Showing papers in "Reviews of Modern Physics in 1993"
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TL;DR: A comprehensive review of spatiotemporal pattern formation in systems driven away from equilibrium is presented in this article, with emphasis on comparisons between theory and quantitative experiments, and a classification of patterns in terms of the characteristic wave vector q 0 and frequency ω 0 of the instability.
Abstract: A comprehensive review of spatiotemporal pattern formation in systems driven away from equilibrium is presented, with emphasis on comparisons between theory and quantitative experiments. Examples include patterns in hydrodynamic systems such as thermal convection in pure fluids and binary mixtures, Taylor-Couette flow, parametric-wave instabilities, as well as patterns in solidification fronts, nonlinear optics, oscillatory chemical reactions and excitable biological media. The theoretical starting point is usually a set of deterministic equations of motion, typically in the form of nonlinear partial differential equations. These are sometimes supplemented by stochastic terms representing thermal or instrumental noise, but for macroscopic systems and carefully designed experiments the stochastic forces are often negligible. An aim of theory is to describe solutions of the deterministic equations that are likely to be reached starting from typical initial conditions and to persist at long times. A unified description is developed, based on the linear instabilities of a homogeneous state, which leads naturally to a classification of patterns in terms of the characteristic wave vector q0 and frequency ω0 of the instability. Type Is systems (ω0=0, q0≠0) are stationary in time and periodic in space; type IIIo systems (ω0≠0, q0=0) are periodic in time and uniform in space; and type Io systems (ω0≠0, q0≠0) are periodic in both space and time. Near a continuous (or supercritical) instability, the dynamics may be accurately described via "amplitude equations," whose form is universal for each type of instability. The specifics of each system enter only through the nonuniversal coefficients. Far from the instability threshold a different universal description known as the "phase equation" may be derived, but it is restricted to slow distortions of an ideal pattern. For many systems appropriate starting equations are either not known or too complicated to analyze conveniently. It is thus useful to introduce phenomenological order-parameter models, which lead to the correct amplitude equations near threshold, and which may be solved analytically or numerically in the nonlinear regime away from the instability. The above theoretical methods are useful in analyzing "real pattern effects" such as the influence of external boundaries, or the formation and dynamics of defects in ideal structures. An important element in nonequilibrium systems is the appearance of deterministic chaos. A greal deal is known about systems with a small number of degrees of freedom displaying "temporal chaos," where the structure of the phase space can be analyzed in detail. For spatially extended systems with many degrees of freedom, on the other hand, one is dealing with spatiotemporal chaos and appropriate methods of analysis need to be developed. In addition to the general features of nonequilibrium pattern formation discussed above, detailed reviews of theoretical and experimental work on many specific systems are presented. These include Rayleigh-Benard convection in a pure fluid, convection in binary-fluid mixtures, electrohydrodynamic convection in nematic liquid crystals, Taylor-Couette flow between rotating cylinders, parametric surface waves, patterns in certain open flow systems, oscillatory chemical reactions, static and dynamic patterns in biological media, crystallization fronts, and patterns in nonlinear optics. A concluding section summarizes what has and has not been accomplished, and attempts to assess the prospects for the future.
6,145 citations
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TL;DR: The mathematical theory of the method is explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices.
Abstract: Magnetoencephalography (MEG) is a noninvasive technique for investigating neuronal activity in the living human brain. The time resolution of the method is better than 1 ms and the spatial discrimination is, under favorable circumstances, 2-3 mm for sources in the cerebral cortex. In MEG studies, the weak 10 fT-1 pT magnetic fields produced by electric currents flowing in neurons are measured with multichannel SQUID (superconducting quantum interference device) gradiometers. The sites in the cerebral cortex that are activated by a stimulus can be found from the detected magnetic-field distribution, provided that appropriate assumptions about the source render the solution of the inverse problem unique. Many interesting properties of the working human brain can be studied, including spontaneous activity and signal processing following external stimuli. For clinical purposes, determination of the locations of epileptic foci is of interest. The authors begin with a general introduction and a short discussion of the neural basis of MEG. The mathematical theory of the method is then explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices. Finally, several MEG experiments performed in the authors' laboratory are described, covering studies of evoked responses and of spontaneous activity in both healthy and diseased brains. Many MEG studies by other groups are discussed briefly as well.
4,533 citations
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TL;DR: The field of electron transfer processes has been studied extensively in chemistry, electrochemistry, and biology as mentioned in this paper, and some history, recent trends, and my own involvement are described.
Abstract: Since the late 1940s, the field of electron transfer processes has grown enormously in chemistry, electrochemistry, and biology. The development of the field, experimentally and theoretically, as well as its relation to the study of the other kinds of chemical reactions, presents an intriguing history in which many threads have been brought together. In this article, some history, recent trends, and my own involvement are described.
3,008 citations
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TL;DR: In this paper, a broad range of experiments are reviewed and compared with theory, including the behavior of the mass-abundance spectra, polarizabilities, ionization potentials, photoelectron spectra and optical spectra.
Abstract: The study of simple metal clusters has burgeoned in the last decade, motivated by the growing interest in the evolution of physical properties from the atom to the bulk solid, a progression passing through the domain of atomic clusters. On the experimental side, the rapid development of new techniques for producing the clusters and for probing and detecting them has resulted in a phenomenal increase in our knowledge of these systems. For clusters of the simplest metals, the alkali and noble metals, the electronic structure is dominated by the number of valence electrons, and the ionic cores are of secondary importance. These electrons are delocalized, and the electronic system exhibits a shell structure that is closely related to the well-known nuclear shell structure. In this article the results from a broad range of experiments are reviewed and compared with theory. Included are the behavior of the mass-abundance spectra, polarizabilities, ionization potentials, photoelectron spectra, optical spectra, and fragmentation phenomena.
2,469 citations
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TL;DR: Chaotic time series data are observed routinely in experiments on physical systems and in observations in the field as mentioned in this paper, and many tools have been developed for the analysis of such data.
Abstract: Chaotic time series data are observed routinely in experiments on physical systems and in observations in the field. The authors review developments in the extraction of information of physical importance from such measurements. They discuss methods for (1) separating the signal of physical interest from contamination ("noise reduction"), (2) constructing an appropriate state space or phase space for the data in which the full structure of the strange attractor associated with the chaotic observations is unfolded, (3) evaluating invariant properties of the dynamics such as dimensions, Lyapunov exponents, and topological characteristics, and (4) model making, local and global, for prediction and other goals. They briefly touch on the effects of linearly filtering data before analyzing it as a chaotic time series. Controlling chaotic physical systems and using them to synchronize and possibly communicate between source and receiver is considered. Finally, chaos in space-time systems, that is, the dynamics of fields, is briefly considered. While much is now known about the analysis of observed temporal chaos, spatio-temporal chaotic systems pose new challenges. The emphasis throughout the review is on the tools one now has for the realistic study of measured data in laboratory and field settings. It is the goal of this review to bring these tools into general use among physicists who study classical and semiclassical systems. Much of the progress in studying chaotic systems has rested on computational tools with some underlying rigorous mathematics. Heuristic and intuitive analysis tools guided by this mathematics and realizable on existing computers constitute the core of this review.
1,691 citations
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TL;DR: In this article, the authors survey the hierarchy of theoretical approximations leading to the jellium model, including various extensions, including local density approximation to exchange and correlation effects, which greatly simplifies self-consistent calculations of the electronic structure.
Abstract: The jellium model of simple metal clusters has enjoyed remarkable empirical success, leading to many theoretical questions. In this review, we first survey the hierarchy of theoretical approximations leading to the model. We then describe the jellium model in detail, including various extensions. One important and useful approximation is the local-density approximation to exchange and correlation effects, which greatly simplifies self-consistent calculations of the electronic structure. Another valuable tool is the semiclassical approximation to the single-particle density matrix, which gives a theoretical framework to connect the properties of large clusters with the bulk and macroscopic surface properties. The physical properties discussed in this review are the ground-state binding energies, the ionization potentials, and the dipole polarizabilities. We also treat the collective electronic excitations from the point of view of the cluster response, including some useful sum rules.
1,357 citations
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TL;DR: The Kochen-Specker Theorem as discussed by the authors is one of the most famous no-hidden-variables theorems, and it has transparently simple proofs, which can be converted without additional analysis into a powerful form of the Bell's Theorem.
Abstract: Although skeptical of the prohibitive power of no-hidden-variables theorems, John Bell was himself responsible for the two most important ones. I describe some recent versions of the lesser known of the two (familiar to experts as the "Kochen-Specker theorem") which have transparently simple proofs. One of the new versions can be converted without additional analysis into a powerful form of the very much better known "Bell's Theorem," thereby clarifying the conceptual link between these two results of Bell.
1,012 citations
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TL;DR: In this article, theoretical and experimental approaches to flow, hydrodynamic dispersion, and miscible and immiscible displacement processes in reservoir rocks are reviewed and discussed, and two different modeling approaches to these phenomena are compared.
Abstract: In this paper, theoretical and experimental approaches to flow, hydrodynamic dispersion, and miscible and immiscible displacement processes in reservoir rocks are reviewed and discussed. Both macroscopically homogeneous and heterogeneous rocks are considered. The latter are characterized by large-scale spatial variations and correlations in their effective properties and include rocks that may be characterized by several distinct degrees of porosity, a well-known example of which is a fractured rock with two degrees of porosity---those of the pores and of the fractures. First, the diagenetic processes that give rise to the present reservoir rocks are discussed and a few geometrical models of such processes are described. Then, measurement and characterization of important properties, such as pore-size distribution, pore-space topology, and pore surface roughness, and morphological properties of fracture networks are discussed. It is shown that fractal and percolation concepts play important roles in the characterization of rocks, from the smallest length scale at the pore level to the largest length scales at the fracture and fault scales. Next, various structural models of homogeneous and heterogeneous rock are discussed, and theoretical and computer simulation approaches to flow, dispersion, and displacement in such systems are reviewed. Two different modeling approaches to these phenomena are compared. The first approach is based on the classical equations of transport supplemented with constitutive equations describing the transport and other important coefficients and parameters. These are called the continuum models. The second approach is based on network models of pore space and fractured rocks; it models the phenomena at the smallest scale, a pore or fracture, and then employs large-scale simulation and modern concepts of the statistical physics of disordered systems, such as scaling and universality, to obtain the macroscopic properties of the system. The fundamental roles of the interconnectivity of the rock and its wetting properties in dispersion and two-phase flows, and those of microscopic and macroscopic heterogeneities in miscible displacements are emphasized. Two important conceptual advances for modeling fractured rocks and studying flow phenomena in porous media are also discussed. The first, based on cellular automata, can in principle be used for computing macroscopic properties of flow phenomena in any porous medium, regardless of the complexity of its structure. The second, simulated annealing, borrowed from optimization processes and the statistical mechanics of spin glasses, is used for finding the optimum structure of a fractured reservoir that honors a limited amount of experimental data.
946 citations
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TL;DR: In this paper, the authors review the detailed understanding of asymptotic kinetics, spatial correlations, percolative structure, etc., which is emerging for these far-from-equilibrium processes.
Abstract: Irreversible random sequential adsorption (RSA) on lattices, and continuum "car parking" analogues, have long received attention as models for reactions on polymer chains, chemisorption on single-crystal surfaces, adsorption in colloidal systems, and solid state transformations. Cooperative generalizations of these models (CSA) are sometimes more appropriate, and can exhibit richer kinetics and spatial structure, e.g., autocatalysis and clustering. The distribution of filled or transformed sites in RSA and CSA is not described by an equilibrium Gibbs measure. This is the case even for the saturation "jammed" state of models where the lattice or space cannot fill completely. However exact analysis is often possible in one dimension, and a variety of powerful analytic methods have been developed for higher dimensional models. Here we review the detailed understanding of asymptotic kinetics, spatial correlations, percolative structure, etc., which is emerging for these far-from-equilibrium processes.
898 citations
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TL;DR: In this article, a summary of the statistical mechanical theory of learning a rule with a neural network, a rapidly advancing area which is closely related to other inverse problems frequently encountered by physicists, is presented.
Abstract: A summary is presented of the statistical mechanical theory of learning a rule with a neural network, a rapidly advancing area which is closely related to other inverse problems frequently encountered by physicists. By emphasizing the relationship between neural networks and strongly interacting physical systems, such as spin glasses, the authors show how learning theory has provided a workshop in which to develop new, exact analytical techniques.
422 citations
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TL;DR: In this paper, the physics of the latent image formation and development steps are reviewed, as well as the application and transfer of heat in the fixing step, and a detailed review of the physical properties of large area films and small particles is presented.
Abstract: Electrophotography is one means of arranging 100 million pigmented plastic particles on a sheet of paper to faithfully replicate an original. It is based on many diverse phenomena and employs many properties of matter. These include gaseous ionization in the charging step; photogeneration and charge transport through disordered solid-state materials in the latent-image-formation step; triboelectricity in the particle-charging step; mechanical, electrostatic, and magnetic forces to detach particles in the development and transfer steps; and the application and transfer of heat in the fixing step. In addition, it relies on a precise balance of thermorheological, chemical, and mechanical properties of large area films and small particles. This article reviews the physics of the latent-image formation and development steps.
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TL;DR: In the past seven years, many examples of periodic crystals closely related to quasicrystalline alloys have been discovered, and these crystals have been termed approximants, since the arrangements of atoms within their unit cells closely approximate the local atomic structures in quasicalrystals.
Abstract: Over the past seven years, many examples of periodic crystals closely related to quasicrystalline alloys have been discovered. These crystals have been termed approximants, since the arrangements of atoms within their unit cells closely approximate the local atomic structures in quasicrystals. This colloquium focuses on these approximant structures, their description, and their relationship to quasicrystals.
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TL;DR: In this paper, a Lagrangian path-integral quantization is used to analyze the fractional quantum Hall effect in two-dimensional electron fluids subject to a strong, transverse magnetic field.
Abstract: The main purpose of this paper is to further our theoretical understanding of the fractional quantum Hall effect, in particular of spin effects, in two-dimensional incompressible electron fluids subject to a strong, transverse magnetic field. As a prerequisite for an analysis of the quantum Hall effect, the authors develop a general formulation of the many-body theory of spinning particles coupled to external electromagnetic fields and moving through a general, geometrically nontrivial background. Their formulation is based on a Lagrangian path-integral quantization and is valid in arbitrary coordinates, including coordinates moving according to a volume-preserving flow. It is found that nonrelativistic quantum theory exhibits a fundamental, local U(1)\ifmmode\times\else\texttimes\fi{}SU(2) gauge invariance, and the corresponding gauge fields are identified with physical, external fields. To illustrate the usefulness of their formalism, the authors prove a general form of the quantum-mechanical Larmor theorem and discuss some well-known effects, including the Barnett-Einstein-de Haas effect and superconductivity, emphasizing the implications of U(1)\ifmmode\times\else\texttimes\fi{}SU(2) gauge invariance. They then consider two-dimensional, incompressible quantum fluids in more detail. Exploiting U(1)\ifmmode\times\else\texttimes\fi{}SU(2) gauge invariance, they calculate the leading terms in the effective actions of such systems as functionals of the U(1) and SU(2) gauge fields, on large-distance and low-frequency scales. Among the applications of these results are a simple proof of the Goldstone theorem for spin waves and the linearresponse theory of two-dimensional, incompressible Hall fluids, including a Hall effect for spin currents and sum rules for the response coefficients. For two-dimensional, incompressible systems with broken parity and time-reversal symmetry, a particularly significant implication of U(1)\ifmmode\times\else\texttimes\fi{}SU(2) gauge invariance is a duality between the physics inside the bulk of the system and the physics of gapless, chiral modes propagating along the boundary of the system. These modes form chiral $\stackrel{^}{\mathrm{u}}(1)$ and $\mathrm{s}\stackrel{^}{\mathrm{u}}(2)$ current algebras. The representation theory of these current algebras, combined with natural physical constraints, permits one to derive the quantization of the response coefficients, such as the Hall conductivity. A classification of incompressible Hall fluids is outlined, and many examples, including one concerning a superfluid $^{3}\mathrm{He}$-$\frac{A}{B}$ interface, are discussed.
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TL;DR: Correlation functions are one of the key tools used to study the structure of the QCD vacuum and can be calculated using quantum-field-theory methods, such as lattice gauge theory as discussed by the authors.
Abstract: Correlation functions are one of the key tools used to study the structure of the QCD vacuum They are constructed out of the fundamental fields and can be calculated using quantum-field-theory methods, such as lattice gauge theory One can obtain many of these functions using the rich phenomenology of hadron physics They are also the object of study in various quark models of hadronic structure This review begins with available phenomenological information about the correlation functions, with their most important properties emphasized These are then compared with predictions of various theoretical approaches, including lattice numerical simulations, the operator product expansion, and the interacting instanton approximation
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TL;DR: In this paper, the authors present a review of the recent progress in both experiment and interpretation of Penning ionization in larger systems and assess the prospects for attaining a global understanding of the reaction.
Abstract: Molecular-beam experiments have exposed a new wealth of detail on the general reaction ${A}^{*}+B\ensuremath{\rightarrow}A+{B}^{+}+{e}^{\ensuremath{-}}$ first suggested by Penning in 1927. The new capabilities not available to traditional swarm techniques include mass and electron spectroscopy on the reaction products and angle-resolved measurements of the scattering of both reagents and products. These new results have stimulated the recent development of both the electronic structure and the dynamical theories necessary for a first-principles description of at least the simplest of these reactions, those involving small atomic and diatomic species $B$. Recent progress in both experiment and interpretation is critically reviewed, and the prospects for attaining a global understanding of Penning ionization in larger systems are assessed.
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TL;DR: Radar is a powerful technique that has furnished otherwise unavailable information about solar system bodies for three decades as mentioned in this paper, and the advantages of radar in planetary astronomy result from (1) the observer's control of all the attributes of the coherent signal used to illuminate the target, especially the wave form's time/frequency modulation and polarization; (2) the ability of radar to resolve objects spatially via measurements of the distribution of echo power in time delay and Doppler frequency; (3) the pronounced degree to which delay-Doppler measurements constrain orbits and spin vectors;
Abstract: Radar is a powerful technique that has furnished otherwise unavailable information about solar system bodies for three decades. The advantages of radar in planetary astronomy result from (1) the observer's control of all the attributes of the coherent signal used to illuminate the target, especially the wave form's time/frequency modulation and polarization; (2) the ability of radar to resolve objects spatially via measurements of the distribution of echo power in time delay and Doppler frequency; (3) the pronounced degree to which delay-Doppler measurements constrain orbits and spin vectors; and (4) centimeter-to-meter wavelengths, which easily penetrate optically opaque planetary clouds and cometary comae, permit investigation of near-surface macrostructure and bulk density, and are sensitive to high concentrations of metal or, in certain situations, ice. Planetary radar astronomy has primarily involved observations with Earth-based radar telescopes, but also includes some experiments with a spaceborne transmitter or receiver. In addition to providing a wealth of information about the geological and dynamical properties of asteroids, comets, the inner planets, and natural satellites, radar experiments have established the scale of the solar system, have contributed significantly to the accuracy of planetary ephemerides, and have helped to constrain theories of gravitation. This review outlines radar astronomical techniques and describes principal observational results.
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TL;DR: In this article, the fundamental nuclear reactions are classified into binary processes and few-particle processes, and the possibility of electron-screened cold fusion is remarked, while the special features of dense plasmas rest in the enhancement of reaction rates over these fundamental processes due to internuclear manyparticle process.
Abstract: The review begins by grouping the fundamental nuclear reactions into two classifications, namely, the usual binary processes and few-particle processes. In the few-particle processes, the possibility of electron-screened cold fusion is remarked. The special features of dense plasmas rest in the enhancement of reaction rates over these fundamental processes due to internuclear many-particle processes. The manyparticle processes arise from a modification of the short-range correlations between reacting nuclei and are the effects related closely to differences between Coulombic chemical potentials before and after the nuclear reactions. Quantum statistical-mechanical formulation of the enhancement factors is presented. Thermodynamic functions for various realizations of dense plasmas, pertinent directly to the reaction-rate theories through the screening properties and free energies, are summarized. Those analyses are then applied to the estimation of nuclear reaction rates in specific examples of dense astrophysical plasmas, namely, the Sun, brown dwarfs, giant planets, white-dwarf progenitors of supernovae, and helium burning on the degenerate stars, as well as in those dense laboratory plasmas that are found in the inertial confinement fusion experiments, in metal hydrides such as PdD and Ti${\mathrm{D}}_{2}$, in cluster-impact fusion experiments, and in ultrahigh-pressure liquid metals. The essential similarity between the nuclear fusion reactions in supernovae and those projected in the ultrahigh-pressure liquid metals is particularly emphasized.
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TL;DR: A review of the current status of both brown dwarf theory and the searches for these elusive substellar objects can be found in this article, where the physics of brown dwarfs and their interiors are reviewed and an analytic model of the lower edge of the hydrogen main sequence is presented.
Abstract: This review summarizes the current status of both brown dwarf theory and the searches for these elusive substellar objects. The conceptual continuity between the brown dwarf and the well-studied M dwarf branches is emphasized throughout. The physics of their atmospheres and interiors is reviewed and an analytic model of both brown dwarf evolution and the lower edge of the hydrogen main sequence is presented. An extensive discussion of brown dwarf searches in the field, in binaries, around white dwarfs, in clusters, in the solar neighborhood, in the galactic halo, and using proper-motion catalogs is provided, as is a tentative list of candidates in the field. The theory near and below the edge of the main sequence, while sophisticated, is only now being successfully challenged by optical and infrared observations. The near future promises a productive explosion in our knowledge of this problematic galactic population.
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TL;DR: In this paper, a review of the influence of polymer topology on the critical properties of self-avoiding walks, lattice trees, and related geometrical models is presented.
Abstract: Self-avoiding walks, lattice trees, and related geometrical models provide a link between the physics of polymers and the study of critical phenomena. In particular, these models in the presence of a surface provide insight into surface adsorption in dilute polymer systems in a good solvent. The theme of this review is the influence of polymer structure (topology) on the critical properties of these models. Emphasis is placed on recent results by rigorous methods, scaling theory, and conformal covariance theory. Numerical results that may be used to test the predictions of scaling of scaling and conformal covariance theories are also summarized. Related topics such as the adsorption of directed polymers, the semidilute regime, the theta point and theta solvents, and percolation (polymer gels) are briefly discussed in the final section.
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TL;DR: In this article, the slow dynamics of spin glasses is more accurately described by a model based on rather compact droplets which can flip thermally, or by a picture of more diffuse sets of flipping spins with properties described by hierarchical dynamics.
Abstract: It is an open question whether the slow dynamics of spin glasses is more accurately described by a model based on rather compact droplets which can flip thermally, or by a picture of more diffuse sets of flipping spins with properties described by hierarchical dynamics. Techniques have been developed for analyzing spontaneous fluctuations in mesoscopic samples which can directly address this question. In a well-known spin glass, $\mathrm{Cu}\mathrm{Mn}$, the experimental results are better fit by the hierarchical picture. Previously unexplored properties of the space of metastable configurations are directly measurable by these mesoscopic methods.
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TL;DR: Theory and experiment have revealed that novel behavior occurs when a Cs surface is exposed to vapor as mentioned in this paper, which forms only a microscopically thin film as the vapor pressure increases from zero to its saturated value.
Abstract: Theory and experiment have revealed that novel behavior occurs when a Cs surface is exposed to $^{4}\mathrm{He}$ vapor. For temperature $T$ below the wetting temperature (${T}_{w}\ensuremath{\simeq}2$ K), $^{4}\mathrm{He}$ forms only a microscopically thin film as the vapor pressure $P$ increases from zero to its saturated value. For intermediate values of $T ({T}_{w}\ensuremath{\le}T\ensuremath{\le}{T}_{c}\ensuremath{\simeq}2.5 \mathrm{K})$, the film thickness jumps discontinuously at a prewetting transition pressure ${P}_{\mathrm{pw}}(T)$. For $Pg{P}_{\mathrm{pw}}$, and for all $P$ if $Tg{T}_{c}$, the film grows continuously to infinite thickness as saturation is approached. Microscopic theories of these phenomena are discussed in terms of the basic physics of electrons and atomic interactions. Initial experimental observations are summarized. Related phenomena of interest are described, including observation of prewetting with adsorbates other than He and substrates other than Cs.
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TL;DR: The formalism necessary to understand the phenomenon of nonconservation as observed in the neutral-kaon system is presented in this article, and the level of understanding of the phenomenon in the standard model is reviewed.
Abstract: The formalism necessary to understand the phenomenon of $\mathrm{CP}$ nonconservation as observed in the neutral-kaon system is presented. The distinction between indirect $\mathrm{CP}$ violation and direct $\mathrm{CP}$ violation is made, and the level of understanding of the phenomenon in the standard model is reviewed. Attention is placed on new experimental efforts that could definitely establish a first-order or direct effect. The authors analyze the potential for such an observation in both kaon and $B$-meson decays and give the range of predictions from the standard model. Other possible models are considered briefly.
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TL;DR: An up-to-date review of the nucleon-nucleon scattering situation in the intermediate-energy region (100 MeV up to a few GeV) is presented in this paper.
Abstract: An up-to-date review of the nucleon-nucleon scattering situation is presented in the intermediate-energy region (100 MeV up to a few GeV). Total cross-section measurements are discussed, but the main emphasis is on the spin physics. Technical advances for polarized beams and targets are presented. The most recent spin-dependent NN data are reviewed and their influence in phase-shift analyses is discussed. The direct reconstruction of the scattering amplitudes is studied and results are compared to those obtained by phase-shift analyses. Finally future plans and expected improvements are detailed.
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TL;DR: The properties of the WKB method in the discrete representation of the tridiagonal band matrices are reviewed in this paper, where the effect of the core on the pattern of the Rydberg atom level splitting is studied.
Abstract: The properties of the WKB method in the discrete representation are reviewed. The method provides the eigenvalues and the eigenvectors of the three-term recursion relations or, which is the same thing, the tridiagonal band matrices. Applications of the method to the splitting of the Rydberg atom levels in the external electric and magnetic fields are considered. Analytical treatment is given to the problem of the oscillator strength distribution in the quadratic Zeeman and the Stark-Zeeman spectra. In the case of the nonhydrogenic Rydberg atoms, the effect of the core on the pattern of the splitting is studied. Certain alternative applications of the discrete WKB method are considered in brief (the quasienergy spectra of nonlinear oscillators in resonant fields, rotational molecular spectra, calculation of infinite continued fractions).
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TL;DR: In this article, theoretical estimates of spatial, spin, and isospin correlations among the nucleons in nuclei are compared with the observed correlation effects in the inclusive scattering of electrons from nuclei, at energies ranging from a few hundred MeV to several GeV.
Abstract: The authors review theoretical estimates of spatial, spin, and isospin correlations among the nucleons in nuclei. The momentum distribution and spectral function of nucleons in nuclei are also discussed. The theoretical estimates are compared with the observed correlation effects in the inclusive scattering of electrons from nuclei, at energies ranging from a few hundred MeV to several GeV. The observed transparencies of nuclei to protons ejected in inclusive [ital e],[ital e][prime][ital p] reactions are also compared with their theoretical estimates. Finally, the quenching of exclusive single-quasiparticle-type reactions, indicative of the overall strength of correlations in nuclei, is discussed. There appears to be a qualitative agreement between theory and experiment, but a firm quantitative understanding is still to be obtained.
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TL;DR: A review of the current situation in the field of rare $K$ decays can be found in this article, where the authors present the relevant phenomenology, the present experimental situation, and the prospects for the near future.
Abstract: This article reviews the current situation in the field of rare $K$ decays: the relevant phenomenology, the present experimental situation, and prospects for the near future. Study of rare $K$ decays can make a significant contribution in a number of different frontier areas of research in high-energy physics. In the area of $\mathrm{CP}$ violation, study of such rare decays as ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{e}^{+}{e}^{\ensuremath{-}}$, ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{
u}\overline{\ensuremath{
u}}$, and muon polarization in ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ can provide important complementary information to what has been learned from the decay ${K}_{L}^{0}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$. Even though experiments with sufficient accuracy to make a meaningful study of $\mathrm{CP}$ violation are still a few years away, significant progress has been made in this general area during the last decade. A second major area of interest in the field of rare $K$ decays is the search for processes forbidden in the Standard Model, e.g., ${K}_{L}^{0}\ensuremath{\rightarrow}\ensuremath{\mu}e$ and ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\mu}}^{+}{e}^{\ensuremath{-}}$. Various extensions of the Standard Model predict that these processes will occur with branching fractions in the range of ${10}^{\ensuremath{-}10}$ to ${10}^{\ensuremath{-}15}$. Experiments of the last decade have pushed the limits into the ${10}^{\ensuremath{-}10}$ to ${10}^{\ensuremath{-}11}$ range, and further improvements in sensitivity of one to two orders of magnitude can be expected in the next few years. $K$ decays allow one also to study higher-order weak-interaction processes such as ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, ${K}_{L}^{0}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$, ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{
u}\overline{\ensuremath{
u}}$, which are forbidden to first order in the Standard Model. Because of strong suppression, these decay modes offer potential windows on new physics; in addition, they may offer the most reliable measurement of ${V}_{\mathrm{td}}$, one of the elements of the weak mixing matrix in the quark sector. The studies of the ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ channel have achieved data samples of close to 1000 events; the other two modes should be observed for the first time in the next few years. Finally, as a byproduct of these studies, one has been able to look simultaneously for new light particles into which the $K$ meson could decay. Limits obtained for various hypothetical particles are summarized.
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TL;DR: In this paper, a nonrelativistic Hamiltonian containing two-and three-nucleon interactions, and correlated variational wave functions as approximate solutions of the many-body Schrodinger equation are presented.
Abstract: A major goal in nuclear physics is to understand the stability, structure, and reactions of nuclei as a consequence of the interactions between individual nucleons. This colloquium describes one attempt to build a consistent picture of nuclear systems ranging in size from deuterons to neutron stars. The main ingredients are a nonrelativistic Hamiltonian containing two- and three-nucleon interactions, and correlated variational wave functions as approximate solutions of the many-body Schr\"odinger equation. A model that fits both two-body scattering data and nuclear masses will provide the best theoretical input for neutron star properties.
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CERN1
TL;DR: In this article, the authors describe the detection and imaging of ionizing radiation using the Nobel lecture delivered by the author on December 10, 1992, which is based on the article of the same year.
Abstract: This articles is based on the Nobel lecture delivered by the author on December 10, 1992. It describes the detection and imaging of ionizing radiation. (AIP)
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TL;DR: The role played by dynamic symmetries and supersymmetries in nuclear physics is described and interpreted with experimental examples in this article, and their implications for other fields of physics are reviewed briefly.
Abstract: The role played by dynamic symmetries and supersymmetries in nuclear physics is described and interpreted with experimental examples. Implications for other fields of physics are reviewed briefly.