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arXiv · 2112.06688

Quaternion algebras and square power classes over biquadratic extensions

Frank Chemotti·Jan Minac·Tung T. Nguyen·Andrew Schultz·John Swallow·Nguyen Duy Tan
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Abstract

Recently the Galois module structure of square power classes of a field $K$ has been computed under the action of $\text{Gal}(K/F)$ in the case where $\text{Gal}(K/F)$ is the Klein $4$-group. Despite the fact that the modular representation theory over this group ring includes an infinite number of non-isomorphic indecomposable types, the decomposition for square power classes includes at most $9$ distinct summand types. In this paper we determine the multiplicity of each summand type in terms of a particular subspace of $\text{Br}(F)$, and show that all "unexceptional" summand types are possible.

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Frank Chemotti, Jan Minac, Tung T. Nguyen, Andrew Schultz, John Swallow, Nguyen Duy Tan. 2021-12-13. Quaternion algebras and square power classes over biquadratic extensions. https://arxiv.org/abs/2112.06688

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