A Derivation Of The Scalar Propagator In A Planar Model In Curved Space

Given that the free massive scalar propagator in 2 + 1 dimensional Euclidean space is $D(x-y)=\frac{1}{4\pi \rho} 0.25cm e^{-m \rho}$ with $\rho^2=(x-y)^2$ we present the counterpart of $D(x-y)$ in curved space with a suitably modified version of the Antonsen - Bormann method instead of the familiar Schwinger - de Witt proper time approach, the metric being defined by the rotating solution of Deser et al. of the Einstein field equations associated with a single massless spinning particle located at the origin.Comment: 4pages,Presented at FFP10,Nov.24 - 26,2009,UWA,Perth,To appear in AIP Conference Proceeding

Summary of GaAs Solar Cell Performance and Radiation Damage Workshop

The workshop considered the GaAs solar cell capability and promise in several steps: (1) maximum efficiency; (2) space application; (3) major technology problems (AR coating optimization, contacts); (4) radiation resistance; (5) cost and availability; and (6) alternatives. The workshop believes that GaAs solar cells are fast approaching the fulfillment of their potential as candidates for space cells. A maximum efficiency of 20 to 31 percent AMO can be reasonably expected from GaAs based cells, and this may go a little higher with concentration. The use of concentration in space needs to be more carefully evaluated

GaAs workshop report

The advantages of GaAs over silicon are discussed. The substrate problem in solar cell fabrication was reviewed. Future trends in solar energy technology were predicted with special emphasis on cost of production

Electron Radiation Damage of (alga) As-gaas Solar Cells

Solar cells (2 cm by 2 cm (AlGa) As-GaAs cells) were fabricated and then subjected to irradiation at normal incidence by electrons. The influence of junction depth and n-type buffer layer doping level on the cell's resistance to radiation damage was investigated. The study shows that (1) a 0.3 micrometer deep junction results in lower damage to the cells than does a 0.5 micrometer junction, and (2) lowering the n buffer layer doping density does not improve the radiation resistance of the cell. Rather, lowering the doping density decreases the solar cell's open circuit voltage. Some preliminary thermal annealing experiments in vacuum were performed on the (AlGa)As-GaAs solar cells damaged by 1-MeV electron irradiation. The results show that cell performance can be expected to partially recover at 200 C with more rapid and complete recovery occurring at higher temperature. For a 0.5hr anneal at 400 C, 90% of the initial power is recovered. The characteristics of the (AlGa)As-GaAs cells both before and after irradiation are described

Medium energy proton radiation damage to (AlGa)As-GaAs solar cells

The performance of (AlGa)As-GaAs solar cells irradiated by medium energy 2, 5, and 10 MeV protons was evaluated. The Si cells without coverglass and a number of GaAs solar cells with 12 mil coverglass were irradiated simultaneously with bare GaAs cells. The cell degradation is directly related to the penetration of depth of protons with GaAs. The influence of periodic and continuous thermal annealing on the GaAs solar cells was investigated

An exact evaluation of the Casimir energy in two planar models

The method of images is used to calculate the Casimir energy in Euclidean space with Dirichlet boundary conditions for two planar models, namely: i. the non-relativistic Landau problem for a charged particle of mass m for which - irrespective of the sign of the charge - the energy is negative, and ii. the model of a real, massive, noninteracting relativistic scalar field theory in 2 + 1 dimensions, for which the Casimir energy density is non-negative and is expressed in terms of the Lerch transcendent xxx and the polylogarithm xxx with 0 < xxx < 1 and n = 2, 3.Comment: 5 pages, 2 figures,IMFP2009 conference,to appear in forthcoming AIP Conf.Proc.1150 Request:There are three mathematical symbols denoted by xxx in the abstract below which are otherwise present in the abstract of the submission.Could you please include them so that the abstract below is complet

GaAs solar cells for concentrator systems in space

Cells for operation in space up to more than 100 suns were made, and an AMO efficiency of 21% at 100 suns with these cells was obtained. The increased efficiency resulted not only from the higher open circuit voltage associated with the higher light intensity (higher short circuit current); it also benefitted from the increase in fill factor caused by the lower relative contribution of the generation recombination current to the forward bias current when the cell's operating current density is increased. The experimental cells exhibited an AMO efficiency close to 16% at 200 C. The prospect of exploiting this capability for the continuous annealing of radiation damage or for high temperature missions (e.g., near Sun missions) remains therefore open. Space systems with concentration ratios on the order of 100 suns are presently under development. The tradeoff between increased concentration ratio and increased loss due to the cell's series resistance remains attractive even for space applications at a solar concentrator ratio of 100 suns. In the design of contact configuration with low enough series resistance for such solar concentration ratios, the shallow junction depth needed for good radiation hardness and the thin AlGaAs layer thickness needed to avoid excessive optical absorption losses have to be retained

Structure models for the hydrated and dehydrated nitrate-intercalated layered double hydroxide of Li and Al

Imbibition of LiNO3 into gibbsite results in the formation of a single phase layered double hydroxide of the composition LiAl2(OH)6(NO3)·1.2H2O. This phase undergoes reversible dehydration along with the compression of the basal spacing accompanied by the reorientation of the nitrate in the interlayer gallery. The hydrated phase is a solid solution of two lattices: (i) a hexagonal lattice defining the ordering of atoms within the metal hydroxide layer, and (ii) a lattice of orthorhombic symmetry defining the ordering of atoms within the interlayer. DFT calculations of the hydration behaviour show that there is no registry between the two sublattices. In the dehydrated phase, the nitrate ion is intercalated with its molecular plane parallel to the metal hydroxide layer and the crystal adopts a structure of hexagonal symmetry

Optical studies of novae

We review the observational characteristics of classical and recurrent novae in the optical region, in the context of observational programmes carried out using telescopes at the Vainu Bappu Observatory (VBO) and the Indian Astronomical Observatory (IAO) of the Indian Institute of Astrophysics. The article discusses the different classes of novae, based on either their outburst light curve properties, or their spectral development. Also provided is a brief discussion on the quiescence properties of novae