Search

Quantum physics is a long established content in high school curricula. More recently, alternative approaches based on information-theoretical formulations of quantum theory have been discussed, in which conceptual emphases change in comparison to established didactical approaches. In particular, the notions of "superposition" and "entanglement" are brought into the center of discussion in these approaches. Likewise, there is a broad public interest in the new applications of quantum physics such as quantum computing, which has led to a variety of popular depictions. In this paper we identify common inaccuracies and errors in these representations, explain the technical background and make first recommendations to avoid misunderstandings. Our initial focus is on the notion of "superposition". -- Die Quantenphysik ist seit vielen Jahren ein etablierter Inhalt der Oberstufenphysik. In j\"ungerer Zeit werden alternative Zug\"ange \"uber die informationstheoretische Formulierung der Quantentheorie diskutiert, bei denen sich konzeptionelle und begriffliche Schwerpunkte im Vergleich zu etablierten Elementarisierungen ver\"andern. Im Besonderen die Begriffe "Superposition" und "Verschr\"ankung" werden bei diesen Zug\"angen in das Zentrum der Diskussion ger\"uckt. Ebenfalls besteht ein breites \"offentliches Interesse an den neuen Anwendungen der Quantenphysik wie dem Quanten-computer, das zu einer Vielzahl popul\"arer Darstellungen gef\"uhrt hat. In dieser Arbeit identifizieren wir verbreitete Ungenauigkeiten und Fehler in diesen Darstellungen, erl\"autern den fachlichen Hintergrund und machen erste Empfehlungen, um Missverst\"andnisse zu vermeiden. Unser Schwerpunkt liegt dabei zun\"achst auf dem Begriff der "Superposition"., Comment: in German language

Interference of more and more massive objects provides a spectacular confirmation of quantum theory. It is usually regarded as support for "wave-particle duality" and in an extension of this duality even as support for "complementarity". We first give an outline of the historical development of these notions. Already here it becomes evident that they are hard to define rigorously, i.e. have mainly a heuristic function. Then we discuss recent interference experiments of large and complex molecules which seem to support this heuristic function of "duality". However, we show that in these experiments the diffraction of a {\em delocalized} center-of-mass wave function depends on the interaction of the {\em localized} structure of the molecule with the diffraction element. Thus, the molecules display "dual features" at the same time, which contradicts the usual understanding of wave-particle duality. We conclude that the notion of "wave-particle duality" deserves no place in modern quantum physics., Comment: 15 pages, 1 figure

In 1900 Lord Kelvin identified two problems for 19th century physics, two "clouds" as he puts it: the relative motion of the ether with respect to massive objects, and Maxwell-Boltzmann's theorem on the equipartition of energy. These issues were eventually solved by the theory of special relativity and by quantum mechanics. In modern quotations, the content of Kelvin's lecture is almost always distorted and misrepresented. For example, it is commonly claimed that Kelvin was concerned about the UV-catastrophe of the Rayleigh-Jeans law, while his lecture actually makes no reference at all to blackbody radiation. I rectify these mistakes and explore reasons for their occurrence., Comment: 10 pages, no figures. Accepted by the American Journal of Physics

On April 7, 2001 the Muon g-2 Experiment at Fermilab presented its first results which lead to a 4.2$\sigma$ discrepancy between the world average of the muon anomalous magnetic dipole moment and the standard model prediction of this quantity. I take issue with the statistical meaning of this finding., Comment: 3 pages, 1 idea, no figures. In v2 the proper meaning of the p-value has been made more explicit

According to the received view Feynman diagrams are a bookkeeping device in complex perturbative calculations. Thus, they do not provide a representation or model of the underlying physical process. This view is in apparent tension with scientific practice in high energy physics, which analyses its data in terms of `channels'. For example the Higgs discovery was based on the observation of the decay $H \rightarrow \gamma\gamma$ -- a process which can be easily represented by the corresponding Feynman diagrams. I take issue with this tension and show that on closer analysis the story of the Higgs discovery should be told differently., Comment: 23 pages, 6 Figures

Planck's law for black-body radiation marks the origin of quantum theory and is discussed in all introductory (or advanced) courses on this subject. However, the question whether Planck really implied quantisation is debated among historians of physics. We present a simplified account of this debate which also sheds light on the issue of indistinguishability and Einstein's light quantum hypothesis. We suggest that the teaching of quantum mechanics could benefit from including this material beyond the question of historical accuracy., Comment: 14 pages, no figures

In recent years several far-field microscopy techniques have been developed which manage to overcome the diffraction limit of resolution. A unifying classification scheme for them is clearly desirable. We argue that existing schemes based on the information capacity of the optical system can not easily be extended to cover e.g., STED microscopy or techniques based on single molecule imaging. We suggest a classification based on a reconstruction of the Abbe limit.

Capacity estimation is an important tool for the design and dimensioning of pedestrian facilities. The literature contains different procedures and specifications which show considerable differences with respect to the estimated flow values. Moreover do new experimental data indicate a stepwise growing of the capacity with the width and thus challenge the validity of the specific flow concept. To resolve these differences we have studied experimentally the unidirectional pedestrian flow through bottlenecks under laboratory conditions. The time development of quantities like individual velocities, density and individual time gaps in bottlenecks of different width is presented. The data show a linear growth of the flow with the width. The comparison of the results with experimental data of other authors indicates that the basic assumption of the capacity estimation for bottlenecks has to be revised. In contradiction with most planning guidelines our main result is, that a jam occurs even if the incoming flow does not overstep the capacity defined by the maximum of the flow according to the fundamental diagram., Comment: Traffic flow, pedestrian traffic, crowd dynamics, capacity of bottlenecks (16 pages, 8 figures); (+ 3 new figures and minor revisions)

Bohmian mechanics is an alternative interpretation of quantum mechanics. We outline the main characteristics of its non-relativistic formulation. Most notably it does provide a simple solution to the infamous measurement problem of quantum mechanics. Presumably the most common objection against Bohmian mechanics is based on its non-locality and its apparent conflict with relativity and quantum field theory. However, several models for a quantum field theoretical generalization do exist. We give a non-technical account of some of these models., Comment: Invited talk at the spring meeting of the Deutsche Physikalische Gesellschaft, Dortmund, 2006. Forthcoming in Physics and Philosophy

This note collects, classifies and evaluates common criticism against the de Broglie Bohm theory, including Ockham's razor, asymmetry in the de Broglie Bohm theory, the ``surreal trajectory'' problem, the underdetermination of the de Broglie Bohm theory and the question of relativistic and quantum field theoretical generalizations of the de Broglie Bohm theory. We argue that none of these objections provide a rigorous disproof, they rather highlight that even in science theories can not solely be evaluated based on their empirical confirmation., Comment: 15 pages, 1 figure. Due to many comments significantly improved version, refrences added, main conclusion unaltered

In the spirit and style of John S. Bell's well known paper on How to Teach Special Relativity it is argued, that a ``Bohmian pedagogy''provides a very useful tool to illustrate the relation between classical and quantum physics and illuminates the peculiar features of the latter., Comment: 7 pages, 1 figure

Event shape distributions in $e^+e^-$ annihilation are determined from the DELPHI data taken between 183 and 207\gev. From these the strong coupling $\alpha_s$ is extracted with several techniques. Together with the results from other LEP2 energies and at about $m_Z$ this allows both, a combined measurement of $\alpha_s$ and a test of the scale dependence of the strong interaction. Alternatively the renormalisation group invariant (RGI) perturbation theory is applied to measure the $\beta$ function of strong interaction. The results are good agreement with the QCD expectation and allow to exclude the existence of light gluinos with a mass below 30\gev in a model independent way., Comment: Talk presented at the QCD02 conference, Montpellier 2002

This note reviews the latest measurements of $\alpha_s$ from event shapes in $e^+e^-$ annihilation at LEP1 and LEP2. A critical review of different methods to extract \as is offered., Comment: to be published in the proceedings of the DIS03 workshop, St. Petersburg 23.-27.april, 2003 (references added)