The charge correlations and the local charge compensation mechanism in rapidity space for quark jets are analysed in the framework of the quark-cascade jet-production model. The calculated results are compared with those observed experimentally in antineutrino-nucleon processes, and for the short range charge correlations observed ine⁺e⁻ annihilation experiments. The results appear consistent with the quark-cascade model.

We use Schwinger’s action principle in quantum mechanics to obtain the quantisation from Lagrangian for the fermionic variables, as well as when it contains auxiliary coordinates. We illustrate this with a supersymmetric Lagrangian which naturally includes auxiliary variables. We further show that the action principle also leads to Feynman’s path integral quantisation, which is aesthetically pleasing.

We give here a review of the recent developments of grand unified theories based onN=1 supergravity. We start with a brief introduction of supersymmetry and supergravity multiplets, and then discuss the construction of an invariant Lagrangian. The phenomena of gravity-induced weak symmetry breaking via the super Higgs effect at the tree level, corresponding to the conventional SU(5) gauge group, are then considered. We then extend this idea to the larger group SO(10), showing two possible breaking chains given as (i) SO(10)×susy→SU(2)_L×U(1)_R×U(1)_B-L×SU(3)_C (≡ G₂₁₁₃)×susy→U(1)_em×SU(3)_C (G_LE) predicting a secondZ-boson having mass lower than 1 TeV, and (ii) SO(10)×susy→SU(2)_L×SU(2)_R×SU(4)→(≡G₂₂₄)×susy→ SU(2)_L×U(1)_Y×SU(3)_C (≡ G₂₁₃)×susy→U(1)_em×SU(3)_C. We also consider the radiative breaking of weak symmetry via renormalisation group effects, which predicts the top quark mass. Some experimental signatures of the supersymmetric particles are investigated and possible future outlook is discussed.

We consider here a variational method for describing composite particles. We use equal time anticommutators/commutators, and regard the field operators as arbitrary except for the constraint from the above. The expectation value of the Hamiltonian is extremized both with respect to the field operators and with respect to the wave functions, the former extremization being the new feature here. Comparison with other calculations has been made, and correspondence with them has also been established. We further show here how an “effective mass” can arise from a potential.

The meson masses are considered to retain total relativistic effects for spinors instead of Fermi-Breit approximation. This necessitates a diagonalization approach instead of solutions of differential equations. Correction over Fermi-Breit form appears to be significant. For heavy quark systems agreement with experiment is found. The method will be quite useful if the quark-antiquark dynamics becomes sufficiently known.

We discuss here some non-perturbative techniques of field theory as applied to nuclear physics. We first describe Walecka’s mean field approach and its generalizations with a many-body description. We next apply to nuclear matter a new approach to strongly interacting systems, of which Walecka’s method becomes a specific approximation. The phenomenological implications of the same are also discussed.

We study the vacuum structure in QCD in a nonperturbative manner using a variational approach with gluon condensates. We show that in Coulomb gauge as the coupling becomes moderately strong, the perturbative vacuum of QCD becomes unstable leading to gluon condensates and a gauge dependent effective mass for the gluons related to the gauge independent value of 〈vac‖G_μν^aG^aμν‖vac〉 of Shifmanet al.