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arXiv · 1805.04670

On the decomposability of mod 2 cohomological invariants of Weyl groups

Christian Hirsch
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Abstract

We compute the invariants so of Weyl groups in mod 2 Milnor K-theory and more general cycle modules, which are annihilated by 2. Over a base field of characteristic coprime to the group order, the invariants decompose as direct sums of the coefficient module. All basis elements are induced either by Stiefel-Whitney classes or specific invariants in the Witt ring. The proof is based on Serre's splitting principle that guarantees detection of invariants on elementary abelian 2-subgroups generated by reflections.

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Christian Hirsch. 2018-05-12. On the decomposability of mod 2 cohomological invariants of Weyl groups. https://arxiv.org/abs/1805.04670

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