Primary 11E39 ; Secondary 11E81
Submission: 2006, Feb 3
Harrison's criterion characterizes the isomorphy of the Witt rings of two fields in terms of properties of these fields. In this article, we discuss about the existence of such characterizations for the isomorphism of Witt groups of hermitian forms over certain algebras with involution. In the cases where we consider the Witt group of a quadratic extension with its non-trivial automorphism or the Witt group of a quaternion division algebra with its canonical involution, such criteria are proved. In the framework of global fields, the first of these criteria is reformulated in terms of properties involving real places of the considered fields.
2000 Mathematics Subject Classification: Primary 11E39 ; Secondary 11E81
Keywords and Phrases: Harrison's criterion, Witt equivalence, reciprocity equivalence, algebras with involution
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