abstract

This is the first of two articles containing the definition and a detailed mathematical analysis of the concept of electromagnetic deviation in pseudo-Riemannian geometry. It presents a study of both the Lorentz equations of motion and the notion of the first electromagnetic deviation together with its equations of evolution, whereas the second article, which will follow soon, will be dealing with the notion of the second electromagnetic deviation. An interrelation of properties of the initial value problems for the Lorentz and the deviation equations is investigated. The analysis makes use of a formalism that is reparametrisation covariant and invariant under gauges of deviations defined in the paper. It is shown that by specialisations of gauges one can obtain particular kinds of deviation, some of which were not discussed so far.

abstract

This is Part II of an article by the authors (Acta Phys. Pol. B18, 601 (1987)), on generalization of the concept of geodesic deviation to the case in which an electromagnetic field is present. Whereas in Part I the consideration was limited to the first electromagnetic (e.m.) deviation, which as was indicated is an approximation, Part II extends the construction introduced in Part I to the case of the second e.m. deviation being a successive approximation to the notion considered in the two parts. The last section contains a summary of both Part I and II of the article.

abstract

Attempts to explain the \({\mit \Delta }I = 1/2\) rule in K \(\to \pi \pi \) decays are discussed. The standard effective Hamiltonian approach to non-leptonic decays is shortly reviewed. Recent long distance approaches, some of which give encouraging results, are described. It is concluded that long distance approaches to the penguin diagram improves the understanding of the \({\mit \Delta }I = 1/2\).

abstract

This paper reviews some aspects of the hydrodynamics of quark–gluon plasmas. Various stages of ultra-relativistic heavy ion collisions are described. Several estimates of the maximum energy density expected to be achieved in these collisions are compared. Discontinuities which may be induced in the hydrodynamic flow by a phase transition are described and a convenient numerical method designed to deal with such discontinuous flows is briefly presented. Finally, the correlations between particle transverse momenta and multiplicities are analyzed and one discusses to which extent these correlations could signal the occurrence of a phase transition in heavy ion collisions.

abstract

The forward–backward correlations in \(p \bar p\), collisions are calculated using the Giovannini-Van Hove model with identical clusters. The results are shown to be in disagreement with the data at 540 GeV c.m. energy. Possible generalizations of the model are suggested.