Physicien célèbre : Max von Laue

Max von Laue est un physicien théoricien allemand spécialiste de la diffraction des ondes, de la relativité et de la superconductivité. Il propose en 1912 de sonder l’arrangement périodique de la matière avec des faisceaux de courtes longueurs d’onde, les rayons X ; et sera récompensé par le prix Nobel de Physique en 1914. La découverte de la diffraction des rayons X par des cristaux sera à l’origine d’avancées majeures dans les 100 ans qui suivirent, de la découverte de la structure de l’ADN à celle des quasi-cristaux.

The Path to Type-II Superconductivity

Following the discovery of superconductivity by Heike Kamerlingh Onnes in 1911, research concentrated on the electric conductivity of the materials investigated. Then, it was Max von Laue who in the early 1930s turned his attention to the magnetic properties of superconductors, such as their demagnetizing effects in a weak magnetic field. As a consultant at the Physikalisch-Technische Reichsanstalt in Berlin, von Laue was in close contact with Walther Meissner at the Reichsanstalt. In 1933, Meisner together with Robert Ochsenfeld discovered the perfect diamagnetism of superconductors (Meissner–Ochsenfeld effect). This was a turning point, indicating that superconductivity represents a thermodynamic equilibrium state and leading to the London theory and the Ginzburg–Landau theory. In the early 1950s in Moscow, Nikolay Zavaritzkii carried out experiments on superconducting thin films. In the theoretical analysis of his experiments, he collaborated with Alexei A. Abrikosov and for the first time they considered the possibility that the coherence length ξ can be smaller than the magnetic penetration depth λ m . They called these materials the “second group”. Subsequently, Abrikosov discovered the famous Abrikosov vortex lattice and the superconducting mixed state. The important new field of type-II superconductivity was born.

Laue’s theorem revisited: Energy–momentum tensors, symmetries, and the habitat of globally conserved quantities

The energy–momentum tensor for a particular matter component summarises its local energy–momentum distribution in terms of densities and current densities. We re-investigate under what conditions these local distributions can be integrated to meaningful global quantities. This leads us directly to a classic theorem by Max von Laue concerning integrals of components of the energy–momentum tensor, whose statement and proof we recall. In the first half of this paper, we do this within the realm of Special Relativity (SR) and in the traditional mathematical language using components with respect to affine charts, thereby focusing on the intended physical content and interpretation. In the second half, we show how to do all this in a proper differential-geometric fashion and on arbitrary spacetime manifolds, this time focusing on the group-theoretic and geometric hypotheses underlying these results. Based on this we give a proper geometric statement and proof of Laue’s theorem, which is shown to generalise from Minkowski space (which has the maximal number of isometries) to spacetimes with significantly less symmetries. This result, which seems to be new, not only generalizes but also clarifies the geometric content and hypotheses of Laue’s theorem. A series of three appendices lists our conventions and notation and summarises some of the conceptual and mathematical background needed in the main text.