[en] (Abstract damaged) The 2PI (two particle irreducible) effective action is a general field theoretic tool for addressing this problem. In constructing it one introduces sources for both the fields and their two-point bilinears.

[en] The problem I shall address in detail in this talk is pair production of either bosons or fermions from strong electric fields which are functions only of time t, or only of the fluid proper time τ = (t² - z²)^1/2. I shall compare the results of the numerical simulation of this problem (for the degradation of the field, the particle spectra, etc.) with a semi-classical transport approach using a Schwinger-inspired source term

[en] This report discusses the concept of baryon and lepton number violation in the Weinberg-Salam theory. The topics discussed are: periodic vacua in quantum mechanics; tunnelling at finite temperature and classical thermal activation; calculation of the rate; an O(3) nonlinear sigma model; and the transition rate in the O(3) model

[en] The status of baryon and lepton number violation in the standard Weinberg-Salam electroweak theory at energies of order M_W/αW and higher is reviewed

[en] In the standard Weinberg-Salam electroweak theory baryon and lepton number (B and L) are NOT exactly conserved. The nonconservation of B and L can be traced to the existence of parity violation in the electroweak theory, together with the chiral current anomaly. This subtle effect gives negligibly small amplitudes for B and L violation at energies and temperatures significantly smaller than M_w sin² θ_w/α ∼ 10 TeV. However, recent theoretical work shows that the rate for B and L nonconservation is unsuppressed at higher energies. The consequences of this for cosmology and the baryon asymmetry of the universe, as well as the prospects for direct verification at the SSC are discussed. 13 refs., 3 figs

[en] Vacuum fluctuations are an essential feature of quantum field theory. Yet, the smallness of the scalar curvature of our universe suggests that the zero-point energy associated with these fluctuations does not curve spacetime. A possible way out of this paradox is suggested by the fact that microscopic fluctuations are generally accompanied by dissipative behavior in macroscopic systems. The intimate relation between the two is expressed by a fluctuation-dissipation theorem which extends to general relativity. The connection between quantum fluctuations and dissipation suggests a mechanism for the conversion of coherent stresses in the curvature of space into ordinary matter or radiation, thereby relaxing the effective cosmological ''constant'' to zero over time. The expansion of the universe may be the effect of this time-asymmetric relaxation process

[en] The zero energy Dirac equation of a massless isovector particle in the background field of the 't Hooft--Polyakov magnetic monopole is shown to have only two normalizable solutions. 4 references

[en] Several aspects of Yang-Mills instanton solutions in nonabelian gauge field theories are considered. First, a systematic graphical approach to the evaluation of fermion amplitudes in the presence of instantons is presented. In the multi-instanton dilute gas limit, the method is equivalent to that of the effective Lagrangian approach. This effective Lagrangian is then applied to a model with spinless fields to clarify several paradoxical aspects of U(1) chiral symmetry breaking. For the case of two fermion species (flavors), the model explicitly demonstrates the resolution of the U(1) problem through instanton effects. Further, the absence of any conflict with current algebra relations of chiral perturbation theory point to a clearer understanding of the gauge theory vacuum theta-periodicity in the case of broken chiral symmetries. The methods developed for treating the quantum fluctuations about the instanton solutions are also used to fine the normalizable zero energy eigenmodes of the 't Hooft-Polyakov magnetic monopoles, by exploiting the formal similarity of the problems in the Prasad-Sommerfield limit of the monopole model. The relevance of the results to the spin of the quantized monopole is examined

[en] An effective action technique for the time evolution of a closed system consisting of a mean field interacting with charged fluctuations is presented, and applied specifically to Quantum Electrodynamics. The effective action of QED is first developed in a systematic expansion in 1/N where N is the number of distinct fermion species. Then by making use of the Schwinger-Keldysh closed time path (CTP) formulation of field theory, causality of the resulting equations of motion is ensured. In QED this technique may be used to study the quantum non-equilibrium effects of pair creation in strong electric fields and the scattering and transport processes of a relativistic e⁺e^- plasma. Numerical results for these processes in lowest order are presented. The renormalization procedure, connection to quantum transport theory and extension to QCD and other applications of the method are also discussed

[en] The zero energy eigenvalue problem for quantum fluctuations about the 't Hooft-Polyakov monopole solution is solved explicitly in the Prasad-Sommerfield limit, by exploiting the formal similarity with self-dual euclidean field configurations. The relevance of the results of the spin of the quantized monopole is examined. (Auth.)