Submission: 2003, Mar 5
A correspondence between quartic etale algebras over a field and quadratic etale extensions of cubic etale algebras is set up and investigated. The basic constructions are laid out in general for sets with a profinite group action and for torsors, and translated in terms of etale algebras and Galois algebras. In the final section, a parametrization of cyclic quartic algebras is given.
2000 Mathematics Subject Classification: 12F10, 12G05
Keywords and Phrases: etale algebras, Galois cohomology
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