A comparison between optically active CdZnSe/ZnSe and CdZnSe/ZnBeSe self-assembled quantum dots: effect of beryllium

The composition and size of optically active Cd_xZn_1−xSe/ZnSe quantum dots are estimated with a previously developed method. The results are then compared with those obtained for Cd_xZn_1−xSe/Zn_0.97Be_0.03Se QDs. We show that introducing Be into the barrier material enhances both Cd composition and quantum size effect of optically active quantum dots.     

Eikonal Approximation to 5D Wave Equations and the 4D Space-Time Metric

We apply a method analogous to the eikonal approximation to the Maxwell wave equations in an inhomogeneous anisotropic medium and geodesic motion in a three dimensional Riemannian manifold, using a method which identifies the symplectic structure of the corresponding mechanics, to the five dimensional generalization of Maxwell theory required by the gauge invariance of Stueckelberg's covariant classical and quantum dynamics. In this way, we demonstrate, in the eikonal approximation, the existence of geodesic motion for the flow of mass in a four dimensional pseudo-Riemannian manifold. These results provide a foundation for the geometrical optics of the five dimensional radiation theory and establish a model in which there is mass flow along geodesics. We then discuss the interesting case of relativistic quantum theory in an anisotropic medium as well. In this case the eikonal approximation to the relativistic quantum mechanical current coincides with the geodesic flow governed by the pseudo-Riemannian metric obtained from the eikonal approximation to solutions of the Stueckelberg–Schrödinger equation. The locally symplectic structure which emerges is that of a generally covariant form of Stueckelberg's mechanics on this manifold.     

Phonon scattering from the boundaries of small crystals embedded in a dielectric porous-glass matrix

The thermal conductivity of porous glass with randomly distributed connecting pores ～70 Å in size (glass porosity ～25%), as well as of a porous glass + NaCl composite, was measured in the temperature range 5–300 K. NaCl filled one fourth of the pores in the composite. The experimental results on the composite thermal conductivity can be accounted for only by assuming that phonons scatter from the boundaries of NaCl nanocrystals embedded in channels of the porous glass.     

Neutron activation and the JFK assassination, Part I. Data and interpretation

Five lead fragments from bullet cores from the assassination of American President John F. Kennedy in 1963 were analyzed twice by NAA, first by the FBI in 1964 and then by Vincent P. Guinn in 1977. Their concentrations of Sb have provided invaluable information about the number and origin of bullets that hit Kennedy and Texas Governor John B. Connally. While both analyses appeared to group the fragments into a body shot and a head shot, the FBI set contained a systematic error and Guinn's results from quarters of test bullets showed that the indicator element Sb varied enough over quarters to potentially merge the groups. The latter problem was resolved by the FBI replicate analyses, which showed that antimony was nearly homogeneos on the small scales of the fragments, and by the mechanism by which jacketed bullets break when hitting bone, which generates tiny fragments from a single break near the middle of the lead core. They collectively meant that the fragments within each group were formed on the scale of subfragments. The two groups were just as they appear because the larger quarter-bullet heterogeneities did not apply. This result substantiates Guinn's original conclusion that two and only two bullets from Lee Harvey Oswald's rifle struck the two men. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the Definition of Temperature in FPU Systems

It is usually assumed, in classical statistical mechanics, that the temperature should coincide, apart from a suitable constant factor, with the mean kinetic energy of the particles. We show that this is not the case for Fermi–Pasta–Ulam systems, in conditions in which energy equipartition between the modes is not attained. We find that the temperature should be rather identified with the mean value of the energy of the low frequency modes.     

The Calogero–Bogoyavlenskii–Schiff Equation in 2+1 Dimensions

We use the classical and nonclassical methods to obtain symmetry reductions and exact solutions of the (2+1)-dimensional integrable Calogero–Bogoyavlenskii–Schiff equation. Although this (2+1)-dimensional equation arises in a nonlocal form, it can be written as a system of differential equations and, in potential form, as a fourth-order partial differential equation. The classical and nonclassical methods yield some exact solutions of the (2+1)-dimensional equation that involve several arbitrary functions and hence exhibit a rich variety of qualitative behavior.     

Universality and summability of trigonometric polynomials and trigonometric series

Periodica Mathematica Hungarica -     

The Hochschild class of the Chern character for semifinite spectral triples

We provide a proof of Connes’ formula for a representative of the Hochschild class of the Chern character for (p,∞)-summable spectral triples. Our proof is valid for all semifinite von Neumann algebras, and all integral p?1. We employ the minimum possible hypotheses on the spectral triples.