An exploration of commonly observed stylized facts with data from experimental asset markets

We analyze data from experimental asset markets with pooled linear regression models to shed some light on the emergence of fat tails and volatility clustering in return distributions. Our data suggest that the arrival of new information is the most important cause for both stylized facts. After new information arrives we see spikes in volatility as this information is digested in the market. We also find that uninformed traders contribute significantly more to fat tails than do informed traders and that the heterogeneity in fundamental information leads to larger returns.     

An investigation of the oxidized Ni/InAs interface

Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O₂ atmosphere. The anneal temperature and time were 450 °C and 2.5 h, respectively. X-ray diffraction of the oxidized Ni/InAs sample revealed the formation of In₃Ni₂ and In₂O₃ on the front suggesting inter diffusion of In, Ni and O. NiO was not detected by X-ray diffraction. In a preliminary study, using glass as a substrate, NiO readily formed when using these oxidation parameters. Conductivity measurements of the oxidized Ni/InAs surface revealed a conducting front and insulating rear surface while TEM of the Ni/InAs interface revealed an intermediate amorphous diffusion zone between the “oxidized” Ni layer and the bulk InAs. A closer investigation of the intermediate layer supports the X-ray diffraction results, suggesting compound formation due to diffusion of oxygen and nickel into the substrate, and out-diffusion of In and As from the bulk of the sample. AES was used to further elucidate these results.     

Magnetically trapped atoms for compact atomic clocks

We investigate the hyperfine transition of magnetically trapped non-condensed atoms. The two principal frequency shifts, the second order Zeeman effect and the mean field interaction are considered. Analytic models of the mean frequency and its trap induced spread are developed. Comparisons with existing experiments evaluate the role of the atoms’ oscillatory motion. The analytic model proves to be equivalent to existing Monte Carlo simulations. The formulae provide a simple tool for optimising the design of a new experiment. Applied to the two-photon transition |F=1,m _F =−1〉→|F=2,m _F =1〉 in ⁸⁷Rb and the conditions of a typical atom chip experiment, a line spread as small as 11 mHz is predicted giving a quality factor of 10¹². The system is promising for application in precision instruments such as compact atomic clocks.     

Transition between corrugated metal films and?split-ring-resonator arrays

We fabricate split-ring-resonator arrays via direct laser writing of polymers, followed by atomic-layer deposition of titania, chemical vapor deposition of silver, and focused-ion-beam milling. While structures like that have been fabricated previously by other means, our approach here allows for a direct comparison with the optical properties of corrugated metal surfaces, which are fabricated along the same lines. This comparison reveals substantial differences regarding the magnetic metamaterial properties. In particular, we find that the optical response of the corrugated metal surfaces is due to a higher-order magnetic resonance, whereas that of the split-ring resonators stems from their fundamental magnetic resonance.     

The role of substrate surface termination in the deposition of?(111)?CdTe on?(0001) sapphire

The small lattice mismatch and sixfold symmetry offered by the (0001) planes of sapphire make it an ideal substrate candidate for the deposition of (111) CdTe films. There, however, exists a wide disparity in film quality among various researchers with both single crystal and highly twinned, multidomain films being reported. We have developed a pulsed laser deposition process that enables us to deposit nearly single-domain (111) CdTe films exhibiting excellent surface morphology. Such films are deposited on as-received sapphire substrates in vacuum conditions where oxygen is readily available. If, however, film deposition is preceded by the deposition of a submonolayer of aluminum prior to film growth then a secondary CdTe domain emerges with an in-plane orientation having a 180°-in-plane offset from the first domain. These multidomain films show poor crystallographic and morphological properties, similar to what has been reported elsewhere. It is concluded that the singly terminated (0001) sapphire substrates are a prerequisite for the deposition of high-quality (111) CdTe films.     

Use of chlorinated carbon and silicon precursors for epitaxial growth of 4H‐SiC at very high growth rates

A possibility to apply the advantages of chlorinated carbon precursors, which had been previously used in low‐temperature epitaxial growth of 4H‐SiC, to achieve very high growth rates at higher growth temperatures was investigated. Silicon tetrachloride was used as the silicon precursor to suppress gas‐phase homogeneous nucleation. The temperature increase from 1300 °C (which is the temperature of the previously reported low‐temperature halo‐carbon epitaxial growth) to 1600 °C enabled an increase of the precursor flow rates and consequently of the growth rate from 5 to more than 100 μm/h without morphology degradation. High quality of the epilayers was confirmed by low‐temperature photoluminescence spectroscopy and time‐resolved luminescence. No evidences of homogeneous nucleation were detected, however, liquid Si droplet formation on the epilayer surface seems to remain a bottleneck at very high growth rate. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Boom and bust in continuous time evolving economic model

We show that a simple model of a spatially resolved evolving economic system, which has a steady state under simultaneous updating, shows stable oscillations in price when updated asynchronously. The oscillations arise from a gradual decline of the mean price due to competition among sellers competing for the same resource. This lowers profitability and hence population but is followed by a sharp rise as speculative sellers invade the large un-inhabited areas. This cycle then begins again.     

Superfluid to Mott insulator quantum phase transition in a 2D permanent magnetic lattice

The accessibility of the critical parameters for the superfluid to Mott insulator quantum phase transition in a 2D permanent magnetic lattice is investigated. We determine the hopping matrix element J, the on-site interaction U, and hence the ratio J/U, in the harmonic oscillator wave function approximation. We show that for a range of realistic parameters the critical values of J/U, predicted by different methods for the Bose-Hubbard model in 2D, such as mean field theory and Monte Carlo simulations, are accessible in a 2D permanent magnetic lattice. The calculations are performed for a 2D permanent magnetic lattice created by two crossed arrays of parallel rectangular magnets plus a bias magnetic field.     

Photoluminescence and X-Ray Photoelectron Spectroscopy of p-Type Phosphorus-Doped ZnO Films Prepared by MOCVD

Reproducible p-type phosphorus-doped ZnO （p-ZnO：P） films are prepared on semi-insulating InP substrates by metal-organic chemical vapour deposition technology. The electrical properties of these films show a hole concentration of 9.02 × 10^17 cm ^-3, a mobifity of 1.05 cm^2 /Vs, and a resistivity of 6.6 Ω.cm. Obvious acceptorbound-exciton-related emission and P-induced zinc vacancy （Vzn） emission are observed by low-temperature photoluminescence spectra of the films, and the acceptor binding energy is estimated to be about 125meV. The local chemical bonding environments of the phosphorus atoms in the ZnO are also identified by x-ray photoelectron spectra. Our results show direct experimental evidence that Pzn-2Vzn shallow acceptor complex most likely contributes to the p-type conductivity of ZnO：P films.