A class of models of spontaneous chiral symmetry breaking is considered, based on the Hamiltonian with an instantaneous potential interaction of fermions. An explicit mass term \(m \overline \psi \psi \) is included and the physical meaning of the mass parameter discussed. It is shown that if the Hamiltonian is normal-ordered (i.e. self-energy omitted), then the mass \(m\) introduced in the Hamiltonian is not the current mass appearing in the current algebra relations.
Evidence for the generation structure of quarks and leptons is reviewed. The two main aspects of the generation problem are emphasized. The concept and possible problems of horizontal symmetries are discussed. Two different mechanisms for horizontal symmetries are considered leading to a generalized permutation symmetry in SU(2)\(_{\rm L} \times \) U(l) in one case. The second mechanism uses the discrete unbroken subgroup of an axial U(1) with hypercolour anomalies in composite models. A concrete realization in the rishon model is investigated. The two different approaches produce almost identical quark mass matrices for three generations. In addition to a correct prediction for the Cabibbo angle the models yield a very small Kobayashi–Maskawa mixing angle \(\theta _3\) and thus provide for a natural explanation of the smallness of CP violation.
Various properties (spectra, decays, mixings, etc.) of quarkonium states are studied systematically by using potential models, quark pair creation models, and unitarized quarkonium models.
The aim of this paper is to remove the contradiction between two previously given values of the coefficient \(\gamma \) with which the longitudinal part of the electromagnetic field enters into the total action.
The solutions of hydrodynamic equations describing a longitudinally expanding quark–gluon plasma produced in central collisions of two large nuclei are investigated. It is argued that a fair description of the transverse flow of plasma is given — irrespective of the initial conditions — by the relativistic simple wave of Riemann, modulated by a factor resulting from cooling due to the plasma longitudinal expansion. The role of fluctuations in the flow of plasma is also briefly discussed.
Hydrodynamic equations describing the Lorentz-boost-invariant fluid with azimuthal symmetry are generalized to include the rotational motion around the symmetry axis. The solution with no radial motion does not exist for fluids whose entropy is proportional to an arbitrary power of temperature.
