Particle acceleration by shocks in supernova remnants

Particle acceleration occurs on a range of scales from AU in the heliosphere to Mpc in clusters of galaxies and to energies ranging from MeV to EeV. A number of acceleration processes have been proposed, but diffusive shock acceleration (DSA) is widely invoked as the predominant mechanism. DSA operates on all these scales and probably to the highest energies. DSA is simple, robust and predicts a universal spectrum. However there are still many unknowns regarding particle acceleration. This paper focuses on the particular question of whether supernova remnants (SNR) can produce the Galactic CR spectrum up to the knee at a few PeV. The answer depends in large part on the detailed physics of diffusive shock acceleration.Comment: Invited talk at the 33rd International Cosmic Ray Conference, Rio de Janeiro, Brazil, 2-9 July 2013. Submitted for publication in a special issue of the Brazilian Journal of Physic

Bell's theorem as a signature of nonlocality: a classical counterexample

For a system composed of two particles Bell's theorem asserts that averages of physical quantities determined from local variables must conform to a family of inequalities. In this work we show that a classical model containing a local probabilistic interaction in the measurement process can lead to a violation of the Bell inequalities. We first introduce two-particle phase-space distributions in classical mechanics constructed to be the analogs of quantum mechanical angular momentum eigenstates. These distributions are then employed in four schemes characterized by different types of detectors measuring the angular momenta. When the model includes an interaction between the detector and the measured particle leading to ensemble dependencies, the relevant Bell inequalities are violated if total angular momentum is required to be conserved. The violation is explained by identifying assumptions made in the derivation of Bell's theorem that are not fulfilled by the model. These assumptions will be argued to be too restrictive to see in the violation of the Bell inequalities a faithful signature of nonlocality.Comment: Extended manuscript. Significant change

Not throwing out the baby with the bathwater: Bell's condition of local causality mathematically 'sharp and clean'

The starting point of the present paper is Bell's notion of local causality and his own sharpening of it so as to provide for mathematical formalisation. Starting with Norsen's (2007, 2009) analysis of this formalisation, it is subjected to a critique that reveals two crucial aspects that have so far not been properly taken into account. These are (i) the correct understanding of the notions of sufficiency, completeness and redundancy involved; and (ii) the fact that the apparatus settings and measurement outcomes have very different theoretical roles in the candidate theories under study. Both aspects are not adequately incorporated in the standard formalisation, and we will therefore do so. The upshot of our analysis is a more detailed, sharp and clean mathematical expression of the condition of local causality. A preliminary analysis of the repercussions of our proposal shows that it is able to locate exactly where and how the notions of locality and causality are involved in formalising Bell's condition of local causality.Comment: 14 pages. To be published in PSE volume "Explanation, Prediction, and Confirmation", edited by Dieks, et a

Energy Efficency In Housing: An Evaluation Of The Importance Of Increased Wall Thickness

In April 2002 revisions to Part L of the Building Regulations were introduced, to improve the energy efficiency of UK buildings. For many housing schemes using traditional masonry cavity walls this may result in an increased cavity width and a consequent increase in the dwelling footprint. The potential impact that this may have on site utilisation, particularly in the light of planning guidance aimed at increasing site densities, has raised concern within the development community. Developers argue that even minor increases in wall thickness may reduce the number of dwellings on sites, thereby reducing overall profitability. This paper analyses these concerns by investigating the impact of increased wall thickness in the context of two developments constructed in the late 1990s. The existing site layouts were analysed under different footprint assumptions and an assessment made of the capacity of the layout to accommodate footprint increases. The theoretical analysis demonstrates that dwelling numbers are unlikely to be reduced as a result of the standards introduced in 2002. It is only when anticipated future improved standards are applied that dwelling numbers may be affected. However, the paper demonstrates also that dwelling loss is not inevitable and that it is perfectly possible to produce very low energy housing, while still achieving densities in line with planning requirements and with no reduction in the overall quality of a scheme. In the end it is not a matter of wall thickness but of good site layout and good house type design

Process for preparing higher oxides of the alkali and alkaline earth metals

High purity inorganic higher oxides of the alkali and alkaline earth metals are prepared by subjecting the hydroxide of the alkali and alkaline earth metal to a radio frequency discharge sustained in oxygen. The process is particulary adaptable to the production of high purity potassium superoxide by subjecting potassium hydroxide to glow discharge sustained in oxygen under the pressure of about 0.75 to 1.00 torr