Production of UCN by Downscattering in superfluid He4

Ultra-cold neutrons (UCN) are neutrons with energies so low they can be stored in material bottles and magnetic traps. They have been used to provide the currently most accurate experiments on the neutron life time and electric dipole moment. UCN can be produced in superfluid Helium at significantly higher densities than by other methods. The predominant production process is usually by one phonon emission which can only occur at a single incident neutron energy because of momentum and energy conservation. However UCN can also be produced by multiphonon processes. It is the purpose of this work to examine this multiphonon production of UCN. We look at several different incident neutron spectra, including cases where the multiphonon production is significant, and see how the relative importance of multiphonon production is influenced by the incident spectrum.Comment: 3 figures, improved presentation after comments from xxx reader

Far from dominating EU decision-making, France and Germany are among the least successful EU states at negotiating legislation and budget contributions.

A common assumption is that the largest EU countries get their way most often in negotiations within the EU’s institutions. Contrary to this perspective, Jonathan Golub finds that smaller states like Finland tend to be far more successful at negotiating EU legislation than countries like France and Germany. He also finds little evidence for the idea that Member States might ‘buy influence’ by trading legislative outcomes for contributions to the EU budget. Indeed, the same countries which are successful at negotiating legislation are also likely to pay less than their fair share into the budget

Impact of Coulomb interaction and Kondo effect on transport in quantum dots

We examine the impact of Coulomb electron-electron interaction on transport in a junction with a quantum dot described by Kondo Hamiltonian. We analyze the Fermi liquid regime and consider the limit of zero temperature. With the help of Keldysh technique we calculate the non-linear current and shot noise as a function of applied voltage. We show that Coulomb interaction markable influences the universal effective charge of current-carrying particles e*=5/3e which can be measured in shot-noise experiments. The electron-electron interaction modifies this universal value by a factor (e*=5/3eF) which is less then one and also voltage dependent.Comment: 6 pages, 5 figures. Revised version with added calculations of shot noise and effectve charge. Complete 1/N expansion is presente

Spin Splitting Induced Photogalvanic Effect in Quantum Wells

A theory of the circular photogalvanic effect caused by spin splitting in quantum wells is developed. Direct interband transitions between the hole and electron size-quantized subbands are considered. The photocurrent excitation spectrum is shown to depend strongly on the form of the spin-orbit interaction. In the case of structure inversion asymmetry induced (Rashba) spin-splitting, the current is a linear function of light frequency near the absorption edge, and for the higher excitation energy the spectrum changes its sign and has a minimum. In contrast, when the bulk inversion asymmetry (Dresselhaus splitting) dominates, the photocurrent edge behavior is parabolic, and then the spectrum is sign-constant and has a maximum.Comment: 5 pages, 5 figure