On pseudoparticle solutions in Yang's theory of gravity

Within the framework of differential geometry, Yang's parallel-displacement gauge theory is considered with respect to pure gravitational fields. In afour-dimensional Riemannian manifold it is shown that thedouble self-dual solutions obey Einstein's vacuum equations with the cosmological term, whereas the doubleanti-self-dual configurations satisfy the Rainich conditions of Wheeler'sgeometrodynamics. Conformal methods reveal that the gravitational analog of the instanton or pseudoparticle solution of Yang-Mills theory was already known to Riemann.     

Axion condensate as a model for dark matter halos

Localized solutions of an axion-like scalar model with a periodic self-interaction are analyzed as a model of dark matter halos. It is shown that such a cold Bose–Einstein type condensate can provide a substantial contribution to the observed rotations curves of galaxies, as well provide a soliton type interpretation of the dark matter ‘bullets’ observed via gravitational lensing in merging clusters.     

Advances in Phase-Transfer Catalysis [New synthetic methods (20)]

Phase-transfer catalysis (PTC) has grown into a versatile preparative method in the last few years. The most notable new developments include the use of crown ethers as phase-transfer catalysts and the introduction of solid-liquid PTC. Some representative examples have been selected from the large number of new PTC reactions and some of them are summarized in tables.     

The Approach Towards Equilibrium in a Reversible Ising Dynamics Model: An Information-Theoretic Analysis Based on an Exact Solution

We study the approach towards equilibrium in a dynamic Ising model, the Q2R cellular automaton, with microscopic reversibility and conserved energy for an infinite one-dimensional system. Starting from a low-entropy state with positive magnetisation, we investigate how the system approaches equilibrium characteristics given by statistical mechanics. We show that the magnetisation converges to zero exponentially. The reversibility of the dynamics implies that the entropy density of the microstates is conserved in the time evolution. Still, it appears as if equilibrium, with a higher entropy density is approached. In order to understand this process, we solve the dynamics by formally proving how the information-theoretic characteristics of the microstates develop over time. With this approach we can show that an estimate of the entropy density based on finite length statistics within microstates converges to the equilibrium entropy density. The process behind this apparent entropy increase is a dissipation of correlation information over increasing distances. It is shown that the average information-theoretic correlation length increases linearly in time, being equivalent to a corresponding increase in excess entropy.     

EPR and ENDOR investigations of Ge,Sn and Pb impurities in CdSe

Electron paramagnetic resonance (EPR) experiments of light activated Ge, Sn and Pb impurities in wurtzite type CdSe crystals are presented. These²S_1/2 centres exhibit a large hyperfine structure which shows a variation with temperature. 25 shells of neighbour nuclei are resolved for CdSeSn by means of the Electron nuclear double resonance (ENDOR) technique. All shells belong to one of three distinct shell symmetries of the lattice thus confirming a high symmetry defect. Additional Sn respectively Ge related spectra are described and interpreted as complex centres correlated with lithium.