Heisenberg notation

This expression may again be written in a variety of forms, e.g., in terms of the invariant trace, or in terms of the Heisenberg notation,... 

Classical moment expressions. Spectral moments expressed in the Heisenberg notation can be immediately interpreted in terms of classical physics. For a discussion of classical moments, we consider the moments Af of the spectral density, J co), which are related to the moments, y , of the absorption coefficient, a(co), according to Eq. 5.8. By combining that equation with Eq. 5.16, we get at once... 

For the classical Heisenberg model and using the notations of Eq. 1, the correlation function F is given by ... 

P.A.M. Dirac, who shared the 1933 Nobel prize for physics with Schrodinger (the 1932 price went to Heisenberg), was one of the greatest pioneers of quantum mechanics. Most of his achievements entered textbooks so fast that his original papers are hardly cited. Nobody, who uses Dirac s bra-ket notation or his function would cite the original references [1]. The same is true of Dirac s time-dependent perturbation theory [2] or of the Dirac equation [3], the basis of relativistic quantum mechanics or of his subsequent work on positrons and holes [4]. 

With this notation, Heisenberg s expression reads... 

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