Since Pauli’s hypothesis of their existence in 1930, neutrinos never ceased to bring into play novel ideas and to add new pieces of physics in the whole picture of fundamental interactions. They are only weakly interacting and, at odds with Standard Model’s predictions, have a mass less than one millionth of the electron mass, which makes the investigation of their properties very challenging. The issue of the measurement of neutrino’s rest mass gained a wider and wider consensus since its discovery through neutrino oscillations in 1998. Various neutrino sources are available for experiments, ranging from nuclear collisions of cosmic rays in the Earth atmosphere and supernova explosions to neutrino beams produced by accelerators and power reactors. These suggest different approaches to the experimental detection and measurement of the absolute value of the neutrino mass. In this paper, we retrace the intriguing story of this endeavor, focusing mainly on direct mass determination methods. The puzzling issue of the nature of massive neutrinos is addressed as well with explicit reference to the phenomenon of double beta-decay as a viable experimental tool to discriminate between Dirac’s and Majorana’s nature.

Abstract Classical and quantum mechanics are two very different theories, each describing the world within its own range of validity. It is often stated that classical mechanics emerges from quantum mechanics in a certain limit. This is known as the correspondence principle. According to Planck’s version of the correspondence principle, classical mechanics is recovered when the limit in which a dimensionless parameter containing Planck’s constant h goes to zero is taken, while Bohr’s version entails taking the limit of large quantum numbers. However, despite what is usually stated in textbooks, the relation between the two theories is much more complex to state and understand. Here we deal with this issue by analysing some key examples, in some of which also the analogously subtle relation between wave and geometric optics is considered. Implications for quantum mechanics teaching at undergraduate level are carefully discussed.

We demonstrate the construction and utilization of an affordable apparatus using readily available materials to accurately measure in a quantitative manner the wavelengths reflected by a compact disc (CD) under skimming light rays. In fact, only a limited number of wavelengths can be revealed when light rays from a white lamp are directed at a CD (or a DVD) in a manner that specifically selects the rays that graze the surface of the horizontally held disc. We compare the results with the ones obtained with a commercial spectrometer, finding that they are in good agreement among them and with the theoretical predictions.

A teaching-learning module, aimed at introducing basic concepts of general relativity at the high school level, is proposed. Emphasis is on conceptual rather than technical aspects, and only familiarity with simple calculus is required on the mathematical side. The starting point is a critical overview of the principles of Newtonian mechanics, in particular the role of fictitious forces, as well as of the limits of special relativity. Part of the module is devoted to the discussion and the reproduction of key thought or real experiments, for example experiments involving non-inertial frames, or the Einstein elevator.

The onset and the development of the concept of exchange force in quantum physics are historically reconstructed, starting from Heisenberg's seminal contributions in 1926 and going through the great developments in nuclear physics, which allowed the emergence of the idea of force mediating virtual quanta. Although most of such work was performed in Europe, the last and decisive effort in this long path was carried out by Japanese scientists in the 1930s. This is the main focus of the present work, which retraces the achievements of Yukawa and Tomonaga, whose results and mutual interactions are carefully analyzed and related to those of European physicists.

It is shown that the non-unitary Newtonian gravity (NNG) model admits a simple interpretation in terms of the Feynman path integral, in which the sum over all possible histories is replaced by a summation over pairs of paths. Correlations between different paths are allowed by a fundamental decoherence mechanism of gravitational origin and can be interpreted as a kind of communication between different branches of the wave function. The ensuing formulation could be used in turn as a motivation to introduce non-unitary gravity itself.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation R. De Luca, M. Di Mauro, O. Fiore, A. Naddeo; Erratum: “A compact disc under skimming light rays” [Am. J. Phys. 86(3), 169 (2018)]. American Journal of Physics 1 June 2023; 91 (6): 487. https://doi.org/10.1119/5.0146809 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAmerican Association of Physics TeachersAmerican Journal of Physics Search Advanced Search |Citation Search

The broad debate on foundational issues in quantum mechanics, which took place at the famous 1957 Chapel Hill conference on The Role of Gravitation in Physics, is here critically analyzed with an emphasis on Richard Feynman’s contributions. One of the most debated questions at Chapel Hill was whether the gravitational field had to be quantized and its possible role in wave function collapse. Feynman’s arguments in favor of the quantization of the gravitational field, based essentially on a series of gedanken experiments, are here discussed. Then the related problem of the wave function collapse, for which Feynman hints to decoherence as a possible solution, is discussed. Finally, another topic is analyzed, concerning the role of the observer in a closed Universe. In this respect, Feynman’s many-worlds characterization of Everett’s approach at Chapel Hill is discussed, together with later contributions of his, including a kind of Schrödinger’s cat paradox, which are scattered throughout the 1962-63 Lectures on Gravitation. Philosophical implications of Feynman’s ideas in relation to foundational issues are also discussed.

An account of Richard Feynman’s work on gravitational waves is given. Feynman’s involvement with this subject can be traced back to 1957, when he attended the famous Chapel Hill conference on the Role of Gravitation in Physics. At that conference, he presented in particular the celebrated sticky bead argument, which was devised to intuitively argue that gravitational waves must carry energy, if they exist at all. While giving a simple argument in favor of the existence of gravitational waves, Feynman’s thought experiment paved the way for their detection and stimulated subsequent efforts in building a practical detecting device. Feynman’s contributions were systematically developed in a letter to Victor Weisskopf, completed in February 1961, as well as in his Caltech Lectures on Gravitation, delivered in 1962-63. There, a detailed calculation of the power radiated as gravitational radiation was performed, using both classical and quantum field theoretical tools, leading to a derivation of the quadrupole formula and its application to gravitational radiation by a binary star system. A comparison between the attitudes of Feynman and of the general relativity community to the problems of gravitational wave physics is drawn as well.

During typical general relativity courses, the so-called frame-dragging effect is explained by emphasizing the presence of a gravitational Coriolis-like force term. The key difference is that, unlike the usual Coriolis force, this is not a fictitious force but agravitational force caused by the rotating body. In general, textbooks do not discuss also the possibility of a gravitational centrifugal-like force. In this paper, which has a didactic aim, we analyze this further gravitational term. The analysis we perform can be valuable in undergraduate courses of general relativity.

The response of a detector carried by an observer in a circular motion at a constant angular velocity to an incident plane wave is considered here. It is shown that, despite a formal analogy with Unruh effect, a power spectrum is obtained, which is very different from the thermal one. We find a discrete spectrum depending on the frequency of the original plane wave and on the frequency of the rotating motion of the observer. We propose a possible experiment to verify the predicted effect using Josephson junctions.

Many topics in modern physics are currently included in the curricula of the last year of high school in many countries, as for example in Italy. A consistent part of the curriculum should be devoted to the special theory of relativity. A particularly interesting phenomenon in this framework is the so-called Terrell–Penrose effect (TPE), which the students may find especially intriguing in view of its association with the name of one of the 2020 Nobel Prize winners. Although it is not possible to rigorously analyse this optical effect at the high school level, we show that is possible to tackle the topic anyway, during some of the in-depth lectures on modern physics that can be organized for high school students in our area. In particular, we found that this physical context can be useful for stimulating young students to use goniometric relations. Since trigonometry is a very important topic in mathematics, being always present in the written test for the final graduation exam, it is useful to show how it can be fruitfully used to tackle physical problems. The aim of this paper is to summarize our lecture on the TPE effect in the classroom, where we consider the case of a rod moving at high constant velocity, oriented with different angles with respect to the observer, and the case of a uniformly accelerated body (in the Newtonian approximation).

A teaching-learning sequence designed to introduce some fundamental concepts of quantum physics to high school teachers is proposed. Some parts of the proposal can be adapted to be taught to advanced high school students themselves. The inspiration came from the recognition of the fact that the roots of many pivotal concepts of quantum physics, namely light quanta, wave-particle duality, and probability, were introduced for the first time in some paper by Albert Einstein. Moreover, this was done in a characteristically deep and illuminating way. A critical study of Einstein’s papers should therefore be useful for teachers and students as well, in view of the fact that such concepts are often misconceived. The teaching-learning sequence can supplement usual historically oriented treatments of elementary quantum physics and can in turn be complemented by a discussion of some elementary tools of statistical physics, which may be not part of the learners’ background. Preliminary results obtained with both teachers and pupils in high schools in southern Italy, which are very promising, are presented.

A detailed and updated account is given of De Filippo’s non-unitary fourth-derivative gravity and its Newtonian limit, by pointing out the crucial role of non-unitarity in addressing transition to classicality and specifically localization of macroscopic bodies, microscopic foundation of the second law of thermodynamics, and measurement problem; furthermore, it provides a quantum field theory of gravity possibly not only renormalizable but even finite, with a cancelation mechanism analogous to supersymmetric field theories where cancelations are due to superpartners whereas here to negative energy fields. Finally, this non-unitary proposal addresses the long-standing black hole information loss problem and this according to an unorthodox view at variance with the mainstream endeavors to save unitarity at the expense of changing general relativity in vague unspecified ways. Last but not least, motivations and conceptual framework are given, as the author could not present them in his first papers written in a hurry since he was aware that in a little time he would be unable to use PC keyboard or to write on paper due to the progressing of motor neuron disease.

Wave-function collapse following a measurement process is a longstanding controversial issue of quantum physics. It introduces an element of strong non-linearity and irreversibility in an otherwise unitary and reversible dynamics. Several proposals of modification of Quantum Mechanics have been put forward in the past few decades in order to solve such a dichotomy. Among them, some approaches and explicit models considered the possible role of gravity in the wave-function collapse as a result of the incompatibility of general relativity and unitary time evolution of Quantum Mechanics. In this contribution we present some results based on one of such models, De Filippo's Nonunitary Newtonian Gravity, which shows several appealing features: while reproducing at a macroscopic level the ordinary Newtonian interaction, it presents a mass threshold for gravitational localization. In particular, it provides a mechanism for the evolution of macroscopic coherent superpositions of states into ensembles of pure states. On one hand, we show the results of a numerical simulation of a simple system, i.e. two particles in a harmonic trap interacting via an 'electrical' delta-like potential and gravitational interaction. Starting from an energy eigenstate within the ordinary setting, we find that, while energy expectation remains constant, a slow net variation of the von Neumann entropy for the system as a whole takes place, with a small modulation induced on the relative entanglement entropy of the two particles. On the other hand, we explicitly show how a one-parameter generalization of the model, reproducing the nonlinear Newton-Schrodinger equation as the parameter goes to infinity, is free from any causality-violation problem for any finite value of it.

We retrace an ab initio relativistic derivation of the inhomogeneous Maxwell's equations that was developed by Feynman in unpublished notes, clarifying the analogies and the differences with analogous treatments present in the literature. Unlike the latter, Feynman's approach stands out because it considers electromagnetic potentials as primary, reflecting his ideas about the quantum foundations of electromagnetism.