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v2010.10.26 - Convex Optimization

v2010.10.26 - Convex Optimization

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5.4. EDM DEFINITION 407We provide a rigorous complete more geometric proof of this fundamentalSchoenberg criterion in5.9.1.0.4. [ [isedm(D) ] on Wıκımization]0 0TBy substituting G =0 −VN TDV (908) into D(G) (903),N[ ]0D =δ ( [−VN TDV ) 1 T + 1 0 δ ( ) ] [ ]−VNDV T T 0 0TN − 2N0 −VN TDV (1009)Nassuming x 1 = 0. Details of this bijection are provided in5.6.2.5.4.2.2 0 geometric centerAssume the geometric center (5.5.1.0.1) of an unknown list X is the origin;X1 = 0 ⇔ G1 = 0 (911)Now consider the calculation (I − 1 N 11T )D(G)(I − 1 N 11T ) , a geometriccentering or projection operation. (E.7.2.0.2) Setting D(G) = D forconvenience as in5.4.2.1,G = − ( D − 1 N (D11T + 11 T D) + 1N 2 11 T D11 T) 12 , X1 = 0= −V DV 1 2V GV = −V DV 1 2∀X(912)where more properties of the auxiliary (geometric centering, projection)matrixV I − 1 N 11T ∈ S N (913)are found inB.4. V GV may be regarded as a covariance matrix of means 0.From (912) and the assumption D ∈ S N h we get sufficiency of the more popularform of Schoenberg’s criterion:D ∈ EDM N⇔{−V DV ∈ SN+D ∈ S N h(914)Of particular utility when D ∈ EDM N is the fact, (B.4.2 no.20) (887)tr ( ( )∑−V DV 2) 1 =1∑d2N ij = 12N vec(X)T Φ ij ⊗ I vec Xi,ji,j= tr(V GV ) , G ≽ 0∑= trG = N ‖x l ‖ 2 = ‖X‖ 2 F , X1 = 0l=1(915)

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