Geometric representability of 1-cycles on rationally connected threefolds

Abstract

We prove that for any rationally connected threefold $X$, there exists a smooth projective surface $S$ and a family of $1$-cycles on $X$ parameterized by $S$, inducing an Abel-Jacobi isomorphism $\mathrm{Alb}(S)\cong J^3(X)$. This statement was previously known for some classes of smooth Fano threefolds.

Final version, to appear in the Collino memorial volume "Perspectives on four decades: Algebraic Geometry 1980-2020"