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Opposite Skew Left Braces and Applications

Koch, Alan; Truman, Paul

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Alan Koch


Given a skew left brace B, we introduce the notion of an \opposite" skew left brace B0, which is closely related to the concept of the opposite of a group, and provide several applications. Skew left braces are closely linked with both solutions to the Yang-Baxter Equation and Hopf-Galois structures on Galois field extensions. We show that the set-theoretic solution to the YBE given by B0 is the inverse to the solution given by B. Every Hopf-Galois structure on a Galois field extension L=K gives rise to a skew left brace B; if the underlying Hopf algebra is not commutative, then one can construct an additional, \commuting" Hopf-Galois structure (see [10], which relates the Hopf-Galois module structures of each); the corresponding skew left brace to this second structure is precisely B0. We show how left ideals (and a newly introduced family of quasi-ideals) of B0 allow us to identify the intermediate fields of L=K which occur as fixed fields of sub-Hopf algebras under this correspondence. Finally, we use the opposite to connect the inverse solution to the YBE and the structure of the Hopf algebra H acting on L=K; this allows us to identify the group-like elements of H.


Koch, A., & Truman, P. (2020). Opposite Skew Left Braces and Applications. Journal of Algebra, 218-235.

Acceptance Date Oct 1, 2019
Publication Date Mar 15, 2020
Journal Journal of Algebra
Print ISSN 0021-8693
Publisher Elsevier
Pages 218-235
Keywords Skew left braces, Hopf-Galois structure, Yang-Baxter equation
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