The European Physical Journal H最新文献

The main focus is on the Hamilton–Jacobi techniques in classical general relativity that were pursued by Peter Bergmann and Arthur Komar in the 1960s and 1970s. They placed special emphasis on the ability to construct the factor group of canonical transformations, where the four-dimensional diffeomorphism phase space transformations were factored out. Equivalence classes were identified by a set of phase space functions that were invariant under the action of the four-dimensional diffeomorphism group. This is contrasted and compared with approaches of Paul Weiss, Julian Schwinger, Richard Arnowitt, Stanley Deser, Charles Misner, Karel Kuchař—and especially the geometrodynamical program of John Wheeler and Bryce DeWitt where diffeomorphism symmetry is replaced by a notion of multifingered time. The origins of all of these approaches are traced to Elie Cartan’s invariant integral formulation of classical dynamics. A related correspondence concerning the thin sandwich dispute is also documented.

Gullstrand’s and Oseen’s papers on the Gullstrand–Painlevé coordinates are translated from German into English, and their significance and their connection with Einstein’s Nobel prize are commented upon.

We reconstruct the genesis of the CPT theorem in quantum field theory from the first proofs of the spin-statistics theorem in 1939/1940 to the discovery of parity violation in 1957. Centrally, we highlight that the original motivation for pursuing the CPT theorem lay primarily in the attempt to identify the correct formulation of time reversal in relativistic quantum field theories.

The present year 2021 celebrates the 75th anniversary of the nuclear magnetic resonance method (NMR), which has had an immense importance for several branches of physics, chemistry and biology. The splitting of resonances and the shifts in their positions are seemingly inexhaustible sources of information for organic chemistry and biology. It was first introduced for the study of nuclear spins and their associated magnetic properties and when it was observed that resonance lines were broadened by the action of fluctuating local magnetic fields it was first seen as a limitation for the exact determination of nuclear properties. However, it was soon realized that the broadening contained important information on the dynamics of atoms, molecules or cooperative spin systems surrounding the nuclei and spin perturbations became a well-developed tool for investigation of internal dynamics in liquids and solids, over time-ranges from seconds down to femtoseconds. The present article is an attempt to review this latter line of development and to pick out a series of examples of internal dynamics in different physical systems published over the past 75 years. Examples include motions of particles in solids, magnetic resonance imaging (MRI), critical phenomena around phase transitions, functioning of biomolecules and recent applications to spintronics and quantum computing. Other spin-based spectroscopies followed in the tracks of NMR with use of electron spins (in electron spin resonance ESR also called electron paramagnetic resonance EPR, and ferromagnetic resonance, FMR), excited nuclear states (by observation of perturbations in angular correlation of gamma-rays, PAC) and later also muon spins (muon spin relaxation, MuSR), from which other examples are selected.

At the turn of the 1980s and 1990s, on the eve of the great leap in scale from the resonant bars to the long-baseline interferometers LIGO and Virgo, the four European groups then engaged in the field of interferometric gravitational wave detection in Germany, UK, France and Italy tried to set up a common strategy, with the aim of establishing a network of three long-based antennas in Europe. The paper analyzes the main causes of the failure of those early plans. An attempt is made to outline the parallels and differences with the current times, on the eve of the new leap of scale toward the third generation of gravitational wave interferometers, while the negotiations for the European-born project Einstein Telescope are taking place.

We carry out a detailed analysis of the contribution of the outstanding liquid crystal scientist Hans Zocher to the study of mineral mesophases. The work is placed in the context of progress achieved by the liquid crystal scientists, who conducted research both before and after Zocher. The article also includes a brief scientific biography of Zocher.

In this paper, we deal with the historical origins of Fermi–Dirac statistics, focusing on the contribution by Enrico Fermi of 1926. We argue that this statistics, as opposed to that of Bose–Einstein, has been somewhat overlooked in the usual accounts of the old quantum theory. Our main objective is to offer a critical analysis of Fermi’s seminal paper and its immediate impact. Secondly, we are also interested in assessing the status of the particle concept in the years 1926–1927, especially regarding the germ of quantum indistinguishability. We will see, for example, that the first applications of the Fermi–Dirac statistics to the study of metals or stellar matter had a technical nature, and that their main instigators barely touched upon interpretative matters. Finally, we will discuss the reflections and remarks made in these respects in two famous events in physics of 1927, the Como conference and the fifth Solvay congress.

Boltzmann’s reply to Loschmidt’s reversibility paradox (1877) has baffled many readers, owing to imprecise language and unproven assumptions. Based on a new translation and detailed commentary, it will be shown that this text nevertheless contains the essentials of a correct, insightful interpretation of thermodynamic irreversibility in statistico-mechanical context.