Abstract The general analysis of binary reactions involving particles with arbitrary spin is reformulated in such a way, that it applies equally well to relativistic particles (including photons).… Expand

The limitations to the concept of parity of quantum-mechanical states and, in particular, of intrinsic parity of elementary particles are discussed. These limitations are shown to follow from… Expand

A boundary condition at t = ± ∞ (t being the “relative” time variable) is obtained for the four-dimensional wave function of a two-body system in a bound state. It is shown that this condition… Expand

Abstract It is shown that the introduction of a negative metric in quantum mechanics can lead to a unitary S-matrix, provided that all stable particle states are of positive square length. Such a… Expand

The general algebraic relations between space inversion, time reversal, and the internal symmetry group are analyzed within the framework of a Lorentz-invariant local field theory. The problem of… Expand

The theoretical possibility that in a limited domain in space the expectation value 〈φ(x)〉 of a neutral spin-0 field may be abnormal (that is to say quite different from its normal vacuum expectation… Expand

The customary notion of superselection rule stipulates the vanishing of those matrix elements of the density matrix that connect states separated by the superselection rule, i.e., the relative phases… Expand