Showing papers in "Physics Today in 1979"
612 citations
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TL;DR: In this paper, the authors discuss how a combination of fusion and fission power might be much closer, and might be very helpful both to fission and fusion power, and they also discuss how fusion power can be used to power a nuclear power plant.
Abstract: In the last few years nuclear fusion by magnetic confinement has made great progress. However, an economical pure fusion power plant is still many years away. In this article I will discuss how a combination of fusion and fission power might be much closer, and might be very helpful both to fission and fusion power.
114 citations
TL;DR: This book leads the designer in this "natural" direction, beyond the familiar limitations of the right angle and the cube and into a richer world of forms based on the triangle, the hexagon, and generalpolyhedra, as well as saddle polyhedra spanned by minimal continuous surfaces.
93 citations
TL;DR: Abreu et al. as discussed by the authors reported that both open and closed confinement systems have performed up to expectations, rekindling the old optimism that has lain nearly dormant for 15 years.
Abstract: Impressive advances have been reported in controlled fusion experiments during the past four years. Both open and closed confinement systems have performed up to expectations, rekindling the old optimism that has lain nearly dormant for 15 years. As a result, breakeven experiments are being proposed, designed and built in several laboratories.
75 citations
TL;DR: In this paper, the authors reviewed recent experiments and theoretical models of this coupling and the ways to destroy it and depin the charge density wave in low temperature transition metal compounds, and proposed methods to destroy this coupling.
Abstract: At low temperatures some transition metal compounds have a phase transition to a state in which the electronic charge density and the positions of the ions have long period modulations. The relative positions of this modulation and the host lattice are directly coupled if the two periods are commensurate and indirectly through impurities otherwise. Recent experiments and theoretical models of this coupling and the ways to destroy it and depin the charge density wave are reviewed.
73 citations
TL;DR: For example, the authors argued that science, like the arts, admits aesthetic criteria; we seek theories that display a proper conformity of the parts to one another and to the whole, while still showing some strangeness in their proportion.
Abstract: Science, like the arts, admits aesthetic criteria; we seek theories that display “a proper conformity of the parts to one another and to the whole” while still showing “some strangeness in their proportion.”
TL;DR: In this paper, the authors describe the growing influence of theories involving pseudopotentials on solid state or condensed matter physics and describe how these theories can be used to solve problems in physics.
Abstract: Webster's dictionary defines panacea as a “remedy for all ills or difficulties; a cure‐all.” A pseudopotential is an approximation to the real potential an electron feels in a solid. In what sense can it be called a cure‐all? What are the ills it cures, the difficulties it overcomes or the problems it solves? And how does it help solve problems? Our object here will be to supply some answers to these questions and to describe the growing influence of theories involving pseudopotentials on solid state or condensed matter physics.
TL;DR: Extensive work on the fabrication of thin-film microstructures began in the early 1960's when it became apparent that thousands or even millions of circuits could potentially be integrated into a single piece of silicon less than a centimeter on a side as discussed by the authors.
Abstract: Extensive work on the fabrication of thin‐film microstructures began in the early 1960's when it became apparent that thousands or even millions of circuits could potentially be integrated into a single piece of silicon less than a centimeter on a side. In the years since, the potential has been realized, as one can see from figure 1, and has produced the well‐known dramatic growth of the microelectronics industry. The same technologies that make large‐scale integrated circuits possible also make possible a variety of other devices of scientific and technological interest, including magnetic bubble devices, high‐speed computer switching circuits based on the Josephson effect, surface acoustic‐wave devices, integrated optical circuits, Josephson microbridges and zone‐plate lenses for focusing soft x rays.
TL;DR: In this article, a new direct detection method for radioisotope dating is proposed, which is based on counting individual atoms of radioactive isotopes that have been ionized, accelerated to high energies, and then selected and identified.
Abstract: A new method of detecting radioactive isotopes promises to have a revolutionary impact on the field of radioisotope dating. The technique, which was developed over the past two and a half years, consists of counting individual atoms of radioactive isotopes that have been ionized, accelerated to high energies, and then selected and identified. By detecting all—or a substantial fraction—of the atoms in the beam, this method has much greater sensitivity than the standard method, which detects only the tiny fraction of the atoms that decay during the counting period. The new “direct detection” method therefore will allow one to use much smaller samples and to measure much greater ages than the older “decay detection” method.
TL;DR: The anomalous Hall effect is observed when a magnetic field is applied to a metal through which a current flows: the current carriers are deflected in the field, giving rise to a transverse electric field.
Abstract: The Hall effect is observed when a magnetic field is applied to a metal through which a current flows: The current carriers are deflected in the field, giving rise to a transverse electric field. In a ferromagnetic metal the embedded magnetic moments produce an anomalous Hall effect. Because it depends on both electronic and magnetic properties of the metal, the anomalous Hall effect has become a useful experimental tool for solid‐state physicists. In our laboratory in Julich, for example, we have used the effect to study extremely thin magnetic layers and to observe the propagation of conduction electrons in a metal.
TL;DR: White dwarfs are the terminal points of stellar evolution and provide clues to the physical processes that take place during the rapid and often spectacular evolutionary stages near the ends of stellar lifetimes as discussed by the authors.
Abstract: White dwarf stars, so called because of the color of the first few to be discovered, occupy a key position in astrophysical theory. Together with neutron stars and black holes, they are the terminal points of stellar evolution. Their properties thus provide clues to the physical processes that take place during the rapid and often spectacular evolutionary stages near the ends of stellar lifetimes. In addition, white dwarfs provide astrophysical “laboratories” for “measuring” the physical properties of matter under extreme conditions. These extend from conditions like those in laser‐produced plasmas to those typical of the solid crusts of neutron stars. White‐dwarf stars also occur as components of cataclysmic binary systems—novae, dwarf novae and related objects—and knowledge of the properties of white dwarfs is essential to the development of satisfactory theoretical models for these systems.
TL;DR: The cosmological abundance of helium-4 fixes an upper limit of 8 on the number of quark varieties (flavors) in models that have a symmetry between quarks and leptons.
Abstract: Over the past decade or so, great progress has been made in two diverse areas of physics—cosmology and elementary‐particle physics. In spite of the obvious differences of the two fields (figure 1), each has begun to illuminate the other, making interdisciplinary work involving them not only possible but even exciting. Thus, for example, the cosmological abundance of helium‐4 fixes an upper limit of 8 on the number of quark varieties (“flavors”) in models that have a symmetry between quarks and leptons. And developments in the grand unified theories of elementary processes may resolve the puzzle of why there are roughly a billion photons for every baryon in the universe. As our knowledge of the fundamental particles and their interactions increases, and as our determination of cosmological observables improves (or new observables are discovered) the close relationship of these two disciplines promises to continue to be an exciting one.
TL;DR: Although the Sun is frequently labeled as an “alternative” energy source, it has in fact produced almost all of man's energy throughout history as mentioned in this paper, and the world's energy economy now runs primarily on fossil fuels, a form of solar capital saved over geological time scales.
Abstract: Although the Sun is frequently labeled as an “alternative” energy source, it has in fact produced almost all of man's energy throughout history. The world's energy economy now runs primarily on fossil fuels, a form of “solar capital” saved over geological time scales. Because this capital is apparently rather modest in amount and is not being renewed by nature at a rate comparable to our demands, we may eventually exhaust it. We will therefore be forced to turn either to the use of larger non‐solar capital stocks such as primordial methane (if it exists), uranium‐238 and deuterium, or to the use of regular “solar income” derived from the Sun's daily radiation.
TL;DR: In this article, a resonance in the cross section for electrons scattering off helium changed the tradition, and by now there is a long catalog of observed resonances in atoms and molecules and an accompanying body of theoretical work that seeks to account for the newly discovered states and explain their behavior.
Abstract: Observing resonances in cross‐section‐versus‐energy curves has long been a way of life for nuclear and particle physicists, for whom this is often the only way to detect short‐lived quantum states. Atomic physicists, on the other hand, have traditionally used other means for observing internal energy states of atoms and molecules. But sixteen years ago a resonance in the cross section for electrons scattering off helium changed the tradition, and by now there is a long catalog of observed resonances in atoms and molecules and an accompanying body of theoretical work that seeks to account for the newly discovered states and explain their behavior.
TL;DR: At the 1968 conference on controlled fusion in Novosibirsk a group from Kurchatov, USSR, led by L. A. Artsimovitch, presented convincing evidence that one conceptually simple method for confining plasmas in a ring showed great promise for future developments as mentioned in this paper.
Abstract: At the 1968 conference on controlled fusion in Novosibirsk a group from Kurchatov, USSR, led by L. A. Artsimovitch, presented convincing evidence that one conceptually simple method for confining plasmas in a ring showed great promise for future developments. The name for their early machine, the tokamak, has now become the generic name for all such devices. The Russian successes led to a rapid expansion of research with tokamaks, so that while in 1968 there were only nine of them, all in the USSR, there are now more than a hundred; they are in the USSR, the US, Europe, Japan, and elsewhere.
TL;DR: Weisskopf as mentioned in this paper referred to the excitement caused by experimental claims that the selection rule known as the ΔS = ΔQ rule did not hold and showed the New Yorker cartoon reprinted opposite.
Abstract: At the end of his concluding remarks, summarizing the reports at the 1962 International Conference on High Energy Physics at CERN, Victor Weisskopf referred to the excitement caused by experimental claims that the selection rule known as the ΔS = ΔQ rule did not hold and showed the New Yorker cartoon reprinted opposite.
TL;DR: In 1879, the world was considerably darker than the nocturnal world of today as mentioned in this paper, and artificial illumination was limited to kerosene lamps, illuminating gas, the just emerging arc lamp for street lighting and a few lingering candles.
Abstract: Night‐time in 1879, but a scant 100 years ago, was considerably darker than the nocturnal world of today. Artificial illumination was limited to kerosene lamps, illuminating gas, the just‐emerging arc lamp for street lighting and a few lingering candles.
TL;DR: The discovery of the neutron in 1932, which indirectly led to the potentially catastrophic development of nuclear weapons on the one hand and to the beneficial development of the nuclear generated electricity on the other, has had another, less well-known, but scientifically important consequence: the provision of a uniquely sensitive and pervasive tool for probing condensed matter as mentioned in this paper.
Abstract: The discovery of the neutron in 1932, which indirectly led to the potentially catastrophic development of nuclear weapons on the one hand and to the beneficial development of nuclear‐generated electricity on the other, has had another, less well‐known, but scientifically important consequence: the provision of a uniquely sensitive and pervasive tool for probing condensed matter. Because they are neutral and because they interact mainly with nuclei, neutrons can penetrate into bulk material and provide information that is difficult to obtain with x rays or charged particles. Until recently, nuclear reactors provided the highest‐intensity neutron sources. But lately another kind of source is promising to overcome the limitations of reactors. In these sources high‐energy protons are made to collide with heavy nuclei, splitting off a large number of neutrons. The process is rather like making chips fly by hitting a rock with a hammer—what the geologists call “spallation.” These neutron spallation sources toge...
TL;DR: FeFeynman gave a delightful talk, "There's Plenty of Room at the Bottom." He said at first that he imagined that experimental physicists must often look with envy at men like Heike Kamerlingh Onnes, who opened the field of low temperatures, which seems to be bottomless, or Percy Bridgman who, in designing a way to obtain high pressure, opened up another new field as mentioned in this paper.
Abstract: Just about twenty years ago, at the Christmas, 1959, meeting of The American Physical Society at Cal Tech, Richard P. Feynman gave a delightful talk, “There's Plenty of Room at the Bottom.” He said at first that he imagined that experimental physicists must often look with envy at men like Heike Kamerlingh Onnes, who opened the field of low temperatures, which seems to be bottomless—one can go down and down, or Percy Bridgman who, in designing a way to obtain high pressure, opened up another new field—in which one can go up and up. Attainment of ever higher vacuum, he said, was a continuing development of the same kind. He then went on to say that he wanted “to describe a field, in which little has been done, but in which an enormous amount can be done in principle.” This was the field of miniaturization, the problem of manipulating and controlling things on a small scale.
TL;DR: Abrahams, Anderson, Licciardello, and Ramakrishnan as discussed by the authors showed that thin wires do not exhibit true metallic conductivity at 0 K. The work of the Rutgers-Bell-Princeton team is a further realization of the ideas of David Thouless (Yale) who had predicted nonmetallic behavior at low temperatures for thin wires whose impurity resistances exceeded 10 kilo-ohms.
Abstract: When does a metal not act like one? When it is a two‐dimensional thin film at 0 K. So says a recent theory by Elihu Abrahams (Rutgers), Philip W. Anderson (Princeton and Bell Labs), Donald C. Licciardello (Princeton) and T. V. Ramakrishnan (on leave at Princeton from the Indian Institute of Technology). Their surprising prediction that thin films never exhibit true metallic conductivity, and the renormalization‐group scheme used to obtain this result, both created such a stir at the Gordon Conference on Quantum Liquids and Solids (held in July in Plymouth, N.H.) that next year's conference may be heavily devoted to this topic. The work of the Rutgers–Bell–Princeton team (since dubbed “the gang of four”) is a further realization of the ideas of David Thouless (Yale) who had predicted nonmetallic behavior at low temperatures for thin wires whose impurity resistances exceeded 10 kilo‐ohms.