[en] We present some results about the interplay between the chiral and deconfinement phase transitions in parity-conserving QED₃ (with N flavours of massless 4 component fermions) at finite temperature. Following Grignani et al. , confinement is discussed in terms of an effective sine-Gordon (SG) theory for the timelike component of the gauge field A₀ . But whereas in the fermion mass m is a Lagrangian parameter, we consider the m=0 case and ask whether an effective SG theory can again be derived with m replaced by the dynamically generated mass Σ which appears below T_ch , the critical temperature for the chiral phase transition. The fermion and gauge sectors are strongly interdependent, but as a first approximation we decouple them by taking Σ to be a constant, depending only on the constant part A-tilde₀ of the gauge field. We argue that the existence of a low-temperature confining phase may be associated with the generation of Σ ; and that, analogously, the vanishing of Σ for T>T_ch drives the system to its deconfining phase. The effect of the gauge field dynamics on mass generation is also indicated

[en] In this book, which is based on lectures given at the British Universities Summer School on Theoretical Particle Physics, 1979, the theoretical and physical ideas behind gauge field theories are discussed. The question of symmetry, hidden and manifest, global and local, and especially the relation between local symmetry and dynamics, is considered. Some of the technical aspects of canonical quantisation of gauge fields are explained and some topics related to renormalisation are introduced. (U.K.)

[en] The lecture course was divided into eight topics, and included: the quantum field, the Lagrange-Hamilton formulation relativity, massive particles and fermions, interactions in quantum field theory, symmetries in quantum field theory, and the GSW electroweak theory. (U.K.)

[en] The paper is a lecture course which was presented to the 'School for Young High Energy Physicists' at the Rutherford Appleton Laboratory, 1987. The lectures concerned the formalism for the quantum field, interactions in quantum field theory, symmetries in quantum field theory, and the GSW electroweak theory. (U.K.)

[en] Berry's work on quantum systems described by adiabatically varying Hamiltonians is introduced. Some simple systems exhibiting the ''Berry phase'' phenomenon are discussed, including: a spin-1/2 particle in a slowly varying magnetic field, linearly polarised light propagation down a helically wound optical fibre, and dynamic Jahn-Teller E x ε systems. The way in which the Berry phase concept illuminates the origin of anomalies in chiral gauge field theories, and the fermionic behaviour of solitons in certain scalar field theories (skyrmions), is also indicated. (orig.)

[en] Linear single-variable integral equations are derived for 'generalized isobar amplitudes' describing the interactions of pairs of pions in a three-pion state. Discontinuity relations deduced from two-body unitarity in the pair channels are combined with dispersion relations to give generalized isobar amplitudes satisfying two-body unitarity and having no spurious singularities. The integral equations are identical to those derived using the Khuri-Treiman approach (Phys. Rev.; 119;1115 (1960)). Explicit expressions are given for all the kernels in the ω → πrho and Al → πrho, πepsilon channels. The equations give information both about the pair sub-energy variation, and about the three-body mass dependence; under the first aspect they provide corrections to the non-unitarized isobar model, and under the second a form of 'minimal' relativistic three-body theory of 3π states. (author)

No abstract available

[en] In contemporary theories of the structure of matter at very short distance scales, various properties (some of them hypothetical as yet) of the vacuum are of crucial importance. The technical framework for such studies is quantum field theory. The aim of this article is to provide access, for a non-specialist readership, to the physics of the vacuum as presently understood in quantum field theory. To do this, heavy reliance is placed on a fundamental analogy. The basic theoretical entity-the quantum field-is here regarded as analogous to a quantum-mechanical system with (infinitely) many degrees of freedom. A system of interacting quantum fields is then analogous to a complicated system in solid state physics; it can exist in different energy states, namely the ground state and various excited states. The excited states of the field systems are characterized by the presence of excitation quanta, which are the particles (electrons, quarks, photons...) of which our material world is composed. In the ground state of the field system there are no excitation quanta, and hence no particles, present: the vacuum is this ground state. Consequently, different features of the vacuum may be modelled by the ground states of various appropriate solid state systems. For example, the vibrational ground state of a crystal models the electromagnetic field vacuum, a semiconductor models the Dirac vacuum, and superconductors may model aspects of the vacuum as regards the strong and weak forces. These and other models are used in qualitative discussions of many phenomena which involve the properties and structure of the vacuum: for example, spontaneous emission and the Lamb shift, pair creation and the associated screening of charge by vacuum polarization, the origin of mass for the W and Z bosons, and the confinement of quarks. Finally, several of the themes are gathered together in a brief introduction to the hypothesis that the universe itself is the grossly inflated result of a vacuum fluctuation. (author)

[en] This is a review of some recent work in which a derivative expansion technique is used to calculate terms in an effective Lagrangian, starting from some more fundamental Lagrangian. 70 refs., 1 fig., 1 tab. (author)

[en] An elementary discussion is given of the mechanism whereby the Wess-Zumino term determines the quantization of the Skyrme soliton. The work of Balachandran et al. is drawn upon to make explicit the remark of Wu and Zee that Wess-Zumino term acts like a monopole in the space of scalar fields of the non-linear σ-model. The origin of the monopole structure and its influence on quantization is discussed in terms of the Berry (adiabatic) phase. 47 refs. (author)