The European Physical Journal H最新文献

This essay concerns the study of gravitation and general relativity at King’s College London (KCL). It covers developments since the nineteenth century but its main focus is on the quarter of a century beginning in 1955. At King’s research in the twenty-five years from 1955 was dominated initially by the study of gravitational waves and then by the investigation of the classical and quantum aspects of black holes. While general relativity has been studied extensively by both physicists and mathematicians, most of the work at King’s described here was undertaken in the mathematics department.

We analyze Feynman’s work on the response of an amplifier performed at Los Alamos and described in a technical report of 1946, as well as lectured on at the Cornell University in 1946–47 during his course on Mathematical Methods. The motivation for such a work was Feynman’s involvement in the Manhattan Project, for which the necessity emerged of feeding the output pulses of counters into amplifiers or several other circuits, with the risk of introducing distortion at each step. In order to deal with such a problem, Feynman designed a theoretical “reference amplifier”, thus enabling a characterization of the distortion by means of a benchmark relationship between phase and amplification for each frequency, and providing a standard tool for comparing the operation of real devices. A general theory was elaborated, from which he was able to deduce the basic features of an amplifier just from its response to a pulse or to a sine wave of definite frequency. Moreover, in order to apply such a theory to practical problems, a couple of remarkable examples were worked out, both for high-frequency cutoff amplifiers and for low-frequency ones. A special consideration deserves a mysteriously exceptional amplifier with best stability behavior introduced by Feynman, for which different physical interpretations are here envisaged. Feynman’s earlier work then later flowed in the Hughes lectures on Mathematical Methods in Physics and Engineering of 1970–71, where he also remarked on causality properties of an amplifier, that is on certain relations between frequency and phase shift that a real amplifier has to satisfy in order not to allow output signals to appear before input ones. Quite interestingly, dispersion relations to be satisfied by the response function were introduced.

The Einstein Archives contain a considerable collection of calculations in the form of working sheets and scratch paper, documenting Einstein’s scientific preoccupations during the last three decades of his life until his death in 1955. This paper provides a brief description of these documents and some indications of what can be expected from a more thorough investigation of these notes.

This paper offers background and perspective on a little-known memoir by Ludvig Lorenz on light scattering by spheres, which was published in Danish in 1890. It is a companion to an English translation of the memoir appearing separately. Apart from introducing Lorenz and some of his contributions to optics and electrodynamics, the paper focuses on the emergence, content and reception of the 1890 memoir and its role in what is often called the Lorenz-Mie theory. In addition to the historical analysis, the paper illuminates aspects of modern Lorenz-Mie theory and its many applications, with an eye to Lorenz’s original work.

This paper aims at contributing to the history of early computational statistical mechanics. The topic concerns the physics near a critical point and how long it took for Monte Carlo (MC) simulations to be seriously considered by the community as a valid and important tool to analyze critical phenomena. We will focus on one of the leading scientific figures behind this effort: Kurt Binder, whose scientific achievements were acknowledged by the award of the Boltzmann medal in 2007. Kurt Binder, who is now 75, has retired, some years ago, from a Professorship at the University of Mainz.

In the mid-1980s, the cost of investment in infrastructure for particle accelerators and colliders at the highest energy had risen to such level that the host laboratory (CERN) could no longer afford the cost of development of new detector technology required for the experiments. Large particle colliders were identified by the tools of the future for high-energy physics research, and a long-term view of their development was already conjured up in the late 1970s. It was based on this appraisal that a separate project, called LAA, which addresses the development of the technologies that are required to fully exploit the potential of the new infrastructure, was conceived. The project, specifically funded by the Italian government, centers on advanced microelectronics, and it is largely thanks to this development that the experiments at the large hadron collider (LHC) at CERN were equipped with performant detectors. Some of this equipment features in (i) the Italian School project to observe Extreme Energy Events (EEE), (ii) the Alpha Magnetic Spectrometer (AMS) experiment in the International Space Station and (iii) the time-of-flight (TOF) detector of the LHC heavy ion experiment ALICE at CERN. Several spin-offs for applications in medical instrumentation and advanced electronics were also initiated by development in the framework of the LAA project. The project also covers development work on superconductors and high field superconducting magnets for a future very LHC. The impact of LAA on technology is widely acknowledged.

élie Cartan’s “généralisation de la notion de courbure” (1922) arose from a creative evaluation of the geometrical structures underlying both, Einstein’s theory of gravity and the Cosserat brothers generalized theory of elasticity. In both theories groups operating in the infinitesimal played a crucial role. To judge from his publications in 1922–24, Cartan developed his concept of generalized spaces with the dual context of general relativity and non-standard elasticity in mind. In this context it seemed natural to express the translational curvature of his new spaces by a rotational quantity (via a kind of Grassmann dualization). So Cartan called his translational curvature “torsion” and coupled it to a hypothetical rotational momentum of matter several years before spin was encountered in quantum mechanics.

The traveling-wave tube is a critical subsystem for satellite data transmission. Its role in the history of wireless communications and in the space conquest is significant, but largely ignored, even though the device remains widely used nowadays. This paper presents, albeit non-exhaustively, circumstances and contexts that led to its invention, and its part in the worldwide (in particular in Europe) expansion of TV broadcasting via microwave radio relays and satellites. We also discuss its actual contribution to space applications and its conception. The originality of this paper comes from the wide period covered (from first slow-wave structures in 1889 to present space projects) and from connection points made between this device and commercial exploitations. The appendix deals with an intuitive pedagogical description of the wave–particle interaction.