I have a strong belief in the fact that understanding the limits of the Markovian process is required to fully elucidate the quantum-classical transition. This paper takes an interesting approach, but what’s a “spin star” model? They give what appears to be a mathematical description but never seem to say why the word “star” is used. First rule of writing papers (and of course one I regularly violate): define or explain as much as possible to increase the audience for your paper.
In this paper they didn’t give any background on the development of a tensor form of the Dirac equation. While not absolutely necessary, I am a firm believer in understanding the basic history of a problem and making sure papers on the problem include a paragraph or two of background. In this particular case, the Dirac equation was not originally written in tensor form and it was C.G. Darwin (Charles’ grandson) who first pointed this out. Eddington, inspired by Darwin’s observation, was the first to write the Dirac equation in tensor form and this work grew into his Fundamental Theory.
Finally, I’m working with a friend and colleague on a paper (possible two) on some forgotten aspects to the history of the laser. One that surprised me quite a bit was that improvement of astronomical instruments, namely detection of certain emission lines (e.g. the 21-cm line of hydrogen), was a factor driving the development of both masers and lasers. In fact one of the early papers was the undergraduate senior thesis of Bob Griffiths working under Bob Dicke. Dicke’s name, of course, will forever be associated with the cosmic microwave background, but it was in fact Dicke who first recognized that an optical cavity only required two mirrors and none of the “coffee can” ideas used in microwave cavities. A general recap of the other things we noticed will appear in the next Quantum Times.