On the dual positive cones and the algebraicity of a compact K\"ahler manifold

We investigate the algebraicity of compact K"ahler manifolds admitting a positive rational Hodge class of bidimension $(1,1)$. We prove that if the dual K"ahler cone of a compact K"ahler manifold $X$ contains a rational class as an interior point, then its Albanese variety is projective. As a consequence, we answer the Oguiso–Peternell problem for Ricci-flat compact K"ahler manifolds. We also study related algebraicity problems for threefolds.