Fluid Dynamical Description of the Chiral Transition

We investigate the dynamics of the chiral transition in an expanding quark-anti-quark plasma. The calculations are made within a linear sigma model with explicit quark and antiquark degrees of freedom. We solve numerically the classical equations of motion for chiral fields coupled to the fluid dynamical equations for the plasma. Fast initial growth and strong oscillations of the chiral field and strong amplification of long wavelength modes of the pion field are observed in the course of the chiral transition.Comment: 9 pages LaTeX, 4 postscript figure

Correlation-induced conductance suppression at level degeneracy in a quantum dot

The large, level-dependent g-factors in an InSb nanowire quantum dot allow for the occurrence of a variety of level crossings in the dot. While we observe the standard conductance enhancement in the Coulomb blockade region for aligned levels with different spins due to the Kondo effect, a vanishing of the conductance is found at the alignment of levels with equal spins. This conductance suppression appears as a canyon cutting through the web of direct tunneling lines and an enclosed Coulomb blockade region. In the center of the Coulomb blockade region, we observe the predicted correlation-induced resonance, which now turns out to be part of a larger scenario. Our findings are supported by numerical and analytical calculations.Comment: 5 pages, 4 figure

Real-Time Tune Measurements on the CERN Antiproton Decelerator

A novel system for real-time tune measurement during deceleration of a low-intensity particle beam is presented. The CERN Antiproton Decelerator decelerates low intensity (2x107) antiproton beams from 3.5 GeV/c to 100 MeV/c. Because of the eddy-currents in the magnets, a tune-measurement during a pause in the deceleration would not be representative. One must thus be able to measure the tune in real time during the deceleration. The low intensity of the antiproton beam prevents the use of standard Schottky techniques, and swept Beam Transfer Function (BTF) measurements are too slow. A system was therefore developed which uses an M-shaped power spectrum, exciting the beam in a band around the expected frequency of a betatron side-band. Excitation at the betatron frequency, where beam response is highest, is thus minimized and measurements of BTF, and therefore the tune, can be made with much reduced emittance blow-u

The origin of flux-flow resistance oscillations in BiSrCaCuO: Fiske steps in a single junction?

We propose an alternative explanation to the oscillations of the flux-flow resistance found in several previously published experiments with BiSrCaCuO stacks. It has been argued by the previous authors that the period of the oscillations corresponding to the field needed to add one vortex per two intrinsic Josephson junctions is associated with a moving triangular lattice of vortices (out-of-phase mode), while the period corresponding to one vortex per one junction is due to the square lattice (in-phase mode). In contrast, we show that both type of oscillations may occur in a single-layer Josephson junction and thus the above interpretation is inconsistent

One Dimensional Kondo Lattice Model Studied by the Density Matrix Renormalization Group Method

Recent developments of the theoretical investigations on the one-dimensional Kondo lattice model by using the density matrix renormalization group (DMRG) method are discussed in this review. Short summaries are given for the zero-temperature DMRG, the finite-temperature DMRG, and also its application to dynamic quantities. Away from half-filling, the paramagnetic metallic state is shown to be a Tomonaga-Luttinger liquid with the large Fermi surface. For the large Fermi surface its size is determined by the sum of the densities of the conduction electrons and the localized spins. The correlation exponent K_rho of this metallic phase is smaller than 1/2. At half-filling the ground state is insulating. Excitation gaps are different depending on channels, the spin gap, the charge gap and the quasiparticle gap. Temperature dependence of the spin and charge susceptibilities and specific heat are discussed. Particularly interesting is the temperature dependence of various excitation spectra, which show unusual properties of the Kondo insulators.Comment: 18 pages, 23 Postscript figures, REVTe

Particle-scale structure in frozen colloidal suspensions from small angle X-ray scattering

During directional solidification of the solvent in a colloidal suspension, the colloidal particles segregate from the growing solid, forming high-particle-density regions with structure on a hierarchy of length scales ranging from that of the particle-scale packing to the large-scale spacing between these regions. Previous work has mostly concentrated on the medium- to large-length scale structure, as it is the most accessible and thought to be more technologically relevant. However, the packing of the colloids at the particle-scale is an important component not only in theoretical descriptions of the segregation process, but also to the utility of freeze-cast materials for new applications. Here we present the results of experiments in which we investigated this structure across a wide range of length scales using a combination of small angle X-ray scattering and direct optical imaging. As expected, during freezing the particles were concentrated into regions between ice dendrites forming a microscopic pattern of high- and low-particle-density regions. X-ray scattering indicates that the particles in the high density regions were so closely packed as to be touching. However, the arrangement of the particles does not conform to that predicted by any standard inter-particle pair potentials, suggesting that the particle packing induced by freezing differs from that formed during equilibrium or steady-state densification processes

Volume-energy correlations in the slow degrees of freedom of computer-simulated phospholipid membranes

Constant-pressure molecular-dynamics simulations of phospholipid membranes in the fluid phase reveal strong correlations between equilibrium fluctuations of volume and energy on the nanosecond time-scale. The existence of strong volume-energy correlations was previously deduced indirectly by Heimburg from experiments focusing on the phase transition between the fluid and the ordered gel phases. The correlations, which are reported here for three different membranes (DMPC, DMPS-Na, and DMPSH), have volume-energy correlation coefficients ranging from 0.81 to 0.89. The DMPC membrane was studied at two temperatures showing that the correlation coefficient increases as the phase transition is approached