bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetism Of Metals And Alloys
Authors: Chikazumi Sōshin , Graham, Jr C D
Published: November 2023

Of all the metallic elements, ferromagnetism occurs only in three of the3dtransition metals (Fe, Co, and Ni), and in heavy rare-earth metals such as Gd, Th, Dy, etc. The3dtransition metals have high Curie points and exhibit ferromagnetism with large spontaneous magnetizations at room temperature, so that alloys containing these metals are used as magnetic materials in a wide range of practical applications. The carriers of the magnetism, the3delectrons, are located relatively far from the atomic core, and are considered to be moving among the atoms (or itinerant), rather than localized at individual atoms. In other words, they form a band structure. On the other hand, the carriers of magnetism in rare-earth metals are 4felectrons, which are located deep inside the atoms (see Section 3.2), so that their magnetic moments are well localized at individual atoms. We shall discuss such cases in Sections 8.2 and 8.3.
Magnetism Of Compounds
Authors: Chikazumi Sōshin , Graham, Jr C D
Published: November 2023

In this chapter, we discuss the magnetism of compounds composed of electropositive3dtransition elements or4frare earth elements combined with electronegative elements which belong to the Illb, IVb, Vb, VIb and Vllb groups. The electronegative elements which belong to these groups are listed in Table 10.1. Some elements such as Al, Ga, In, Tl, Sn and Pb, which belong to Illb and IVb groups, have metallic character, so that they could have been treated as intermetallic compounds in Section 8.4.
Observation Of Domain Structures
Authors: Chikazumi Sōshin , Graham, Jr C D
Published: November 2023

Weiss pointed out in his famous paper on spontaneous magnetization in 1907 that ferromagnetic materials are not necessarily magnetized to saturation, because the spontaneous magnetization takes different directions in different domains.
Technical Magnetization
Authors: Chikazumi Sōshin , Graham, Jr C D
Published: November 2023

When a magnetic material is subjected to an increasing magnetic field, its magnetization is increased and finally reaches a limiting value called thesaturation magnetization.This process is calledtechnical magnetization,because it is essentially achieved by a change in the direction of domain magnetization and can be distinguished from a change in the intensity of spontaneous magnetization.
Various Phenomena Associated With Magnetization
Authors: Chikazumi Sōshin , Graham, Jr C D
Published: November 2023

In magnetic materials, the spins can undergo thermal motion. Therefore magnetic materials exhibit an additional or ‘anomalous’ specific heat in addition to the normal specific heat caused by the thermal motion of the crystal lattice (see Section 6.1). In other words, magnetic materials have additional entropy due to the presence of spins. This entropy is controllable by an external magnetic field.
Engineering Applications Of Magnetic Materials
Authors: Chikazumi Sōshin , Graham, Jr C D
Published: November 2023

Engineering applications of ferromagnetic materials are divided into three major categories: first is soft magnetic materials for AC applications in magnetic cores of transformers, motors, inductors and related devices. For this purpose, high permeability, low coercive field, and low hysteresis loss are required. SecmLd is hard magnetic materials for permanent magnets. For this purpose, high coercive field, high residual magnetization, and accordingly high energy product (see Section 1.6) are required. Third is the semi-hard magnetic materials for magnetic recording. For this purpose, moderately high coercive field and high residual magnetization are required.
Summary Tables Of Particle Properties
Authors: Group Particle Data
Published: November 2023

In keeping with the current interest in tests of conservation laws, we collect together a Table of experimental limits on all weak and electromagnetic decays, mass differences, and moments, and on a few reactions, whose observation would violate conservation laws. The Table is given only in the full Review of Particle Properties, not in the Particle Physics Booklet. For the benefit of Booklet readers, we include the best limits from the Table in the following text.
The one-dimensional electron gas
Authors: Kelly M J
Published: November 2023

The role of 2D systems in elucidating details of quantum transport in semiconductors was a key theme of the previous chapter, which concluded with an investigation of the transition between three and two dimensions. Until recently, 1D systems have been the playground of the theorist; some of the most intractable problems in many-body physics admit analytical or transparent numerical solutions (Lieb and Mattis 1966). It has long been appreciated that an infinitesimal amount of disorder is sufficient to localize all electron states in one dimension (Mott and Twose 1961). Thouless’s ideas, described in Chapter 4, Section 4.3.2, were advanced on the basis of 1D arguments. Once the extent of the applications of Q2D systems had been appreciated (cf. Chapter 16), attempts were made to extend the technology to realize QlD systems and to investigate the Q2D-Q1D transition. It has been important to find ways to confine the Q2D electron gas spatially in one of the two in-plane directions; an increasing number of methods have been found. In this chapter, we mirror the previous one, and describe the wealth of phenomena in QlD systems, as investigated in the 1D electron gas (lDEG). In later chapters (11, 12, and 15) we consider other aspects of physics in QlD systems not considered here.
Hot electron phenomena
Authors: Kelly M J
Published: November 2023

Much interesting physics, and most device applications, are associated with carriers that have been excited in some manner to have an energy well in excess of their energy when in thermal equilibrium. In some cases the carriers behave in a manner that can be associated with an elevated temperature, giving rise to the name hot carrier. The name is used more widely to refer to any highly excited carrier. We discussed the velocity-field curves for bulk Si and GaAs in Chapter 1, Section 1.7. We described the transition from Ohm’s law behaviour at low electric fields, where the carriers are little perturbed from equilibrium, through to the regime of saturated drift velocity at high electric fields. Here the carriers are in a steady state; they are highly excited but are giving up their excess energy to the lattice (via phonon emission) at the same rate that they acquire energy from the electric field. We also introduced the idea of avalanching in very high electric fields where very hot electrons excite further electron-hole pairs, and we related the uncontrolled form of this phenomenon to dielectric breakdown. In Chapter 5, Section 5.6, we described the reduction of mobility seen in a 2DEG as a function of increased applied field. In Chapter 6, Section 6.6, we briefly discussed the current-voltage characteristics of a QlDEG in the presence of a strong electric field where eventually there is less current for a greater applied bias. In this chapter we gather together the main hot carrier effects in semiconductor multilayers, associated with the non-linear response to strong electric or optical fields. Using hetero junctions, one can inject carriers from wider-gap into narrowergap semiconductors. The injected carriers are initially very hot, having an initial velocity as much as 10 times that of the saturated drift velocity, and we can study the detailed mechanisms by which they lose their excess energy and momenta and return to thermal equilibrium temperatures. The modification to the density of states in less than three dimensions slows down the rate of relaxation of hot carriers.
Superlattices and minibands
Authors: Kelly M J
Published: November 2023

The repetition of a pair or more of multilayers (say repeats of m monolayers of GaAs and n monolayers of AlAs) introduces a new periodicity into a crystal structure. The new underlying lattice is called a super lattice; it retains the lattice constant of GaAs in the plane of the layers, but has a new lattice constant in the perpendicular direction set by m<-GaAs + nd  AlAs, where the d  i are the interlayer spacings of the component materials in the direction of the crystal growth. There is an interaction between the discrete bound states found in 1D wells when they are placed adjacent to each other. A narrow band, called a miniband, is formed in the direction of the crystal growth. Its width in energy is determined by the thicknesses and heights of the AlGaAs or AlAs barriers, while its mean energy is determined by the thickness of the GaAs layers. The attraction of super lattices is that new crystals are being prepared which are not available in nature. We can engineer the electronic and optical properties of these crystals at the stage of preparing the growth specification for the multilayers. In this chapter we discuss the theory and experimental results relating to superlattices and minibands.
Vibrational, thermal, and other properties
Authors: Kelly M J
Published: November 2023

So far, we have concentrated on the electronic and optical properties of semiconductor multilayers. In this chapter, we consider the vibrational properties of the host lattice, including the effects of the multilayers themselves. The lattice vibrational dispersion relations for bulk GaAs and AlAs are given in Chapter 1, Fig. 1.6. Such phonon spectra are derived from theories of varying complexity, in an attempt to reproduce experimental data in great detail, but a simple model involving bond-stretching and bondbending forces is sufficient to generate a semi quantitative understanding (Harrison 1980). We can use such a model to describe the lattice vibrations of a superlattice, and the various acoustic, optic, and interface phonon modes that can arise. We describe a number of optical and transport experiments used to detect phonons. The interactions between electrons and phonons play an important role, already considered in Chapter 7, in relaxing hot carriers that have been excited optically or with an electric field.
Silicon and silicon hetero junctions
Authors: Kelly M J
Published: November 2023

The generation and detection of microwave signals for both communications and radar is one area of application where devices with hetero junctions and precision semiconductor multilayers have found rapid deployment. These have been largely two-terminal devices. We begin this chapter with a short introduction to the basic device principles, and then take several diode structures and show how the physics of the preceding chapters has been translated into commercially successful devices. One feature of microwave systems has helped this rapid exploitation, namely that many of the highest performance systems are still hybrid, and there is an immediate role for improved discrete devices in each part of the system. This is particularly so, as the new generation devices have similar radiofrequency impedance properties as the earlier devices, and can therefore be used as instant retrofits. Indeed, the superior properties of the new generation devices have been exploited to improve the overall system specification or to relax the burden on some other critical component of the system. While the discrete devices have improved efficiency or sensitivity, as appropriate, a whole range of secondary attributes are also important. For example the sensitivity of the new devices to ambient temperature is much reduced, and the dynamic range and robustness increased, so that a system can be simplified by dispensing with circuits that compensate for temperature variations or protect formerly delicate components. In monolithic integrated circuit applications, many extra constraints in terms of overall chip compatibility must be satisfied, and it may be some time before some of these discrete devices are deployed in such circuits. The debate between hybrid technology and monolithic integration is active and ongoing, typified by the systems proposed for automotive radar. The hybrid systems are available earlier and will compete on cost until a one-chip solution is found.
Towards 2000
Authors: Kelly M J
Published: November 2023

Contemporary semiconductor science and technology has a momentum that allows one to make predictions on the progress over the next few years based on the experience of the last 20 years. We are concerned in this chapter with the future of materials, technology, structures, physics, and devices in mainstream multilayer semiconductor science and technology. In the concluding chapter, we consider some of the radical alternatives to this mainstream that are being pursued in research and development. In conventional ultra-largescale-integration Si technology, the current developments in the various fabrication steps (lithography, etching, metallization, etc.)will ensure a steady progress in the memory and computational capability through this decade and into the next century. Extrapolations from the 1970s and 1980s are a reasonable guide for the 1990s, as far as the technology is concerned (but see Section 21.8 for a more global picture). The science in Si technology is increasingly concerned with the effects of the intrinsic small scale of the devices, particularly including those of high electric fields, and we review this area more fully in section 21.7. The advances in multilayer semiconductor science have relied on the technology for fabricating the test structures, and the interdependence of science, technology, and devices is becoming more complete, a principal reason for the structure of this book. The science and technology of low-dimensional semiconductors is having a large impact on the science of metrology, and we include a discussion of this in the penultimate section of this chapter.
Polyelectrolytes in solution
Authors: Sedlák Marián
Published: November 2023

Polyelectrolytes can be defined as compounds which are macromolecules or supramolecular entities carrying a large number of ionizable groups. These groups dissociate in solution under certain conditions. As a result, the macro molecule becomes highly charged and is referred to as a polyion. The dissociation of each group on the polyion results in the creation of one counterion of opposite charge with respect to the polyion. If the polyion charge is Q = Ze (e being the electron charge), then each polyion is ‘accompanied’ by Z counterions. Figure 4.1 shows schematically the situation in a polyelectrolyte solution.
Combined static and dynamic light scattering
Authors: Burchard Walther
Published: November 2023

Dynamic light scattering (DLS) has been applied in polymer and colloid science for about 30 years and many review articles and several books have been published on the topic Although the theory is well developed, there are probably several reasons why another review is timely. The first is that research in polymer science has been mainly concerned with flexible linear chains or with rigid rods in the dilute and semi-dilute solution regimes. Recently, however, polymer scientists have become increasingly interested in the behaviour and characterization of other polymeric architectures such as semi-flexible or worm-like chains, cyclic macromolecules, star-branched macromolecules, randomly branched and hyper-branched structures, but systematic studies have not been made and an overview has not yet appeared.
Light scattering and chromatography in combination
Authors: Lloyd Linda L , Kennedy John F , Knill Charles J
Published: November 2023

The need to understand the relationships between the physicochemical characteristics of macromolecules has been the driving force for the development of instrumentation for the characterization of such molecules. Polymer chemists and biochemists have constantly strived for analytical instrumentation and methods which enable molecular weight and structure information to be generated, as it has long been recognized that these are fundamental properties which influence the physical properties of polymeric materials. Many methods have been utilized, such as thermogravimetric analysis, osmometry, viscometry, and light scattering, which provide information on the bulk characteristics of a material, and separation systems, such as liquid chromatography, which attempt to separate the molecules prior to characterization. By combining the separation methodologies with the characterization methods, an exceptionally powerful method becomes available for determining not just bulk characteristics but also distributions of these characteristics.
Regularization
Authors: Ripka Georges
Published: November 2023

The regularization of an effective theory is not just a mathematical trick designed to eliminate whatever infinities happen to occur. It is a physical process and, as such, an integral part of a model. If we knew how to derive a low energy effective theory from QCD, we would know how the theory becomes regularized. For example, the instanton induced interaction (section 3.2) involves delocalized fields, which introduce a non-locality which in turn regularizes the effective theory. More often than not, we adopt a given regularization scheme for convenience. This is tantamount to admitting our ignorance as to its origin. Regularization of an effective theory should also be distinguished from renormalization. A renormalizable model has the attractive feature that it can predict observables which do not depend on the cut-off, which can be taken to infinity. Many of the un-pleasant properties encountered when an effective theory is regularized disappear when the cut-off is sent to infinity.
Correlation Functions: Basic Properties
Authors: Ripka Georges
Published: November 2023

Correlation functions are ground state or thermal expectation values of timeordered products of operators. Two-point correlation functions are also commonly called propagators or Green’s functions. They allow us to study the response of a system to specific probes. The poles of correlation functions correspond to the eigenvalues of the hamiltonian and to on-shell masses of mesons and baryons. The residues at the poles correspond to transition matrix elements of operators between the ground state and the excited states. Correlation functions are thus closely related to experimental data. The application of correlation functions to hadronic physics is reviewed in [9, 92, 93]. Correlation functions are also the objects which are calculated (it is often said that they are ‘measured’) in QCD lattice calculations [10, 94].
Rotations Of Solitons In Flavor Space
Authors: Ripka Georges
Published: November 2023

The underlying physical picture is that of a slowly rotating deformed state. Indeed, if we rotate a hedgehog solution, a degenerate solution is obtained. There is no restoring force opposing spatial rotations. The only energy acquired by the rotation is a kinetic energy, proportional to the squared angular momentum and inversely proportional to a moment of inertia. One expects then that the low-lying excited states of the system, those which dominate the partition function, should consist of a rotational band generated by the rotating soliton. However, further effects need to be taken into account. The angular momentum acquired by the rotating soliton is quantized and cannot therefore take arbitrarily small values. The rotation gives rise to Coriolis forces which deform the soliton. They tend to align the spins with the rotation axis.
Introduction
Authors: Coey J M D
Published: November 2023

The magnetization of a piece of ferromagnetic material has its origin in the spin and orbital magnetic moments of the atomic electrons. These moments arise from the angular momentum of the electrons. Nuclear magnetism is negligible by comparison. Summing the elementary contributions in a volume that is large on the atomic scale, one defines a local magnetization vector, M, that represents the magnetic moment per unit volume. In general, M is not uniform throughout a sample of macroscopic dimensions, but when the sum is carried out within a domain, the magnitude of M, known as the spontaneous magnetization Ms, is uniform; the direction of magnetization varies from domain to domain and typically lies along a crystallographic axis.
Interstitial modification
Authors: Skomski R
Published: November 2023

In 1990, Coey and Sun [Coe90] discovered that the magnetic properties of Sm 2Fe 17 are dramatically altered by nitrogen introduced from a gas in a low-temperature reaction. In the simplest case, gas-phase nitrogenation is conducted on finely ground Sm2Fe17 powder in a pressure of about 1 bar nitrogen gas; at typical nitrogenation temperatures (400-500 °C) the nitrogenation reaction takes a few hours, depending on the particle size.
Actuators
Authors: Howe D
Published: November 2023

The emergence of high-energy rare-earth permanent magnets has facilitated the development of new and improved forms of limited motion actuators, both linear and rotary. Applications span all market sectors, from disk head drives and industrial robots to pneumatic pumps and automatic car door locks. Thus, requirements regarding power and displacement, speed of response, positional accuracy and duty cycle are very wide. In general, however, all actuators provide a force acting directly to move a load, and thus tend to be simpler electromagnetic structures than rotary motors with gears.
A non-linear oscillator in an optical field
Authors: Akhmanov S A , Nikitin S YU
Published: November 2023

A model of a non-linear oscillator. The perturbation method. An oscillator with quadratic non-linearity. Optical second-harmonic generation. An oscillator with cubic non-linearity. The dependence of the oscillation frequency on amplitude. Oscillation phase variations caused by an external field. Self-action effects of light: self-focusing of optical beams and self-modulation of pulses. Optical third-harmonic generation. Non-linear resonance and hysteresis. Optical stability. Parametric generation of light. Parametric resonance. Raman scattering of light. A model of non-linearly bonded oscillators. A non-homogeneous ensemble of non-linear oscillators. “Photon echo”.
Optical waves in linear isotropic media
Authors: Akhmanov S A , Nikitin S YU
Published: November 2023

The dispersion and absorption of light in a linear isotropic medium. The facts confirming Lorentz dispersion theory. Methods of investigation of optical dispersion and absorption. Optical spectroscopy. The propagation of an optical pulse in a dispersive medium.
The Conserved-Order-Parameter Using Model
Authors: Newman M E J , Barkema G T
Published: November 2023

In the last two chapters we have looked in detail at the using model, which is primarily of interest as a model of a ferromagnet. In this chapter we look at a variation on the using model idea, the conserved-order-parameter using model. Although mathematically similar to the normal using model, the conserved-order-parameter using model is used to model very different systems. In particular, it can be used to study the properties of lattice gases.
Analysing Monte Carlo Data
Authors: Newman M E J , Barkema G T
Published: November 2023

In the preceding chapters of this book we have looked at Monte Carlo algorithms for measuring the equilibrium properties of a variety of different models. The next few chapters are devoted to an examination of Monte Carlo methods for the study of out-of-equilibrium systems. But before we embark on that particular endeavour, we are going to take a look at some techniques for the analysis of data from equilibrium simulations. There are no new Monte Carlo algorithms in this chapter, but it does describe several methods of data analysis which can significantly improve the quality of the results we extract from the raw data spit out by the algorithms of the previous chapters.
Elastic and inelastic scattering
Authors: Sakaguchi H
Published: November 2023

When we bombard a nucleus with a nucleon or with light ions like deuterons, 3He, a-particles, etc., various nuclear phenomena occur, including elastic scattering, inelastic scattering, nucleon transfer reactions, and projectile fragmentation, depending on the projectile species and the bombarding energy. The simplest among these phenomena—and one with the smallest amount of internal freedom—is the elastic scattering of a nucleon by a nucleus which we treat in this chapter.

In elastic scattering the target nucleus is not excited, so its initial and final states are the same. Furthermore, the initial states in such experiments are the target ground states, the charge distributions of which can be measured precisely by electron scattering. The wave function of the proton part of the target ground state is restricted and almost defined by the experiment. Thus elastic scattering is an appropriate type of reaction to use as a probe for the interactions and the dynamics which occur inside the nucleus. It is quite understandable that the first successful attempt to explain nuclear reactions microscopically began with elastic scattering.
Deeply bound pionic atoms
Authors: Toki H , Hirenzaki S , Matsuoka N
Published: November 2023

The structure and the formation of DBPAs have been studied theoretically by two groups extensively [1-13]. We follow here the papers by Toki et al. [2,6] to describe the theoretical methods employed in the analysis. We then discuss the experimental methods using direct reactions with hadrons. We would like to mention here that the DBPA states were discovered very recently at GSI using (d, 3He) reactions on 208Pb [14], after some indications of DBPAs were observed at TRIUMF with (n, d) reactions and at the Research Center for Nuclear Physics (RCNP) with (p,2He) reactions.
Neutron properties
Authors: Willis B T M , Carlile C J
Published: November 2023

Neutrons have a number of properties which distinguish them from X-rays. They have a weak interaction with matter and so have high penetrating capacity: walls of furnaces, cryostats, pressure vessels and others present little obstacle to the experimentalist. The atomic scattering amplitude is not linked to the number of shell electrons and so the magnitude of the interaction is different for the different isotopes of an element. The spin of the neutron interacts with the magnetic moments of unpaired electrons, allowing the study of magnetic materials. The energy and wavelength of thermal neutrons are comparable to the thermal energy and spacing of the atoms in solids; therefore, neutron scattering is the natural method for studying excitations, such as phonons and magnons, in crystals.
Neutron detection
Authors: Willis B T M , Carlile C J
Published: November 2023

The neutron is a very weak probe, and so neutron scattering does not unduly disturb the properties of the sample under investigation. From the point of view of scattering theory this is a significant advantage, as it allows us to use the Born approximation (whereby the scattering process is treated by first-order perturbation theory) in describing the neutron–nucleus interaction. However, the weakness of its interaction with matter also renders neutrons difficult to detect directly. Thermal neutrons produce negligible ionization and they can only be detected by the production of secondary ionization arising after neutron absorption. The absorption process leads to the formation of a compound nucleus, which decays either by the emission of a gamma ray or by a splitting of the compound nucleus into two charged nuclei. In neither case the energy of the incident neutron can be measured directly, as the absorption reactions are strongly exothermic with the release of several MeV of energy.
Polarized neutrons and magnetic neutron diffraction
Authors: Willis B T M , Carlile C J
Published: November 2023

Atoms such as iron, cobalt, manganese and nickel, in the first transition series of elements, have incomplete 3d electronic shells with unpaired electrons. These unpaired electrons give rise to a resultant magnetic moment, and the interaction of this atomic moment with the magnetic moment of the neutron gives rise to magnetic neutron scattering. In this chapter, we shall be concerned with the magnetic scattering of polarized neutron beams by magnetic materials. Magnetic neutron scattering is always accompanied by nuclear neutron scattering, as described in Chapter 7.
Small-angle neutron scattering
Authors: Willis B T M , Carlile C J
Published: November 2023

The theory and practice of small-angle X-ray scattering (SAXS) dates back to the 1930s and is well described in the classic book of Guinier and Fournet (1955). Small-angle neutron scattering (SANS) came much later. It was not until the early 1970s, when position-sensitive detectors on cold neutron guides became available, that systematic studies began using small-angle neutron scattering, but after this relatively late start the technique rapidly became one of the most popular and productive of all neutron scattering methods. SANS has been applied to a very wide range of problems, including the study of polymer conformations and morphology, the study of biological structures, the characterization of voids and precipitates in alloys, and the study of flux-line lattices in superconducting materials. The technique of ‘contrast variation’ is largely responsible for the success of SANS, especially in the study of soft condensed matter and biological systems. There are over 30 SANS instruments in operation worldwide at both reactor and spallation sources. In spite of an apparent wealth of instruments, the demand for beam time considerably outstrips the time available.
Neutron optics
Authors: Willis B T M , Carlile C J
Published: November 2023

Neutron optics refers to phenomena which arise from the interference between the incident and the scattered neutron waves. This is in contrast to the topics in earlier chapters of this book, where we have been concerned with interference between the scattered waves alone. The wave Halban and Preiswerk (1936) and by Mitchell and Powers (1936) using ‘white’ neutrons from a radium–beryllium source, and more convincingly by Zeilinger et al. (1988) using monochromatic neutrons from a reactor source. The subject of neutron optics itself began with the work of Fermi and Zinn (1946), who demonstrated the mirror reflection of a collimated beam of thermal neutrons. Since then nearly all the classical optical phenomena of reflection, refraction and interference have been shown to occur with neutrons.
Introduction
Authors: Dendy R O
Published: November 2023

The solid, liquid, and gaseous states of matter which occur at the surface of our planet are not typical of matter in the universe at large. Most of the visible matter in the universe exists as plasma, whereas lightning and the aurora are the only natural manifestations of the plasma state on Earth. In a plasma, the energy of the particles is so great that the electric forces which bind the atomic nucleus to its electrons are overcome. One might think of the resulting assembly of positively and negatively charged particles as a gas, but the waves that occur in it have much in common with waves in electrically conducting solids, and its bulk behavior is best described using terminology and equations developed for fluids: hence the fact that plasma is referred to as the fourth state of matter. For these reasons, when studying plasma physics, one often needs to rearrange and reapply concepts already acquired elsewhere, rather than deal with topics that are unfamiliar.
Early Developments
Authors: Luchini P , Motz H
Published: November 2023

An undulator is a device for generating electromagnetic radiation in a narrow spectral interval at frequencies ranging from radio or millimetre waves to X-rays. This is achieved by letting an electron beam with energy ranging from 1 MeV, say, to 1000 MeV pass through an array of magnets. If the device is placed into an optical resonator with mirrors at both ends, coherent radiation may be produced. By analogy with conventional lasers, it is then called a Free-electron Laser (FEL) (this term was introduced by Madey 1971a, b), although its manner of functioning is rather different from that of atomic or molecular lasing media.
Overview of The General Operational Principles
Authors: Luchini P , Motz H
Published: November 2023

In the following chapters a detailed theory of the workings of undulators and free-electron lasers based on Hamiltonian mechanics will be presented. It will be useful to precede it here with an exposition of the various points of view from which the problem may be surveyed.
Small-Signal, Small-Gain Free-Electron Laser
Authors: Luchini P , Motz H
Published: November 2023

When an electromagnetic wave of approximately the same frequency as the spontaneous undulator emission is driven through the undulator simultaneously with the electron beam, an interaction between the beam and the wave takes place which can lead to a noticeable exchange of energy. In this case the undulator becomes a coherent electromagnetic amplifier capable of working from microwaves to visible and shorter than visible wavelengths, and takes on the name of Free-Electron Laser (FEL).
Undulator Operation
Authors: Luchini P , Motz H
Published: November 2023

This chapter deals with a collection of problems which do not pertain to the physics of the undulator proper, but rather to its interaction with the other parts that contribute to forming a working instrument, in particular the particle accelerator that produces the electron beam and the optical cavity that allows the undulator to be transformed into a freeelectron laser.
Rare Earth Magnetism
Authors: Jensen Jens , Mackintosh Allan R
Published: November 2023

The aim of the authors in this monograph has been to present a general review of the magnetic properties of the rare earth metals, and a comprehensive, unified, and coherent account of the magnetic structures and excitations. These both reflect the nature of the fundamental interactions, and determine many of the characteristic properties of the metals. The authors have tried to concentrate on the essential principles and their applications to typical examples, generally restricting the discussion to the pure elements and considering alloys and compounds only when they are necessary to illuminate particular topics. Both authors have been involved for some time in the effort that has been made in Denmark to study, both theoretically and experimentally, the magnetic structures and especially the excitations in the rare earths. This account of the subject represents the results of their experience, and it is has been written in the hope that it will be useful not only to those who have a special interest in rare earth magnetism, but also to a wider audience who wish to learn something about the techniques and achievements of modern research in magnetism.
Magnetic Scattering Of Neutrons
Authors: Jensen Jens , Mackintosh Allan R
Published: November 2023

The scattering of low-energy neutrons provides an extremely powerful experimental technique for studying the properties of solids. The neutron has a number of special characteristics, on which its utility as a tool for examining magnetic materials depends. Because it is a neutral particle, it can penetrate deeply into most crystals, interacting through its magnetic moment with the electronic moments strongly enough to be measurably scattered, but without disturbing the magnetic system too severely. As a consequence, the great majority of neutrons participate in at most one scattering event, and they sense the properties of the unperturbed crystal. Thermal neutrons, with energies of the order of 25 meV, corresponding to wavelengths of the order of 2 Å, match both the interatomic spacings and the energies and momenta of the magnetic excitations, and are generated with adequate intensity by research reactors. Cold neutrons, with energies around 5 meV and wavelengths about 4Å, which are emitted from cooled moderators in reactors, may be even more ideally suited for studying the spatial arrangement and the dynamics of the magnetic moments.
Spin Waves In Periodic Structures
Authors: Jensen Jens , Mackintosh Allan R
Published: November 2023

Because of the modification of the translational symmetry, the spin waves in modulated magnetic structures display certain interesting aspects which are not shared by the simple ferromagnetic structure. However, this same feature makes their experimental study considerably more difficult, and the results which have been obtained on such systems are still relatively sparse. This chapter is correspondingly short, and in its two sections we distinguish between structures incommensurable with the lattice periodicity, when the translational symmetry in the direction of the wave-vector is, in principle, destroyed, and commensurable structures, in which this symmetry is only modified, though possibly quite drastically.
Calculational Methods for Quantum Electrodynamics
Authors: Pike frs E R , Sarkar Sarben
Published: November 2023

In the previous chapters we have developed the general structure of quantum electrodynamics. It is now necessary to give detailed rules for calculating processes of interest. Our use of the path integral for this purpose is mainly due to Feynman. The method that we will present is perturbation theory and also is widely applicable to theories other than quantum electrodynamics.
Par Tially Attractive Chains: Experimental Results
Authors: Cloizeaux Jacques des , Jannink Gerard
Published: November 2023

The behaviour of polymer solutions at various temperatures shows the existence of a demixtion phenomenon similar to that observed with binary mixtures of small molecules. Moreover, specific properties have been noted, characterizing the polymer state in poor solvent, and the progressive collapse of chains in dilute solutions when the temperature is lowered.
The Ubiquitous Photon
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

The authors' aim in this book is to give a pedagogical introduction to the helicity method, illustrated by many examples, and to summarize some ten years of research on the subject. Only some degree of familiarity with Feynman diagrams and Dirac algebra is required from the reader. The book also provides an extensive list of helicity amplitudes and cross-sections for many of the most important QED and QCD processes at high energies, some being new and not available in the literature previously.
Introduction
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

With energy galore, one can explore proton’s core more and more. Of all fundamental interactions in nature, the electromagnetic interactions between charged particles were the first to be studied extensively. The development of renormalized perturbation theory by Tomonaga, Schwinger, Feynman and Dyson [1] in the late 1940’s made quantum electrodynamics (QED) into an extremely successful theory which yielded many very precise predictions which were repeatedly confirmed by experiment, two prominent examples being the Lamb shift [2] and the anomalous magnetic moments of the electron and the muon [3]. QED, a relativistic quantum field theory based on an Abelian gauge symmetry, became the prototype field theory for all other interactions.
Helicity states
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

A deep emotion comes from true devotion to the right notion of spin in motion. In the following chapters, we shall only work in the high energy limit, which means that we shall neglect the fermion masses. Later on, in Chapter 7, we shall present the modifications to the helicity method which are necessary when the finiteness of the fermion mass has to be considered. For massless fermions, helicity states are Lorentz invariant notions. It is the aim of this book to show how much easier it is to calculate first the helicity amplitudes for a given process and to add their squared absolute values to obtain the cross section rather than following the procedures of Chapter 2. Of course, in Chapter 2, we only treated simple examples, for which the summation of |M|2 over the polarization states was not such a tremendous amount of work. However, when a process is described by n Feynman diagrams, it amounts to writing down n(n + 1)/2 traces. In the case of e+e-  →e+e- γ, γ, we have 40 Feynman diagrams, and, if we include Z-exchange, this number increases to n = 80.
Single Bremsstrahlung in QCD
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

Color is a complication for gluon radiation:Its nicest implication is jet fragmentation. We now want to apply the helicity amplitude method for the calculation of QCD processes. Compared to QED calculations, there are three major sources of complications:There is a complication due to the appearance in the Feynman diagrams of color matrices or SU(3) structure constants. We shall see that a good choice for the polarization vectors of the gluons has the net result that one or more Feynman diagrams can be made to vanish. In this way, the helicity amplitude method reduces the amount of color algebra one has to perform to obtain cross section formulae.
Finite Mass Effects
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

The mere neglect of a mass effect is quite suspect and often not correct. In the previous chapters, we developed a general formalism for calculating multiple bremsstrahlung in gauge theories at high energies. By considering the limit of vanishing fermion masses, we were able to obtain simple expressions for the various helicity amplitudes. For high energy processes, the massless fermion limit is a good approximation unless nearly collinear particle configurations are encountered. In these kinematical situations, finite mass corrections have to be introduced for a correct description of the process.
Summary of QED formulae
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

All the following formulae are presented in the centre-of-mass system, with total energy denoted by 2E. Unless otherwise stated, we take the positive The indication m = 0 in the section headings implies that, throughout the section, we neglect the effects of a finite electron and/or muon mass. Consequently, the formulae are not valid in certain kinematical configurations. For a discussion of the ranges of validity of the approximation, we refer to Section 3. 4. Alternatively, the indication m ≠0 implies that the formulae in the section are valid to leading order in the fermion masses.
Beamstrahlung
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

Photons mediate,but electrons radiate:The loss of counting rate makes people fulminate. In this book, the helicity method is applied to a variety of processes. These processes are conveniently described in terms of Feynman diagrams, and as a result all formulae obtained so far, including those of Chapters 9 and 10, are each proportional to powers of the relevant coupling constants. Such applications of the helicity method are by now completely understood, although the calculations remain to be worked out for processes involving more particles, and further simplifications can be achieved in some cases.
Outlook
Authors: Gastmans R , Wu Tai Tsun
Published: November 2023

The use of helicity is not an eccentricity:It is pure simplicity which brings felicity. The ubiquity of the photon is a well-known fact in particle physics. Photons are necessarily present whenever charged particles take part in a process. The same is true for gluons when strongly interacting particles collide or decay. Photons and gluons being the carriers of the electromagneticforce and the strong force, they play a fundamental role in particle physics and their ubiquity only underscores this fact. It is therefore essential to study carefully the processes in which they take part. To understand their behaviour is to understand two fundamental forces in nature and the helicity method is a key ingredient in this exploration.We hope that, by now, the reader is convinced that the helicity method is an efficient way for obtaining cross section formulae in the high-energy limit. Nevertheless, we learn from the examples studied in the previous chapters that the final result of the calculation is often much simpler than the intermediate formulae which had to be worked out. This is because the starting point of the calculation usually consists of many Feynman diagrams. As a result, we strongly suspect that there is still room for improvement in the helicity method.
Statistical Physics of Fracture and Breakdown in Disordered Systems
Authors: Chakrabarti Bikas K , Gilles Benguigui L
Published: November 2023

Under extreme conditions the mechanical or electrical properties of solids tend to be destabilized and failure or breakdown occurs. In practice these instabilities in the solid often nucleate or spread from disorders in the structure of the solid. This book investigates the modelling of such failure and breakdown processes. The basic principles are illuminated with a large number of computer simulations and laboratory simulations or `table top' experiments. Three particular case studies of failure are presented: electrical failures like fuse and dielectric breakdown; mechanical fracture; and earthquakes as an example of dynamic failure.
Electrical Breakdown in Disordered Solids
Authors: Chakrabarti Bikas K , Gilles Benguigui L
Published: November 2023

In this chapter we shall begin with the problems associated with failures in disordered solids under the influence of an electric field, because this kind of failure is simpler than the mechanical failure or fracture. However, all the cases of failure present some common features, so that the study of electric failures will provide a convenient framework for introducing several important concepts.
Entangled polymer dynamics
Authors: Rubinstein Michael , Colby Ralph H
Published: November 2023

The Edwards tube model of polymer entanglements was already discussed in Section 7.3.1. The topological constraints imposed by neighbouring chains on a given chain restrict its motion to a tube-like region (see Fig. 7.10) called the confining tube. The motion of the chain along the contour of the tube (the primitive path) is unhindered by topological interactions. Displacement of monomers in the direction perpendicular to the primitive path is restricted by surrounding chains to an average distance a, called the tube diameter.
The development of an evidence-based approach to tackling health inequalities in Britain
Authors: Kelly Michael P
Published: November 2023

In Britain there has been a profound shift in the way that health inequalities have been defined and tackled, politically and scientifically, over the last three decades. The approach has altered from being an interesting academic problem of somewhat worthy concern, to becoming highly politicized and then demonized and, most recently, to being one of the key targets for an evidence-based approach to policy.
What Works for Children
Authors: Liabo Kristin , Frost Sarah , McNeish Diana , Sheldon, Trevor , Roberts Helen
Published: November 2023

Following the UK Government’s guidance that services be based on the best evidence of what works (Department of Health 1998), various initiatives tasked with getting research into practice have emerged in health and social care (CEBSS 2003; NICE 2005; Research in Practice 2005). Research evidence indicates that interventions in early childhood can make a difference to inequalities and other important outcomes in later life (Roberts 1997, 2000; Hertzman and Power 2004), and Government programmes have increasingly paid attention to this (Glass 1999, 2001).
The National Institute for Health and Clinical Excellence
Authors: Littlejohns Peter
Published: November 2023

The National Institute for Clinical Excellence (NICE) was established in 1999 to provide guidance to the National Health Service (NHS) on the clinical and cost effectiveness of health care interventions. During its first 6 years NICE produced 87 appraisals (with 54 in development), 37 clinical guidelines (with 42 in development), and 112 interventional procedures (with 61 in development). On 1 April 2005 the National Institute for Health and Clinical Excellence (also to be called NICE) was established by the transfer of the functions of the Health Development Agency to the National Institute for Clinical Excellence.