Smoothed analysis of k(A)

  • Authors:
  • Mario Wschebor

  • Affiliations:
  • Centro de Matemática, Facultad de Ciencias, Universidad de la República, Calle Iguá 4225, Montevideo 11400, Uruguay

  • Venue:
  • Journal of Complexity
  • Year:
  • 2004

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Abstract

Let A = ((aij)) be an m × m (m ≥ 3) real random matrix, with independent Gaussian entries with a common variance σ2. Denote by M the matrix of expected values of the entries of A. For x 0 we prove that P(κ(A)m.x x;(1/4√2πm + C(M, σ, m)) with C(M, σ, m) = 7(5+4||M||2(1+logm)/σ2m)1/2 Here κ(A) = ||A|| ||A-1|| is the usual condition number of A, ||.|| is Euclidean operator norm. This implies that if 0 M|| ≥ 1 then, for x 0, P(κ(A) m.x) K/σx where K is a universal constant.