On Quaternion Algebras Split by a Given Extension, Clifford Algebras and Hyperelliptic Curves

Haile, Darrell;Rowen, Louis;Tignol, Jean-Pierre
(2020) Algebras and Representation Theory — Vol. 23, n° 4, p. 1807-1826 (2020)

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Authors
  • Haile, DarrellIndiana University
    Author
  • Rowen, LouisBar-Ilan University
    Author
  • Tignol, Jean-Pierreorcid-logoUCLouvain
    Author
Abstract
Given a monic separable polynomial P of degree 2n over an arbitrary field and a scalar a, we define generic algebras H_P and HR_{aP} for the decomposition of P into a product of two polynomials of degree n and for the factorization aP=Q^2 respectively. We investigate representations of degree 1 or 2 of these generic algebras. Every representation of degree 1 of H_P factors through an étale algebra of degree C^n_{2n}, whereas HR_{aP} has no representation of degree 1. We show that every representation of degree 2 of H_P or HR_{aP} factors through the Clifford algebra of some quadratic form, pointed or not, and thus obtain a description of the quaternion algebras that are split by the étale algebra F_P defined by P of by the function field of the hyperelliptic curve X_{aP} with equation y^2=aP(x). We prove that every quaternion algebra split by the function field of X_{aP} is also split by F_P, and provide an example to show that a quaternion algebra split by F_P may not be split by the function field of any curve X_{aP}.
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Citations

Haile, D., Rowen, L., & Tignol, J.-P. (2020). On Quaternion Algebras Split by a Given Extension, Clifford Algebras and Hyperelliptic Curves. Algebras and Representation Theory, 23(4), 1807-1826. https://doi.org/10.1007/s10468-019-09914-3 (Original work published 2020)