Lysario – by Panagiotis Chatzichrisafis

"ούτω γάρ ειδέναι το σύνθετον υπολαμβάνομεν, όταν ειδώμεν εκ τίνων και πόσων εστίν …"

Archive for the ‘Kay: Modern Spectral Estimation, Theory and Application’ Category

In [1, p. 34 exercise 2.9] we are asked to prove that the rank of the complex n\times n matrix
\mathbf{A}=\sum\limits_{i=1}^{m} d_{i}\mathbf{u}_i\mathbf{u}_{i}^{H} (1)

where the \mathbf{u}_i are linearly independent complex n \times 1 vectors and the d_i‘s are real and positive, is equal to m if m \leq   n. Furthermore we are asked what the rank equals to if m > n. read the conclusion >
In exercise [1, p. 34 exercise 2.8] we are asked to find the inverse of the  n\times n hermitian matrix \mathbf{R} given by [1, (2.27)] by recursively applying Woodbury’s identity. This should be done by considering the cases where f_{1},f_{2} are arbitrary and where f_{1}=k/n, f_{2}=l/n for k,l beeing distinct integers in the range \left[ -n/2,n/2-1 \right] for n even and \left[ -(n-1)/2,(n-1)/2 \right] for n odd. read the conclusion >
In exercise [1, p. 34 exercise 2.7] it is requested to find the inverse of the real symmetric Toeplitz matrix
\mathbf{A} = \left[ {\begin{array}{*{20}c}
   1 & { - a} & {a^2 }  \\
   { - a} & 1 & { - a}  \\
   {a^2 } & { - a} & 1  \\
\end{array}} \right] (1)

and show that it is symmetric and persymmetric. read the conclusion >
In problem [1, p. 34 exercise 2.6] we are asked to prove that if \mathbf{A} and \mathbf{B} are complex n\times n Hermitian matrices and \mathbf{A}-\mathbf{B} is positive semidefinite, then \left[\mathbf{A}\right]_{ii} \geq \left[\mathbf{B}\right]_{ii} . read the conclusion >
In exercise [1, p. 34 exercise 2.3] we are asked to prove that the normalized DFT matrix given in [1, p. 21, (2.22)] is unitary. read the conclusion >

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