The European Physical Journal H最新文献

This paper provides a detailed and unified historical account of early debates over wave-function realism, the modern term for the view that the wave function of quantum theory is physically real. As this paper will show, the idea of physical waves associated with particles had its roots in work by Einstein and de Broglie, who both originally thought of these waves as propagating in three-dimensional physical space. De Broglie quickly turned this wave–particle duality into an early pilot-wave theory, on which a particle’s associated “phase wave” piloted or guided the particle along its trajectory. Schrödinger built on de Broglie’s phase-wave hypothesis to provide a comprehensive account of the nascent quantum theory. However, Schrödinger’s new “undulatory mechanics” came at the cost of replacing de Broglie’s phase waves propagating in physical space with a wave function propagating in a system’s abstract configuration space. The present work will argue that this move from three-dimensional physical space to a many-dimensional configuration space was a decisive reason why the founders of quantum theory uniformly abandoned the physical reality of the wave function. This paper will further clarify that de Broglie introduced two distinct pilot-wave theories, and will then argue that it was Bohm’s rediscovery of the second of these two pilot-wave theories over two decades later, as well as Bohm’s vociferous defense of wave-function realism, that were responsible for resurrecting the idea of an ontological wave function. Finally, this paper will describe how the influence of Schrödinger and Bohm ended up playing a central role in Everett’s development of the many worlds interpretation.

In quantum mechanics, the concept of entropy was introduced by von Neumann in his canonical 1932 book. More than seventy years later, a debate has developed within the Philosophy of Science community, about the relevance of a thought experiment introduced by von Neumann. This debate is presently still open, and has developed along various paths. The present paper focuses on this thought experiment. It is proposed first to respect the approach followed by von Neumann. It is then stressed that when thermodynamic arguments implying exchanges of matter between parts of the system of interest are introduced into its analysis, these exchanges should be analyzed with the right thermodynamic concept. This concept, introduced more than 140 years ago, is now called the chemical potential. In the literature discussed in the present paper, that failure to use the chemical potential concept first led to the claim of wrong thermodynamic results. A second consequence was a premature introduction of quantum measurements together with an undue rejection of the step with a thermodynamic treatment developed by von Neumann in his analysis of his experiment. The analysis of his thought experiment with phenomenological thermodynamics led von Neumann to propose that the entropy of a quantum system in a state described by the density operator (rho ) should be (-<Lnrho >=-Tr(rho Lnrho ) )(or ( -k<Lnrho>) in non-reduced units, k: the Boltzmann constant, Tr: the Trace). The present paper shows that this proposal by von Neumann was right.

This contribution, based on a talk delivered at the Workshop Ukrainian Contributions to Particle Physics: History and Prospects, offers a personal memoir of Gleb Wataghin (1899–1986) and his role in the institutional development of modern physics at the University of São Paulo and in Brazil. Born in what is now Ukraine and educated in Turin, Wataghin joined the newly created university in São Paulo in 1934, where he helped establish a physics department and research school. He developed an internationally recognized cosmic-ray program and encouraged exchanges of students and researchers with leading scientific centres abroad. His students included Cesar Lattes, who participated in the discovery of the pion in 1947. After returning to Italy in 1949, Wataghin rebuilt the physics department in Turin while preserving strong ties with Brazil. This memoir is not intended as an archival study in the history of science. Instead, it is written from the perspective of a physicist who knew Wataghin in Campinas and whose career in ultra-high-energy cosmic rays traces back to him through her PhD advisor, Cesar Lattes. Viewed through this scientific lineage, Wataghin’s legacy combines scientific vision, institutional commitment, and intellectual leadership.

This work analyzes the extent to which the “blurred orbits” of the current model for the atom, drafted by Heisenberg in 1926, fits with the image of a bunch of wandering electrons around a nucleus. We will deal with early appearances of the concept of indistinguishable particles within the frame of quantum mechanics. Few studies have examined the use of this concept in Heisenberg’s 1926 papers on helium, in contrast to the large number of studies on its use in Bose–Einstein’s 1924 papers. We will discuss to what extent Heisenberg’s approach leads to a purely statistical interpretation of this concept. We will also study the viewpoint of Dirac, who dealt with the same topic a few months later. Although the indistinguishability of the electrons and indeterminacy are common explanations for the blurring of electron orbits, we argue that such an image is an oversimplification which masks interesting aspects of the dynamics of bound electrons, exchange processes, and the role of superposed exchanged configurations.

In this paper, I recount the early experiments leading to the observation of the two-photon interference phenomenon commonly referred to as the “Hong–Ou–Mandel effect,” observed in 1987 at the University of Rochester by Chung Ki Hong, Zhe-Yu Ou, and Leonard Mandel, and now widely used for quantum technologies. I show that Mandel and his collaborators originally designed their experiment not to probe the nonclassical properties of radiation, as one might think, but to perform ultrahigh-precision timing measurements on photon pairs produced through a nonlinear optical process, namely spontaneous parametric down-conversion. More broadly, I argue that the Hong–Ou–Mandel experiment resulted from the convergence of three distinct lines of research: nonlinear optics, the quantum properties of radiation, and, more unexpectedly, the foundations of quantum mechanics. Within this framework, I bring to light the work of physicists whose names do not appear in the acronym “HOM,” but whose contributions proved crucial to the demonstration of two-photon interference—notably Stephen Friberg and Rupamanjari Ghosh within Mandel’s laboratory, Yanhua Shih and Carroll Alley at the University of Maryland, and John Rarity and Paul Tapster in England.

The 1935 Einstein–Podolsky–Rosen (EPR) paper, “Can Quantum–Mechanical Description of Physical Reality Be Considered Complete?”, stands as a landmark in the foundational debates over quantum mechanics. While the paper has since become one of Einstein’s most cited works, it initially received little attention, and the feature of non-locality, which was central to the argument in the paper, was largely neglected for decades. In this paper, I offer two reasons for this early neglect of non-locality in the immediate aftermath of EPR. First, early responses to the EPR paper defended the completeness of quantum mechanics by reformulating the thought experiment the authors had presented, thereby obscuring the feature of quantum mechanics the authors had wished to highlight. Bohr’s influential reply, for instance, substituted the specific thought experiment presented by EPR with the two-slit experiment, thus suppressing the entanglement between spatially separated systems. A second reason for the marginalization of non-locality was the tendency to see Einstein’s critique of quantum mechanics as proceeding from a commitment to determinism, though this in fact played no role in the EPR paper or in his later writings and correspondence. This paper argues that the failure to recognize non-locality was partly a result of the rhetorical manoeuvring by EPR’s critics, but also to a broader philosophical climate dominated by concerns over determinism, which effectively eclipsed all other conceptual issues, Only with Bell’s theorem in the 1960s did non-locality return as a serious focus of foundational inquiry.

The determination of the tropical year constitutes a fundamental problem at the intersection of celestial mechanics, astronomy, and historical timekeeping. As a physically defined quantity arising from the combined effects of orbital motion and axial precession, the tropical year provides the natural reference for civil calendar systems. This study examines the historical development of Julian-derived calendars as successive approximations to the tropical year, interpreted within a unified physical and mathematical framework. From the Julian calendar through the Gregorian reform to the Revised Julian system of Milutin Milanković, these calendars are analyzed as rational approximations to a slowly varying astronomical quantity. Within this framework, an adjusted Julian scheme is introduced as a theoretical extension of this tradition. Rather than constituting a proposal for reform, it serves to elucidate the limiting behavior of fixed calendrical systems when applied to a time-dependent physical quantity. The analysis demonstrates that calendar design is inherently epoch-dependent and reflects a continuous interaction between physical theory, mathematical structure, and historical practice. The results contribute to the understanding of timekeeping as a physical as well as cultural problem.

The tumultuous history of measurements of the deceleration parameter q₀, one of a few key cosmological parameters, yields historical, theoretical, and epistemological reasons for studying it. A wide variety of observational methods and techniques, combined with evolutionary, astrophysical, cosmological, and observational selection effects, as well as various, and often contradictory assumptions behind various models, led to widely differing values of q₀ (from − 2 to + 36!) over a span of half a century. Moreover, there was an inevitable epistemic trade-off between observational sensitivity and statistical wealth of data. While there certainly was a diversity of theoretical predictions for q₀ among various cosmological models, our analysis indicates that the main historical cause of such a large and confusing scatter of empirical values was the persistent failure to appreciate the scope and tempo of evolutionary change in various astronomical sources. We survey and sort out this historical context, providing some preliminary general lessons for ongoing and future endeavors of similar complexity.

The development of scintillation materials science has been profoundly shaped by the work of Ludmyla Nagorna from the Institute for Single Crystals in Kharkiv. In 1992, Nagorna proposed the use of lead tungstate (PbWO₄) crystals for particle physics experiments. Her belief in the potential of PbWO₄, combined with her persistence in developing methods for growing high-quality large crystals was instrumental in convincing the global scientific community of the material's promise. Today, these crystals are at the heart of the electromagnetic calorimeters in the ALICE and CMS detectors at CERN’s Large Hadron Collider (LHC), where they have been essential for data collection since 2008. Nagorna's scientific legacy continues through her research group’s ongoing development of next-generation scintillation single crystals. Besides high-energy calorimetry, attention is currently focused on low-background nuclear spectrometry, a field requiring materials with extreme radiopurity and unique physical characteristics. These scintillators are designed for experiments targeting rare physical phenomena at the frontier of the Standard Model. This research includes the search for non-baryonic dark matter interactions and the detection of neutrinoless double beta decay. Furthermore, these materials are being optimized for investigating the radioactive decay of long-lived isotopes and for studying neutrinos from core-collapsing supernovae stars using coherent elastic neutrino-nuclear scattering (CEνNS).

The special theory of relativity as we understand it today owes much to the figure of Hermann Minkowski. His are several fundamental concepts that appear in current textbooks. However, his contributions are not always recognized. Furthermore, some historians of science judge him with a certain severity, undermining the importance of his contributions. He himself provoked this attitude to some extent by arguing in his articles that mathematicians were in a better position than physicists to understand the new theory. This article is devoted to the figure of Minkowski in two aspects. On the one hand, we analyze the status of Minkowski’s original ideas in the special theory of relativity as currently studied and taught. We show that some textbooks of reference in physics do not properly acknowledge the contributions of Minkowski. On the other hand, we will illustrate with some examples how the figure of Minkowski is perceived by historians. We see that even today he has his supporters and detractors.