‎"BOHR, NIELS und L. ROSENFELD.‎
‎Zur Frage der Messbarkeit der elektromagnetischen Feldgrössen.‎

‎København (Copenhagen), Levin & Munksgaard, 1933. Orig. printed wrappers. Backstrip with 2 small nicks and frontcover a bit faded at margins. 65 pp. (Det Kgl. Danske Videnskabernes Selskab, Mathematisk-fysiske Meddelelser XII,8).‎

Reference : 38701

‎First edition of this fundamental papers in the development of quantum field theory. The process of measuring electromagnetic fields involves the observation of charged test bodies in those fields. Therefore the theory of electrodynamics is an inseparable extension of mechanics. A quantum theory of fields thus inherits, in some form, the limitations of measurement which lie at the foundation of quantum mechanics. In 1931 Landau and Peierls published a critical analysis of the consequences of such limitations in a relativistic quantum theory of fields. Landau and Peierls came to the negative conclusion that in several cases, the concept of momentum was without physical meaning and quantities such as the strength of a field was un-measurable. In their famous paper from 1933 Bohr and Rosenfeld (the work offered) carefully reviewed the arguments of Landau and Peierls and showed, through the use of particular measuring arrangements, that a consistent quantum theory of fields is possible without further limitations than the ones which secure the consistency of quantum mechanics. The BR-paper is often credited with having laid the foundation for quantum electrodynamics. Bohr continued his work in this field, and in 1937 he completed a manuscript entitled ""Field and Charge Measurement in Quantum Theory"", but this was never published. When, in the late 1940s the important work on QED by Tomonaga, Schwinger, Dyson, and Feynman appeared in The Physical Review, Bohr and Rosenfeld again joined and published the essentials of the 1937 manuscript in the same journal.See Abraham Pais: Bohr's Times, pp.358-364. Mehra & Rechenberg: The Historical Development of Quantum Theory, vol. 6, pp.697-703. Collected Works of Niels Bohr, vol. 7, pp.3-33.‎