Compute ˜U2 ∈ RX× H , the matrix whose columns are the right singular vectors of ˜P (t) 3, 2 associated with its largestH singular values

Compute ˜U3, ˜U1 ∈ RX× H , the matrices whose columns are, respectively, the left, right singular vectors of ˜P (t) 3, 1 associated with its largest H singular values