Chapter 6: Problem 11
Let \(A\) be an \(n \times n\) matrix and let \(B=A+I\). Is it possible for \(A\) and \(B\) to be similar? Explain.
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Chapter 6: Problem 11
Let \(A\) be an \(n \times n\) matrix and let \(B=A+I\). Is it possible for \(A\) and \(B\) to be similar? Explain.
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Let \(A\) be a Hermitian matrix and let \(\mathbf{x}\) be a vector in \(\mathbb{C}^{n} .\) Show that if \(c=\mathbf{x} A \mathbf{x}^{H},\) then \(c\) is real.
For each of the following matrices, compute the determinants of all the leading principal submatrices and use them to determine whether the matrix is positive definite: (a) \(\left(\begin{array}{rr}2 & -1 \\ -1 & 2\end{array}\right)\) (b) \(\left(\begin{array}{ll}3 & 4 \\ 4 & 2\end{array}\right)\) (c) \(\left(\begin{array}{rrr}6 & 4 & -2 \\ 4 & 5 & 3 \\ -2 & 3 & 6\end{array}\right)\) (d) \(\left(\begin{array}{rrr}4 & 2 & 1 \\ 2 & 3 & -2 \\ 1 & -2 & 5\end{array}\right)\)
Let \(A\) be an \(n \times n\) positive stochastic matrix with dominant eigenvalue \(\lambda_{1}=1\) and linearly independent eigenvectors \(\mathbf{x}_{1}, \mathbf{x}_{2}, \ldots, \mathbf{x}_{n},\) and let \(\mathbf{y}_{0}\) be an initial probability vector for a Markov chain \\[ \mathbf{y}_{0}, \mathbf{y}_{1}=A \mathbf{y}_{0}, \mathbf{y}_{2}=A \mathbf{y}_{1}, \dots \\] (a) Show that \(\lambda_{1}=1\) has a positive eigenvector \(\mathbf{x}_{1}\) (b) Show that \(\left\|\mathbf{y}_{j}\right\|_{1}=1, j=0,1, \ldots\) (c) Show that if \\[ \mathbf{y}_{0}=c_{1} \mathbf{x}_{1}+c_{2} \mathbf{x}_{2}+\cdots+c_{n} \mathbf{x}_{n} \\] then the component \(c_{1}\) in the direction of the positive eigenvector \(\mathbf{x}_{1}\) must be nonzero. (d) Show that the state vectors \(\mathbf{y}_{j}\) of the Markov chain converge to a steady-state vector. (e) Show that \\[ c_{1}=\frac{1}{\left\|\mathbf{x}_{1}\right\|_{1}} \\] and hence the steady-state vector is independent of the initial probability vector \(\mathbf{y}_{0}\)
Show that if \(A\) is a symmetric positive definite matrix, then \(A\) is nonsingular and \(A^{-1}\) is also positive definite.
Show that if \(A\) is skew Hermitian and \(\lambda\) is an eigenvalue of \(A,\) then \(\lambda\) is purely imaginary (i.e., \(\lambda=b i\) where \(b\) is real
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