary subgroups” (defined below) for which the answer to the analogous question is ”yes.”

This post is a very short summary of a paper I wrote (still unpublished) which can be downloaded here.

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