bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spherically Symmetric Potentials
Authors: De Lange O L , Raab R E 
Published: November 2023

Abstract
A number of quantum-mechanical problems involve a potential that is spherically symmetric, at least to a first approximation. For such potentials one can consider a ‘onedimensional’ problem, namely the eigenvalue equation for the radial Hamiltonian (see (5.26)), and in this chapter we use operator methods to treat certain important cases for which exact solutions are possible.
The Isotropic Harmonic Oscillator In An Angular Momentum Basis
Authors: De Lange O L , Raab R E 
Published: November 2023

Abstract
In Chapter 4 we considered a ‘twodimensional’ problem in which L2 and Lz constitute a c.s.c.o. and we derived shift operators for the angular momentum quantum numbers l and m in the eigenkets |lm&gt; of these observables. In Chapter 5 we discussed a ‘one-dimensional’ problem, namely the eigenvalue equation for the radial Hamiltonian (eqn (5.25)). Here we use results from Chapters 4 and 5 to construct shift operators for the eigenkets of the three dimensional problem (5.11)–(5.13).
Relativistic Spherically Symmetric Problems
Authors: De Lange O L , Raab R E 
Published: November 2023

Abstract
In Section 12.1 we discuss some elementary properties of the Klein Gordon and Dirac equations with a spherically symmetric electrostatic potential. In Section 12.2 a simple similarity transformation is applied to the Dirac equation. The main result of this section is (12.70), which applies to the Schrodinger, Klein-Gordon, and (transformed) Dirac equations with a Coulomb potential. Shift operators for energy in the eigenkets of (12.70) are derived (Section 12.3) and they are used to obtain energy eigenvalues (Section 12.4). Expectation values and coordinate space wave functions for the Klein Gordon and Dirac Coulomb problems are calculated in Sections 12.5 and 12.6. A relativistic (Dirac) oscillator is discussed in Sections 12.8-12.10.
The multidimensional importance of time domain magnetic resonance
Authors: Ernst R R 
Published: November 2023

Abstract
It is sometimes claimed that the expansive development that led to the present importance of magnetic resonance in chemistry, biology, and medicine occurred after the introduction of Fourier transform spectroscopy in the late 1960s. It should, however, be recalled that all the basic principles had been known and investigated in detail before, many of them by Professor Erwin L. Hahn. These early investigations may be categorized in three classes: molecular beam magnetic resonance, continuous wave (c.w.) magnetic resonance, and time domain magnetic resonance. Surprisingly, molecular beam magnetic resonance has been the first successful method of observing resonance properties of nuclear spins [1-4], although it presents one of the most demanding approaches. Many important concepts have first been applied in these studies, such as continuous wave absorption, refocusing in inhomogeneous magnetic fields, and pulsed radiofrequency (r.f.) fields. In some sense, molecular beam studies have to be classified as frequency selective time domain experiments, as the particles rapidly move through the fields and the time-scale is provided by the beam velocity. The spectrum is recorded point by point by varying the frequency of the r.f. perturbation.
On the possibility of nuclear self-spin-locking in ferromagnets
Authors: Redfield A G 
Published: November 2023

Abstract
Nuclear spin systems in ferromagnets and antiferromagnets can bend the electronic magnetization, via their hyperfine interaction, so as to produce an apparent magnetic field that is proportional to the transverse nuclear spin magnetization and parallel to it. A nuclear spin system in any solid can also be ‘spin-locked’ by application of a resonant r.f. field along a transverse nuclear magnetization, and transverse spin relaxation is then prevented by the r.f. field. In this Article we combine these ideas and conclude that nuclear spin systems in (anti)ferromagnets might be placed in a transient self-locked state. The plausibility criterion for observation of self-locking is shown to be that the apparent field produced by the maximum nuclear magnetism be larger than the ordinary NMR linewidth. A simple treatment of the coupled electron-nuclear resonance frequency shift is given for the case of small or large tilt of the nuclear magnetization, and we show that if the small-tilt shift is greater than the NMR linewidth, self-locking might be attainable. There is an analogy between the self-locked state, and the random-phase representation of the BCS superconductor provided by Anderson. The self-locked state might be observed by looking for a longT2decay after a suitably chosen preparation.
High-temperature superconductivity and an apparent breakdown of causality
Authors: Weger M 
Published: November 2023

Abstract
Erwin Hahn’s discovery of spin echoes surprised the scientific community because it seemed to be a violation of the second law of thermodynamics. The formation of the echo seemed to indicate a violation of time reversal. Violating causality is one of the strictest taboos of theoretical physics, and the formation of spin echoes seemed to break this taboo. As a graduate student of Hahn I was particularly impressed by the demonstration of the ink strip in glycerol between rotating plastic cylinders, which can be made to disappear and reappear in apparent contradiction of the most basic principles of physics. At present, we encounter a mystery in our understanding of (or, rather the failure to understand) high temperature superconductivity. The experiments are simple, clear, definitive, and very detailed; but the theory is apparently missing. I shall try here to make the point that the cause of this difficulty is over-sensitivity to the apparent breakdown of causality.
The two-pulse spin echo revisited
Authors: Walstedt R E 
Published: November 2023

Abstract
A formulation of the two-pulse spin echo problem appropriate to inhomogeneously broadened NMR lines in solids is presented and discussed. The classical formulation is discussed in the text, with the (equivalent) quantum case outlined in an appendix. The in-phase and quadrature components of the echo signal are given by integrals over the lineshape functiong(w);these integrals can be evaluated numerically in a straightforward fashion. An exact expression is given for the area under the echo waveform, relating it to the areas under the two r.f. pulse field profiles H1(t). The echo area is directly proportional to the lineshape amplitude at the applied r.f. frequencyg(wrr),Thus, one can in principle resolve structure of arbitrary complexity by recording the area under the echo. Numerical calculations are presented to show the dependence of the echo waveforms on pulse shape and length, and on the r.f. frequency relative to the peaks of symmetric and asymmetric NMR lines. The exact phase symmetries of spin echoes are shown to be useful in eliminating unwanted electrical transients from experimental echo signals. A practical example is given.
Coherent Raman beats in electron paramagnetic resonance spectroscopy
Authors: Bowman M K , Massoth R J , Yannoni C S 
Published: November 2023

Abstract
Coherent Raman beats are discussed in the context of electron paramagnetic resonance spectroscopy in the solid state. A general formula is found in the case of many nuclei coupled to a single effective spin S = paramagnetic centre. The results correspond exactly to the idealized three-level model described earlier by Brewer and Hahn in optical spectroscopy in the gas phase. Methods for generating coherent Raman beats are discussed. A single preparation pulse approximating the Hartmann-Hahn match for cross-polarization between the electron spin in its rotating frame and the nuclear spins in their effective field can generate coherent Raman beats. The electron spin echo envelope modulation (ESEEM) is found to be intimately related to coherent Raman beats. Experimental observation of coherent Raman beats is described for free radicals in a single crystal of irradiated malonic acid at room temperature. The coherent Raman beats occur at one of the nuclear ENDOR frequencies.
Optical excitation and detection of spin precession
Authors: Mehring M , Wäckerle G , Appelt S 
Published: November 2023

Abstract
Soon after the discovery of the principal phenomenon of nuclear magnetic resonance (NMR) by Purcellet al.[1] and Blochet al.[2] , it was Hahn [ 3] who realized that spin precession can be observed directly in the rotating frame as a transient phenomenon called free induction decay (FID). In linear response theory, both phenomena, the continuous wave (c.w.) observation and the free precession are related to each other by Fourier transformation. Within the same year, however, Hahn realized that there is more to the motion of spins than just a linear response to radiofrequency field excitation and discovered the spin echo phenomenon [ 4] which led to the foundation of modern NMR spectroscopy and nonlinear optical spectroscopy. In this contribution we want to present a special view on how these early principles of Hahn influenced the development of Optical Excitation and Detection of Spin Precession. For this purpose we consider a very simple physical system, namely an atomic vapour. In optical pumping spectroscopy it is well known that the transmitted light intensity is modulated by irradiating the system with resonant radiofrequency (r.f.) fields [5-8]. By monitoring the transmission of light as a function of the r.f., sublevel splittings of the optically connected states can thus be measured, which are usually not resolved in the Dopplerbroadened optical spectrum.
The manifold Model for space-time
Authors: Joshi Pankaj S 
Published: November 2023

Abstract
By the space-time manifold we mean a four-dimensional differentiable manifold M together with an indefinite Lorentzian metric tensor g which has signature (-, +,+,+). The space-time (M, g) will be assumed to be space and time orientable and will obey several necessary topological regularity conditions such as the Hausdorffness, connectedness and so on, as we shall point out here. Such conditions provide physical reasonability to the space-time model being considered. In this chapter, we specify this basic model of space-time universe which is fundamental to the general theory of relativity and which underlies our considerations here on the global aspects in gravitation and cosmology.
Solutions to the Einstein equations
Authors: Joshi Pankaj S 
Published: November 2023

Abstract
The purpose of this chapter is to discuss several useful space-times which are exact solutions of Einstein equations, and to review some of their properties that are referred to in later chapters. The Einstein equations form a highly non-linear system of differential equations and due to their complexity, a completely general solution is not known. Thus, the known exact solutions usually assume a rather high degree of symmetry such as the spherical or axial symmetry, and the existence of necessary Killing vector fields on the space-time, and to that extent represent an idealized situation. However, such space-time examples provide a good idea of what is possible within the framework of the general theory of relativity outlined in the previous chapter.
Singularities in general relativity
Authors: Joshi Pankaj S 
Published: November 2023

Abstract
In this chapter, we consider the question of nature and existence of spacetime singularities in the general theory of relativity. After Einstein proposed the general theory describing the gravitational force in terms of space-time curvature and proposed the field equations relating the geometry and matter content of the space-time manifold, the earliest solutions found for the field equations were the Schwarzschild metric representing the gravitational field around an isolated body such as a spherically symmetric star, and the Friedmann cosmological models. Each of these solutions contained a space-time singularity where the curvatures and densities were infinite and the physical description would break down.
Gravitational collapse and cosmic censorship
Authors: Joshi Pankaj S 
Published: November 2023

Abstract
In this chapter, we investigate the issue of the final fate of a gravitationally collapsing massive star and the associated cosmic censorship problem. When the star is heavier than a few solar masses, it could undergo an endless gravitational collapse without achieving any equilibrium state. This happens when the star has exhausted its internal nuclear fuel which provides the outwards pressure against the inwards pulling gravitational forces. The theory of singularities discussed in Chapter 5 then implies that for a wide range of reasonable initial data, a space-time singularity must develop. The conjecture that such a singularity of gravitational collapse from a regular initial surface must always be hidden behind the event horizon of gravity is called the cosmic censorship hypothesis (Penrose, 1969). Thus, cosmic censorship implies that the final outcome of gravitational collapse of a massive star must necessarily be a black hole which covers the resulting space-time singularity. Then, causal messages from the singularity cannot reach the external observer at infinity and the predictability in space-time is fully preserved. This hypothesis lies at the foundation of currently well developed and applied theory of black hole physics.
A dynamical systems approach to time series analysis
Authors: Mullin Tom 
Published: November 2023

Abstract
The aim of this chapter is to show how the information extracted from a physical experiment or numerical computation may be analysed using modern signal processing techniques and indicate how the results can be related to ideas from finite-dimensional dynamical systems. The ultimate objective is to see whether a direct connection can be made between the information contained in the time series obtained from a continuous infinite-degree-of-freedom system and the well-developed field of chaos in ordinary differential equations and maps. Before we proceed with the description of the modern nonlinear techniques, we will first of all briefly discuss the traditional linear methods of signal processing. Next we will introduce the concepts of phase portrait reconstruction using the straight-forward ‘method of delays’. The principles are extended by a discussion of the singular value decomposition technique which provides a systematic way of selecting a coordinate system in which the attractor can be constructed and which also deals with the universal problem of noise in experimental observations. A brief discussion of the construction of Poincare maps is then presented as a useful technique for reducing the dimension of the reconstructed attractor. Finally, we discuss the merits and practical limitations of methods of obtaining quantitative estimates from these nonlinear signal processing techniques.
Cooling The Stored Ions
Authors: Ghosh Pradip K 
Published: November 2023

Abstract
The ions trapped, whether in the Paul trap or in the Penning trap, usually have energies of the order of 1 eV, that is, a temperature of about 10 000 K. High temperature means high kinetic energy, and this is un favourable to most trap-based experiments for the following reasons. First, with high kinetic energy, amplitudes of ion oscillations are high and consequently the chances of ion losses are high; this results in loss of sensitivity. Second, high kinetic energy enhances both the first-order and the second-order Doppler effects; so, unless the ions are cooled, all spectroscopic experiments are adversely affected in a major way. While isolation of the ions in the trapped condition does not permit ion energy to be easily dissipated to the surroundings, for the same reason, the trapped ions can be effectively cooled and, once cooled, they can be retained cold in the trap. In recent years, most of the trap-based experiments have used ion cooling of one kind or the other. In this chapter we present an overview of various cooling methods and their applications.
Introduction
Authors: Kimsey Lynn S , Bohart Richard M 
Published: November 2023

Abstract
Gold wasps or cuckoo wasps are common names often applied to the family Chrysididae. Their frequently metallic coloration justifies the former, and cleptoparasitic habits refer to the latter. This brilliant aspect is best observed on a sunny day as the female wasp is searching a nesting site of a favoured wasp host. The sunlight reflects from the parasite and seems to accentuate the metallic colours—blue, green, purple, red, copper, brass, and gold—in various combinations. Most chrysidids are small and, although not all are brilliant, the tiny ones often make up for in colour what they lack in size. The sight of a Hedychridium moving erratically over the sand like a drop of pure gold never fails to astonish the collector. In the Western Hemisphere most chrysidids are metallic blue, green, and purple, in various combinations. In the old world, especially in the southern USSR and Africa, these wasps are often more colourful. A single specimen may be green, blue, purple, copper, gold, and red; all somewhat iridescent. These are interference colours. The true pigment shades of red, brown, and white are not so common. In addition to the often bright integument are the myriads of tiny impressions or punctures which are nearly always present. These modify and often enhance the coloration.
Introductory remarks
Authors: Jones D M 
Published: November 2023

Abstract
Barber Conable, the President of the World Bank, in a speech on Development and the Environment given in Tokyo two months ago, highlighted the significance of global human population growth in environmental change. It took about 130 years for the world’s population to grow from 1 to 2 billion. It will take just 10 years, to the end of the century, to grow from its current level of 5 billion to 6 billion. Ninety per cent of that growth will be in the developing world and in some countries, many of which (such as Kenya and Brazil) are of particular interest to us in this room, the population will double in the next 20-30 years. The most optimistic scenario predicts that world population will stabilize at between 8 and 9 billion sometime in the third decade of the next century, provided that the fundamental and closely linked problems of under-development, poverty, misuse of resources (especially of energy) and environmental ignorance are actively tackled.
Life after extinction
Authors: Seal U S 
Published: November 2023

Abstract
There has emerged on the rapidly changing face of our planet a pattern of an increasing number of animal and plant species reduced in distribution, populations and numbers. Species relatively numerous in total numbers are being fragmented into small isolates with no exchange between them. Small populations face genetic, demographic and environmental risks as a result of their small size and isolation (Ralls, Brugger & Ballou 1979; Ralls & Ballou 1983; Soule 1987). In the extreme case a species is reduced to one population, oscillating and shrinking in numbers, losing genetic diversity and subject to abrupt reductions or extinction through the random whims of natural events or man (Franklin 1980; Gilpin & Soule 1986; Lacy 1987; Goodman 1987).
Analysis of polygamous systems using DNA fingerprinting
Authors: Amos Bill 
Published: November 2023

Abstract
DNA fingerprinting is a method for resolving genetic differences between closely related individuals. In many species the levels of variabilty revealed are sufficient to allow positive paternity analysis. Unfortunately considerable logistic problems are encountered wherever sample sizes are large and putative fathers have not been identified by prior behavioural observations. Clearly the worst cases involve species with highly polygamous mating systems.
Induced genetic variations
Authors: Jablonka Eva , Lamb Marion J 
Published: November 2023

Abstract
In the previous chapter we considered how new genetic information present in somatic cells could cross ‘Weismann’s barrier’ and become part of the germ line. In each of the cases we looked at, the new information was assumed to have arisen through random mutation. Cells with new mutations were subject to Darwinian selection before they, or their DNA, entered the germ line. Although the outcome was Lamarckian, the mechanism was not. The inheritance of acquired characters requires not only that information from the soma is transferred to the germ cells, but also that the environment is instrumental in producing the new variations. Mutations should arise as specific responses to environmental change. They should be directed, not random.
The inheritance of directed epigenetic variations
Authors: Jablonka Eva , Lamb Marion J 
Published: November 2023

Abstract
With classical imprinting, parents transmit to their offspring chromatin marks carrying the stamp of the parent’s sex. The mark is usually transient, and is reversed in the next generation if it passes through the germ line of the opposite sex. Imprinting is therefore a rather special case of the transmission of epigenetic information between generations. A few cases in which a mark is transmitted in a sex-independent fashion and in a more permanent manner have been found with imprinted transgenes, but transgenes are in many ways atypical an’d differ from normal genes. To show that epigenetic inheritance can occur between generations and can have direct evolutionary significance, similar sex-independent and more permanent transmission must be found with normal genes.
The role of epigenetic inheritance systems in adaptive evolution
Authors: Jablonka Eva , Lamb Marion J 
Published: November 2023

Abstract
Our aim in this chapter and the next is to show how, by broadening Darwinian theory to give a role to the biochemically well-recognized EISs discussed in Chapter 4, it is possible to give an explanation of some aspects of evolutionary history that is more satisfying than that based on natural selection of random DNA variations. Both the direct and indirect effects of epigenetic inheritance have been important in evolution. We first discuss the way in which high mutation and epimutation rates may have been moulded by natural selection, and how the frequency of epialleles changes in populations. We then argue that the evolution of complex multicellular organisms was made possible by EISs that already existed in unicellular organisms, and that EISs have shaped some of the developmental strategies seen in higher animals and plants. We also discuss the role of epigenetic variations in macroevolutionary changes.
The evolution and diversity of bats
Authors: Altringham John D 
Published: November 2023

Abstract
Bats are currently placed in a single order, the Chiroptera. They are divided into two sub orders, the Mega- and Microchiroptera, commonly referred to as the megabats and micro bats. The megabats are the Old World fruit bats: large (for bats, 20-1500 g), exclusively plant-eating (i.e. they eat fruit, flowers, nectar, and pollen), and confined to Africa, tropical Asia, and Inda-Australasia. There are about 175 living species, all belonging to one family, the Pteropodidae. Microbats on the other hand are found on every continent except Antarctica, and on many isolated islands. They are, as their name implies, generally smaller than megabats (1.5-150 g), and they eat all sorts of things, as we’ll discover later, although the ancestral microbat almost certainly ate insects and other arthropods. The approximately 790 species are distributed among 17 families. Figure 1.1 will fulfil our immediate needs as we look at the origins of bats, and the source of this diversity. It shows the known fossil bats in relation to a simplified evolutionary tree of extant bats.