Existence of CMC Cauchy surfaces from a spacetime curvature condition

In this note we present a result establishing the existence of a compact CMC Cauchy surface from a curvature condition related to the strong energy condition.     

On the properties of real cadmium telluride surfaces

Optical and electrical properties of lapped, mechanically polished, and etched cadmium telluride surfaces have been studied by ellipsometry, infrared transmission, reflectivity, and sheet resistance measurements. They have been related to the characteristics of Schottky barriers realized by deposition of gold on these surfaces. These experiments indicate that the electrical behaviour of devices made of cadmium telluride critically depends on the surface damages produced during the sample preparation: while good diodes can be made when bromine in methanol etching is used, lapping and polishing produce a disturbed layer of poor electrical and optical properties whose thickness is related to the size of the abrasive powder used during the preparation.     

On the determination of the statistical properties of light from photoelectric measurements

A relation is derived between the probability distribution of the integrated intensity of light incident on a photoelectric detector and that of the emission ofn photoelectrons in a time interval (t, t +T) from the properties of a quantized electromagnetic field. Both the direct and the inverse relations are derived, thereby enabling the statistical properties of light to be determined from photoelectric measurements. An explicit expression is given for the coefficients for calculating the moments W ^k by means of the moments n ^j (j=1,2, ...,k). The correctness of the operations in which generalized functions occur is confirmed by some direct calculations.     

A restriction on the topology of Cauchy surfaces in general relativity

It is shown that, in a globally hyperbolic and geodesically complete space-time, a part of a partial Cauchy surface that is bounded by a uniformly convex sphere is compact and simply connected.     

On the Differentiability of Compact Cauchy Horizons

We construct an example of a compact Cauchy horizon that is not a differentiable manifold. This answers in the negative the question of whether a compact Cauchy horizon that arises from a space-like hypersurface is necessarily smooth.     

On the projected spectra from a deformed correlated intrinsic state

It is argued that the residual interaction being relatively of long range, should produce Random Phase Approximation (RPA) type of correlations in the Hartree-Fock (HF) intrinsic state. A model is described to take these correlations inti account in the intrinsic state. A comparison of the projected spectra from this state with the exact shell model diagonalization for a model problem bears out this point. An application of the model is distinguishing two almost degenerate HF solutions for the 2s-1d shell nuclei is mentioned.     

Ab initio determination of the optical properties of bulk Au and free surfaces of Au

The optical properties of bulk Au and a (100) free surface of Au are determined by solving the Helmholtz–Fresnel equations for a geometry reflecting layered systems. This approach is based on the use of the microscopical conductivity tensor evaluated fully relativistically and, for later purposes, does include the option of choosing an arbitrary uniform direction of a possibly present magnetization. It will be shown that, while so-called experimental bulk data agree reasonably well with their theoretically obtained counterparts, in the case of free surfaces of Au (semi-infinite systems) they not only disagree substantially in size between different experiments but also with the theoretical values. The shapes of the curves for the real and the imaginary parts of the diagonal permittivity tensor elements ? _xx and ? _zz , however, are rather similar.     

On the Cauchy problem foe Einstein's equations

The mechanism of nonuniqueness of the solution to the problem with initial conditions for the equations of the free gravitational field is elucidated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 32–34, September, 1980.I thank V. L. Bonch-Bruevich, N. S. Kardashov, and I. D. Novikov for interest and assistance.     

On the topographic and optical properties of SiC/SiO2 surfaces

The roughness of the semiconductor surface substantially influences properties of the whole structure, especially when thin films are created. In our work 3C SiC, 4H SiC and Si/a-SiC:H/SiO₂ structures treated by various oxidation a passivation procedures are studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). Surface roughness properties are studied by fractal geometry methods. The complexity of the analysed surface is sensitive to the oxidation and passivation steps and the proposed fractal complexity measure values enable quantification of the fine surface changes. We also determined the optical properties of oxidized and passivated samples by using visual modelling and stochastic optimization.      

On the intrinsic conductivity of polysulphur-nitride

Polysulphur-nitride, (SN), is an unusually interesting polymer. Its solid phase and that of the parent molecular crystal have the same space group symmetry, with the same atoms and electrons per unit cell and very slight differences in bond lengths. Yet, they have completely different electronic properties. Accurate electronic structure calculations have been carried out for the polymer and molecular crystal phases at Hartree-Fock, Hartree and Local density Approximation levels. The results are qualitatively the same at these levels, and they are consistent with experimental observations. This shows that correlation does not play a deciding role. The results also re-emphasize a way to synthesize conducting polymers by polymerizing monomer molecules from their crystal phase. Simulations like in this work can be valuable to guide synthesis.     

On the Cauchy problem of the relativistic Boltzmann equation

It is shown that the relativistic Boltzmann equation has a local solution through an initial distribution function, if the scattering cross section is bounded for high energies and if the initial distribution falls off exponentially with the energy.Supported by the National Aeronautics and Space Administration under Grant No. NGR 44-004-042.On leave from the University of Heidelberg.     

Helium scattering from metal surfaces: potential determination and crystallography

We describe a method for determining the interaction potential between a helium atom and a metal surface from diffraction data. Results are presented for He/Ni(110) and He/Cu(110). For He/Cu(110) the potential 3s in good agreement with a first principles calculation but this is not true for He/Ni(110). We also show that a surface relaxation of 10% produces measurable changes in intensities.     

On the flow of thermal defects from the bulk to surfaces

This paper treats flow of defects between bulk and surface sites, as a crystal passes towards equilibrium, for some practical cases. These include the realistic but quite elaborate example in which vacancy flow from the bulk is coupled to surface step edges, acting as sinks, by reaction with adatoms that are believed to dominate transport on metal surfaces. It is shown how surface processes modify the defect flow from the bulk only at short times. Lacking accurate parameters (such as concentrations) for surface defects, a crude modeling of the theoretical results is offered in order to explore likely generic behavior. The model employs a recently described approximate universality of behavior, scaled to the melting temperature, relevant mainly to fcc (1 1 1) surfaces. Under a range of conditions it is the reaction of advacancies with adatoms that provides the important channel for bulk vacancy flow. Adatom flow onto the terraces from surface step edge sinks is the bottleneck to flow above a crossover temperature (depending on step spacing) and equilibrium recombination is the bottleneck below the crossover.     

On the correlation of geometrical structure and electronic properties at clean semiconductor surfaces

In their LEED patterns most clean semiconductor surfaces show extra spots in addition to the normal beams as expected for a continuation of the bulk lattice up to the topmost layer. This means, that these surfaces are reconstructed. The (111) surfaces of silicon and germanium crystals exhibit another interesting feature: the cleaved surfaces show a metastable superstructure which irreversibly converts to a new modification upon heat treatments above about $\text{1}\text{3}$ of the melting temperatures. The structural changes are correlated with changes in the electronic properties of the surfaces. This has been shown by investigations of surface conductivity, surface photoconductivity, surface photovoltage, internal reflection, electron energy-loss spectroscopy, photoemission, and work function. Recent theoretical studies have also revealed a distinct correlation between geometrical arrangements of the surface atoms and the corresponding band structures of the surface states. However, the atomic positions of the surface atoms used in these calculations are only a model since a detailed analysis of the LEED-intensity-versus-energy curves have not been carried out up to now.     

On the intrinsic definition of local observables

In a theory of local field algebras satisfying the split property, we introduce an algebra generated by the local energy-momentum operators obtained from the canonical local implementation of translations, and possibly by the local charges operators. We discuss the relations of this algebra to the given algebra of local observables and take some steps toward the characterization of theories where they coincide. In the presence of spontaneously broken symmetries, we present a no-go theorem.     

Using evidence from nanocavities to assess the vibrational properties of external surfaces

Internal surfaces of nanocavities are an exceptionally useful laboratory wherein one can spotlight the factors ruling the intricate interplay between morphology and chemistry at silicon surfaces. At the same time, they offer unparalleled opportunities to validate the assignment of vibrational signals of silicon-terminating species under almost ideal experimental conditions. In the case of hydrogen, evidence will be provided of the detailed evolution of H-related species at surfaces depending on their orientation. Also, preliminary results concerning nitrogen at and around nanocavity surfaces will be reported.     

On the intrinsic transverse momentum of partons

Using simple assumptions it is shown that the average transverse momentum of partons is determined by their structure functions. The x-dependence obtained this way agrees well with the experimental data. The size is controlled by the invariant mass of the nucleon core and the behaviour of the structure functions near x = 1. We obtain a lower limit for the intrinsic contribution to 〈k_⊥〉_μμ of ～ 400 MeV.     

Electron emission from metal surfaces by ultrashort pulses: determination of the carrier-envelope phase

The phase varphi of the field oscillations with respect to the peak of a laser pulse influences the light field evolution as the pulse length becomes comparable to the wave cycle and, hence, affects the interaction of intense few-cycle pulses with matter. We theoretically investigate photoelectron emission induced by an intense, few-cycle laser pulse from a metal surface (jellium) within the framework of time-dependent density functional theory and find a pronounced varphi dependence of the photocurrent. Our results reveal a promising route to measuring varphi of few-cycle light pulses (tau<6 fs at lambda=0.8 microm) at moderate intensity levels (I(p) approximately 10(12) W/cm(2)) using a solid-state device.     

On the thermodynamics of surfaces

Isotropic macroscopic thermodynamics is used to treat a classical model of surfaces. An equation of the Gibbs-Duhem type is derived from which the relation between surface stress and specific surface free energy follows. This derivation specifically considers the pressure dependence on size of a spherical particle bounded by an isotropic surface and hence is not restricted to the usual constant pressure assumptions. It follows from the conditions of thermodynamic equilibrium and the above Gibbs-Duhem relation that surface stress is the fundamental parameter controlling the internal hydrostatic pressure of isotropic particles as well as equilibrium vapor pressure and other phenomena dependent on internal pressure.