Léon Rosenfeld

Léon Rosenfeld (14 August 1904 – 23 March 1974) was a Belgian physicist and close collaborator of Niels Bohr.

Quotes

 * Wesentliche Fortschritte in der Formulierung der allgemeinen Quantengesetze der elektromagnetischen und materiellen Wellenfelder haben neuerdings Heisenberg und Pauli… erzielt, indem sie die von Dirac erfundene "Methode der nochmaligen Quanteln" systematisch entwickelten. Neben gewissen sachlichen Schwierigkeiten, die viel tiefer liegen, trat dabei eine eigentumliche Schwierigkeit formaler Natur auf: der zum skalaren Potential kanonisch konjugierte Impuls verschwindet identisch, so daß die Aufstellung der Hamiltonischen Funktion und der Vertauschungsrelationen nicht ohne weiteres gelingt. Zur Beseitigung dieser Schwierigkeit sind bisher drei Methoden vorgeschlagen worden, die zwar ihren Zweck erfullen, aber doch schwerlich als befriedigend betrachtet werden können. (Heisenberg and Paull have recently made significant progress in the formulation of the general quantum laws of electromagnetic and material wave fields by systematically developing the "method of repeated quantization" invented by Dirac. In addition to certain factual difficulties which lie much deeper, a peculiar difficulty of a formal nature arose: the momentum which is canonically conjugated to the scalar potential vanishes identically, so that the establishment of the Hamiltonian function and the commutation relations is not easy. To overcome this difficulty, three methods have been proposed which, although they fulfil their purpose, can hardly be regarded as satisfactory.)


 * No physical concept is sufficiently defined without the knowledge of its domain of validity.
 * As quoted in


 * Each word is a singularity, or is connected with a singularity, in our way of understanding existence.
 * As quoted in A Question of Physics: Conversations in Physics and Biology (1979), Paul Buckley and F. David Peat, Routledge and Kegan Paul, London, p. 29.

Quotes about Rosenfeld

 * In the history of science literature Rosenfeld is largely a blank sheet, but he was at the centre of modern physics as one of the pioneers of quantum field theory and quantum electrodynamics in the late 1920s and the 1930s. Today he is best known for his publications with Niels Bohr in 1933 and 1950 on measurability in quantum electrodynamics and as the fierce spokesman of Bohr's interpretation of quantum mechanics after the Second World War.
 * Anja Saar Jacobsen,


 * Dear $$\sqrt{\text{Trotsky×Bohr}} = \text{Rosenfeld}$$!
 * Wolfgang Pauli to Rosenfeld, 28 Sep 1954.