Introduction to Quantum Mechanics · Problem A.8

Afterword — David J. Griffiths

Physics — Quantum Mechanics · matrices

Problem

Given the following two matrices: A=(−11i2032i−2i2),B=(20−i010i32),\mathsf{A} = \begin{pmatrix} -1 & 1 & i \\ 2 & 0 & 3 \\ 2i & -2i & 2 \end{pmatrix}, \quad \mathsf{B} = \begin{pmatrix} 2 & 0 & -i \\ 0 & 1 & 0 \\ i & 3 & 2 \end{pmatrix}, compute: (a) A+B\mathsf{A} + \mathsf{B}, (b) AB\mathsf{A}\mathsf{B}, (c) [A,B][\mathsf{A},\mathsf{B}], (d) A~\tilde{\mathsf{A}}, (e) A∗\mathsf{A}^*, (f) A†\mathsf{A}^\dagger, (g) det⁡(B)\det(\mathsf{B}), and (h) B−1\mathsf{B}^{-1}. Check that BB−1=1\mathsf{B}\mathsf{B}^{-1} = \mathbf{1}. Does A\mathsf{A} have an inverse?

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