DOI link for REPRESENTATION THEORY
REPRESENTATION THEORY book
The bra and ket vectors, as well as linear operators, are somewhat abstract mathematical quantities. Although the logic behind representing physical states and observables, respectively, by ket (or bra) vectors and self adjoint linear operators is perfect and, having developed the algebra for these quantities, we have been able to deduce therefrom some general results, identities and corollaries, yet these abstract quantities are not the ones in terms of which we can carry out numerical calculations and arrive at numbers to be compared with the experimental results. So we ask if it is possible to find more convenient mathematical quantities to represent ket vectors and linear operators that can be handled more conveniently. The answer is in the affirmative.