Chow groups of symmetric products of projective space

Abstract

We prove that the integral cycle class map for $\SP^d(\PP^n)$ is split injective, with finite cokernel annihilated by $d!$,and we determine the ranks of Chow groups for $\mathrm{SP}^d(\mathbb{P}^n)$. Compatible integral transfer retractions show that $\CH_q(\SP^d(\PP^n))$ stabilizes for $d\geq q$. An explicit nonalgebraic order two class persists under addition of points, producing a split cokernel summand even in the range $q\leq d$ and in the infinite symmetric product. For the smooth configuration open set, we identify the codimension two cokernel with third unramified cohomology and detect its ramification on a rational resolution. In contrast to addition, even multiplicities annihilate a nonzero Chow class.