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arXiv · 2510.09552

Degree 4 cohomological invariants of algebraic tori

Cyril Demarche·Hanqing Long
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Abstract

In this paper, we determine the motive of the classifying torsor of an algebraic torus. As a result, we give an exact sequence describing the degree 4 cohomological invariants of algebraic tori. Using results by Blinstein and Merkurjev, this provides a formula for the degree 4 unramified cohomology group of an algebraic torus, via a flasque resolution.

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Cyril Demarche, Hanqing Long. 2025-10-10. Degree 4 cohomological invariants of algebraic tori. https://arxiv.org/abs/2510.09552

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