The symplectic left companion of a Littlewood-Richardson-Sundaram tableau and the Kwon condition
As a consequence of the Littlewood-Richardson commuters coincidence and the Kumar-Torres branching model via Kushwaha-Raghavan-Viswanath flagged hives, we have solved the Lecouvey-Lenart conjecture on the bijections between the Kwon and Sundaram branching models for the pair (GL_2n(C), Sp_2n(C)) consisting of the general linear group GL_2n(C) and the symplectic group Sp_2n(C).