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Isotropy of symplectic involutions and motivic equivalence for groups of type sfC
Abstract
We extend to arbitrary characteristic a theorem due to Karpenko and Tignol on the isotropy of symplectic involutions after generic index reduction; as a consequence, we also prove the existence of critical varieties for semi-simple algebraic groups of type sf C over arbitrary base fields. The latter result relies on a characteristic-free argument, which involves the computation of the mod $2$ Tate trace of the variety of isotropic ideals of reduced dimension $2$ for a symplectic involution.
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BibTeX
@misc{barry2026isotropy,
title = {{Isotropy of symplectic involutions and motivic equivalence for groups of type $\sfC$}},
author = {Demba Barry and Charles De Clercq and Anne Quéguiner-Mathieu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25363},
eprint = {2610.25363},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25363},
}
RIS
TY - UNPB
TI - Isotropy of symplectic involutions and motivic equivalence for groups of type sfC
AU - Demba Barry
AU - Charles De Clercq
AU - Anne Quéguiner-Mathieu
PY - 2026
DA - 2026/10/18
PB - arXiv
DO - 10.48550/arxiv.2610.25363
UR - https://arxiv.org/abs/2610.25363
AB - We extend to arbitrary characteristic a theorem due to Karpenko and Tignol on the isotropy of symplectic involutions after generic index reduction; as a consequence, we also prove the existence of critical varieties for semi-simple algebraic groups of type sf C over arbitrary base fields. The latter result relies on a characteristic-free argument, which involves the computation of the mod $2$ Tate trace of the variety of isotropic ideals of reduced dimension $2$ for a symplectic involution.
ER -