Reviews of Modern Physics

This article reviews observations and models of the diffuse ionized gas that permeates the disk and halo of our Galaxy and others. It was inspired by a series of invited talks presented during an afternoon scientific session of the 65th birthday celebration for Professor Carl Heiles held at Arecibo ...

Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here perturbative QED at finite temperature is used for calculating various important pr...

The trivalent alkali fulleride solids of generic composition A₃C₆₀ , where C₆₀ is the fullerene molecule and A=K , Rb, and Cs, are a well-established family of molecular superconductors. The superconductive electron pairing is of regular s -wave symmetry and is accounted for by conventional cou...

All our former experience with application of quantum theory seems to say that what is predicted by quantum formalism must occur in the laboratory. But the essence of quantum formalism—entanglement, recognized by Einstein, Podolsky, Rosen, and Schrödinger—waited over 70   years to enter ...

This article reviews the physics of multipolar interactions and multipolar order in f -electron systems, using the actinide dioxides as a paradigm. In the past few years, these apparently simple cubic compounds have been studied intensively, and many new phenomena have been discovered. Here the exp...

Wetting phenomena are ubiquitous in nature and technology. A solid substrate exposed to the environment is almost invariably covered by a layer of fluid material. In this review, the surface forces that lead to wetting are considered, and the equilibrium surface coverage of a substrate in contact wi...

Guiding-center theory provides the reduced dynamical equations for the motion of charged particles in slowly varying electromagnetic fields, when the fields have weak variations over a gyration radius (or gyroradius) in space and a gyration period (or gyroperiod) in time. Canonical and noncanonical ...

After reviewing the ideal Bose-Einstein gas in a box and in a harmonic trap, the effect of interactions on the formation of a Bose-Einstein condensate are discussed, along with the dynamics of small-amplitude perturbations (the Bogoliubov equations). When the condensate rotates with angular velocity...

Statistical physics has proven to be a fruitful framework to describe phenomena outside the realm of traditional physics. Recent years have witnessed an attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. A wide ...

Evidence for the applicability of random-matrix theory to nuclear spectra is reviewed. In analogy to systems with few degrees of freedom, one speaks of chaos (more accurately, quantum chaos) in nuclei whenever random-matrix predictions are fulfilled. An introduction into the basic concepts of random...

The progress in our understanding of several aspects of turbulent Rayleigh-Bénard convection is reviewed. The focus is on the question of how the Nusselt number and the Reynolds number depend on the Rayleigh number Ra and the Prandtl number Pr, and on how the thicknesses of the thermal and the kine...

The investigation of high-order harmonic generation (HHG) of femtosecond laser pulses by means of laser-produced plasmas is surveyed. This kind of harmonic generation is an alternative to the HHG in gases and shows significantly higher conversion efficiency. Furthermore, with plasma targets there is...

In this Colloquium, the main features of the electron-lattice interaction are discussed and high values of the critical temperature up to room temperature could be provided. While the issue of the mechanism of superconductivity in the high T_c cuprates continues to be controversial, one can state t...

In systems possessing spatial or dynamical symmetry breaking, Brownian motion combined with unbiased external input signals, deterministic and random alike, can assist directed motion of particles at submicron scales. In such cases, one speaks of “Brownian motors.” In this review the constructiv...

In addition to the striking beauty inherent in their complex nature, fractals have become a fundamental ingredient of nonlinear dynamics and chaos theory since they were defined in the 1970s. Moreover, fractals have been detected in nature and in most fields of science, with even a certain influence...

This review covers the latest developments in continuous-variable quantum-state tomography of optical fields and photons, placing a special emphasis on its practical aspects and applications in quantum-information technology. Optical homodyne tomography is reviewed as a method of reconstructing the ...

Actinide elements produce a plethora of interesting physical behaviors due to the 5f states. This review compiles and analyzes progress in the understanding of the electronic and magnetic structure of the 5f states in actinide metals. Particular interest is given to electron energy-loss spectros...

Intense ultrashort light pulses comprising merely a few wave cycles became routinely available by the turn of the millennium. The technologies underlying their production and measurement as well as relevant theoretical modeling have been reviewed in the pages of Reviews of Modern Physics (Brabec and...

This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or t...

In materials with strong local Coulomb interactions, simple defects such as atomic substitutions strongly affect both macroscopic and local properties of the system. A nonmagnetic impurity, for instance, is seen to induce magnetism nearby. Even without disorder, models of such correlated systems are...

Dusty plasmas are ubiquitous in low-temperature laboratory discharges as well as in the near-earth environment, planetary rings, and interstellar spaces. In this paper, updated knowledge of fundamentals of collective dust-plasma interactions and several novel phenomena are presented that have been o...

Maxwell’s demon was born in 1867 and still thrives in modern physics. He plays important roles in clarifying the connections between two theories: thermodynamics and information. Here the history of the demon and a variety of interesting consequences of the second law of thermodynamics are present...

The American Physical Society regularly produces reports on issues of public import that require technical understanding and for which an objective and authoritative analysis would be of particular use to the public and policy makers. This report, entitled Energy Future: Think Efficiency, is the lat...

After the fundamental structure of semicrystalline polymers - plate-like crystallites with thicknesses in the nanometer range being embedded in a liquid matrix - had been discovered in the late 1950s, attention turned to the mechanism of formation. After intense, controversial discussions an approach put forward by Hoffman and Lauritzen prevailed and was broadly accepted. The picture envisaged by the treatment - plate-like crystallites with atomically smooth side faces and a surface occupied by chain folds, growing side-ways layer by layer with a secondary nucleation as rate determining step - was easy to grasp and yielded simple relationships. The main control parameter is the supercooling below the equilibrium melting point of a macroscopic crystal, Tf, which determines both the thickness of the crystallites and their lateral growth rate. The impression of many in the community that the mechanism of polymer crystallization is principally understood and the issue essentially settled however was wrong. Experiments carried out during the last decade on various polymer systems provided surprising new insights which are now completely changing the understanding. They revealed a number of laws which control polymer crystallization and melting in bulk, showing in particular that the crystal thickness is inversely proportional to the distance to a temperature Tc which is located above the equilibrium melting point and that crystal growth stops already at a temperature Tzg which is below Tf. The observations indicate that the pathway followed in the growth of polymer crystallites includes an intermediate metastable phase. In a model proposed by us a thin layer with mesomorphic inner structure forms between the lateral crystal face and the melt. The first step in the growth process is an attachment of the coiled chain sequences of the melt onto the mesomorphic layer which subsequently is transformed into the crystalline state. The transitions between melt, mesomorphic layers and lamellar crystallites can be described with the aid of a temperature-thickness phase diagram. Tc and Tzg are identified with the temperatures of the (hidden) transitions between the mesomorphic and the crystalline phase, and between the liquid and the mesomorphic phase, respectively. Comparison of the predictions of the model theory with experimental results from small angle X-ray scattering, optical microscopy and calorimetry yields in addition to the three equilibrium transition temperatures latent heats of transition and surface free energies.

A fundamental question of physics is what ultimately happens to matter as it is heated or compressed. In the realm of very high temperature and density the fundamental degrees of freedom of the strong interaction, quarks and gluons, come into play and a transition from matter consisting of confined baryons and mesons to a state with 'liberated' quarks and gluons is expected. The study of the possible phases of strongly interacting matter is at the focus of many research activities worldwide. In this article we discuss physical aspects of the phase diagram, its relation to the evolution of the early universe as well as the inner core of neutron stars. We also summarize recent progress in the experimental study of hadronic or quark-gluon matter under extreme conditions with ultrarelativistic nucleus-nucleus collisions.

A.c. impedance measurements of ion-conducting glasses provide considerable insight into the nature of the ionic motions in disordered solids. However, interpreting the a.c. impedance has been a matter of considerable debate, particularly in regards to how best to represent the relaxation process which is the result of a transition from correlated to uncorrelated ion hopping. Although interpretations based upon the electric modulus have featured prominently in the earlier literature, direct analysis of the complex conductivity in the frequency domain is gaining popularity as it provides direct (via Fourier transform) information regarding the microscopic mean-squared displacement of ions; a quanitity which most directly ties to theoretical models. Here, we review many recent findings using this approach and provide some guidelines for the casual researcher in how best to interpret a.c. impedance results. *Electronic address: sidebottom@creighton.edu

Intergalactic space is filled with a pervasive medium of ionized gas, the Intergalactic Medium (IGM). A residual neutral fraction is detected in the spectra of Quasi-Stellar Objects at both low and high redshifts, revealing a highly fluctuating medium with temperatures characteristic of photoionized gas. The statistics of the fluctuations are well-reproduced by numerical gravity-hydrodynamics simulations within the context of standard cosmological structure formation scenarios. As such, the study of the IGM offers an opportunity to probe the nature of the primordial density fluctuations on scales unavailable to other methods. The simulations also suggest the IGM is the dominant reservoir of baryons produced by the Big Bang, and so the principal source of the matter from which galaxies formed. The detection of metal systems within the IGM shows that it was enriched by evolved stars early in its history, demonstrating an intimate connection between galaxy formation and the IGM. The author presents a comprehensive review of the current understanding of the structure and physical properties of the IGM and its relation to galaxies, concluding with comments on prospects for furthering the study of the IGM using future ground-based facilities and space-based experiments.

Interference with atomic and molecular matter waves is a rich branch of atomic physics and quantum optics. It started with atom diffraction from crystal surfaces and the separated oscillatory fields technique used in atomic clocks. Atom interferometry is now reaching maturity as a powerful art with many applications in modern science. In this review we first describe the basic tools for coherent atom optics including diffraction by nanostructures and laser light, three-grating interferometers, and double wells on atom chips. Then we review scientific advances in a broad range of fields that have resulted from the application of atom interferometers. These are grouped in three categories: (1) fundamental quantum science, (2) precision metrology and (3) atomic and molecular physics. Although some experiments with Bose Einstein condensates are included, the focus of the review is on linear matter wave optics, i.e. phenomena where each single atom interferes with itself.

The dynamics and stability of thin liquid films have fascinated scientists over many decades: the observations of regular wave patterns in film flows down a windowpane or along guttering, the patterning of dewetting droplets and the fingering of viscous flows down a slope are all examples that are familiar in daily life. Thin films flows occur over a wide range of length scales and are central to numerous areas of engineering, geophysics and biophysics; these include nano- and microfluidics, coating flows, intensive processing, lava flows, dynamics of continental ice sheets, tear-film rupture and surfactant replacement therapy. These flows have attracted considerable attention in the literature, which have resulted in many significant developments in experimental, analytical and numerical research in this area. These include advances in understanding dewetting, thermocapillary- and surfactant-driven films; falling films and films flowing over structured, compliant and rapidly rotating substrates; evaporating films as well as those manipulated via use of electric fields to produce nano-scale patterns. These developments are reviewed in this paper and open problems and exciting research avenues in this thriving area of fluid mechanics are also highlighted.

The nbsp;symmetry associated with a possible heavy nbsp;would have profound implications for particle physics and cosmology. The motivations for such particles in various extensions of the standard model, possible ranges for their masses and couplings, and classes of anomaly-free models are discussed. Present limits from electroweak and collider experiments are briefly surveyed, as are prospects for discovery and diagnostic study at future colliders. Implications of a nbsp;are discussed, including an extended Higgs sector, extended neutralino sector, and solution to the m problem in supersymmetry; exotic fermions needed for anomaly cancellation; possible flavor changing neutral current effects; neutrino mass; possible nbsp;mediation of supersymmetry breaking; and cosmological implications for cold dark matter and electroweak baryogenesis.

Accurate x-ray scattering techniques to measure the physical properties of dense plasmas have been developed for applications in high-energy density physics. This class of experiments produces short-lived hot dense states of matter with electron densities in the range of solid density and higher where powerful penetrating x-ray sources have become available for probing. Experiments have employed laser-based x-ray sources that provide sufficient photon numbers in narrow bandwidth spectral lines allowing spectrally-resolved x-ray scattering measurements from these plasmas. The back-scattering spectrum accesses the non-collective Compton scattering regime which provides accurate diagnostic information on the temperature, density and ionization state. The forward scattering spectrum has been shown to measure the collective plasmon oscillations. Besides extracting the standard plasma parameters, density and temperature, forward scattering yields new observables such as a direct measure of collisions and quantum effects. Dense matter theory relates scattering spectra with the dielectric function and structure factors that determine the physical properties of matter. Applications to radiation-heated and shock-compressed matter have demonstrated accurate measurements of compression and heating with up to picosecond temporal resolution. The ongoing development of suitable x-ray sources and facilities will enable experiments in a wide range of research areas including inertial confinement fusion, radiation-hydrodynamics, material science, or laboratory astrophysics.

Complex (dusty) plasmas are composed of a weakly ionized gas and charged microparticles and represent the plasma state of soft matter. Complex plasmas have several remarkable features: Dynamical time scales associated with microparticles are "stretched" to tens of milliseconds, yet the microparticles themselves can be easily visualized individually. Furthermore, since the background gas is dilute, the particle dynamics in strongly coupled complex plasmas is virtually undamped, which provides a direct analogy to regular liquids and solids in terms of the atomistic dynamics. Finally, complex plasmas can be easily manipulated in different ways - also at the level of individual particles. Altogether, this gives us a unique opportunity to go beyond the limits of continuous media and study - at the kinetic level - various generic processes occurring in liquids or solids, in regimes ranging from the onset of cooperative phenomena to large strongly coupled systems. In the first part of the review we highlight some of the basic and new physics which complex plasmas enable us to study, and in the second (major) part we focus on strong coupling phenomena in an interdisciplinary context. We emphasize the connections with complex fluids and address a number of generic liquid and solid state issues. In summary, we also briefly discuss application oriented research.

Laser-driven plasma-based accelerators, which are capable of supporting fields in excess of 100nbsp;GV/m, are reviewed. This includes the laser wakefield accelerator, the plasma beat wave accelerator, the self-modulated laser wakefield accelerator, plasma waves driven by multiple laser pulses, and highly-nonlinear regimes. The properties of linear and nonlinear plasma waves are discussed, as well as electron acceleration in plasma waves. Methods for injecting and trapping plasma electrons in plasma waves are also discussed. Limits to the electron energy gain are summarized, including laser pulse diffraction, electron dephasing, laser pulse energy depletion, and beam loading limitations. The basic physics of laser pulse evolution in underdense plasmas is also reviewed. This includes the propagation, self-focusing, and guiding of laser pulses in uniform plasmas and with preformed density channels. Instabilities relevant to intense short-pulse laser-plasma interactions, such as Raman, self-modulation, and hose instabilities, are discussed. Experiments demonstrating key physics, such as the production of high-quality electron bunches at energies of 0.1-1nbsp;GeV, are summarized.

Quantum key distribution (QKD) is the first quantum information task to reach the level of mature technology, already fit for commercialization. It aims at the creation of a secret key between authorized partners connected by a quantum channel and a classical authenticated channel. The security of the key can in principle be guaranteed without putting any restriction on the eavesdropper's power. The first two sections provide a concise up-to-date review of QKD, biased toward the practical side. The rest of the paper presents the essential theoretical tools that have been developed to assess the security of the main experimental platforms (discrete variables, continuous variables and distributed-phase-reference protocols).