Wigner's Last Lunch with Kim

This lunch took place at a seafood restaurant near Princeton in 1991. In 33 AD, there was a much more elegant meeting somewhere in Jerusalem. We do not have a photo of this dinner meeting, but Leonardo da Vinci painted the scene.

Athough I was a graduate student at Princeton (1958-61), Wigner was not my thesis advisor. My advisor was Sam Treiman. Yet, I am known as Wigner's student among my physics colleagues. How did this happen?

Wigner's 1939 paper on the inhomogeneous Lorentz group. Wigner in this paper formulated his "little groups" which dictate the internal space-time symmetries of particles in the Lorentz-covariant world. Here he concludes that the symmetry for a massive particle is lie the three-dimensional rotation group. This symmetry leads to the concept of spin.

For massless particles, Wigner observed the symmetry group is isomorphic to the two-dimensional Euclidean group or E(2), consisting of one rotational and two translational degrees of freedom. It is easy to associate the rotational degree to the helicity. What about the translational degree of freedom? This question was not completely addressed until 1990, 51 years after 1939.

copyright@2014 by Y. S. Kim, unless otherwise specified.