The role of diffusion in broadband infrared absorption in chalcogen-doped silicon

Sulfur doping of silicon beyond the solubility limit by femtosecond laser irradiation leads to near-unity broadband absorption of visible and infrared light and the realization of silicon-based infrared photodetectors. The nature of the infrared absorption is not yet well understood. Here we present a study on the reduction of infrared absorptance after various anneals of different temperatures and durations for three chalcogens (sulfur, selenium, and tellurium) dissolved into silicon by femtosecond laser irradiation. For sulfur doping, we irradiate silicon in SF₆ gas; for selenium and tellurium, we evaporate a film onto the silicon and irradiate in N₂ gas; lastly, as a control, we irradiated untreated silicon in N₂ gas. Our analysis shows that the deactivation of infrared absorption after thermal annealing is likely caused by dopant diffusion. We observe that a characteristic diffusion length—common to all three dopants—leads to the reduction of infrared absorption. Using diffusion theory, we suggest a model in which grain size of the resolidified surface layer can account for this characteristic diffusion length, indicating that deactivation of infrared absorptance may be caused by precipitation of the dopant at the grain boundaries.     

Cosmic microwave background and first molecules in the early universe

Besides the Hubble expansion of the universe, the main evidence in favor of the big-bang theory was the discovery, by Penzias and Wilson, of the cosmic microwave background (hereafter CMB) radiation. In 1990, the COBE satellite (Cosmic Background Explorer) revealed an accurate black-body behavior with a temperature around 2.7 K. Although the microwave background is very smooth, the COBE satellite did detect small variations—at the level of one part in 100 000—in the temperature of the CMB from place to place in the sky. These ripples are caused by acoustic oscillations in the primordial plasma. While COBE was only sensitive to long-wavelength waves, the Wilkinson Microwave Anisotropy Probe (WMAP)—with its much higher resolution—reveals that the CMB temperature variations follow the distinctive pattern predicted by cosmological theory. Moreover, the existence of the microwave background allows cosmologists to deduce the conditions present in the early stages of the big bang and, in particular, helps to account for the chemistry of the universe. This report summarizes the latest measurements and studies of the CMB with the new calculations about the formation of primordial molecules. The PLANCK mission—planned to be launched in 2009—is also presented.     

Effect of local molecular ordering on the temperature behavior of the relaxation time of order-parameter fluctuations in the isotropic phase of PAA nematic liquid crystal

The behavior of the relaxation time of order-parameter fluctuations in the isotropic phase of PAA nematic liquid crystal was investigated on the basis of the spectra of depolarized (inelastic) light scattering in a wide temperature range including the immediate vicinity to the temperature of the nematic phase transition. The experimental data were analyzed within the Landau—de Gennes theory. The temperature limits of applicability of the Landau—de Gennes theory to the isotropic-phase dynamic properties are obtained. The minimum correlation length is determined, at which the effect of local ordering on the dynamics of slow orientational motion of isotropic-phase molecules is dominant.     

Quantum field theory in curved spacetime,the operator product expansion,and dark energy

To make sense of quantum field theory in an arbitrary (globally hyperbolic) curved spacetime, the theory must be formulated in a local and covariant manner in terms of locally measurable field observables. Since a generic curved spacetime does not possess symmetries or a unique notion of a vacuum state, the theory also must be formulated in a manner that does not require symmetries or a preferred notion of a “vacuum state” and “particles”. We propose such a formulation of quantum field theory, wherein the operator product expansion (OPE) of the quantum fields is elevated to a fundamental status, and the quantum field theory is viewed as being defined by its OPE. Since the OPE coefficients may be better behaved than any quantities having to do with states, we suggest that it may be possible to perturbatively construct the OPE coefficients—and, thus, the quantum field theory. By contrast, ground/vacuum states—in spacetimes, such as Minkowski spacetime, where they may be defined—cannot vary analytically with the parameters of the theory. We argue that this implies that composite fields may acquire nonvanishing vacuum state expectation values due to nonperturbative effects. We speculate that this could account for the existence of a nonvanishing vacuum expectation value of the stress-energy tensor of a quantum field occurring at a scale much smaller than the natural scales of the theory. Fourth Award in the 2008 Essay Competition of the Gravity Research Foundation.     

General models of Einstein gravity with a non-Newtonian weak-field limit

We investigate Einstein theories of gravity, coupled to a scalar field j{\varphi} and point-like matter, which are characterized by a scalar field-dependent matter coupling function e^H(j){e^{H(\varphi)}} . We show that under mild constraints on the form of the potential for the scalar field, there are a broad class of Einstein-like gravity models—characterized by the asymptotic behavior of H—which allow for a non-Newtonian weak-field limit with the gravitational potential behaving for large distances as ln r. The Newtonian term GM/r appears only as sub-leading. We point out that this behavior is also shared by gravity models described by f (R) Lagrangians. The relevance of our results for the building of infrared modified theories of gravity and for modified Newtonian dynamics is also discussed.     

Short-time critical dynamics of statistical systems and field theory

Recent investigation on the short-time dynamic scaling of critical dynamics is reviewed, with the aim of applying it to the field theory. The contents of this paper are as follows: (1) Short-time behavior of the critical relaxation dynamics, (2) Numerical evidence of the short-time scaling—2-dimensional Ising model and Universality, (3) Theoretical background of the generalized scaling form, (4) Application to a field theoretical model—(2+1)-dimensional SU(2) lattice gauge theory at finite temperature, and (5) Concluding remarks. This paper is dedicated to the 70th birthday of Prof. M. Namiki.     

Kinetics of first-order phase transitions in the asymptotic stage

We construct an asymptotic theory that describes the kinetics of first-order phase transitions. The theory is a considerable refinement of the well-known Lifshits-Slezov theory. The main difference between the two is that the Lifshits—Slezov theory uses for the first integral of the kinetic equation an approximate solution of the characteristic equation, which is valid in the entire range of sizes except for the blocking point, i.e., it uses a nonuniformly applicable approximation. At the same time, the behavior of the characteristic solution near the blocking point determines the asymptotic behavior of the size distribution function of the nuclei for the new phase. Our theory uses a uniformly applicable solution of the characteristic equation, a solution valid at long times over the entire range of sizes. This solution is used to find the asymptotic behavior of all basic properties of first-order phase transitions: the size distribution function, the average nucleus size, and the nucleus density. Zh. éksp. Teor. Fiz. 113, 2193–2208 (June 1998)     

Quantum effects for parametric X-ray radiation during channeling: Theory and first experimental observation

The theory of X-ray radiation from relativistic channeled electrons at the Bragg angles—parametric X-ray radiation (PXR) during channeling (PXRC)—is developed while accounting for two quantum effects: the initial population of bound states of transverse motion and the transverse “form-factor” of channeled electrons. An experiment was conducted using a 255 MeV electron beam from a linac at the SAGA Light Source. We have identified a difference in the angular distributions of PXR and PXRC and obtained a fairly good agreement between the theoretical and experimental results.     

New design of interference band-pass infrared filter

The new design of the interference band-pass infrared filters is proposed. The analytic expressions for the analysis structure “layer with the high refractive index — interference mirror — layer with the high refractive index” are obtained. The refractive indices optimal and thicknesses of individual layers that limited interference mirror are obtained.     

Horizons,Constraints, and Black Hole Entropy

Black hole entropy appears to be “universal”—many independent calculations, involving models with very different microscopic degrees of freedom, all yield the same density of states. I discuss the proposal that this universality comes from the behavior of the underlying symmetries of the classical theory. To impose the condition that a black hole be present, we must partially break the classical symmetries of general relativity, and the resulting Goldstone-boson-like degrees of freedom may account for the Bekenstein–Hawking entropy. In particular, I demonstrate that the imposition of a “stretched horizon” constraint modifies the algebra of symmetries at the horizon, allowing the use of standard conformal field theory techniques to determine the asymptotic density of states. The results reproduce the Bekenstein–Hawking entropy without any need for detailed assumptions about the microscopic theory.     

Reflective and photoacoustic infrared spectroscopic techniques in assessment of binding media in paintings

This study proposes a method to estimate the lipid content in binding media in paintings that can be used at any laboratory equipped with an infrared spectrometer. The lipid content estimator, termed greasiness index (GI), is defined as a ratio of lipid ν(C=O) and protein amide I bands at 1743 and 1635 cm⁻¹, respectively. Three Fourier transform infrared (FTIR) sampling techniques were evaluated for GI determination: reflective attenuated total reflection—ATR, specular reflection microscopy—μSR and photoacoustic—PAS. A set of model painting samples containing three tempera binding media (casein, egg, egg + oil), seven pigments and one varnish type were used in the study. Multivariate analysis was used to evaluate the resulting data. A good reproducibility of GI was obtained by ATR and PAS but not with μSR. The discriminative power of the technique is higher for unvarnished samples, but, generally, the GI estimator can be used for the categorisation of binding media in large populations of painting samples analysed with the same FTIR technique (sampling technique, detection, etc.).     

Cosmological solution in the scalar—tensor theory of gravity

We consider the problem of exact integration of the field equations in the scalar—tensor theory of gravity for the case in which matter is an ideal fluid and the metric for space is given in Robertson—Walker form. We obtain a solution (in quadratures) for an arbitrary equation of state and an arbitrary time-dependent density for matter. Tomsk State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 124–127, January, 1997.     

Cosmic rays in the heliosphere

Summary This is a rapporteur paper for the XXIV International Cosmic-Ray Conference covering topics of anomalous cosmic rays, shock acceleration, modulation and transport theory, cosmic-ray gradients, corotating interaction regions, coronal-mass ejections, and solar neutrinos. Among the highlights of the meeting are —conclusive proof that most anomalous cosmic rays are singly charged,—undisputed detection of anomalous cosmic-ray hydrogen,—discovery of unexpectedly large anisotropies of pickup ions,—observation of pronounced solar rotational modulation of cosmic-ray fluxes to the highest heliolatitudes (∼80°) probed by the Ulysses spacecraft, and—new measurements of modulation effects sensitive to particle charge sign. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Scale breaking in neutrino scattering

We consider two types of scale breaking models—one based on asymptotically free gauge theory and the other phenomenological—which have already been fitted to the electron and muon data. Their predictions for the neutrino scattering are worked out and the sensitivity on the model parameters and the input electron data studied. The effects of scale breaking at very lowQ ² and of a finite longitudinal cross-section are incorporated in analogy withep data. The predictions are compared with the recent neutrino scattering data.     

Possibility of the levitation of droplets in the atmosphere when they are charged by induction in an electric field under nonuniform evaporation conditions

The behavior of droplets in the atmosphere in an electric field has important bearing on the theory of thunderstorms. One of the possible mechanisms by which droplets become charged—the induction mechanism in the presence of nonuniform evaporation—is investigated in greater detail on the basis of recent experimental results (V. A. Saranin, Zh. Tekh. Fiz. 65(6), 21 (1995) [Tech. Phys. 40, 332 (1995)]). Zh. Tekh. Fiz. 68, 16–21 (February 1998)     

Quasilocal density functional theory in nuclei and its extension to include pairing correlations

We propose first a generalization of the Density Functional Theory. This theory leads to single-particle equations of motion with a quasilocal mean-field operator, which contains a quasiparticle position-dependent effective mass and a spin—orbit potential. The energy density functional is constructed using the extended Thomas—Fermi approximation. Some ground-state properties of doubly magic nuclei are considered within the framework of this approach. Calculations are performed using the finite-range Gogny D1S forces, and the results are compared with the exact Hartree—Fock calculations. Next, we present an extension of the density functional theory to include pairing correlations without formal violation of the particle-number condition. This problem, which is nonlocal, can be simplified by a suitable quasilocal reduction, which is also briefly discussed in this paper. The text was submitted by the authors in English.     

From two mesons and (V-A) weak currents to the standard model of quark and lepton interactions

This retrospective paper traces the conceptual evolution of two theories in which the author was involved—the two-meson theory (with H A Bethe) in 1947 and the universal (V-A) theory of weak interactions (with E C G Sudarshan) in 1957—into the present-day standard model of particle interactions. Part 1 is entitled ‘From the pion to QCD and pseudo-Goldstone bosons” and Part 2 “From the muon and neutrino to QFD and chiral anomalies’. Adapted from two lectures delivered at the University of Rochester in October, 1987.     

Particles and events in classical off-shell electrodynamics

Despite the many successes of the relativistic quantum theory developed by Horwitz et al., certain difficulties persist in the associated covariant classical mechanics. In this paper, we explore these difficulties through an examination of the classical. Coulomb problem in the framework of off-shell electrodynamics. As the local gauge theory of a covariant quantum mechanics with evolution paratmeter τ, off-shell electrodynamics constitutes a dynamical theory of ppacetime events, interacting through five τ-dependent pre-Maxwell potentials. We present a straightforward solution of the classical equations of motion, for a test event traversing the field induced by a “fixed” event (an event moving uniformly along the time axis at a fixed point in space). This solution is seen to be unsatisfactory, and reveals the essential difficulties in the formalism at the classical levels. We then offer a new model of the particle current—as a certain distribution of the event currents on the worldline—which eliminates these difficulties and permits comparison of classisical off-shell electrodynamics with the standard Maxwell theory. In this model, the “fixed” event induces a Yukawa-type potential, permitting a semiclassical identification of the pre-Maxwell time scale λ with the inverse mass of the intervening photon. Numerical solutions to the equations of motion are compared with the standard Maxwell solutions, and are seen to coincide when λ≳10⁻⁶ seconds, providing an initial estimate of this parameter. It is also demonstrated that the proposed model provides a natural interpretation for the photon mass cut-off required for the renormalizability of the off-shell quantum electrodynamics.     

The three-boson bound state in massive QED2

We derive the (matrix-valued) Feynman rules of mass perturbation theory of the massive Schwinger model for non-zero vacuum angleϑ. Further, we discuss the properties of the three-boson bound state and compute — by a partial resummation of the mass perturbation series — its mass and its partial decay widths. This work was supported by a research stipendium of the Vienna University.     

Polymerization of 2-methylaniline and 2-methoxyaniline in water/pentane biphasic system

We report on chemical polymerization of two aniline derivatives — 2-methylaniline and 2-methoxyaniline — in a two-phase water/pentane system. We have found that poly(2-methylaniline) is produced in form of an amorphous material regardless of the fact whether the monomer is initially dissolved in aqueous or organic phase. The behavior of 2-methoxyaniline is significantly different. The oxidation of this monomer generally results in formation of a water soluble oligomer and an insoluble polymeric product. In consequence, depending on the experimental setup, the polymer is prepared in form of a thin film at the organic/aqueous interface or as micrometer-sized spherical particles dispersed in the aqueous phase. Electronic supplementary material Supplementary Online Material