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Milestone 6

Spin's nuclear sibling

Isospin

Nature Physics volume 4, pages S8–S9 (2008)Cite this article

To Heisenberg's nose, this had a whiff of an uncovered symmetry about it. Appropriating the mathematics that Wolfgang Pauli had used to describe spin (Milestone 3), he postulated that the proton and neutron were two states of the same particle, the nucleon. These states differed only in a quantity analogous to spin — the 'isotopic spin', or isospin as it came to be known. The nuclear force conserved isospin, which accounted for the similarities between protons and neutrons. Other forces, such as electromagnetism, broke isospin symmetry, which explained the nucleons' differences

As Eugene Wigner wrote of the isospin concept in a 1937 paper, “no such states are known to be of any importance [...] [but they] will turn out to be very useful”. In that paper, he used isospin to predict correctly the energies of all nuclei up to atomic number 42; more recent work has extended that success to even heavier nuclei. Much like the quantum-relativistic prediction of a spinning electron by Paul Dirac (Milestone 4), isospin was an example of what Wigner would later, in a celebrated essay, describe as the “unreasonable effectiveness” of mathematics in predicting physical phenomena.

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References

ORIGINAL RESEARCH PAPERS

  1. Heisenberg, W. Über den Bau der Atomkerne. Z. Phys. 77, 1–11 (1932)

    Article  ADS  Google Scholar 

  2. Yukawa, H. On the interaction of elementary particles. Proc. Phys. Math. Soc. Jap. 17, 48–57 (1935)

    MATH  Google Scholar 

  3. Wigner, E. On the consequences of the symmetry of the nuclear Hamiltonian on the spectroscopy of nuclei. Phys. Rev. 51, 106–119 (1937)

    Article  ADS  Google Scholar 

  4. Yang, C. N. & Mills, R. L. Conservation of isotopic spin and isotopic gauge invariance. Phys. Rev. 96, 191–195 (1954)

    Article  ADS  MathSciNet  Google Scholar 

  5. Gell-Mann, M. Symmetries of baryons and mesons. Phys. Rev. 125, 1067–1084 (1962)

    Article  ADS  MathSciNet  Google Scholar 

FURTHER READING

  1. Wigner, E. The unreasonable effectiveness of mathematics in the natural sciences. Comm. Pure Appl. Math. 13, 1–14 (1960)

    Article  ADS  Google Scholar 

  2. Robson, D. Isospin in nuclei. Science 179, 133–139 (1973)

    Article  ADS  Google Scholar 

  3. Warner, D. D., Bentley, M. A. & Van Isacker, P. The role of isospin symmetry in collective nuclear structure. Nature Phys. 2, 311–318 (2006)

    Article  ADS  Google Scholar 

  4. Anderson, R. & Joshi, G. C. Interpreting mathematics in physics: charting the applications of SU(2) in 20th century physics, arXiv.org[online] (2006)

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  1. Senior Editor, Nature News & Views,

    Richard Webb

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Webb, R. Spin's nuclear sibling. Nature Phys 4 (Suppl 1), S8–S9 (2008). https://doi.org/10.1038/nphys861

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