Thermodynamics of quantum degenerate gases in optical lattices

The entropy-temperature curves are calculated for non-interacting Bose and Fermi gases in a 3D optical lattice. These curves facilitate understanding of how adiabatic changes in the lattice depth affect the temperature, and we demonstrate regimes where the atomic sample can be significantly heated or cooled by the loading process. We assess the effects of interactions on a Bose gas in a deep optical lattice, and show that interactions ultimately limit the extent of cooling that can occur during lattice loading.Comment: 6 pages, 4 figures. Submitted to proceedings of Laser Physics 2006 Worksho

Possibility of cold nuclear compression in antiproton-nucleus collisions

We study the dynamical response of the oxygen-16 nucleus to an incident antiproton using the Giessen Boltzmann-Uehling-Uhlenbeck microscopic transport model with relativistic mean fields. A special emphasis is put on the possibility of a dynamical compression of the nucleus induced by the moving antiproton. Realistic antibaryon coupling constants to the mean meson fields are chosen in accordance with empirical data. Our calculations show that an antiproton embedded in the nuclear interior with momentum less than the nucleon Fermi momentum may create a locally compressed zone in the nucleus with a maximum density of about twice the nuclear saturation density. To evaluate the probability of the nuclear compression in high-energy antiproton-nucleus collisions, we adopt a two-stage scheme. This scheme takes into account the antiproton deceleration due to the cascade of antiproton-nucleon rescatterings inside the nucleus (first stage) as well as the nuclear compression by the slow antiproton before its annihilation (second stage). With our standard model parameters, the fraction of antiproton annihilation events in the compressed zone is about $10^{-5}$ for $\bar p ^{16}$O collisions at $p_{\rm lab}=3-10$ GeV/c. Finally, possible experimental triggers aimed at selecting such events are discussed.Comment: 40 pages, 15 figures, new Sect. V on the in-medium modifications of annihilation, modified conclusions, added references, version accepted in Phys. Rev.

The Mass of the Neutrinos

In the theory of the Dirac equation and in the standard model, the neutrino is massless. Both these theories use Lorentz invariance. In modern approaches however, spacetime is no longer smooth, and this modifies special relativity. We show how such a modification throws up the mass of the (electron) neutrino.Comment: 14 pages, late

Transmission needs across a fully renewable European power system

The residual load and excess power generation of 27 European countries with a 100% penetration of variable renewable energy sources are explored in order to quantify the benefit of power transmission between countries. Estimates are based on extensive weather data, which allows for modelling of hourly mismatches between the demand and renewable generation from wind and solar photovoltaics. For separated countries, balancing is required to cover around 24% of the total annual energy consumption. This number can be reduced down to 15% once all countries are networked together with uncon- strained interconnectors. The reduction represents the maximum possible benefit of transmission for the countries. The total Net Transfer Capacity of the unconstrained interconnectors is roughly twelve times larger than current values. However, constrained interconnector capacities six times larger than the current values are found to provide 97% of the maximum possible benefit of cooperation. This motivates a detailed investigation of several constrained transmission capacity layouts to determine the export and import capabilities of countries participating in a fully renewable European electricity system