Approximation of matrices
نویسنده
چکیده
We improve here two results from the preprints [DK], [AFKK] on approximating matrices by random submatrices. We use a construction of a random subset of a finite set, which is different from what was suggested in [AFKK]. Instead of taking a random q-element subset of an n-element set, we consider independent {0, 1}-valued random variables δ1, . . . , δn, taking value 1 with probability δ = q/n. These variables serve as selectors. Namely, we define a random set I = {j ∈ {1, . . . , n} | δj = 1}. Then E|I| = E n ∑
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