Classical Planar Scattering By Coulombic Potentials

Astronomy as well as molecular physics describe non-relativistic motion by an interaction of the same form: By Newton's respectively by Coulomb's potential. But whereas the fundamental laws of motion thus have a simple form, the n-body problem withstood (for n > 2) all attempts of an explicit solution. Indeed, the studies of Poincare at the end of the last century lead to the conclusion that such an explicit solution should be impossible. Poincare himselfopened a new epoch for rational mechanics by asking qual itative questions like the one about the stability of the solar system. To a largeextent, his work, which was critical for the formation of differential geometry and topology, was motivated by problems arising in the analysis of the n-body problem ([38], p. 183). As it turned out, even by confining oneselfto questions ofqualitativenature, the general n-body problem could not be solved. Rather, simplified models were treated, like planar motion or the restricted 3-body problem, where the motion of a test particle did not influence the other two bodies.

Here, the concept of indistinguishability is defined for identical particles by the symmetry of the state, therefore applying to both the classical and the quantum framework. The author describes symmetric statistical operators and classifies these by means of extreme points. He derives de Finettis theorem for the description of infinitely extendible interchangeable random variables, and presents generalisations covering the Poisson limit and the central limit. Finally, a characterisation and interpretation of the integral representations of classical photon states in quantum optics are derived in abelian subalgebras, and unextendible indistinguishable particles are analysed in the context of non-classical photon states. Suitable for mathematical physicists and philosophers of science.

Our DMV Seminar on 'Classical Nonintegrability, Quantum Chaos' intended to introduce students and beginning researchers to the techniques applied in nonin tegrable classical and quantum dynamics. Several of these lectures are collected in this volume. The basic phenomenon of nonlinear dynamics is mixing in phase space, lead ing to a positive dynamical entropy and a loss of information about the initial state. The nonlinear motion in phase space gives rise to a linear action on phase space functions which in the case of iterated maps is given by a so-called transfer operator. Good mixing rates lead to a spectral gap for this operator. Similar to the use made of the Riemann zeta function in the investigation of the prime numbers, dynamical zeta functions are now being applied in nonlinear dynamics. In Chapter 2 V. Baladi first introduces dynamical zeta functions and transfer operators, illustrating and motivating these notions with a simple one-dimensional dynamical system. Then she presents a commented list of useful references, helping the newcomer to enter smoothly into this fast-developing field of research. Chapter 3 on irregular scattering and Chapter 4 on quantum chaos by A. Knauf deal with solutions of the Hamilton and the Schr6dinger equation. Scatter ing by a potential force tends to be irregular if three or more scattering centres are present, and a typical phenomenon is the occurrence of a Cantor set of bounded orbits. The presence of this set influences those scattering orbits which come close.

This volume contains three interrelated, beautiful, and useful topics of quantum scattering theory: inverse scattering theory, algebraic scattering theory and supersymmetrical quantum mechanics. The contributions cover such issues as coupled-channel inversions at fixed energy, inversion of pion-nucleon scattering cross-sections into potentials, inversions in neutron and x-ray reflection, 3-dimensional fixed-energy inversion, inversion of electron scattering data affected by dipole polarization, nucleon-nucleon potentials by inversion versus meson-exchange theory, potential reversal and reflectionless impurities in periodic structures, quantum design in spectral, scattering, and decay control, solution hierarchy of Toda lattices, etc.

At the time I learned quantum field theory it was considered a folk theo rem that it is easy to construct field theories fulfilling either the locality or the spectrum condition. The construction of an example for the latter case is particularly easy. Take for instance an irreducible representation of the Poincare group with positive energy, and as an algebra of observables all compact operators in that representation space. This algebra of observables is even an asymptotically Abelian algebra. Since it has only a single repre sentation - except for multiples of this one - it is hardly possible to replace locality in order to obtain a theory with a reasonable physical structure. This example shows that it is not sufficient to replace locality by asymptotic Abelian-ness. The construction of a theory fulfilling locality without a pos itive energy representation was first done by Doplicher, Regge, and Singer [DRS]. However, modern investigations on the locality ideal in the algebra oftest functions, started by Alcantara and Yngvason [AY], seem to indicate that this is a general feature; this means that most of the algebras of ob servables fulfilling the locality condition will not have representations that also fulfil the spectrum condition. This discussion shows that quantum field theory becomes a subject of interest only if both conditions are satisfied at the same time.

As a limit theory of quantum mechanics, classical dynamics comprises a large variety of phenomena, from computable (integrable) to chaotic (mixing) behavior. This book presents the KAM (Kolmogorov-Arnold-Moser) theory and asymptotic completeness in classical scattering. Including a wealth of fascinating examples in physics, it offers not only an excellent selection of basic topics, but also an introduction to a number of current areas of research in the field of classical mechanics. Thanks to the didactic structure and concise appendices, the presentation is self-contained and requires only knowledge of the basic courses in mathematics. The book addresses the needs of graduate and senior undergraduate students in mathematics and physics, and of researchers interested in approaching classical mechanics from a modern point of view.

The methods developed to deal with the computational aspects of physi cal problems are useful in an increasing number of situations, from chem istry, biology and geology to engineering, communications and economics. In fact, computational physics has evolved into a trans-disciplinary field now concerned with the creative use of computers in scientific research. More over, computational methods often help students to develop a deeper under standing of key concepts, and enhance their problem-solving abilities. There fore, computational physics is recognized as having an important educational value, and educators face the task of outlining appropriate curricula to take advantage of these unique features. This is an important motivation for the publication of the contents of the Seminar on Computational Physics which is held in Granada every two years. The seminar aims at bringing together small groups of students and active researchers on different aspects of computational physics. It is part of the doctoral programme of the University of Granada. The proceedings of the previous editions were published as II Granada Lectures in Computational Physics (World Scientific, Singapore 1993) and Third Granada Lectures in Computational Physics (Lecture Notes in Physics, vol. 448, Springer, Berlin 1995) by the same editors. The present book contains the invited lecture notes and a very brief account of contributions by participants at the 4th Granada Seminar on Computational Physics (Granada, Spain, 9-14 September 1996).

The authors study dynamical effects of incident compressional and distortional elastic waves on a layer of planar, cylindrical, or spherical geometry, especially focusing on the stress fields surrounding the layer. These results are derived from the exact solutions for elastic wave scattering from such interfaces developped in the first part of the book. Comparisons of numerical solutions of special problems with the analytical solutions are given and it is shown how the latter help to simplify the numerical treatment. The material presented in this monograph will help in developing composite materials with improved chemical and physical properties and in non-destructive testing of such materials. Engineers, physicists, and workers in applied mathematics will welcome this well written text. It may also be used for additional reading in a course on elasto-mechanics.

This book analyses in depth the geometrical aspects of the simplicial quantum gravity model known as the dynamical triangulations approach. The authors provide a compact and convenient account suitable both to introduce the non-expert reader to the spirit of the subject and to provide a well-chosen mathematical route to the heart of the matter for the expert. The techniques described in the book are novel and allow points of current interest in the subject of simplicial quantum gravity to be addressed. The authors discuss piecewise linear manifolds and give entropy estimates of the number of triangulations of 3- and 4-manifolds. Continuum physics is recovered through scaling limits and computer simulation is used to study simplicial quantum gravity extensively. The beginner will appreciate the introduction to the field and the expert the comprehensive account of recent results and developments.