Showing papers in "Physics Today in 1994"
825 citations
TL;DR: In this paper, the authors present a model for scalar fields with spin and canonical quantization, and the nature of perturbative cross-sections for high-energy scattering.
Abstract: Part I. Scalar Fields: 1. Classical fields and symmetries 2. Canonical quantization 3. Path integrals, perturbation theory and Feynman rules 4. Scattering and cross sections for scalar fields Part II. Fields with Spin: 5. Spinors, vectors and gauge invariance 6. Spin and canonical quantization 7. Path integrals for fermions and gauge fields 8. Gauge theories at lowest order Part III. Renormalization: 9. Loops, regularization and unitarity 10. Introduction to renormalization 11. Renormalization and unitarity of gauge theories Part IV. The Nature of Perturbative Cross Sections: 12. Perturbative corrections and the infrared problem 13. Analytic structure and infrared finiteness 14. Factorization and evolution in high energy scattering 15. Epilogue: bound states and the limitations of perturbation theory Appendices References Index.
665 citations
TL;DR: An approach to design electro‐optical systems that measure and undo the effects of clear‐air turbulence in real time, delivering near‐diffraction‐limited performance at infrared and visible wavelengths at optical wavelengths.
Abstract: Optical observations by ground‐based astronomers have long been limited by the distorting effects of the Earth's atmosphere. Primary mirrors have been polished to exquisite accuracy for telescopes with apertures as large as 10 meters, but at optical wavelengths these can deliver an angular resolution typically no better than that of a 25‐cm telescope, as atmospheric turbulence deforms the image on a millisecond time scale. One (highly expensive) approach to overcome this problem has been to loft instruments such as the Hubble Space Telescope above the atmosphere. Another approach, pursued by instrument builders in the astronomy community and their counterparts in the military, has been to design electro‐optical systems that measure and undo the effects of clear‐air turbulence in real time. (See figure 1.) A number of such adaptive optic devices have already been built and operated on large ground‐based telescopes, delivering near‐diffraction‐limited performance at infrared and visible wavelengths. With th...
643 citations
TL;DR: The 23-volume "Encyclopedia of Applied Physics" seeks to demonstrate the synergy between physics and technological applications as discussed by the authors, and provides a broad overview of the main aspects of physics and their applications.
Abstract: The 23-volume "Encyclopedia of Applied Physics" seeks to demonstrate the synergy between physics and technological applications. Information is presented according to the following subject areas: general aspects; mathematical and information techniques; measurement sciences, general devices and/or methods; nuclear and elementary particle physics; atomic and molecular physics; electricity and magnetism; optics (classical and quantum); acoustics; thermodynamics and properties of gases; fluids and plasma physics; condensed matter - structure and mechanical properties; thermal, acoustic, and quantum properties; electronic properties; magnetic properties; dielectrical and optical properties; surfaces and interfaces; materials science; physical chemistry; energy research and environmental physics; biophysics and medical physics; geophysics, meteorology, space physics and aeronautics.
613 citations
TL;DR: In this article, Benedetto and Mitrea introduced the idea of irregular sampling in the construction of wavelet transform on Discrete Sets, and showed that the sampling theorem can be expressed as a regular sampling problem.
Abstract: Core Material Construction of Orthonormal Wavelets, R.S. Strichartz An Introduction to the Orthonormal Wavelet Transform on Discrete Sets, M. Frazier and A. Kumar Gabor Frames for L2 and Related Spaces, J.J. Benedetto and D.F. Walnut Dilation Equations and the Smoothness of Compactly Supported Wavelets, C. Heil and D. Colella Remarks on the Local Fourier Bases, P. Auscher Wavelets and Signal Processing The Sampling Theorem, Phi-Transform, and Shannon Wavelets for R, Z, T, and ZN, M. Frazier and R. Torres Frame Decompositions, Sampling, and Uncertainty Principle Inequalities, J.J. Benedetto Theory and Practice of Irregular Sampling, H.G. Feichtinger and K. Grochenig Wavelets, Probability, and Statistics: Some Bridges, C. Houdre Wavelets and Adapted Waveform Analysis, R.R. Coifman and V. Wickerhauser Near Optimal Compression of Orthonormal Wavelet Expansions, B. Jawerth, C.-C. Hsiao, B. Lucier, and X. Yu Wavelets and Partial Differential Operators On Wavelet-Based Algorithms for Solving Differential Equations, G. Beylkin Wavelets and Nonlinear Analysis, S. Jaffard Scale Decomposition in Burgers' Equation, F. Heurtaux, F. Planchon, and V. Wickerhauser The Cauchy Singular Integral Operator and Clifford Wavelets, L. Andersson, B. Jawerth, and M. Mitrea The Use of Decomposition Theorems in the Study of Operators, R. Rochberg
369 citations
TL;DR: Introductory digital image processing optical techniques intensity based analysis methods temporal phase measurement methods spatial phase measurements methods phase unwrapping methods analysis methods in speckle photography and PIV applications.
Abstract: Introductory digital image processing optical techniques intensity based analysis methods temporal phase measurement methods spatial phase measurement methods phase unwrapping methods analysis methods in speckle photography and PIV applications.
271 citations
TL;DR: The Superconducting Super Collider (SSC) was cancelled by the International Organization for Standardization (IOSS) in 2003 as discussed by the authors, leading to an examination of possible alternative concepts for investigating some of the same physics.
Abstract: High‐energy accelerators have been physicists’ main tools for exploring the building blocks of matter for more than 60 years. During this time the particle energy has increased exponentially as a result of a combination of improvements in existing machines and the invention of new acceleration techniques. Historically, whenever a given type of accelerator has reached the limit of its performance, an innovative idea for particle manipulation, storage, cooling or acceleration has made possible experiments at ever higher energies. The tremendous increase in the energy of accelerators has not, however, been without an increase in capital costs. The cancellation of the Superconducting Super Collider makes timely an examination of possible alternative concepts for investigating some of the same physics.
270 citations
TL;DR: In this paper, the authors describe the surface properties of semiconductors with Zincblende structures and show that the surface states and surface band-bending regions in non-equilibrium are occupied.
Abstract: 1. Introduction.- 2. Surface Space-Charge Region in Thermal Equilibrium.- 3. Surface States.- 4. Occupation of Surface States and Surface Band-Bending in Thermal Equilibrium.- 5. Surface S pace-Charge Region in Non-Equilibrium.- 6. Interface States.- 7. Cleaved {110} Surfaces of III-V and II-VI Compound Semiconductors.- 8. {100} Surfaces of III-V, II-VI, and I-VII Compound Semiconductors with Zincblende Structure.- 9. {100} Surfaces of Diamond, Silicon, Germanium, and Cubic Silicon Carbide.- 10. Diamond, Silicon, and Germanium {111}-2 x 1 Surfaces.- 11. Si(111)-7 x 7 and Ge(111)-c(2 x 8) Surfaces.- 12. Phase Transitions on Silicon and Germanium {111} Surfaces.- 13. {111} Surfaces of Compounds with Zincblende Structure.- 14. Monovalent Adatoms.- 15. Group-III Adatoms on Silicon Surfaces.- 16. Group-V Adatoms.- 17. Oxidation of Silicon and III-V Compound Semiconductors.- 18. Surface Passivation by Adsorbates and Surfactants.- 19. Semiconductor Interfaces.- References.- Index of Reconstructions and Adsorbates.
251 citations
TL;DR: In this article, Thorne describes the quest to understand Einstein's general theory of relativity and its predictions about the universe, and how to determine where and how Einstein's theory fails and what then replaces it.
Abstract: During the last 30 years Kip Thorne has had the joy of participating in a great quest. The quest to understand Einstein's general theory of relativity and its predictions about the universe, and the quest to discern where and how Einstein's theory fails and what then replaces it. This quest has lead him through the labyrinths of exotic objects: black holes, white dwarfs, neutron stars, singularities, gravitational waves, worm-holes and yes, even time machines. The quest, with its hundreds of participants scattered over the globe has led him to appreciate the international character of science, the different ways that scientific enterprise is organized in different societies, and the inexorable manner in which science bas been intertwined with political currents, especially the Soviet/American conflict. This book is the author's attempts to share these insights with lay readers, and the scientists who work in fields other than his. A book of many interlocking themes held together by a thread of history; the history of the development of our times about curved space and warped time, and most especially black holes.
244 citations
TL;DR: A similar scenario was played out at the end of the last century, when some great physicists declared that only minor problems remained to be solved as mentioned in this paper, and the vaunted "theory of everything" was invoked to declare that no new and exciting problems appeared in physics.
Abstract: Are we moving toward a time when no new and exciting problems appear in physics? Would the vaunted “theory of everything” mean the end of creative physics? A similar scenario was played out at the end of the last century, when some great physicists declared that only minor problems remained to be solved.
TL;DR: An Interpretive Introduction to Quantum Field Theory as discussed by the authors presents the basic ideas of quantum field theory in a way that is understandable to readers who are familiar with non-relativistic quantum mechanics.
Abstract: Quantum mechanics is a subject that has captured the imagination of a surprisingly broad range of thinkers, including many philosophers of science. Quantum field theory, however, is a subject that has been discussed mostly by physicists. This is the first book to present quantum field theory in a manner that makes it accessible to philosophers. Because it presents a lucid view of the theory and debates that surround the theory, An Interpretive Introduction to Quantum Field Theory will interest students of physics as well as students of philosophy. Paul Teller presents the basic ideas of quantum field theory in a way that is understandable to readers who are familiar with non-relativistic quantum mechanics. He provides information about the physics of the theory without calculational detail, and he enlightens readers on how to think about the theory physically. Along the way, he dismantles some popular myths and clarifies the novel ways in which quantum field theory is both a theory about fields and about particles. His goal is to raise questions about the philosophical implications of the theory and to offer some tentative interpretive views of his own. This provocative and thoughtful book challenges philosophers to extend their thinking beyond the realm of quantum mechanics and it challenges physicists to consider the philosophical issues that their explorations have encouraged.
TL;DR: In this paper, the renormalization group method in the theory of dynamical systems, splitting of separatrices, and problems related to hyperbolic dynamical system are discussed.
Abstract: This book concerns areas of ergodic theory that are now being intensively developed. The topics include entropy theory (with emphasis on dynamical systems with multi-dimensional time), elements of the renormalization group method in the theory of dynamical systems, splitting of separatrices, and some problems related to the theory of hyperbolic dynamical systems.
TL;DR: In this paper, the colored rings shown in figure 1 are a spectacular manifestation of one type of nonlinear optical frequency conversion: parametric amplification of quantum noise produced by the propagation of an intense pulse of ultraviolet radiation through a crystal of barium borate.
Abstract: The colored rings shown in figure 1 are a spectacular manifestation of one type of nonlinear optical frequency conversion: parametric amplification of quantum noise. The amplification in this case is produced by the propagation of an intense pulse of ultraviolet radiation through a crystal of barium borate. When intense electromagnetic radiation propagates through such a material, whose polarization response at optical frequencies manifests a strongly nonlinear dependence on electric field amplitude, nonlinear mixing of the input radiation generates new spectral components. We can exploit this phenomenon to generate coherent radiation at frequencies for which we have no convenient laser sources.
TL;DR: In the process of photosynthesis, the process by which plants convert solar energy into chemical energy, results in about 10 billion tons of carbon entering the biosphere annually as carbohydrate, equivalent to about eight times mankind's energy consumption in 1990.
Abstract: Photosynthesis, the process by which plants convert solar energy into chemical energy, results in about 10 billion tons of carbon entering the biosphere annually as carbohydrate—equivalent to about eight times mankind's energy consumption in 1990. The apparatus used by plants to perform this conversion is both complex and highly efficient. Two initial steps of photosynthesis—energy transfer and electron transfer—are essential to its efficiency: Molecules of the light‐harvesting system transfer electronic excitation energy to special chlorophyll molecules, whose role is to initiate the directional transfer of electrons across a biological membrane; the electron transfer, which takes place in a pigment‐protein complex called the reaction center, then creates a potential difference that drives the subsequent biochemical reactions that store the energy. (Higher plants use two different reaction centers, called photosystems I and II, while purple bacteria make do with a single reaction center. The difference i...
TL;DR: In this article, the authors systematically develop these models from the elementary level, through an introduction to tensor algebra, to the use of group theory in spectroscopy, and show how these models can be applied to the structure of atomic nuclei.
Abstract: applications to the structure of atomic nuclei. The author systematically develops these models from the elementary level, through an introduction to tensor algebra, to the use of group theory in spectroscopy. The book's extensive and detailed appendix includes a large selection of useful formulae of tensor algebra and spectroscopy. The serious graduate student, as well as the professional physicist, will find this complete treatment of the shell model to be an invaluable addition to the literature.
TL;DR: In this article, air trapped in layers of quasipermanent ice in the Arctic and the Antarctic has been used as a record of the Earth's atmospheric composition for nearly 1500 years.
Abstract: Humans are greatly perturbing the global nitrogen cycle. Perhaps the best evidence for this perturbation comes from air trapped in layers of quasipermanent ice in the Arctic and the Antarctic. Ice cores taken from these two polar regions give us a 2000‐year record of the Earth's atmospheric composition. This record indicates a striking constancy in nitrous oxide concentrations, at approximately 285 parts per billion, for nearly 1500 years. (See figure 2.) Since about 1600 AD, however, nitrous oxide concentrations have been increasing, and the present‐day atmospheric burden of this gas is greater than at any other time in the past two millennia. Furthermore, nitrous oxide concentrations continue to increase, currently at a rate of about 0.3% per year. These variations indicate that many nitrogen flows are now larger than in preindustrial times, and other evidence suggests that human activity is responsible. (See figure 1.).
TL;DR: The dream of the all‐optical processing of information has motivated efforts over the past decade to create sensitive semiconductors that have large optical nonlinearities.
Abstract: The dream of the all‐optical processing of information has motivated efforts over the past decade to create sensitive semiconductors that have large optical nonlinearities. Semiconductors have been the medium of choice in part because a well‐developed materials technology has already been built around them. One can design semiconductor structures easily and predict their performance accurately.
TL;DR: In this article, high-L Rydberg States of Helium have been used to model the long-range Casimir interactions of two-electron atoms in Perturbation Theory.
Abstract: An Overview of LongRange Casimir Interactions L. Spruch. Experimental Studies of High-L Rydberg States in Helium S.R. Lundeen. High Precision Calculations for the Rydberg States of Helium G.W.F. Drake. High Rydberg States of Two-Electron Atoms in Perturbation Theory R.J. Drachman. Long-Range Electromagnetic Forces in Quantum Theory J. Sucher, G. Feinberg. Index.
TL;DR: In the Neolithic, discarded materials were left over from the production process or worn out, they were thrown aside or discarded in the backyard, as it were as discussed by the authors, where they were often moved because the waste that people had piled around them had rendered the old location an unsuitable place to live.
Abstract: Throughout human history, industry has been an open system of materials flow. People took natural plant, animal and mineral materials and transformed them into tools, clothing and other products of all kinds. When materials were left over from the production process or worn out, they were thrown aside—dumped in the backyard, as it were. Archaeologists find deposits of discarded materials—scrap stone, flints and potsherds—in the rubbish dumps of the Neolithic. Habitations were often moved because the waste that people had piled around them had rendered the old location an unsuitable place to live.
TL;DR: The success of the ideas of chaos has led to attempts to apply them to a great variety of situations as mentioned in this paper, but the results are not always up to expectations, and in some cases the result is predictably of little interest.
Abstract: The success of the ideas of chaos has led to attempts to apply them to a great variety of situations. This is in principle a good strategy, but the results are not always up to expectations. In some cases the results are predictably of little interest. Suppose you have concocted a mathematical model in biology or economics; you put this model on your computer and you discover a Feigenbaum period‐doubling cascade, which is often a sign that chaos is present. Is this result interesting? Well, probably not. One reason is that the detailed dynamical properties of your model may not have anything to do with the properties of the real‐life system. Another reason why your discovery may be without interest is that the occurrence of a Feigenbaum cascade need not have any particular biological or economic significance: You still have to address the problem of the relevance of your finding for biology or economics.
TL;DR: The field of fiber optics still reserves some surprises as mentioned in this paper and the past few years have seen stunning developments in reaction to advances in rare earth-doped fiber amplifiers and nonlinear (or soliton) pulse propagation in fibers.
Abstract: After nearly two decades of research in fiber‐optics technology, what could possibly remain to be discovered? Clearly, the design of optical fibers cannot be improved forever. With current technology, fibers can transmit infrared (1.5‐micron wavelength) light pulses in a single electromagnetic mode with a minimal power loss of 5% per kilometer and without dispersion; such performance is forever fixed by Maxwell's equations and the physics of silica glass waveguides. Yet the field of fiber optics still reserves some surprises. Indeed, the past few years have seen stunning developments in reaction to advances in rare‐earth‐doped fiber amplifiers and nonlinear (or soliton) pulse propagation in fibers.
TL;DR: The question "How does it work?" is the motivation of many physicists as discussed by the authors, and it is especially important in biology to understand the relation between structure and function, which can be sought at the level of the molecule, the cell, the organ, the organism or the social group.
Abstract: The question “How does it work?” is the motivation of many physicists. Condensed matter physics, chemical physics and nuclear physics can all be thought of as descriptions of the relation between structure and properties. The components of a biological system have functional properties that are particularly relevant to the operation of the system. Thus it is especially important in biology to understand the relation between structure and function. Such understanding can be sought at the level of the molecule, the cell, the organ, the organism or the social group.
TL;DR: In this article, the authors present a review of edge-emitting coherent laser arrays, S.R. Chinn vertical cavity surface emitting lasers and arrays, K. Iga and F.L. Koyama grating-coupled surface emitting semiconductor lasers, N.W. Carlson et al. external methods of phase locking and coherant beam addition of diode lasers, J.N. Walpole and L.J. Missaggia.
Abstract: Review of edge-emitting coherent laser arrays, S.R. Chinn vertical cavity surface emitting lasers and arrays, K. Iga and F. Koyama grating-coupled surface emitting semiconductor lasers, N.W. Carlson et al horizontal-cavity surface emitting lasers with integrated beam deflectors, Z.L. Liau et al second order grating surface emitting theory, A. Hardy et al network analysis of two-dimensional laser arrays, R. Amantea and N.W. Carlson external methods of phase locking and coherant beam addition of diode lasers, J. Leger coherence and its effect on laser arrays, M. Lurie microchannel heat sinks for two-dimensional diode laser arrays, J.N. Walpole and L.J. Missaggia.
TL;DR: In this paper, the electronbeam ion trap has made it possible to produce and study any such ion in a modest-sized apparatus (figure 1), and the applications of the most highly charged ions in such isoelectronic sequences are receiving increasing attention.
Abstract: The mention of few‐electron atoms usually brings to mind hydrogen, helium or other light elements in neutral form. However, these simple atoms are part of a sequence of ions having the same number of electrons but different nuclear charges. For example, the hydrogen‐like sequence spans neutral hydrogen through hydrogen‐like uranium, U91+. Both the atomic physics and the applications of the most highly charged ions in such isoelectronic sequences are receiving increasing attention. Recently the electronbeam ion trap has made it possible to produce and study any such ion in a modest‐sized apparatus (figure 1).
TL;DR: H. Marti, Investigation of the NaK ATPase by Scanning Force Microscopy, and 0.0.J Tao, Potentiostatic Deposition of Molecules for Scanning Probe Micro Scopy.
Abstract: 0. Marti, Scanning Probe Microscopy: An Introduction. STM in Biology M. Amrein, H. Gross, and R. Guckenberger, STM of Proteins and Membranes. M.J. Miles and T.J. McMaster, Protein Assemblies and Single Molecules Imaged by STM. D.P.E. Smith and J.E. Frommer, Ordered Organic Monolayers Studied by Tunnelling Microscopy. S.M. Lindsay and N.J Tao, Potentiostatic Deposition of Molecules for Scanning Probe Microscopy. P.G. Arscott and V.A. Bloomfield, STM of DNA and RNA. SFM in Biology: H.-J. Apell, J. Colchero, A. Linder, and 0. Marti, Investigation of the NaK ATPase by Scanning Force Microscopy. J.K.H. Horher, W. Haberle, R Ohnesorge, and G. Binnig, Investigation of Living Cells in Nanometer Region.
TL;DR: The results of recent efforts to mitigate these environmental costs are perceptible, but still modest and very costly as mentioned in this paper, and despite the use of sulfur scrubbers, acid rain remains a serious regional threat, especially with the increased use of low quality coals.
Abstract: Fossil fuel combustion, the technology on which the world relies most heavily for power generation, heating and transportation, was adopted long before its environmental burdens had been fully recognized. The results of our recent efforts to mitigate these environmental costs are perceptible, but still modest and very costly. Despite the use of sulfur scrubbers, acid rain remains a serious regional threat, especially with the increased use of lowquality coals. Catalytic converters have reduced nitrogen oxide and carbon monoxide emissions from automobiles in some countries, but the poor air quality of many of the world's urban areas nonetheless constitutes a severe health threat. New, more efficient power plants and automobiles generate less carbon dioxide per unit of useful energy than did their predecessors, but atmospheric carbon dioxide concentrations continue to rise, intensifying the threat of global warming. Despite our diligent efforts, a major strategic shift in energy production may be required t...