Table of contents

We show that zero-energy flows appear in many particle systems as well as in single particle cases in 2-dimensions. Vortex patterns constructed from the zero-energy flows can be investigated in terms of the eigenstates in conjugate spaces of Gel'fand triplets. Stable patterns are written by the superposition of zero-energy eigenstates. On the other hand vortex creations and annihilations are described by the insertions of unstable eigenstates with complex-energy eigenvalues into the stable patterns. Some concrete examples are presented in the 2-dimensional parabolic potential barrier case. We point out three interesting properties of the zero-energy flows (i) the absolute economy as for the energy consumption, (ii) the infinite variety of the vortex patterns, and (iii) the perfect stability of the vortex patterns.

Entanglement-based attacks, which are subtle and powerful, are usually believed to render quantum bit commitment insecure. We point out that the no-go argument leading to this view implicitly assumes the evidence-of-commitment to be a monolithic quantum system. We argue that more general evidence structures, allowing for a composite, hybrid (classical–quantum) evidence, conduce to improved security. In particular, we present and prove the security of the following protocol Bob sends Alice an anonymous state. She inscribes her commitment b by measuring part of it in the + (for b = 0) or × (for b = 1) basis. She then communicates to him the (classical) measurement outcome R_x and the partmeasured anonymous state interpolated into other, randomly prepared qubits as her evidence-of-commitment.

A parametric relationship between the Pearson–Takai–Halicioglu–Tiller (PTHT) and the Kaxiras–Pandey (KP) empirical potential energy functions is developed for the case of 2-body interaction. The need for such relationship arises when preferred parametric data and adopted software correspond to different potential functions. The analytical relationship was obtained by equating the potential functions' derivatives at zeroth, first and second order with respect to the interatomic distance at the equilibrium bond length, followed by comparison of coefficients in the repulsive and attractive terms. Plots of non-dimensional 2-body energy versus the nondimensional interatomic distance verified the analytical relationships developed herein. The discrepancy revealed in theoretical plots suggests that the 2-body PTHT and KP potentials are more suitable for curve-fitting "softer" and "harder" bonds respectively.

This experiment is mainly aimed to determine which one of various available formulas is the most satisfactory for describing the drag force experienced by a moving object of different shape, size and material in viscous fluid in a long cylindrical container. The interesting problem on drag coefficient C_d and drag function f(R/D, Re) for moving objects of finite-length cylinders are also investigated. We find that Oseen's formula is the best for steel spheres whereas the Happel and Brenner's cylinder formula is satisfactory for Cu and Al cylinders.

This paper presents an investigation of induced focusing of two laser beams (i.e., a pump beam and another probe beam) in a medium possessing cubic quintic nonlinearity. Third and fifth order nonlinear susceptibilities in presence of two interacting waves have been evaluated. These susceptibilities are then employed to derive two coupled nonlinear Schrödinger equations. Variational formalism has been employed to derive relevant equations which govern different characteristics of propagating beams. Extensive numerical simulation has been performed to investigate the influence of the pump beam on the propagation characteristics of the probe beam. Among several important .ndings, most noteworthy one is that a very weak probe beam can be guided and focused with a pump beam even if its power is well below threshold value of focusing of the pump beam alone. It has been found that induced focusing of the probe beam is more effective when its wavelength is smaller and initial beam width larger than the corresponding quantities of the pump. The roles of fifth order nonlinear coefficient on induced focusing have been investigated. Particularly, it has been established that even an initially defocusing pump can focus a very weak probe.

The Coulomb focusing effects on the bremsstrahlung spectrum are investigated in anisotropic bi-Lorentzian distribution plasmas. The electron–ion bremsstrahlung cross section is obtained by the Bethe–Heitler formula and the Coulomb focusing factor. The Coulomb correction effect on the bremsstrahlung emission rate in the bi-Lorentzian distribution plasma is investigated as a function of the bremsstrahlung photon energy, temperature, and spectral index. The results show that the Coulomb correction effect on the bremsstrahlung emission rate for T_|| > T_⊥ is found to be more significant than that for T_|| ≤ T_⊥ where T_|| and T_⊥ are the parallel and perpendicular temperatures, respectively. It is also found that the Coulomb focusing effect decreases with increasing spectral index.

We have studied Cd/n-Si (33 dots) Schottky barrier diodes (SBDs). Si surfaces have been prepared by the usual chemical etching, and the evaporation of metal has been carried out in a conventional vacuum system. The effective Schottky barrier heights (SBHs) and ideality factors obtained from the current–voltage (I–V) characteristics differ from diode to diode although the samples were identically prepared. The SBH for the Cd/n-Si diodes ranged from 0.605 eV to 0.701 eV, and ideality factor n from 1.213 to 1.913. The reason for that the experimental data differ from diode to diode has been analyzed by applying thermionic emission theory (TET) of inhomogeneous Schottky contacts together with standard TET and thus the effect of series resistance on the relationship between barrier heights and ideality factors of the inhomogeneous SBDs has clearly been shown. A laterally homogeneous SBH value of approximately 0.770 eV for Cd/n-Si SDs has been obtained by the barrier inhomogeneity model.

Random iron-palladium alloys of BCC structure and containing up to 10.59 at.% of Pd have been investigated by means of 14.4 keV Mössbauer spectroscopy in ⁵⁷Fe at ambient temperature versus Pd concentration. It has been found that the perturbation of the iron hyperfine field caused by Pd impurity extends to the third co-ordination shell around an iron atom. Perturbations caused by single Pd atom located in the first, second and third co-ordination shell, respectively, were determined. It was found that they depend very weakly on the average Pd concentration in the range of concentrations investigated. On the other hand, similar perturbations of the isomer shift extend to greater distances from the impurity. Individual contributions due to Pd impurity in the first, second and third shell, respectively, are seen up to about 5 at.% of Pd. However they are small compared to the change of the average isomer shift due to more distant impurities. One sees the change of the average shift solely for alloys having higher concentration of Pd than 5 at.%. On the other hand, a contribution to the hyperfine field remains constant beyond the third shell at all Pd concentrations investigated. It is the same as the field in pure iron.

The surprising detection of strong x-ray and Far-Ultraviolet (FUV) emission from comets is the direct result of charge exchange reactions of multiply-charged solar wind ions with the neutral coma of the comet. A future diagnostics use of spectral features in cometary x-ray and FUV emission is currently hampered by the lack of knowledge on one-electron transfer in collisions of multicharged ions on many-electron atoms or molecules, in particular atomic oxygen and carbon monoxide. The objective of this Comment is the identification of the most urgent missing data.

Recent astronomical measurements are of sufficient quality that new experimental and theoretical data on atoms and molecules were needed for their interpretation. With a focus on ultraviolet transitions for interstellar studies, several examples are given to show how the more precise data on oscillator strengths resulted in an improved understanding of atomic and molecular structure. Here we highlight knowledge gained on the effects arising from cancellation in radial dipole matrix elements, on level identification in complex spectra, and on the mixing between levels.

An optical planar multi-pass geometry is presented and the number of passes as well as the total absorption path length is described mathematically. The system is easily aligned, offers a possibility for remote control as well as a simultaneous multi-passing of different laser beams in a flat design. Applications are expected in experiments where space is limited or where an average but easily achievable increase in absorption path length is useful.

The XXIII International Conference on Photonic, Electronic, and Atomic Collisions (23rd ICPEAC) was held in Stockholm, Sweden, from July 23rd to 29th, 2003, following ICPEAC in Sendai, Japan in 1999 and in Santa Fe, New Mexico, USA, in 2001. This was the first ICPEAC in Sweden and the second one in Scandinavia, after the 18th ICPEAC in Aarhus, Denmark in 1993. The next ICPEAC (24th) will be 2005 in Rosario, Argentina.

Cold antihydrogen atoms have been produced in two experiments at CERN's Antiproton Decelerator (AD). Future spectroscopy of antihydrogen has the potential for extremely precise tests of the fundamental symmetry between matter and antimatter. Recent experiments and future developments will be discussed.