Inertia of partial transpose of positive semidefinite matrices

We show that the partial transpose of $9\times 9$ positive semidefinite matrices do not have inertia (4,1,4) and (3,2,4). It solves an open problem in “LINEAR AND MULTILINEAR ALGEBRA, Changchun Feng et al, 2022”. We apply our results to construct some inertia, as well as present the list of all possible inertia of partial transpose of $12\times 12$ positive semidefinite matrices.