The history of the discovery of electron spin and the Pauli principle and the mathematics of spin and quantum statistics are reviewed. Pauli’s theory of the spinning electron and some of its many applications in mathematics and physics are considered in more detail. The role of the fact that the tree-level gyromagnetic factor of the electron has the value g e = 2 in an analysis of stability (and instability) of matter in arbitrary external magnetic fields is highlighted. Radiative corrections and precision measurements of g e are reviewed. The general connection between spin and statistics, the CPT theorem and the theory of braid statistics, relevant in the theory of the quantum Hall effect, are described. “He who is deficient in the art of selection may, by showing nothing but the truth, produce all the effects of the grossest falsehoods. It perpetually happens that one writer tells less truth than another, merely because he tells more ‘truth’.” (T. Macauley, ‘History’, in Essays, Vol. 1, p 387, Sheldon, NY 1860) These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
The history of the discovery of electron spin and the Pauli principle and the mathematics of spin and quantum statistics are reviewed. Pauli’s theory of the spinning electron and some of its many applications in mathematics and physics are considered in more detail. The role of the fact that the tree-level gyromagnetic factor of the electron has the value g e = 2 in an analysis of stability (and instability) of matter in arbitrary external magnetic fields is highlighted. Radiative corrections and precision measurements of g e are reviewed. The general connection between spin and statistics, the CPT theorem and the theory of braid statistics, relevant in the theory of the quantum Hall effect, are described. “He who is deficient in the art of selection may, by showing nothing but the truth, produce all the effects of the grossest falsehoods. It perpetually happens that one writer tells less truth than another, merely because he tells more ‘truth’.” (T. Macauley, ‘History’, in Essays, Vol. 1, p 387, Sheldon, NY 1860) These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
“He who is deficient in the art of selection may, by showing nothing but the truth, produce all the effects of the grossest falsehoods. It perpetually happens that one writer tells less truth than another, merely because he tells more ‘truth’.” (T. Macauley, ‘History’, in Essays, Vol. 1, p 387, Sheldon, NY 1860) Dedicated to the memory of M. Fierz, R. Jost, L. Michel and V. Telegdi, teachers, colleagues, friends. 1 Introduction to ‘Spin ’ 1 It appears that the 21 st Century is witnessing a strong decline in Society’s (the public’s, the politicians’,...) interest in fundamental science, in particular in fundamental theoretical science based on precise mathematical reasoning. It is hard to imagine that a discovery like the deflection of light in the gravitational field of the sun, along with the underlying
Shortly after their introduction, the electron's Zweideutigkeit and Pauli's Ausschliessungsregel were embedded into a growing theoretical framework: from Fermi–Dirac statistics in 1926 (Section 4.2), to the non-relativistic quantum mechanics of the magnetic electron with Pauli's spin matrices in 1927 (Section 4.3); from Wigner and von Neumann's group theoretical derivation of the spin matrices in 1927 (Section 4.4), to Jordan's reinterpretation of Pauli's exclusion principle in terms of anticommutation relations for particle creation and annihilation operators in 1928 (Section 4.5), which paved the way for quantum field theory. The most important step in building up this theoretical framework was the transition from non-relativistic to relativistic quantum mechanics, with Dirac's equation for the electron in 1928 (Section 4.6), which finally allowed the derivation of the electron's spin with its anomalous magnetic moment and hence clarified in a conclusive way the origin of spectroscopic anomalies. The negative energy solutions of the Dirac equation, and Dirac's attempt to accommodate them via the hole theory in 1930, anticipated the experimental discovery of the antiparticle of the electron, the positron. Sections 4.7-4.9 reconstruct Pauli's sustained criticism of Dirac's hole theory. The history of this debate is intertwined with Pauli's search for a spin–statistics connection, which finally culminated in the spin–statistics theorem in 1940. With this theorem, the nomological shift from the status of a phenomenological rule to that of a fundamental scientific principle is finally completed. Introduction The year 1925 was the annus mirabilis for quantum mechanics.
Abstract This chapter describes spin-statistics theorem showcasing its importance in the stability of the Universe and in its explaining magnetism and dwells on the question of why there is no simple explanation that half-integer spin particles obey Pauli exclusion principle while the integer spin particles do not. There is a discussion of the bunching-antibunching of quantum particles known as the Hanbury Brown-Twiss (HBT) effect. Along with its inspiring history, this chapter also describes modern application of HBT in the ultracold atomic physics of the Bose–Einstein condensate. The chapter introduces anyons—particles with arbitrary spin that breaks fermion-boson dichotomy in two dimensions. The years 1925 and 1926 were turning points in the history of physics. In 1924, we had no quantum theory—that is, there was nothing that could substitute Newton’s equations to describe quantum systems.
These lectures were given in the framework of the ``Dixième séminaire rhodanien de physique'' entitled ``Le spin en physique'', given at Villa Gualino, Turin, March 2002. We have shown how the difficulties of interpretation of atomic spectra led to the Pauli exclusion principle and to the notion of spin, and then described the following steps: the Pauli spin with 2$\times$2 matrices after the birth of "new" quantum mechanics, the Dirac equation and the magnetic moment of the electron, the spins and magnetic moments of other particles, proton, neutron and hyperons. Finally, we show the crucial role of statistics in the stability of the world.
Quantum theory is perhaps the theory with the greatest predictive and explanatory success in all the history of physics. To name just a few of its countless achievements: it explains the stability of the stable atoms and nuclei and predicts the decay rates of the unstable ones; it accounts for the different manifestations of matter such as gaseous, liquid and solid, metallic and insulating, magnetic, superfluid and superconducting; it forms the basis of our chemical knowledge; and it provides the conceptual framework of all contemporary models for the fundamental constituents of matter. In addition, some of its predictions, for example that of the ‘electron spin g -factor’ in quantum electrodynamics, are perhaps the most accurate ones ever made in the history of science. Some of its predictions concern matter at extremely high energy and interactions between bits of matter at extremely short distances; others are about matter at extremely low energy and close to the zero of absolute temperature. As far as its technological applications are concerned, its insights are at the heart of the overwhelming technological progress in information technology in the past few decades, it explains why nuclear fission and fusion work as they do, and it forms the basis of the rapidly growing field of nanotechnology. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Following a short history of quantum mechanics, an outline of the contents of this book is given. A model of an electron is derived by time-averaging the motion of a “zittering” electromagnetic singularity, and by adding an apparent force in the form of surface tension in order to remove false electrostatic effects due to the model simplification. This model of a deformable droplet of charge is adopted as a working hypothesis, to see what are the consequences of such a model. The consequences are mathematically worked out and are shown to lead to a quantitatively correct replica of quantum behaviour. Matter waves are shown to correspond to trains of beats in the pulsation of the droplet, and the correct value of Planck's constant is derived. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.