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arXiv · 1109.6733

Anisotropy and the integral closure

Michiel Kosters
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Abstract

Let K be a number field and let A be an order in K. The trace map from K to Q induces a non-degenerate symmetric bilinear form <,>: B x B \to Q/Z where B is a certain finite abelian group of size Δ(A). In this article we discuss how one can obtain information about \mathcal{O}_K by purely looking at this symmetric bilinear form. The concepts of anisotropy and quasi-anisotropy, as defined in another article by the author, turn out to be very useful. We will for example show that under certain assumptions one can obtain \mathcal{O}_K directly from <,>. In this article we will work in a more general setting than we have discussed above. We consider orders over Dedekind domains.

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Michiel Kosters. 2011-09-30. Anisotropy and the integral closure. https://doi.org/10.1016/j.jnt.2013.10.006

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