Towards Bigness equivalence

On the flag variety $\mathcal{F}l_s(E)$ associated to a vector bundle $E,$ , a sequence $s$ and a partition $a,$ there is a line bundle $\it Q^a_s$ on $\mathcal{F}l_s(E).$ The aim of this paper is to prove the following conjecture: $Q^a_s$ on $\mathcal{F}l_s(E)$ is big if only if $\pi_*(Q^a_s)=S_a(E)$ on X is big. The "if" part is proven here, the "only if" part is proven under the V-bigness hypothesis.