The Symmetry, or Lack of it, Between Matter and Antimatter.

The subject of antimatter and its relationship to matter began with Dirac, with the publication of his famous equation in 1928.[1] Today it remains an active area of particle physics. The dominant issue for a number of major experimental programs is to decipher the nature of the difference in the laws of physics for matter and for antimatter. This has been a central issue of my work in the past few years, and a recurring theme in earlier work. Hence when I was asked to review a subject of my choice for this conference, this was the obvious choice for me; a very different focus from any other talk here. (Also, it allows me along the way make reference to both pieces of work for which I was cited in my Dirac award, though neither is central to this story.) Given this opportunity, I decided to start with the early history of the subject, both in honor of Dirac and his essential role in it, and because it is fascinating to look back and see how understanding evolves.