Hodge--Riemann relations for $m$-positive and generalized $m$-positive forms

Abstract

We study Hodge--Riemann relations for ordinary, sequential, and weak $m$-positive real $(1,1)$-forms in complex dimension $d$. For ordinary $m$-positive forms, we prove the fully mixed relations in every permitted bidegree without assuming semipositivity, generalizing results by Xiao. As a generalization of ordinary $m$-positivity, sequential $m$-positivity is defined by the hyperbolicity cones of successive directional derivatives of the determinant. We formulate a generalized mixed Hodge--Riemann conjecture for this condition and prove several cases beyond the scalar inequalities supplied by hyperbolicity. We also consider weak $m$-positivity which corresponds to the pointwise subsolution condition for the complex $m$-Hessian equation. In this setting, we prove the Hodge--Riemann relations for $p\neq q$ and in several diagonal cases, and show that the associated power map induces a pointwise diffeomorphism onto the cone of positive $(d-1,d-1)$-forms. Using Dinh and Nguyên's $L^2$ globalization method, we pass from the pointwise relations to cohomology classes on compact Kähler manifolds. Finally, we propose conjectures on a numerical criterion for sequential positivity and on solvability of the generalized $m$-Hessian equation.