lew@ihuxr.UUCP (Lew Mammel, Jr.) (05/25/84)
Bob Clark wants to know why, if we have anti-matter, don't we have anti-energy. The quick answer is that photons are their own anti-particles. On the other hand (so to speak) there are anti-neutrino's, and since these are (presumably) massless, we could say that they constitute a form of anti-energy. More generally, we could say that the discovery of anti-matter constituted a rounding out of our knowledge of elementary particles, rather than the discovery of a distinct class of particles. Each particle is distinguished by a set of quantum numbers, e.g. charge, spin, isospin, lepton number, and strangeness. Its antiparticle is just the one with the negative of certain of these, including charge, lepton number and strangeness. If these are all zero, the particle is its own antiparticle. The "pi zero" particle is a massive particle which is its own antiparticle. The energy versus matter formulation of the question is based on a false dichotomy. Lew Mammel, Jr. ihnp4!ihuxr!lew
leon@hhb.UUCP (Leon Gordon) (05/25/84)
of a misnomer. An anti-particle is a particle which has a complementary set of certain discrete quantum numbers as compared to the corresponding "ordinary" particle. However, rest energy (i.e. - mass) is not defined in such a way as to ever have a negative value: it is simply the ground-state eigenvalue of the particle's Hamiltonian. A particle can have negative energy, of course, corresponding to a bound state; but the rest energy of a free particle is always positive. Two particles comprise a particle-anti- particle pair if they have the same rest energy, and complementary values of the various discrete, conserved quantum numbers intrinsic to the particle such as charge, iso-spin, etc.