Current Physics - Sources and Comments Series

Over the past few years, finite-size scaling has become an increasingly important tool in studies of critical systems. This is partly due to an increased understanding of finite-size effects by analytical means, and partly due to our ability to treat larger systems with large computers. The aim of this volume was to collect those papers which have been important for this progress and which illustrate novel applications of the method. The emphasis has been placed on relatively recent developments, including the use of the -expansion and of conformal methods.

``String Theory in Four Dimensions'' contains a representative collection of papers dealing with various aspects of string phenomenology, including compactifications on smooth manifolds and more general conformal field theories. Together with the lucid introduction by M. Dine, this material gives the reader a good working knowledge of our present ideas for connecting string theory to nature.

The book includes a selection of papers on the construction of superstring theories, mainly written during the years 1984-1987. It covers ten-dimensional supersymmetric and non-supersymmetric strings, four-dimensional heterotic strings and four-dimensional type-II strings. An introduction to more recent developments in conformal field theory in relation to string construction is provided.

The articles collected in this volume are mainly concerned with the phenomenological description of the 1964 discovery on K° decay that CP invariance was violated in nature. The variety of models developed to explain this CP violation are described together with reprints of more recent definitive experiments, and CP violation in the B° system and the electric dipole moment of the neutron is also covered.

At least eighty percent of the mass of the universe consists of some material which, unlike ordinary matter, neither emits nor absorbs light. This book collects key papers related to the discovery of this astonishing fact and its profound implications for astrophysics, cosmology, and the physics of elementary particles. The book focuses on the likely possibility that the dark matter is composed of an as yet undiscovered elementary particle, and examines the boundaries of our present knowledge of the properties such a particle must possess.

This volume is concerned with the determination of the behaviour of perturbation theory at large orders in quantum mechanics and quantum field theory, and its application to the problem of summation of perturbation series. Perturbation series in quantum field theory and in many quantum mechanics models are only asymptotic and thus diverge for all values of the expansion parameter. Their behaviour at large orders provides information about whether they define the theory uniquely (the problem of Borel summability). It suggests methods to extract numerical information from the series when the expansion parameter is not small. The articles reprinted here deal with the explicit evaluation of large-order behaviour in many quantum mechanics and field theory models. The large-order behaviour is related to barrier penetration effects for unphysical values of the expansion parameter, which can be calculated by WKB or instanton methods. The calculation of critical exponents of 4 field theory is presented as a practical application.

The discovery of the two families of heavy-quark-antiquark bound states, the and quarkonium spectroscopies, has played a crucial role in unravelling the nature of strong interactions. The articles collected together in this volume are concerned with the connection between quarkonia and quantum chromodynamics. They deal with potential models, spin-dependent forces, next-to-leading order QCD corrections for decay widths and energy level differences, hadronic transitions and the quark-antiquark interaction in QCD, based on perturbation theory, lattice gauge theory and QCD sum rules. Finally, a brief guide is given to the existing literature on possible new quarkonium systems which have been conjectured in connection with gluonic degrees of freedom, and with expectations for new heavy particles with colour, such as the top quark and scalar quarks.

The Standard Model of electroweak and strong interactions contains a scalar field which permeates all of space and matter, and whose properties provide the explanation of the origin of the masses. Commonly referred to as the Higgs field, it assumes in the physical vacuum a non-vanishing classical expectation value to which the masses of not only the vector bosons, but all the other known fundamental particles (quarks and leptons) are proportional. This volume presents a concise summary of the phenomenological properties of the Higgs boson.

The method of the QCD sum rules was and still is one of the most productive tools in a wide range of problems associated with the hadronic phenomenology. Many heuristic ideas, computational devices, specific formulae which are useful to theorists working not only in hadronic physics, have been accumulated in this method. Some of the results and approaches which have originally been developed in connection with the QCD sum rules can be and are successfully applied in related fields, such as supersymmetric gauge theories, nontraditional schemes of quarks and leptons etc. The amount of literature on these and other more basic problems in hadronic physics has grown enormously in recent years. This volume presents a collection of papers which provide an overview of all basic elements of the sum rule approach and priority has been given to those works which seemed most useful from a pedagogical point of view.