School of Physics - Research Publications
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ItemStringent constraints on cosmological neutrino-antineutrino asymmetries from synchronized flavor transformation(AMER PHYSICAL SOC, 2002-07-01)We assess a mechanism which can transform neutrino-antineutrino asymmetries between flavors in the early universe, and confirm that such transformation is unavoidable in the near bi-maximal framework emerging for the neutrino mixing matrix. We show that the process is a standard Mikheyev-Smirnov-Wolfenstein flavor transformation dictated by a synchronization of momentum states. We also show that flavor ``equilibration'' is a special feature of maximal mixing, and carefully examine new constraints placed on neutrino asymmetries. In particular, the big bang nucleosynthesis limit on electron neutrino degeneracy xi_e < 0.04 does not apply directly to all flavors, yet confirmation of the large-mixing-angle solution to the solar neutrino problem will eliminate the possibility of degenerate big bang nucleosynthesis.
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ItemRecovering physical parameters from galaxy spectra using MOPED(BLACKWELL SCIENCE LTD, 2001-11-01)We derive physical parameters of galaxies from their observed spectrum, using MOPED, the optimized data compression algorithm of Heavens, Jimenez & Lahav 2000. Here we concentrate on parametrising galaxy properties, and apply the method to the NGC galaxies in Kennicutt's spectral atlas. We focus on deriving the star formation history, metallicity and dust content of galaxies. The method is very fast, taking a few seconds of CPU time to estimate 17 parameters, and so specially suited to study of large data sets, such as the Anglo-Australian 2 degree field galaxy survey and the Sloan Digital Sky Survey. Without the power of MOPED, the recovery of star formation histories in these surveys would be impractical. In the Kennicutt atlas, we find that for the spheroidals a small recent burst of star formation is required to provide the best fit to the spectrum. There is clearly a need for theoretical stellar atmospheric models with spectral resolution better than 1\AA if we are to extract all the rich information that large redshift surveys contain in their galaxy spectra.
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ItemImaging the Sunyaev Zel'dovich Effect using ACBAR on Viper(Cambridge University Press, 2004)During 2001 and 2002, observations of several X-ray bright clusters of galaxies were conducted using the ACBAR Bolometer Array on the South Pole Viper telescope. A multi-frequency analysis of these clusters is currently underway. This multi-frequency analysis includes 150, 220 and 275 GHz data from ACBAR, X-ray imaging and spectroscopy from Chandra and XMM-Newton, and weak lensing data from the CTIO 4m Blanco telescope. We describe here how ACBAR can be used to create fully sampled cluster images and present such images for four of the clusters in our sample; Abell 3266, Abell 3827, Abell S1063 and 1E0657-56. In these images, the Sunyaev-Zel'dovich Effect is clearly detected.
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ItemStress and aging effects on the transformation characteristics in Au-Cd alloys(TRANS TECH PUBLICATIONS LTD, 2000)The effect of martensite agin in a Au-49.5%Cd single crystal has been studied using a pushrod dilatometer with various applied stresses. The reverse transformation temperatures remain constant with aging time, temperature and applied stresses (0 - 0.04 MPa). A critical aging time of approximately 2-3 hours was found to exist for an alloy of this composition and appears to be dependent on the aging temperature.
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ItemSELF-CONSISTENT CURRENT-VOLTAGE CHARACTERISTICS OF SUPERCONDUCTING NANOSTRUCTURES(AMERICAN PHYSICAL SOC, 1995-06-15)
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ItemSelf-consistent interface properties of d- and s-wave superconductors(AMER PHYSICAL SOC, 1998-04-01)
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ItemTilt grain-boundary effects in s- and d-wave superconductors(AMER PHYSICAL SOC, 1999-08-01)
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ItemCoherent potential approximation for d-wave superconductivity in disordered systems(AMER PHYSICAL SOC, 1999-09-01)
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ItemCharge fluctuations in a quantum point contact attached to a superconducting lead(AMER PHYSICAL SOC, 1999-11-01)
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ItemCharge relaxation and dephasing in Coulomb-coupled conductors(AMER PHYSICAL SOC, 2000-01-15)