No CrossRef data available.
Published online by Cambridge University Press: 21 July 2025
Let S and T be smooth projective varieties over an algebraically closed field k. Suppose that S is a surface admitting a decomposition of the diagonal. We show that, away from the characteristic of k, if an algebraic correspondence $T \to S$ acts trivially on the unramified cohomology, then it acts trivially on any normalized, birational and motivic functor. This generalizes Kahn’s result on the torsion order of S. We also exhibit an example of S over
$\mathbb {C}$ for which
$S \times S$ violates the integral Hodge conjecture.
In memory of Noriyuki Suwa
The first author is supported by JSPS KAKENHI Grant (JP20K03566). The second author is supported by JSPS KAKENHI Grant (JP21K03153) and by Chuo University Grant for Special Research.