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Showing papers in "Reports on Progress in Physics in 1987"


Journal ArticleDOI
Kurt Binder1
TL;DR: In this paper, a review of various concepts about first-order phase transitions is given, with particular emphasis on metastable states near first order phase transitions, on the'stability limits' of such states (e.g., the spinodal curve of the gas-liquid transition) and on the dynamic mechanisms by which metastable state decay (nucleation and growth of droplets of a new phase).
Abstract: An introductory review of various concepts about first-order phase transitions is given. Rules for classification of phase transitions as second or first order are discussed, as well as exceptions to these rules. Attention is drawn to the rounding of first-order transitions due to finite-size or quenched impurities. Computational methods to calculate phase diagrams for simple model Hamiltonians are also described. Particular emphasis is laid on metastable states near first-order phase transitions, on the 'stability limits' of such states (e.g. the 'spinodal curve' of the gas-liquid transition) and on the dynamic mechanisms by which metastable states decay (nucleation and growth of droplets of a new phase, etc.).

804 citations


Journal ArticleDOI
TL;DR: In this paper, a wide range of experimental and theoretical studies of two-level or tunnelling states in glasses are discussed, focusing on fundamental physics rather than a detailed comparison of experiment and theory.
Abstract: This review covers a wide range of experimental and theoretical studies of two-level or tunnelling states in glasses. Emphasis is on fundamental physics rather than a detailed comparison of experiment and theory. Sections cover the static and dynamic properties of tunnelling states, their contribution to thermal properties and their response to weak and strong electric and acoustic fields, both steady state and pulsed. A section on metallic glasses focuses on the importance of electron tunnelling-state interactions, and a final section illustrates approaches to a microscopic description by means of selected examples.

711 citations


Journal ArticleDOI
TL;DR: Kaluza-Klein theory is developed starting from the simplest example in which a single extra spatial dimension is compactified to a circle, and a single Abelian gauge field emerges in four dimensions from the higher-dimensional metric.
Abstract: Kaluza-Klein theory is developed starting from the simplest example in which a single extra spatial dimension is compactified to a circle, and a single Abelian gauge field emerges in four dimensions from the higher-dimensional metric. This is generalised to greater dimensionality whence non-Abelian gauge groups may be obtained, and possible mechanisms for achieving the compactification of the extra spatial dimensions are discussed. The spectrum of particles appearing in four dimensions is discussed with particular emphasis on the spectrum of light fermions, and the constraints arising from cancellation of anomalies when explicit higher-dimensional gauge fields are present are studied. Cosmological aspects of these theories are described, including possible mechanisms for cosmological inflation, and relic heavy particles. Finally, an introductory account of Kaluza-Klein supergravity is given leading towards superstring theory.

291 citations


Journal ArticleDOI
TL;DR: Ion implantation is a powerful technique for surface analysis and material modification and a review of the effects of ion implantation on optical properties of insulators can be found in this paper.
Abstract: Ion implantation is a powerful technique for surface analysis and material modification and this review discusses the effects that specifically relate to optical properties of insulators. By selection of ion energy and ion dose one can inject trace impurities that control luminescence, generate optical absorption bands or complex defect aggregates, stimulate production of new crystalline phases or destroy crystallinity. Implantation invariably stimulates luminescence which provides a sensitive means of analysis to measure purity and near-surface defect concentrations. Post-implantation measurements reveal changes in many physical and chemical properties of the materials. Some, such as chemical reactivity, can increase a thousandfold, others such as birefringence, electro-optic and acoustic wave parameters are reduced. One major property which can be controlled is the refractive index; thus optical waveguides, and ultimately, complex integrated optical devices can be precisely defined by ion implantation.

255 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss the one-body dissipation model in its richness of phenomena and compare its predictions to measured data, focusing on the non-equilibrium relation between friction (or mobility) and diffusion.
Abstract: As the study of Brownian movement is the key to the understanding of all dissipative phenomena, the author uses it to introduce the concepts which are then made use of in a specific dissipative model. The author discusses the 'one-body dissipation model' in its richness of phenomena and compares its predictions to measured data. Special attention is paid to the non-equilibrium relation between friction (or mobility) and diffusion.

175 citations


Journal ArticleDOI
TL;DR: In this paper, the current state of knowledge of the structure and surface states of several clean low-index faces of silicon is reviewed, including the (100) face, (111) 7*7 face, the ( 111) 1*1 face, and the (112) 2*1 cleavage face.
Abstract: The author reviews the current state of knowledge of the structure and surface states of several clean low-index faces of silicon. These are the (100) face, the (111) 7*7 face, the (111) 1*1 face and the (111) 2*1 cleavage face. A new model for the latter is also proposed. Aided particularly by scanning tunneling microscopy results there appears to be grounds for some confidence that the structures of most of the above reconstructed surfaces are now understood. In addition to reviewing results from a variety of experimental techniques used on clean surfaces, results for gas covered and metal covered surfaces are also summarised.

173 citations


Journal ArticleDOI
TL;DR: A review of the literature pertinent to wave scattering from rough surfaces is given in this paper, where the early techniques developed for this problem are discussed, including the perturbation technique and the Kirchhoff approximation.
Abstract: The author has performed a review of the literature pertinent to wave scattering from rough surfaces. The early techniques developed for this problem are discussed, including the perturbation technique and the Kirchhoff approximation. The limitations of such models are highlighted. The developments in the theory, since the introduction of these models, are also given. These include: the effects of shadowing; multiple scattering effects; integral equation techniques and variational methods. Results from experimental investigations of rough surface scattering are also reviewed. These results are compared with the theoretical predictions. A brief review is also given of the methods by which the profiles of rough surfaces are measured and the problems inherent in making these measurements. A comparison is made between the assumed profiles, used in the theory, and the measured profiles.

171 citations


Journal ArticleDOI
TL;DR: In this paper, the generator coordinate method is reviewed from the point of view that it provides a versatile tool for formal development, in particular for the derivation of a consistent microscopic theory of large-amplitude collective motion.
Abstract: The generator coordinate method is reviewed from the point of view that it provides a versatile tool for formal development, in particular for the derivation of a consistent microscopic theory of large-amplitude collective motion. The Gaussian overlap approximation is employed to derive the collective mapping of arbitrary microscopic operators which is the starting point for all further derivation, e.g. of collective dynamics and of the equations determining the optimal collective path. The validity of the Gaussian overlap approximation and possible extensions are discussed. it is furthermore pointed out that one needs for nuclear collective motion dynamic paths where a collective mode is expanded by two conjugate parameters. The complications with dynamic paths can be overcome with the help of an adiabatic expansion in powers of the collective momentum. The final outcome is the quantised adiabatic time-dependent Hartree-Fock theory which is then exemplified in various examples.

129 citations


Journal ArticleDOI
TL;DR: A review of the quantized Hall effect is given in this article, which is a most remarkable manifestation of the Landau quantization, including recent developments, and the determination of the fine-structure constant including the quantum Hall method is briefly reviewed.
Abstract: A review of the quantised Hall effect is given. The author surveys experiments and theories on the normal and fractional quantum Hall effect including recent developments. As a background to the effect, which is a most remarkable manifestation of the Landau quantisation, the author starts with the description of the two-dimensional electron system in magnetic fields. As a closely related topic, the author also discusses the singular localisation of states specific to systems under the Landau quantisation in two dimensions. The determination of the fine-structure constant including the quantum Hall method is also briefly reviewed. In giving a self-contained account of the effect we emphasise the special features of the quantised Hall effect, which has an aspect of macroscopic quantum phenomenon on the one hand, and invokes, in the presence of electron-electron interactions, a new quantum liquid state on the other.

116 citations


Journal ArticleDOI
TL;DR: In this article, the main principles which determine the protection of oxide scales on metals in oxidising environments at high temperature are considered and discussed with particular respect to NiO scales on nickel and Cr2O3 and Al 2O3 scales on high-temperature alloys.
Abstract: Some of the main principles which determine the protective nature of oxide scales on metals in oxidising environments at high temperature are considered and discussed with particular respect to NiO scales on nickel and Cr2O3 and Al2O3 scales on high-temperature alloys. Emphasis is given to the transport processes in the scales and the importance of short-circuit diffusion paths. The development of stresses during oxidation are discussed and related to the effectiveness of the scales in resisting mechanical breakdown. Relief of these stresses can occur by deformation of the oxide or metal substrate but, in certain circumstances, may result in fracture and/or loss of adhesion of the scale followed by spalling from the metal surface, sometimes with catastrophic consequences.

110 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a review of the theory of atomic transport in crystalline solids and compare it with the phenomenological framework provided by nonequilibrium thermodynamics.
Abstract: This review is concerned with the fundamentals of the theory of the transport of atoms through crystalline solids, such as may result from the existence of gradients of chemical and isotopic composition, electrical potential, stress, temperature, etc. The main emphasis is on the statistical description of these processes via the theory of mobile lattice imperfections-vacancies and interstitial atoms. Only processes taking place in the bulk of the solid are considered, i.e. enhanced diffusion and migration in the vicinity of dislocations, grain boundaries and other interfaces are not discussed. The various statistical theories available at the present time are reviewed against the phenomenological framework provided by nonequilibrium thermodynamics. One object of this work is to demonstrate the interrelations among the different theories and to disclose where they are equivalent. Another is to show that the means are now available to calculate all the phenomenological transport coefficients which arise in the nonequilibrium thermodynamics of these processes in terms of the assumed properties of the defects, their interactions with solute atoms, etc. Although this review is thus primarily concerned with the theory of atomic transport at an abstract level, the physical aspects of the subject are referred to throughout. Explicit solutions of the transport equations, however, are not considered.

Journal ArticleDOI
TL;DR: In this article, the current status and future prospects of heavy-ion-driven inertial confinement fusion are described, and an account is given of experimental programmes now under way, including beam/plasma interaction and accelerator physics experiments.
Abstract: Fundamental concepts, current status and future prospects of heavy-ion-driven inertial confinement fusion are described. Target physics issues are emphasised. An account is given of experimental programmes now under way, including beam/plasma interaction and accelerator physics experiments. Plans for high-intensity beam/target research using heavy-ion beams from the synchrotron at GSI, Darmstadt, FRG are presented.

Journal ArticleDOI
TL;DR: Langmuir-Blodgett (LB) films are formed by the successive deposition of a series of monolayers of one or more types of amphiphilic molecules initially spread at the interface between water and air as mentioned in this paper.
Abstract: Langmuir-Blodgett (LB) films are formed by the successive deposition of a series of monolayers of one or more types of amphiphilic molecules initially spread at the interface between water and air. This review is mainly addressed to physicists and device engineers but, since the topic is of an interdisciplinary nature, it is hoped that it may also be of use to research workers in other disciplines. The early development and essential technology of the subject are discussed and key papers are referred to. However, the review is mainly devoted to the large amount of recent work in the field. A wide variety of different types of amphiphilic molecule are discussed ranging from simple carboxylic acids via complex heterocyclic compounds to polymers. The various physical techniques used to determine the crystallographic structure of the films together with the influence of deposition methods on this structure are discussed. The study of the electric and optical properties of various LB films is described both in relation to the physical information which may be gained from these studies and also in respect of possible technical applications. The difficulties inherent in attempting to obtain good three-dimensional crystallographic order in films are pointed out together with possible methods of overcoming these difficulties.

Journal ArticleDOI
TL;DR: In this paper, the problem of microscopic nuclear structure theory in large single particle basis systems is reviewed and several approaches are discussed, which attempt to approximate the large model spaces numerically inaccessible in complete shell model expansions of the nuclear wavefunctions.
Abstract: The problem of microscopic nuclear structure theory in large single particle basis systems is reviewed. Several approaches are discussed, which attempt to approximate the large model spaces numerically inaccessible in complete shell model expansions of the nuclear wavefunctions. All of them use symmetry projected Hartree-Fock-Bogoliubov quasiparticle configurations as basic building blocks of the theory. They differ, however, in the degree of sophistication of the variational procedures which are used to determine the corresponding mean fields as well as the configuration mixing, up to a level, on which the construction of the configuration space itself is entirely left to the dynamics of the considered system. The mathematical formalism underlying these models is briefly summarised and the steps towards a numerical realisation are discussed. In several examples the possibilities and the power of the models are demonstrated and their limitations are shown. The models may provide a powerful tool for the analysis of experimental data as well as for predictions in still unexplored regions. On the other hand they may lead to a much better theoretical understanding of effective nuclear interactions as well as the underlying fundamental forces.

Journal ArticleDOI
TL;DR: The (p,n) charge exchange reaction is a powerful tool of nuclear structure physics, with spectroscopic characteristics that are closely related to the free interaction between nucleons as discussed by the authors.
Abstract: The (p,n) charge exchange reaction is a powerful tool of nuclear structure physics, with spectroscopic characteristics that are closely related to the free interaction between nucleons. At proton energies in the range of 150-500 MeV, the interaction probes the spin dynamics in the charge exchange process and is particularly sensitive to nuclear pionic fields. At low energies, say less than 50 MeV bombarding energy, the reaction also probes the isovector density. An outstanding success of the reaction as a structural probe is the elucidation of the Gamow-Teller strength function in the nuclear excitation spectrum. However, the total strength found falls short of sum rule predictions by about 40%. Explanations of this quenching have been advanced along two lines, based on subnuclear degrees of freedom or on configuration mixing into high continuum states. Detailed theoretical arguments support the importance of configuration mixing. The subnuclear degrees of freedom may be comparable, but a decisive test is lacking.

Journal ArticleDOI
TL;DR: In this article, an emphasis is put on the hadroproduction of open heavy flavors and on results from fixed target experiments and hadron colliders, where appropriate a comparison is made with heavy flavour production in photon and neutrino interactions and in e+e- collisions.
Abstract: In this review emphasis is put on hadroproduction of open heavy flavours and on results from fixed target experiments and hadron colliders. It should be complementary to several recent reviews which concentrate on c and b bound states and results from e+e- colliders. The atomic number dependence, the xF and PT dependence and the energy dependence of charmed particle production are discussed. Where appropriate a comparison is made with heavy flavour production in photon and neutrino interactions and in e+e- collisions. It is shown that, contrary to a belief which was widely held until recently, the QCD parton model is not incompatible with present data. Higher-order corrections and interactions between the heavy quarks produced and the quarks in the parent hadron are likely to be important.

Journal ArticleDOI
TL;DR: The physical properties of silicon on sapphire (SOS) thin films and their impact on the operation of integrated devices are systematically reviewed in this paper, with emphasis on autodoping, stress, lattice defects and interface behaviour.
Abstract: The physical properties of silicon on sapphire (SOS) thin films and their impact on the operation of integrated devices are systematically reviewed. The preparation of the SOS material is described from the fabrication of the sapphire substrate and the silicon film heteroepitaxy up to the recently proposed regrowth techniques. The microscopic properties and the relevant methods used for inspection are discussed with emphasis on autodoping, stress, lattice defects and interface behaviour. Following the presentation of average transport and recombination parameters, deduced from measurements involving the contribution of the whole film, the non-homogeneity of the SOS film along the epitaxial direction will be outlined. The electrical properties of the silicon-sapphire interface and of the interfacial transition layer are compared to those of the front Si-SiO2 interface. Attempts are made to correlate the data derived by various characterisation techniques in order to reveal a coherent image of the Si film volume sandwiched by two very dissimilar interfaces. Finally, the processing and the performance of SOS devices are discussed and favourably compared to the case of bulk Si technology.

Journal ArticleDOI
TL;DR: A review of the current status of nuclear astrophysics is given in this paper, where special emphasis is given to primordial and stellar nucleosynthesis of the chemical elements and the laboratory approaches in obtaining relevant reaction rates are discussed.
Abstract: The review describes the current status of nuclear astrophysics, where special emphasis is given to primordial and stellar nucleosynthesis of the chemical elements. The laboratory approaches in obtaining relevant reaction rates are discussed. The authors also focus attention on those processes where new knowledge of nuclear physics may have important astrophysical consequences. The major burning phases in stars and some critical reactions are discussed. Finally, miscellaneous topics of current interest are described.

Journal ArticleDOI
TL;DR: In this article, the magnetic field line reconnection in rarefied plasmas with very high conductivity has been studied, where oppositely directed field lines approach each other and reconnect, resulting in a marked change in the field line topology.
Abstract: The term 'magnetic field line reconnection' has arisen in the physics of rarefied plasmas with very high conductivity. When such a plasma is in motion, the remarkable property of field line 'freezing in' of the plasma manifests itself. However, situations sometimes occur in real plasma motion where this condition is violated, e.g. when oppositely directed field lines approach each other and reconnect. The process of reconnection results in a marked change in the field line topology and is accompanied by the formation of current layers and the conversion of magnetic energy into kinetic and thermal plasma energies. Magnetic field line reconnection plays a key role in many processes in the near-Earth, space and laboratory fusion plasmas.

Journal ArticleDOI
TL;DR: In this paper, a short introduction to those aspects of experiments that require the application of pattern recognition methods, which are discussed in detail and illustrated with examples from high-energy physics experiments of the last 15 years.
Abstract: Pattern recognition is of crucial importance to many high-energy physics experiments during their analysis phase. This review gives a short introduction to those aspects of experiments that require the application of pattern recognition methods, which are discussed in detail and illustrated with examples from high-energy physics experiments of the last 15 years. At the end, a number of papers are recommended dealing with track and vertex fitting.

Journal ArticleDOI
TL;DR: The theories of compound nucleus reactions to discrete and continuum states are reviewed and compared with experimental data in this paper, in particular the Weisskopf-Ewing, Hauser-Feshbach, and Feshbach-Kerman-Koonin theories.
Abstract: The theories of compound nucleus reactions to discrete and continuum states are reviewed and compared with experimental data. In particular, the Weisskopf-Ewing, Hauser-Feshbach, and Feshbach-Kerman-Koonin theories are described and their range of validity investigated. Recent work on the width fluctuation correction and the elastic enhancement factor is included in the review.

Journal ArticleDOI
TL;DR: In this paper, the interplay between atomic and nuclear interactions in collisions between light and heavy ions is studied and the general theoretical description is outlined and analysed in a number of different limits (non-relativistic and relativistic electrons, semiclassical approximation, DWBA, fully quantal description) that have been used in practical applications.
Abstract: The interplay between atomic and nuclear interactions in collisions between light and heavy ions is studied. The general theoretical description is outlined and analysed in a number of different limits (non-relativistic and relativistic electrons, semiclassical approximation, DWBA, fully quantal description) that have been used in practical applications. The two most important physical mechanisms for generating atomic-nuclear interference, i.e. energy conservation and the introduction of additional phase shifts by nuclear reactions, are extracted and their universality in all scattering systems is stressed. The need for choosing different sets of basis states in light and heavy, symmetric and asymmetric systems, in order to achieve an economical theoretical description, is discussed in some detail. The resulting typical coupling matrix elements are analysed for their relative importance in atomic and nuclear excitations. The description of nuclear influence on atomic excitations in terms of a classical time delay caused by nuclear reactions is reviewed and its relationship to the underlying quantal character of the nuclear reaction is extracted.

Journal ArticleDOI
TL;DR: In this article, a general presentation of astrophysical observations in the ultraviolet is given, followed by a brief historical presentation of some of the typical instrumentation used, and the outlook for other projects is mentioned showing that ultraviolet astrophysics is a lively branch of observational space science.
Abstract: A general presentation of astrophysical observations in the ultraviolet is given. First the particular nature of ultraviolet studies is emphasises. This is followed by a brief historical presentation of some of the typical instrumentation used. Then, in the framework of galactic observations, some of the most important results obtained concerning the physics of planetary, solar, stellar and interstellar media are presented. Future instrumentation and, in particular the Hubble Space Telescope, are briefly presented. In this framework extragalactic ultraviolet studies, not covered in this review, will certainly occupy an important place. Finally, the outlook for other projects is mentioned showing that ultraviolet astrophysics is a lively branch of observational space science.

Journal ArticleDOI
TL;DR: In this article, the properties of the five quasi-one-dimensional conductors abbreviated as TEA(TCNQ)2, MTPAs(TCNsQ2), MNEB(TEA)2 and MEM(TCnQ2) were compared with the existing theories of conductors with quarter-filled bands in which the electron-electron interaction is taken into account.
Abstract: The authors review the properties of the five quasi-one-dimensional conductors abbreviated as TEA(TCNQ)2, MTPP(TCNQ)2, MTPAs(TCNQ)2, MNEB(TCNQ)2 and MEM(TCNQ)2. The results from different measurements are compared with the existing theories of conductors with quarter-filled bands in which the electron-electron interaction is taken into account. These interactions are important in all five materials, but they divide into two groups in which the electron-electron interaction is relatively weak: (TEA(TCNQ)2, MTPP(TCNQ)2 and MTPAs(TCNQ)2), and relatively strong: (MNEB(TCNQ)2 and MEM(TCNQ)2).

Journal ArticleDOI
TL;DR: A general review of the theory and phenomenology of exchange mechanisms in hadronic reactions at all energies above the resonance region is presented in this paper, where the main emphasis is on examining how far fairly simple theoretical ideas can be taken in obtaining a general understanding of high energy two-body reactions.
Abstract: A general review of the theory and phenomenology of exchange mechanisms in hadronic reactions at all energies above the resonance region is presented. The main emphasis is on examining how far fairly simple theoretical ideas can be taken in obtaining a general understanding of high energy two-body reactions.

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the observational characteristics (classification, luminosities, composition, etc.) of WR stars and the interaction of the WR stars with their environment.
Abstract: Discusses the observational characteristics (classification, luminosities, composition, etc.) of WR stars. The evolution of WR stars and the interaction of WR stars with their environment are discussed. A brief account of the discovery of WR stars in other galaxies is given. Finally, the main issues in the research into the structure and evolution of WR stars are discussed.

Journal ArticleDOI
TL;DR: Hadron colliders are accelerators in which beams of such particles are made to collide as discussed by the authors, which can give information on the structure of the constituents of the hadrons and also produce new unstable forms of matter which can be studied.
Abstract: Hadrons are elementary particles which interact through the strong interaction. Hadron colliders are accelerators in which beams of such particles are made to collide. Such collisions give information on the structure of the constituents of the hadrons and also produce new unstable forms of matter which can be studied. At low values of the four-momentum transfer squared, Q2, the interaction may consist of a simple elastic scatter which preserves the character of the two colliding hadrons. At higher values of Q2 the probability of such elastic processes falls and elastic scattering between the constituents of the hadrons-quarks and gluons-becomes more dominant. Such processes are characterised by the observation of collimated jets of particles in the collision. A study of these jets gives information on the form of the strong interaction, quantum chromodynamics. Inelastic quark and gluon scattering can lead to the production of new types of quarks. Given sufficiently high energy, collisions between quarks and antiquarks can result in the formation of Z and W bosons, the gauge particles of the weak interaction.

Journal ArticleDOI
Maurice Jacob1, P V Landshoff1
TL;DR: In this article, the authors review evidence that, at scales down to 10-18 m, matter shows a quark-gluon structure and suggest that new interesting phenomena are waiting to be discovered at scales of 10-19 m and provide encouraging hints for a better understanding of the structure of matter on the nucleon level.
Abstract: The authors review evidence that, at scales down to 10-18 m, matter shows a quark-gluon structure. At these distances, the unified picture provided by the standard model, which combines quantum chromodynamics with weak and electromagnetic interactions, gives a good description of experimental data. These successes suggest that new interesting phenomena are waiting to be discovered at scales of 10-19 m and provide encouraging hints for a better understanding of the structure of matter on the nucleon level, that is at scales of 10-15 m.