AUGER-HiRes results and models of Lorentz symmetry violation

The implications of AUGER and HiRes results for patterns of Lorentz symmetry violation (LSV) are examined, focusing on weak doubly special relativity (WDSR). If the Greisen-Zatsepin-Kuzmin (GZK) cutoff is definitely confirmed, the mass composition of the highest-energy cosmic-ray spectrum will be a crucial issue to draw precise theoretical consequences from the experimental results. Assuming that the observed flux suppression is due to the GZK mechanism, data will allow in principle to exclude a significant range of LSV models and parameters, but other important possibilities are expected to remain open : Lorentz breaking can be weaker or occur at a scale higher than the Planck scale, unconventional LSV effects can fake the GZK cutoff, threshold phenomena can delay its appearance... Space experiments appear to be needed to further test special relativity. We also examine the consequences of AUGER and HiRes data for superbradyons. If such superluminal ultimate constituents of matter exist in our Universe, they may provide new forms of dark matter and dark energy.Comment: Talk given at the CRIS (Cosmic Ray International Seminar), La Malfa, September 15-19, 2008. To be published in the Proceeding

A Study on the Integration of a High-Speed Flywheel as an Energy Storage Device in Hybrid Vehicles

The last couple of decades have seen the rise of the hybrid electric vehicle as a compromise between the outstanding specific energy of petrol fuels and its low-cost technology, and the zero tail-gate emissions of the electric vehicle. Despite this, considerable reductions in cost and further increases in fuel economy are needed for their widespread adoption. An alternative low-cost energy storage technology for vehicles is the high-speed flywheel. The flywheel has important limitations that exclude it from being used as a primary energy source for vehicles, but its power characteristics and low-cost materials make it a powerful complement to a vehicle's primary propulsion system. This thesis presents an analysis on the integration of a high-speed flywheel for use as a secondary energy storage device in hybrid vehicles. Unlike other energy storage technologies, the energy content of the flywheel has a direct impact on the velocity of transmission. This presents an important challenge, as it means that the flywheel must be able to rotate at a speed independent of the vehicle's velocity and therefore it must be coupled via a variable speed transmission. This thesis presents some practical ways in which to accomplish this in conventional road vehicles, namely with the use of a variator, a planetary gear set or with the use of a power-split continuously variable transmission. Fundamental analyses on the kinematic behaviour of these transmissions particularly as they pertain to flywheel powertrains are presented. Computer simulations were carried out to compare the performance of various transmissions, and the models developed are presented as well. Finally the thesis also contains an investigation on the driving and road conditions that have the most beneficial effect on hybrid vehicle performance, with a particular emphasis on the effect that the road topography has on fuel economy and the significance of this

Are Stars with Planets Polluted?

We compare the metallicities of stars with radial velocity planets to the metallicity of a sample of field dwarfs. We confirm recent work indicating that the stars-with-planet sample as a whole is iron rich. However, the lowest mass stars tend to be iron poor, with several having [Fe/H]<-0.2, demonstrating that high metallicity is not required for the formation of short period Jupiter-mass planets. We show that the average [Fe/H] increases with increasing stellar mass (for masses below 1.25 solar masses) in both samples, but that the increase is much more rapid in the stars-with-planet sample. The variation of metallicity with stellar age also differs between the two samples. We examine possible selection effects related to variations in the sensitivity of radial velocity surveys with stellar mass and metallicity, and identify a color cutoff (B-V>0.48) that contributes to but does not explain the mass-metallicity trend in the stars-with-planets sample. We use Monte Carlo models to show that adding an average of 6.5 Earth masses of iron to each star can explain both the mass-metallicity and the age-metallicity relations of the stars-with-planets sample. However, for at least one star, HD 38529, there is good evidence that the bulk metallicity is high. We conclude that the observed metallicities and metallicity trends are the result of the interaction of three effects; accretion of about 6 Earth masses of iron rich material, selection effects, and in some cases, high intrinsic metallicity.Comment: 19 pages 11 figure