Newell–Littlewood numbers II: extended Horn inequalities

The Newell–Littlewood numbers N μ,ν,λ are tensor product multiplicities of Weyl modules for classical Lie groups, in the stable limit. For which triples partitions (μ,ν,λ) does >0 hold? Littlewood–Richardson coefficient case is solved by Horn inequalities (in work A. Klyachko and Knutson-T. Tao). We extend these celebrated linear to a much larger family, suggesting general solution.