We explain some results concerning the topology of varieties and stacks equipped with an action of the multiplicative group Gₘ. We apply these techniques to the moduli of Higgs bundles. Our main application is to upgrade the cohomological Nonabelian Hodge Theorem in positive characteristic 9, 17 to an isomorphism of cohomology rings compatible with cup product.
Herrero et al. (Thu,) studied this question.