Abstract
In July a colloquium was held at the Dublin Institute for Advanced Studies at which the following lecturers each gave a, short course of lectures: Prof. C. Møller (Copenhagen), Prof. J. L. Synge (Pittsburgh), Dr. C. G. Powell (Bristol). Prof. Møller discussed the centre of gravity in relativistic quantum mechanics, explaining how this notion can be defined in a quantized field theory and how it is related to the angular momentum and the ‘trembling motion’. Prof. Synge dealt with more mathematical subjects of boundary problems and multiply connected spaces. For the non-mathematician, Dr. Powell's lectures on meson tracks in the photographic emulsion were most interesting. His and Occhialini's discovery of the existence of two kinds of mesons with different masses of which the heavier decays spontaneously into the lighter kind was widely discussed. It seemed most probable that the ordinary cosmic ray meson is identical with the lighter kind, and that at least the heavier meson is the “meson of the nuclear forces” predicted by Yukawa, and is strongly coupled with nuclei. Examples of meson emission in nuclear disintegrations which were shown in the lectures also prove that the general ideas of the meson theory are correct. It is as yet an open question whether also the light meson is strongly coupled with nuclei or not. This depends on further experiments, in particular on the question whether the mesons ejected in nuclear disintegrations are all heavy or also partly light mesons. It depends also on whether the fact that ordinary negative mesons are not captured in light elements (delayed coincidence experiments) can be understood theoretically or not. If it should turn out that the light meson is also a nuclear force meson, then the form of meson theory proposed by Møller and Rosenfeld and modified by Schwinger (vector and pseudoscalar mesons with different masses) is most likely correct.
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Colloquium at the Dublin Institute for Advanced Studies. Nature 160, 393 (1947). https://doi.org/10.1038/160393a0
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DOI: https://doi.org/10.1038/160393a0