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v2007.11.26 - Convex Optimization

v2007.11.26 - Convex Optimization

v2007.11.26 - Convex Optimization

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B.4. AUXILIARY V -MATRICES 543the nullspace N(V )= R(1) is spanned by the eigenvector 1. The remainingeigenvectors span R(V ) ≡ 1 ⊥ = N(1 T ) that has dimension N −1.BecauseV 2 = V (1457)and V T = V , elementary matrix V is also a projection matrix (E.3)projecting orthogonally on its range N(1 T ) which is a hyperplane containingthe origin in R N V = I − 1(1 T 1) −1 1 T (1458)The {0, 1} eigenvalues also indicate diagonalizable V is a projectionmatrix. [303,4.1, thm.4.1] Symmetry of V denotes orthogonal projection;from (1709),V T = V , V † = V , ‖V ‖ 2 = 1, V ≽ 0 (1459)Matrix V is also circulant [118].B.4.1.0.1 Example. Relationship of auxiliary to Householder matrix.Let H ∈ S N be a Householder matrix (1452) defined by⎡ ⎤u = ⎢1.⎥⎣ 11 + √ ⎦ ∈ RN (1460)NThen we have [106,2]Let D ∈ S N h and define[ I 0V = H0 T 0[−HDH = ∆ A b−b T c]H (1461)](1462)where b is a vector. Then because H is nonsingular (A.3.1.0.5) [133,3][ ] A 0−V DV = −H0 T H ≽ 0 ⇔ −A ≽ 0 (1463)0and affine dimension is r = rankA when D is a Euclidean distance matrix.

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