Geometry of Deformed Boson Algebras

Phase-space realisations of an infinite parameter family of quantum deformations of the boson algebra in which the $q$-- and the $qp$--deformed algebras arise as special cases are studied. Quantum and classical models for the corresponding deformed oscillators are provided. The deformation parameters are identified with coefficients of non-linear terms in the normal forms expansion of a family of classical Hamiltonian systems. These quantum deformations are trivial in the sense that they correspond to non-unitary transformations of the Weyl algebra. They are non-trivial in the sense that the deformed commutators consistently quantise a class of non-canonical classical Poisson structures.Comment: 20 pages, late

Opacities and spectra of hydrogen atmospheres of moderately magnetized neutron stars

There is observational evidence that central compact objects (CCOs) in supernova remnants have moderately strong magnetic fields $B\sim10^{11}$ G. Meanwhile, available models of partially ionized hydrogen atmospheres of neutron stars with strong magnetic fields are restricted to $B\gtrsim10^{12}$ G. We extend the equation of state and radiative opacities, presented in previous papers for 10^{12}\mbox{ G}\lesssim B \lesssim 10^{15} G, to weaker fields. An equation of state and radiative opacities for a partially ionized hydrogen plasma are obtained at magnetic fields $B$, temperatures $T$, and densities $\rho$ typical for atmospheres of CCOs and other isolated neutron stars with moderately strong magnetic fields. The first- and second-order thermodynamic functions, monochromatic radiative opacities, and Rosseland mean opacities are calculated and tabulated, taking account of partial ionization, for 3\times10^{10}\mbox{ G}\lesssim B\lesssim 10^{12} G, $10^5$ K $\lesssim T\lesssim 10^7$ K, and a wide range of densities. Atmosphere models and spectra are calculated to verify the applicability of the results and to determine the range of magnetic fields and effective temperatures where the incomplete ionization of the hydrogen plasma is important.Comment: 11 pages, 7 figures, accepted for publication in A&

Appropriate technology for Aboriginal Enterprise Development

RADG has been developing appropriate health technology for use in remote communities in Australia. The greatest need for these technologies has been in Aboriginal communities. In developing appropriate technical artifacts, RADG has confronted two problems. Firstly we require good contact with remote communities for consultation and feedback. Secondly, part of making artifacts appropriate for under-developed countries or regions, is the need to include employment and self-determination as part of the benefits of a technology

Diamond growth in premixed propylene-oxygen flames

Diamond film growth in low-pressure premixed propylene/oxygen flames is demonstrated. Well-faceted films are grown at a pressure of 180 Torr and a fuel/oxygen ratio of 0.47. Using propylene as the fuel may greatly improve the economics of flame synthesis of diamond, since propylene is an order of magnitude cheaper than acetylene

Atmospheres and Spectra of Strongly Magnetized Neutron Stars

We construct atmosphere models for strongly magnetized neutron stars with surface fields $B\sim 10^{12}-10^{15}$ G and effective temperatures $T_{\rm eff}\sim 10^6-10^7$ K. The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars, including radio pulsars, soft gamma-ray repeaters, and anomalous X-ray pulsars. In our models, the atmosphere is composed of pure hydrogen or helium and is assumed to be fully ionized. The radiative opacities include free-free absorption and scattering by both electrons and ions computed for the two photon polarization modes in the magnetized electron-ion plasma. Since the radiation emerges from deep layers in the atmosphere with \rho\ga 10^2 g/cm$^3$, plasma effects can significantly modify the photon opacities by changing the properties of the polarization modes. In the case where the magnetic field and the surface normal are parallel, we solve the full, angle-dependent, coupled radiative transfer equations for both polarization modes. We also construct atmosphere models for general field orientations based on the diffusion approximation of the transport equations and compare the results with models based on full radiative transport. In general, the emergent thermal radiation exhibits significant deviation from blackbody, with harder spectra at high energies. The spectra also show a broad feature (\Delta E/\Ebi\sim 1) around the ion cyclotron resonance \Ebi=0.63 (Z/A)(B/10^{14}{G}) keV, where $Z$ and $A$ are the atomic charge and atomic mass of the ion, respectively; this feature is particularly pronounced when \Ebi\ga 3k\Teff. Detection of the resonance feature would provide a direct measurement of the surface magnetic fields on magnetars.Comment: 29 pages, 11 figures; corrected factor of 2 in He models: minor changes to figs 4 and 9 as a result; other very minor change