3 problems

Let $X$ be a regular connected scheme, flat and proper over $\operatorname{Spec}({\mathbb Z})$, with generic fibre $X\otimes_{\mathbb Z}{\mathbb Q}$ projective over ${\mathbb Q}$.…

Hu's rational cycle class conjecture. For all $d\geq 0$ and $0\leq p\leq n$,

Hu's integral cycle class conjecture. For all $d\geq 0$ and $0\leq p\leq n$,