abstract

Some model-independent properties of the effective string of gauge field systems in the confining phase, for very large quark separations, are described in terms of two-dimensional conformal field theories. The constraints induced by the gauge theory of the boundaries of the effective string induce a Coulomb-like term in the interquark potential which is universal, but different from the one proposed by Lüscher. Some universal relations among the string tension, the thickness of the colour flux tube, the location of the deconfining temperature and the mass of the lowest glueball state are discussed.

abstract

We discuss the attempts to represent quantum gravity in more than two dimensions as a sum over random triangulations. The results are mainly of numerical nature, obtained by Monte Carlo simulations in three and four dimensions. In addition to pure Einstein gravity we also consider generalizations where \(R^2\)-terms or matter fields are added to the Einstein action.

abstract

The continuous left–right (LR) model which is characterized by the orientation angle of SU(2)\(_{\rm R}\) generator in the group space is suggested. This model reproduces all the known LR models. The cross sections of the processes \[Z_n \to {\rm f} \bar {\rm f},\ {\rm pp} \to Z_n+X,\ {\rm p}\bar {\rm p} \to Z_n+X,\ {\rm f} \bar {\rm f} \to W_k^-W^+_l\qquad (n,k,l=1,2)\] are obtained. The comparison of the symmetric version of this model with the experiments is fulfilled.

abstract

A summary is presented of the current status of efforts to solve the problem in which pairs are produced in a strong electric field, are accelerated by it, and then react back on it through the counter-field produced by their current. A review of recent developments in this back-reaction problem is given. A simple version of the theory of pair tunneling from a fixed electric field, is first presented and then a sketch is provided as to how this has been applied to the quark-gluon plasma. Then we turn to a field formulation of the problem for charged bosons, which leads to the need to carry out a renormalization program, outlined again in simple terms. Numerical results for this program are presented for one and for three spatial dimensions, and the corresponding physical behavior of the system is discussed We exhibit a phenomenological transport equation embodying physics that is essentially identical to that of the field formulation Last, we present the extension to the fermion case and to the formulation in terms of boost-invariant variables (as required for the quark-gluon plasma).

abstract

A new method of calculating two-loop Feynman integrals, proposed by Broadhurst et al., is discussed. As an example of its application the calculation of the anomalous magnetic moment of the electron is carried out. The renormalization procedure is illustrated in detail.