On the Origin of the Non-Fermi Liquid Behavior of SrRuO_{3}

Motivated by the unusual features observed in the transport properties of the ferromagnetic "bad metal" $SrRuO_{3}$, we construct a model incorporating essential features of the realistic structure of this nearly cubic material. In particular, we show how the $t_{2g}$orbital {\it orientation} in the perfectly cubic structure determines the peculiar structure of the hybridization matrix, and demonstrate how the local non-Fermi liquid features arise when interactions are switched on. we discuss the effect of the slight deviation from the cubic structure (at low-$T$) qualitatively. The model provides a consistent explanation of the features observed recently in the optical response of $SrRuO_{3}$.Comment: 4 pages. Submitted to Physical Review Letter

Interfaces between highly incompatible polymers of different stiffness: Monte Carlo simulations and self-consistent field calculations

We investigate interfacial properties between two highly incompatible polymers of different stiffness. The extensive Monte Carlo simulations of the binary polymer melt yield detailed interfacial profiles and the interfacial tension via an analysis of capillary fluctuations. We extract an effective Flory-Huggins parameter from the simulations, which is used in self-consistent field calculations. These take due account of the chain architecture via a partial enumeration of the single chain partition function, using chain conformations obtained by Monte Carlo simulations of the pure phases. The agreement between the simulations and self-consistent field calculations is almost quantitative, however we find deviations from the predictions of the Gaussian chain model for high incompatibilities or large stiffness. The interfacial width at very high incompatibilities is smaller than the prediction of the Gaussian chain model, and decreases upon increasing the statistical segment length of the semi-flexible component.Comment: to appear in J.Chem.Phy

Calorons in SU(3) lattice gauge theory

We examine the semiclassical content of SU(3) Yang Mills theory on the lattice at finite temperature. Employing the cooling method, a set of classical fields is generated from a Monte Carlo ensemble. Various operators are used to inspect this set with respect to topological properties. We find pseudoparticle fields, so-called caloron solutions, possessing the remarkable features of (superpositions of) Kraan-van Baal solutions, i.e. extensions of Harrington-Shepard calorons to generic values of the holonomy.Comment: 14 pages, 16 figure

Simulations of the Magneto-rotational Instability in Core-Collapse Supernovae

We assess the importance of the magneto-rotational instability in core-collapse supernovae by an analysis of the growth rates of unstable modes in typical post-collapse systems and by numerical simulations of simplified models. The interplay of differential rotation and thermal stratification defines different instability regimes which we confirm in our simulations. We investigate the termination of the growth of the MRI by parasitic instabilities, establish scaling laws characterising the termination amplitude, and study the long-term evolution of the saturated turbulent state.Comment: 6 pages, 1 figure. To appear in Proceedings of 4th International Conference on Numerical Modeling of Space Plasma Flows (Chamonix 2009