1. The problem statement, all variables and given/known data Let K and L be symmetric PSD matrices of size N*N, with all entries in [0,1]. Let i be any number in 1...N and K’, L’ be two new symmetric PSD matrices, each with only row i and column i different from K and L. I would like to obtain an upper bound of the equation below: where .∗ is an element-wise multiply. 2. Relevant equations |[sum(K' .∗ L') − sum(K .∗ L)] − (2/N)*[sum(K'L'') − sum(KL)] + (1/N*N)*[sum(K')sum(L') − sum(K)sum(L)]| See attached for equation in LaTex/PDF. 3. The attempt at a solution Using simple triangular inequality and bounding the three square brackets respectively, I can bound the above with 12N − 13. However, this is extremely loose. Empirical experiments show that the constant coefficient should be much lower, probably closer to 1N. Can you suggest any linear algebra properties connecting the equation's parts - which may help me get a tighter bound?