bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal-insulator transitions
Authors: Levi Barbara G.
Published: September 2008

In one, two and now three dimensions, the behavior of amorphous materials is challenging the traditional concepts of metals and insulators. Over a year ago experiments showed that one- and two-dimensional disordered materials appear to move continuously rather than abruptly from insulating to metal-like phases as their randomness decreases. Even in the metallic phase, their conductivities do not exhibit the temperature dependence typical of metals with truly periodic lattices. These results confirmed a scaling theory of localization which predicted that at least in two dimensions the electrons remain localized for arbitrarily small amounts of disorder. This theory did not include any effects the electrons might have on one another, although other treatments have indicated that such effects might be important. Recent experiments have now measured properties in addition to conductance, and some have discovered effects indicative of interacting electrons. Clearly, any theory must now incorporate features both of localization and of electronic interactions, although no one knows in exactly which circumstances each effect might dominate. The one theory so far to incorporate both features has received considerable attention, and will no doubt stimulate greater theoretical and experimental activity, aimed at creating order out of these disordered systems.
Exact solution of Kondo problem
Authors: Levi Barbara G.
Published: September 2008

The Kondo problem concerns a simple physical model of magnetic impurities in metals that has required the most sophisticated of mathematical techniques. To theorists, the model not only represents a first step towards understanding the far more complex problem of ferromagnetism but also appears tantalizingly close to exact solution by the techniques employed for renormalizable field theories. In 1975 Kenneth Wilson of Cornell University successfully used renormalization-group techniques to calculate numerically a key parameter in the Kondo problem. This past year Natan Andrei of New York University and independently P. B. Wiegmann of the Landau Institute in Moscow executed a second coup by exactly diagonalizing the Hamiltonian to allow a solution in closed form.
Facilities in the United States
Authors: Rowe Ednor M.
Published: September 2008

With every advance in our ability to generate or use the electromagnetic spectrum has come a quantum leap in both science and technology. Consider, for example, the impact of the invention of the telescope, of the discovery of x rays or of the invention of the klystron. During the past decade we have been witnessing another such quantum leap as synchrotron radiation has come into its own as a powerful tool for many applications in research and technology. Those of us who participated in the developments will remember this exciting period when, in a sense, we were learning to use extremely complex electron accelerators or storage rings simply as light sources.
Research with x rays
Authors: Sparks Cullie J.
Published: September 2008

The brightness of x rays from synchrotron radiation sources has started a renaissance in a field thought to have been left barren by scientists of the first half of this century. By precisely tuning synchrotron radiation to specific electron energy levels researchers are gaining detailed knowledge of the spatial arrangement and electronic structure of atoms in solids. This knowledge promises not only to lead to advances in condensed-matter theory but to aid in the development of materials with physical and chemical properties tailored to meet specific needs. Experimenters are using the x rays of synchrotron radiation to see biological material at great magnification even in the presence of water, to study the atomic structure of catalytic surfaces while the catalyst is in action, to observe the transient behavior of crystal growth or plastic deformation at millisecond intervals, and to determine atomic arrangements and bonding distances from less than a onolayer of material, just to mention a few examples. A byproduct of the unwieldy devices of medium- and high-energy physics, synchrotron radiation is rapidly becoming one of the most useful contributors to the atomic and molecular sciences.
Ultraviolet radiation—an incisive and versatile tool
Authors: Eastman Dean E. , Himpsel Franz J.
Published: September 2008

The growth in the use of ultraviolet and soft x-ray synchrotron radiation has been remarkable in the past decade. The 1970s saw the number of worldwide scientific and technological users of ultraviolet and x-ray synchrotron radiation increase from fewer than perhaps twenty to well over a thousand. In a single decade, an unwanted byproduct of high-energy electron storage machines has turned into the driving force for building a new generation of electron storage rings designed specifically as radiation sources. (See the article by Ednor Rowe, on page 28.) Several new machines with electron energies of 700–1000 MeV are being constructed specifically as sources of ultraviolet and soft x-ray radiation in the regions below about 1000 eV (above about 12 Å in wavelength).
Quantized Hall effect yields e2/h to a part per million
Authors: Schwarzschild Bertram M.
Published: September 2008

Several recent experiments investigating the Hall effect in its quantummechanical limit have made it clear that Nature is providing us with a fundamental unit of resistance. The extraordinary accuracy with which these experiments appear to be obeying the naive theoretical expression for the quantized Hall resistance is at once promising and puzzling.
The social responsibility of scientists
Authors: Sakharov Andrei
Published: September 2008

Because of the international nature of our profession, scientists form the one real worldwide community which exists today. There is no doubt about this with respect to the substance of science: Schrödinger's equation and the formula E = mc2 are equally valid on all continents. But the integration of the scientific community has inevitably progressed beyond narrow professional interests and now embraces a broad range of universal issues, including ethical questions. And I believe this trend should and will continue.
Science, technology and the arms race
Authors: Panofsky Wolfgang K. H.
Published: September 2008

The arms race, in particular the nuclear weapons competition between the Soviet Union and the US, threatens the very existence of man's civilization. One must admit, albeit reluctantly, that the nuclear balance between these two powers deserves at least partial credit for the absence of all-out hostilities for the longest period in recent history. But even in the absence of total conflict, the increase of potential devastation and the growth in the number of states possessing nuclear weapons have created tensions that increasingly overshadow all other concerns of mankind. Many hold science, which led to the release of nuclear energy, responsible for this evolution. But others look to science for the tools to reverse this threat to all humanity.
Wandering surface atoms and the field ion microscope
Authors: Ehrlich Gert
Published: September 2008

Interest in information about individual atoms on crystal surfaces has been strong since the early 1930s. By then it had become clear that to understand technologically important surface phenomena such as crystal and thin-film growth, heterogeneous catalysis, sintering and surface oxidation, it was necessary to understand atomic processes at crystal surfaces. In response to this need for qualitative and quantitative knowledge physicists and chemists developed detailed models of atomic activity on crystal surfaces. However, for many decades there was no way to confront speculation with actual data on atomic behavior—that would require observations of individual atoms. No less a capability is now available (see figure 1) through the use of the field ion microscope. As we will see, observations of individual atoms have not only provided much interesting information on surfaces but they have also become surprisingly routine.
Experiments set limits and a value for neutrino mass
Authors: Lubkin Gloria B.
Published: September 2008

Over thirty years ago the first real attempt to search experimentally for the electron neutrino mass was made by Geoffrey C. Hanna and Bruno Pontecorvo at Chalk River and by S. C. Curran and his collaborators at the University of Glasgow. They studied the end point of the tritium beta-decay spectrum. Since then a number of experimenters have established upper limits on the mass of νe from this spectrum.
Have glueballs been seen?
Authors: Schwarzschild Bertram M.
Published: September 2008

There is general optimism among elementary-particle physicists that quantum chromodynamics will prove to be the correct theory of the strong interactions. Although QCD is constructed in close analogy to quantum electrodynamics, the uniquely successful gauge theory of the electromagnetic interactions, the multiplicity of QCD “color charges” make it considerably more elaborate than QED. Unlike the uncharged photon of QED, “gluons,” the field quanta that mediate the strong interaction between quarks in QCD, are themselves bearers of the color charges.
Astronomers working in industry
Authors: Bless Robert C. , King Ivan R.
Published: September 2008

As everyone is now aware, the academic job market began to go sour in the 1970s, and predictions for the 1980s are even gloomier. Physical science PhDs are more fortunate than their colleagues in other fields, however, because they have the outlet of jobs in industry, where they can use many of the skills they acquired in graduate training. Astronomers are in a special position, however. First, production of PhDs has decreased much less in astronomy than in physics. Second, astronomers are frequently perceived as impractically trained and lacking the skills that industry requires.
The emperor's new clothes—1981
Authors: von Hippel Frank
Published: September 2008

Physicists learn early that no statement should be accepted without question. Indeed at the core of the physicist's approach to both experimental data and theoretical structures is an insistence on asking questions, looking for patterns and checking for consistency. In this context, incorrect data, bad analysis, and overblown claims are subject to immediate challenge to prevent them from being perpetuated and making the already difficult work of understanding natural phenomena even more difficult.
The giant cancer tube and the Kellogg Radiation Laboratory
Authors: Holbrow Charles H.
Published: September 2008

Fifty years ago the W. K. Kellogg Laboratory of the California Institute of Technology was founded as a center of radiation therapy. Seven years later it abandoned medicine to pursue its development into what is today an internationally known center of nuclear physics. The behind-the-scenes negotiations surrounding the laboratory's founding, early history and abrupt change in direction give unusual insight into the administrative style of Robert A. Millikan, Caltech's chief executive. The early history of the laboratory was shaped in important ways by this Nobel Prize winning physicist's successes and failures in raising support money. His efforts, including a 13-year long attempt to take a horse farm away from the University of California, reveal why Millikan was so successful as head of Caltech, and show that it was just as difficult then to get support for pure research in a new field of physics as it is today.
Large new-technology optical telescopes proposed
Authors: Schwarzschild Bertram M.
Published: September 2008

The 5-meter telescope on Mt. Palomar was designed and funded more than fifty years ago. Since its completion shortly after World War II, only one larger optical telescope has been built. And that instrument, the Soviet 6-meter reflector, begun in 1966, has been a disappointment. In recent decades the emphasis in optical-astronomy instrumentation has been primarily on the improvement of light detectors. Modern photon detectors are a hundred times more sensitive than the photographic plates originally exposed at Mt. Palomar.
Cornell plans 100-GeV e+e− ring
Authors: Lubkin Gloria B.
Published: September 2008

Cornell University is hoping to build an electron–positron storage ring with 50 GeV in each beam. With superconducting rf cavities, for a given energy the diameter of the ring can be substantially reduced as can the power bill. If the research and development continues to go well, Cornell plans to submit a proposal to the National Science Foundation next year. The estimated cost is $200 million in 1981 dollars. NSF has supported Cornell's previous accelerators, the 12-GeV electron synchrotron and its successor, the Cornell Electron Storage Ring, CESR, with 8-GeV electrons colliding with 8-GeV positrons.
Superconducting cyclotrons
Authors: Schwarzschild Bertram M.
Published: September 2008

The impending completion of a 500-MeV superconducting heavy-ion cyclotron at Michigan State University—first beam is expected in September—is indicative of two important trends in nuclear physics. Although very few data exist at present on collisions of heavy ions at beam energies between the nuclear Fermi energy (about 36 MeV per nucleon) and the GeV regime of relativistic energies, it is generally believed that this “intermediate” region will soon provide much enlightenment about the properties of nuclear matter. Secondly, there is a growing consensus that superconducting cyclotrons are a particularly efficient and cost-effective way of attaining this region of heavy-ion beams.
Medical imaging systems
Authors: Redington Rowland W. , Berninger Walter H.
Published: September 2008

The invention of the stethoscope in 1816 opened a new era in diagnostic medicine. For perhaps the first time the physician, aided by an instrument of science, could obtain information from the inside of the human body without surgical intervention. With the help of this simple instrument the trained practitioner could form an impression of the state of form and function of a variety of internal organs. The stethoscope can be considered a precursor of modern medical imaging systems, systems designed to provide information about the body's interior with minimum risk to the patient. The 19th century brought two other important medical imaging instruments, the opthalmascope, used to study the retina, and the first x-ray imagers.
Studies revise dose estimates of A-bomb survivors
Authors: Schwarzschild Bertram M.
Published: September 2008

We know very little about the longterm health hazards of human exposure to neutron irradiation—certainly less than we thought we knew a year ago. The painstaking follow-up of the Hiroshima and Nagaski survivors has provided our only extensive data on human neutron exposure. A joint Japanese-American effort has for more than three decades attempted to keep track of the medical history of every person within a few kilometers of Ground Zero who survived the cataclysm and its immediate aftermath in these two ill-fated cities.
Reversed-field pinch stable 8 msec
Authors: Schwarzschild Bertram M.
Published: September 2008

Tokamaks are certainly in the vanguard of the quest for plasma ignition in magnetic-confinement fusion experiments. Nevertheless, the persistent concern that technological difficulties may ultimately render tokamaks of present-day design impractical as power reactors has encouraged a broad search for alternative magnetic-confinement concepts. One such alternative, the reversed field pinch (RFP), is an axisymmetric toroidal scheme very much like the tokamak. But the differences between the two could eventually prove to be of considerable practical significance.
A tandem mirror in place at MFTF
Authors: Schwarzschild Bertram M.
Published: September 2008

Testing is scheduled to begin this month on the first of two gargantuan superconducting magnets that will plug the ends of the tandem Mirror Fusion Test Facility at Livermore. When construction of the 375-ton magnet was begun three years ago, it was intended to serve as a single-mirror machine. But in the wake of a successful small-scale tandem-mirror experiment at Livermore, it was decided last year to expand the MFTF into a tandem mirror machine, MFTF-B (PHYSICS TODAY, October 1980, page 17).
Computer-based instruction in physics
Authors: Bork Alfred
Published: September 2008

Until now, the computer has played only a minor role in the teaching of physics and other subjects. In the next few years we can expect this to change dramatically because of the development and profusion of relatively inexpensive personal computers and because of the growing pressure to streamline the educational system. In the future, computer-based instruction may make practical the organization of colleges in which almost all funds are used for the development of curriculum material and relatively little is spent per student for delivery.
Track-recording solids
Authors: Ahlen Steven P. , Tarlé Gregory , Price P. Buford
Published: September 2008

Since the beginning of the solar system, natural particle detectors have been recording the passage of charged particles from the sun and cosmic rays. Now, in addition to developing the latent images of these fossil trails of damage in solids and learning about the nature of ancient radiation, we are creating new and more sensitive detectors of a similar kind. These detectors, which are finding a wide variety of applications, take advantage of the fact that a highly charged particle penetrating any nonconducting solid leaves a submicroscopic trail that can be chemically amplified. The increased chemical reactivity of the trails of radiationdamaged material is the basis for the so-called etched-track process, by which we make the particle tracks large enough to measure in an optical microscope. As we will see, there is sufficient information in the tracks to allow us to determine a particle's charge and velocity.
APS Plasma Physics Division meets in New York City
Authors: Iorio Jay J.
Published: September 2008

Topics will include space plasma, laser fusion, mirrors, beam fusion, tokamaks, heating and simulation, and general theory
Global atmospheric effects of nuclear-war fires
Authors: Schmidt Jeffrey D.
Published: September 2008

When Yves Laulan says, “We would be returning to the Dark Ages,” the chief economist of the largest bank in France is talking about the economy after a nuclear war. With half the Northern Hemisphere's urban population wiped out by the war's direct blasts alone, those remaining would find themselves in a barter economy trading in nothing more than the basic elements of survival: food, shelter and medical care.
French heavy-ion cyclotron facility starting up
Authors: Schwarzschild Bertram M.
Published: September 2008

At Caen, near the Normandy coast, construction of the French national heavy-ion accelerator facility, GANIL (Grand Accélérateur National d'Ions Lourds), has now been completed. GANIL is a tandem system of two large conventional (not superconducting) cyclotrons, designed to accelerate all ionic species from carbon to uranium. The maximum energy will be about 100 MeV per nucleon for the lighter ions, falling gradually to 10 MeV per nucleon at the heavy end of the periodic table. Thus GANIL will be, for the next few years, the most powerful heavy-ion cyclotron facility in the world.
Some physics not in The Physical Review
Authors: Varney Robert N.
Published: September 2008

Until the end of the nineteenth century—somewhere in the interval between 1880 and 1915—it was the style of published papers in physics, as in other disciplines, to offer extensive discussions of each stage of an experiment, whether successful or not. In this century the style changed: The discussions became curt, impersonal and matter-of-fact, with the result that many significant facts about how discoveries were made, such as mistakes, accidental discoveries, procedural complications, were not mentioned in the published record. This stylistic change may well have improved the clarity of many papers, but at the sacrifice of historically valuable information—at least some of which is also of scientific value. I hope this article can fill a few such lacunae in The Physical Review.
Chandrasekhar vs. Eddington—an unanticipated confrontation
Authors: Wali Kameshwar C.
Published: September 2008

Stellar evolution has for many years been one of the most exciting fields of research in astronomy and astrophysics. In the early 1930s, a young astrophysicist named Subrahmanyan Chandrasekhar certainly felt this excitement when in his theoretical work he found a fundamental parameter that determines the destiny of stars. By appling both relativity and the new quantum mechanics, Chandrasekhar found a critical mass, below which stars end up as white dwarfs, and above which, as later work would show, they end up as neutron stars or black holes.
Communication in physics—the use of journals
Authors: King Donald W. , Roderer Nancy K.
Published: September 2008

Scientific and technical journals began in Europe in 1665 and were published for the first time in the United States in 1839. Since their inception, these scholarly journals have become the mainstay of scientific and technical communication.
New method for determining the phases of diffracted x rays
Authors: von Foerster Thomas
Published: September 2008

Ever since the discovery of x-ray diffraction by Max von Laue in 1912, it has been recognized that there is a serious obstacle to determining the structure of a crystal from its x-ray diffraction pattern: While it is not at all difficult to measure the intensity of the diffracted beam, it is not at all clear how to measure its phase. Over the years crystallographers have developed techniques to get around this problem—techniques that involve chemical substitution in the crystal, excitation of anomalous scattering by some of the atoms, or computational methods to establish the most probable sets of phases. In recent years it has become apparent that another technique, based on interference effects among diffracted beams, may become an extremely useful technique for the direct, experimental determination of the phases of diffracted x rays.
Spallation sources for neutron scattering
Authors: Schwarzschild Bertram M.
Published: September 2008

Low-energy neutrons are particulary well suited to probe crystalline, glassy and biological materials. The de Broglie wavelength of a thermal neutron is of the same order as interatomic spacings, and its anomalously high cross section for scattering off hydrogen nuclei makes it an especially useful probe for hydrogenous substances. Furthermore, because its electromagnetic interactions are limited to its magnetic dipole moment, the slow neutron has a very large penetration depth with little disruption of the sample under study, and it serves as an excellent probe of complex magnetic structures.
New Instruments for astronomy
Authors: Field George B.
Published: September 2008

In this special issue we review the new instruments and observational facilities anticipated over the next decade in five major areas of astronomy—high-energy astrophysics (page 26), radio astronomy (page 36), ultraviolet, optical and infrared astronomy (page 44), planetary sciences (page 54) and solar physics (page 60). These reviews are based on the information contained in the report of the Astronomy Survey Committee, Astronomy and Astrophysics for the 1980s (National Academy of Sciences, Washington, DC, 1982). (My article in April, page 46, provides an overview of the Committee's report.)
High-energy astrophysics
Authors: Clark George W.
Published: September 2008

Ultra-high temperatures and densities, high-energy particles and intense gravitational and magnetic fields exist in many kinds of objects throughout the universe. During the past two decades, the origin and evolution of these conditions have become central topics of astronomy. In many instances, the conditions are so extreme as to be unattainable in terrestrial experiments; astronomical observations are thus a unique source of empirical information about the physical processes that occur under these circumstances. Much of the information is obtained from observations of x rays, gamma rays, and energetic electrons, nuclei, neutrons, and neutrinos. These, together with gravitational radiation, have come to be considered the province of “high-energy astronomy.”
Facilities for US radioastronomy
Authors: Thaddeus Patrick
Published: September 2008

This year radioastronomers are celebrating the 50th anniversary of the birth of their science: the discovery by Karl Jansky, a physicist at Bell Labs studying interference on the trans-Atlantic radiotelephone service, of a source of radio noise fixed on the celestial sphere toward the galactic center. A modern receiver operating at the same wavelength of 14 meters can detect this continuum emission—the synchrotron radiation from cosmicray electrons in the interstellar magnetic field—along the entire galactic plane and, indeed from all directions, albeit with weaker intensities. Large aperture synthesis interferometers such as the Very Large Array near Socorro, New Mexico (figure 1) are now routinely mapping in distant galaxies (figure 2) radiation of a similar character.
Ultraviolet, optical and infrared astronomy
Authors: Wampler E. Joseph
Published: September 2008

While it is possible to trace the history of ultraviolet, optical and infrared astronomy to an era before that of the pre-Christian Greek astronomers at Alexandria, the field is not as static as this maturity might suggest. The flowering of space astronomy and the orders-of-magnitude improvement in detector technology give us exploratory capabilities that are as revolutionary as the invention of the telescope. Decades from now the 1970s will be remembered as a turning point in our understanding of the universe.
Contemporary planetary science
Authors: Belton Michael J. S. , Levy Eugene H.
Published: September 2008

Although its roots are in classical astronomy, planetary science has made great advances over the past twenty years by using robot spacecraft sent to other planets. Because of the wealth of information that has rewarded this exploration, planetary science now attracts the attention of physicists, chemists, geologists, astronomers and atmospheric scientists, among others. Long-held views about cosmic phenomena and about the planets and their origin are changing, and our probing studies are opening new vistas of understanding.
A golden age for solar physics
Authors: Walker Arthur B. C.
Published: September 2008

The Sun occupies a unique position in astrophysics, because it is the only star we can examine in sufficient detail to learn about stellar phenomena at the level of the basic underlying atomic physics, nuclear physics, plasma physics and magnetohydrodynamics. Ongoing solar research affects a large number of models and theories of stellar phenomena. These include the fundamental theory of the generation of thermonuclear energy in stars, theories of energy transport in stellar envelopes, models of stellar structure and evolution, theories of stellar rotation and cycles of activity, models of stellar winds and coronae, and theories of stellar magnetism and the explosive release of stored magnetic energy, which accelerates particles to energies of billions of electron volts per nucleon.
Wilson wins Nobel prize for theory of critical phenomena
Authors: Lubkin Gloria B.
Published: September 2008

The 1982 Nobel prize in physics has been awarded to Kenneth G. Wilson of Cornell University “for his theory for critical phenomena in connection with phase transitions.” In its announcement the Royal Swedish Academy of Sciences said that Wilson's renormalization-group approach to critical phenomena, particularly two Physical Review papers in 1971, “gave a complete theoretical description of the behavior close to the critical point and gave also methods to calculate numerically the crucial quantities.”
Selection of LEP detectors nears finish
Authors: Schwarzschild Bertram M.
Published: September 2008

As contracts are being tendered for the construction of LEP, the gargantuan electron–positron colliding-beam accelerator that will straddle the French–Swiss frontier at CERN, the time has come to settle on the four detectors that will occupy the four underground experimental halls to be used in the first phase of LEP operation, which is scheduled to begin toward the end of 1987. In January, letters of intent outlining detector designs for the four experimental beam-intersection areas were submitted by six large multinational collaborations.
The measurment of thermodynamic temperature
Authors: Guildner Leslie A.
Published: September 2008

We owe the concept of “thermodynamic temperature” to Sadi Carnot, William Thomson and Rudolf Clausius. This very basic property is measured in the Systeme Internationale of units by the kelvin, defined in terms of the thermodynamic temperature of the triple point of water. In principle, any other temperature may be determined by its ratio to this defined temperature. In practice, however, it is almost always more convenient to measure an approximation of the thermodynamic temperature by using one of the familiar thermometers (platinum resistance, thermocouple, radiation pyrometer, and so on).
Debate on radioactive waste disposal. No technical barriers
Authors: Donath Fred A.
Published: September 2008

The “energy crisis” of the 1970s brought with it an unparalleled awareness of this country's energy needs for the future. It became clear that an acceptable standard of living would require the use of all energy alternatives and significant expansion of specific ones. For any reasonable projection this translates into considerable dependence on nuclear energy to meet the energy demands of the next two decades while new technologies (such as solar) and improvements in existing technologies are brought to levels that can meet future demand.
Debate on radioactive waste disposal. Will it stay put?
Authors: Pohl Robert O.
Published: September 2008

In this article I present a somewhat detailed discussion of four examples of nuclear waste policy issues, in the hope that this may better convey an idea of the complexity of the entire topic. The first will show how drastically our perception of the waste-disposal issue has changed in recent years, and should thus teach us some caution with regard to our present understanding. The second is geotechnical: It concerns site for high-level nuclear waste and demonstrates some of its problems. The third concerns uranium mill tailings and will show the environmental risks posed by the very large volumes of low-level radioactive wastes. The last example will address the least predictable aspect of long-term management of nuclear wastes: future human activities, and how they affect the proper planning of nuclear waste disposal.
CERN SPS now running as 540-GeV p̄p collider
Authors: Schwarzschild Bertram M.
Published: September 2008

The CERN Super Proton Synchrotron (SPS) has begun producing ultra-high-energy physics results in its new role as a proton–antiproton colliding-beam accelerator. At the 2nd Topical Workshop on Forward Collider Physics, held in December at the University of Wisconsin (Madison), two CERN collaborations reported their early data on p̄p collisions at a center-of-mass energy of 540 GeV.
ATA: 10-kA pulses of 50-MeV electrons
Authors: Schwarzschild Bertram M.
Published: September 2008

Assembly of the Advanced Technology Accelerator (ATA) began in December at an isolated site 15 miles southeast of the Lawrence Livermore Laboratory. When it is completed in October (the project appears to be on schedule), the 256-foot linear induction accelerator is expected to generate repeated 10-kiloamp pulses of 50-MeV electrons—an order of magnitude higher energy than any previous induction linac capable of high current and high repetition rates.
The Physics of glass
Authors: Phillips James C.
Published: September 2008

Some four thousand years ago man discovered glass in the embers of a fire built somewhere in the deserts of the Near East. A few years from now ultratransparent glass fibers will be transmitting more information than copper wires. Thus glass is at once both one of the oldest and one of the newest materials known to civilization. Yet the science of glass is still in its infancy, and the most basic questions remain largely unanswered.
Density functional theory
Authors: Schlüter Michael , Sham Lu Jeu
Published: September 2008

What are the energies and wavefunctions of electrons under the influence of nuclei as well as other electrons? If we could solve this general theoretical problem, we would gain a fundamental understanding of a healthy chunk of atomic, molecular and solid-state physics.
Ferromagnetism and superconductivity strike a compromise
Authors: Levi Barbara G.
Published: September 2008

Ferromagnetism and superconductivity are two forms of long-range order that may exist in a material at low temperature. When both are present, they compete with one another, and many have wondered under what conditions they might coexist. The answer has been emerging in recent years, primarily through studies of two materials in which a compromise settlement is reached. The latest in a series of experiments—this one on a single crystal—has confirmed and further elucidated the properties of the coexistence phase seen in earlier work: This phase seems to accommodate within a single crystal both superconducting regions with sinusoidally modulated magnetic moments and normal ferromagnetic domains.
RF drives tokamak plasma currents
Authors: Schwarzschild Bertram M.
Published: September 2008

A steady-state scheme for plasma-current drive would greatly enhance the attractiveness of the tokamak as a fusion reactor. The fact that a conventional tokamak reactor would have to operate in a pulsed mode presents serious engineering difficulties. Even though the length of such pulses could be as long as an hour (followed by a recovery time of less than a minute), pulsed operation raises the problem of thermal fatigue.
Electron cooling for light-ion beams
Authors: Schwarzschild Bertram M.
Published: September 2008

The nuclear physicists at the Indiana University Cyclotron Facility are proposing to enhance considerably the capabilities of this light-ion cyclotron by appending to it an electron-cooling storage ring. Electron cooling has been developed over the last decade at Novosibirsk, CERN and Fermilab primarily as a technique for “cooling” antiproton beams—reducing their spread in transverse and longitudinal momentum—for high-energy physics experiments (PHYSICS TODAY, August 1980, page 44). The IUCF would be the first attempt to exploit beam cooling for nuclear-physics ion beams.
Extraterrestrial intelligence: the debate continues. The readers respond to Tipler
Authors: Preuss L. E. , Bolin F. P. , Drake Frank D. , Willburn John Bart , Nadj Henriette , Nadj John , Nadj Miroslav , Klatz Jonathan , Jones Eric M. , Smith Barham W. , Whitney Charles A. , Sai-Halasz George , Cohen N. L. , Benford Gregory , Daugman John , Gerverl Michael
Published: September 2008

We compliment PHYSICS TODAY for its stimulating guest comment in the April ‘81 issue by Frank J. Tipler (“Extraterrestrial beings do not exist,” April, page 9). As research physicists in specialties far removed from astrophysics and extraterrestrial biology, but intrigued by Carl Sagan's (and others') unquestioned assertion that numberless intelligent civilizations exist elsewhere in the universe, we have been struck by the paucity of critical response to this hypothesis. This lack being quite an uncharacteristic reaction by the scientific community to what is a controversial proposition. However, with Tipler's counterpoint, it now appears that an opposite view is alive and well, PHYSICS TODAY and Tipler have provided the required first step for the scientific community's consideration, and the usual and absolutely necessary polemics may now proceed.
Extraterrestrial intelligence: the debate continues. A biologist looks at the numbers
Authors: Ornstein Leonard
Published: September 2008

In the Guest Comment in April (page 9), Frank Tipler argues that if extraterrestrial beings existed, our galaxy would be so full of their Von Neumann machine proxies that we could not have missed them. Tipler replaces Michael Hart's and James Trefil's humanoid colonizers with machines, to circumvent the costs of humanoid support and humanoid fragility. Francis Crick and Leslie Orgel replace them with cargoes of microorganisms in a revival of Svante Arrhenius' century-old “Panspermia” hypothesis.
Extraterrestrial intelligence: the debate continues. the author comments
Authors: Tipler Frank J.
Published: September 2008

The above criticisms of my views can be divided into two classes: (1) those of a technical nature, and (2) those which deal with the sociology of possible extraterrestrial intelligent beings. Most of these criticisms I have discussed in the three Quarterly Journal articles of which the PHYSICS TODAY paper was but a précis. Here I will reply briefly to those criticisms that were answered in the Quarterly Journal; my critics are referred to those papers for more detail on the points in question.
Differential geometry, fiber bundles and physical theories
Authors: Singer Isadore M.
Published: September 2008

Among intellectual disciplines, mathematics occupies a unique position. It is in many respects an art, but it is also the language of science. Although a great deal of mathematics can be traced directly to external influences, much of its creativity is motivated internally: “pour la gloire de l'esprit humain,” as Carl G. T. Jacobi put it. Often the mathematician lets the imagination soar, constrained only by logic, intrinsic structure, and a sense of historical continuity. Yet from time to time these abstract deliberations have important applications in other fields.
Thermodynamics of excitons in semiconductors
Authors: Wolfe James P.
Published: September 2008

During the few microseconds between its laser-induced creation in a pure semiconductor crystal and its destruction by recombination, a bound electron–hole pair, or exciton, is very active. Like the negative and positive charge carriers from which it forms, the exciton exhibits great mobility, whether it is coaxed by an applied force or simply moves under its own thermal energy. And like an atom in free space, it is bound by Coulomb forces, has discrete energy levels and may combine with other excitons into molecules or even condense into a liquid-like state. In a semiconductor crystal such as silicon, all of this occurs at temperatures below about 30 K, for these weakly bound neutral particles ionize easily into electrons and holes at higher temperatures. The study of these particles and their products has occupied many physicists over the last couple of decades, and the investigations continue to uncover interesting new phenomena.
Correction
Authors: Van Horn Hugh M.
Published: September 2008

The article about the APS Industrial Summer Intern Program on page 73 of the September issue contains an error that I wish to correct. Cheryl A. Hanzlik was indeed a Summer Intern at Xerox Corporation. She was not a student from Cornell, however, but she is and has been a graduate student in the department of physics and astronomy of the University of Rochester.
New evidence for anomalously large nuclear fragments
Authors: Schwarzschild Bertram M.
Published: September 2008

Since 1954 there have been sporadic reports that very strange things can happen in the first few centimeters after an energetic nucleus fragments in photographic emulsion. Before the Berkeley Bevalac came along in the mid 1970s to accelerate middle-weight ions to kinetic energies of 2 GeV per nucleon, such reports came entirely from cosmic-ray exposures of very limited statistics. Indeed the anecdotal tone of the early reports generated more skepticism than excitement.
DOE boosts particle-physics funds
Authors: Lubkin Gloria B.
Published: September 2008

Particle physics has fared reasonably well in the Administration's proposed budget for FY 1983. The total amount in the Department of Energy budget (see page 55)—$429 million—is below the figure at which the Trilling report said the US should build Isabelle. Indeed construction funds for Isabelle in FY 1983 would drop to zero. But Brookhaven would get $23 million for research and development on superconducting magnets and alternative accelerator designs. For several months some insiders have proclaimed Isabelle dead. However, one noted particle discoverer has predicted that in a couple of years, a new accelerator will be built in the empty tunnel at Brookhaven. The machine will have 399-GeV protons colliding with 399-GeV protons. Its name—Maybelle.
Microscopy by vacuum tunneling
Authors: Schwarzschild Bertram M.
Published: September 2008

The earliest work on quantum tunneling in solid-state physics, more than fifty years ago, dealt with electron tunneling through a vacuum barrier. But for the next half century we had no clear experimental demonstration of this conceptually simplest of tunneling phenomena. Spectroscopic and technological exploitation of quantum tunneling was developed only with solid tunnel barriers. Metal–vacuum–metal tunneling requires a gap held constant at a few angstroms. At such small distances—just a few atomic widths—it is extraordinarily difficult to control the gap size and insure that surface contamination layers or irregularities do not result in an unwanted contact across the gap.
The birth of elementary-particle physics
Authors: Brown Laurie M. , Hoddeson Lillian
Published: September 2008

By 1930, relativity and quantum mechanics were established, yet the excitement of the new physics was far from over. Indeed, the next half-century was characterized by startling experimental and theoretical discoveries and by new puzzles that appeared wherever one looked.
Astronomy and Astrophysics for the 1980s
Authors: Field George B.
Published: September 2008

Astronomy is in a golden age. Discoveries since 1960 include quasars (1963), the cosmic microwave background radiation (1965), pulsars (1967), neutronstar binaries (1970), superluminal expansion of radio sources (1971), solar coronal holes (1973), evidence for gravitational radiation from a binary pulsar (1974), anomalous solar neutrino flux (1976), a super gamma-ray burst (1979), and a gravitational lens (1979). Radio, infrared, ultraviolet, x-ray, and gamma-ray techniques have made it possible to study phenomena not accessible to optical astronomy alone. Physics has come to play an increasingly important role in providing both the technology for these developments and the theoretical framework for astronomy. Today, atomic, molecular, nuclear, and plasma physics are indispensable tools in interpreting astronomical data; cosmology and the study of superdense configurations depend on general relativity and, increasingly, elementary-particle physics.
Statistical Mechanics algorithm for Monte Carlo optimization
Authors: Schwarzschild Bertram M.
Published: September 2008

The traveling-salesman problem is the classic example of a class of recalcitrant combinatorial-optimization tasks (the “NP-complete” problems) for whose exact solution the only known algorithms require a number of steps that grows at least exponentially with the number of elements in the problem. Finding, by brute force, the shortest path by which a traveling salesman can complete a tour of N cities requires compiling a list of (N−1)1/2 alternative tour lengths—a number that grows faster than any finite power of N and quickly becomes intractable. Finding an exact polynomial algorithm (bounded by a finite power of N) for any one member of the class of NP-complete problems would constitute a proof that all such problems possess an “efficient” exact algorithm; but it is generally believed that no such algorithm exists.
Theory institute thrives in its third year
Authors: Lubkin Gloria B.
Published: September 2008

Gazing out his office window recently, J. Robert Schrieffer saw a whale blowing. That's just one of the attractions at the NSF Institute for Theoretical Physics, now in its third year of operation at the University of California in Santa Barbara. The climate and scenery are delightful, and the office space looks more like an executive suite than a collection of rooms for physicists to work in. But most important, the institute is attracting good physicists who are producing noteworthy research.
Plans for Spain to rejoin CERN
Authors: Lubkin Gloria B.
Published: September 2008

Spain has applied for readmission to CERN. The Director General, Herwig Schopper, and the President of the CERN Council, Sir Alec Merrison, have been authorized to negotiate the conditions for Spain's readmission. Spain had been a member nation from 1961 to 1968, when it resigned, saying it could not afford its share of the CERN budget, which was increasing linearly to support the construction of the Super Proton Synchrotron. The CERN budget is now flat (corrected for inflation) for the next four years while LEP is being constructed. (LEP is the acronym for the Large Electron–Positron colliding-beam device).
Special Issue: liquid crystals
Authors: Litster J. David
Published: September 2008

Many organic crystals melt by passing through intermediate fluid phases that are optically anisotropic. Discovered by the Austrian botanist Friedrich Reinitzer in 1888, such “liquid crystals” were much studied in the early part of this century, but remained no more than a curiosity until recently.
Polymeric liquid crystals
Authors: Samulski Edward T.
Published: September 2008

Soft contact lenses and ablative heat shields for spacecraft require materials with vastly different physical properties. Yet the materials for both—permeable elastic membranes and tenacious high-temperature composities—are products of polymer science.
Defects in liquid crystals
Authors: Brinkman William F. , Cladis Patricia E.
Published: September 2008

The most striking feature of liquid crystals is the wide variety of visual patterns they display. These patterns, such as those shown in figure 1 and on the cover, are due almost entirely to the defect structure that occurs in the long-range molecular order of the liquid. Indeed, historically, the underlying structure of the liquid-crystal phases known as nematic and smectic-A was discovered from a study of stable defects that characterize these phases. Such defects are easily visible in the optical microscope. By examining the thin and thick thread-like structures observed in nematic liquid crystals, Otto Lehman and Georges Friedel deduced that this phase involves long-range orientational ordering of the long axis of the rod-like molecules. (The direction of this orientational ordering is what we now denote by the unit vector n̂, called the director.)
Two-dimensional systems
Authors: Pindak Ronald , Moncton David
Published: September 2008

Nearly all the microscopically small devices that are contributing to the “microtechnological” revolution are composed of thin layers of materials. Such devices are nearly two-dimensional, and many of the questions concerning the ultimate possibilities and limitations of the technology will require investigation of the physical processes in two dimensions. Similarly, questions that arise in such diverse fields as surface physics, membrane biology and catalytic chemistry involve two-dimensional phenomena. At least as important as these practical questions is simple intellectural curiously: How does Nature behave in a world of limited dimensionality?
The molecular physics of liquid-crystal devices
Authors: Kahn Frederic J.
Published: September 2008

Liquid-crystal displays are now ubiquitous in homes, stores, businesses and laboratories—on pocket calculators, wrist watches, clocks and so forth; only 14 years after RCA's initial disclosure of potentially useful liquid-crystal displays, these devices provide the basis for the second largest display industry, second only in dollar volume to cathode-ray tubes. This remarkable growth has been based on the development of a sophisticated understanding of the molecular properties of liquid crystals.