Permutation Symmetric Critical Phases in Disordered Non-Abelian Anyonic Chains

Topological phases supporting non-abelian anyonic excitations have been proposed as candidates for topological quantum computation. In this paper, we study disordered non-abelian anyonic chains based on the quantum groups $SU(2)_k$, a hierarchy that includes the $\nu=5/2$ FQH state and the proposed $\nu=12/5$ Fibonacci state, among others. We find that for odd $k$ these anyonic chains realize infinite randomness critical {\it phases} in the same universality class as the $S_k$ permutation symmetric multi-critical points of Damle and Huse (Phys. Rev. Lett. 89, 277203 (2002)). Indeed, we show that the pertinent subspace of these anyonic chains actually sits inside the ${\mathbb Z}_k \subset S_k$ symmetric sector of the Damle-Huse model, and this ${\mathbb Z}_k$ symmetry stabilizes the phase.Comment: 13 page

Quantum Bit Commitment with a Composite Evidence

Entanglement-based attacks, which are subtle and powerful, are usually believed to render quantum bit commitment insecure. We point out that the no-go argument leading to this view implicitly assumes the evidence-of-commitment to be a monolithic quantum system. We argue that more general evidence structures, allowing for a composite, hybrid (classical-quantum) evidence, conduce to improved security. In particular, we present and prove the security of the following protocol: Bob sends Alice an anonymous state. She inscribes her commitment $b$ by measuring part of it in the + (for $b = 0$) or $\times$ (for $b=1$) basis. She then communicates to him the (classical) measurement outcome $R_x$ and the part-measured anonymous state interpolated into other, randomly prepared qubits as her evidence-of-commitment.Comment: 6 pages, minor changes, journal reference adde

Reply To "Comment on 'Quantum String Seal Is Insecure' "

In Phys. Rev. A. 76, 056301 (2007), He claimed that the proof in my earlier paper [Phys. Rev. A 75, 012327 (2007)] is insufficient to conclude the insecurity of all quantum string seals because my measurement strategy cannot obtain non-trivial information on the sealed string and escape detection at the same time. Here, I clarify that our disagreement comes from our adoption of two different criteria on the minimum amount of information a quantum string seal can reveal to members of the public. I also point out that He did not follow my measurement strategy correctly.Comment: 2 page

Supersaturated dispersions of rod-like viruses with added attraction

The kinetics of isotropic-nematic (I-N) and nematic-isotropic (N-I) phase transitions in dispersions of rod-like {\it fd}-viruses are studied. Concentration quenches were applied using pressure jumps in combination with polarization microscopy, birefringence and turbidity measurements. The full biphasic region could be accessed, resulting in the construction of a first experimental analogue of the bifurcation diagram. The N-I spinodal points for dispersions of rods with varying concentrations of depletion agents (dextran) were obtained from orientation quenches, using cessation of shear flow in combination with small angle light scattering. We found that the location of the N-I spinodal point is independent of the attraction, which was confirmed by theoretical calculations. Surprisingly, the experiments showed that also the absolute induction time, the critical nucleus and the growth rate are insensitive of the attraction, when the concentration is scaled to the distance to the phase boundaries.Comment: 13 pages, 14 figures. accepted in Phsical Review

Hadronic final state predictions from CCFM: the hadron-level Monte Carlo generator CASCADE

We discuss a practical formulation of backward evolution for the CCFM small-$x$ evolution equation and show results from its implementation in the new Monte Carlo event-generator CASCADE.Comment: 20 pages, 8 figure

Self-consistent simulations of a von K\'arm\'an type dynamo in a spherical domain with metallic walls

We have performed numerical simulations of boundary-driven dynamos using a three-dimensional non-linear magnetohydrodynamical model in a spherical shell geometry. A conducting fluid of magnetic Prandtl number Pm=0.01 is driven into motion by the counter-rotation of the two hemispheric walls. The resulting flow is of von K\'arm\'an type, consisting of a layer of zonal velocity close to the outer wall and a secondary meridional circulation. Above a certain forcing threshold, the mean flow is unstable to non-axisymmetric motions within an equatorial belt. For fixed forcing above this threshold, we have studied the dynamo properties of this flow. The presence of a conducting outer wall is essential to the existence of a dynamo at these parameters. We have therefore studied the effect of changing the material parameters of the wall (magnetic permeability, electrical conductivity, and thickness) on the dynamo. In common with previous studies, we find that dynamos are obtained only when either the conductivity or the permeability is sufficiently large. However, we find that the effect of these two parameters on the dynamo process are different and can even compete to the detriment of the dynamo. Our self-consistent approach allow us to analyze in detail the dynamo feedback loop. The dynamos we obtain are typically dominated by an axisymmetric toroidal magnetic field and an axial dipole component. We show that the ability of the outer shear layer to produce a strong toroidal field depends critically on the presence of a conducting outer wall, which shields the fluid from the vacuum outside. The generation of the axisymmetric poloidal field, on the other hand, occurs in the equatorial belt and does not depend on the wall properties.Comment: accepted for publication in Physical Review

Convection and observable properties of late-type giants

We show that contrary to what is expected from 1D stationary model atmospheres, 3D hydrodynamical modeling predicts a considerable influence of convection on the spectral properties of late-type giants. This is due to the fact that convection overshoots into the formally stable outer atmospheric layers producing a notable granulation pattern in the 3D hydrodynamical models, which has a direct influence on the observable spectra and colors. Within the framework of standard 1D model atmospheres the average thermal stratification of the 3D hydro model can not be reproduced with any reasonable choice of the mixing length parameter and formulation of the turbulent pressure. The differences in individual photometric colors -- in terms of 3D versus 1D -- reach up to ~0.2 mag, or \Delta Teff~70K. We discuss the impact of full 3D hydrodynamical models on the interpretation of observable properties of late-type giants, briefly mentioning problems and challenges which need to be solved for bringing these models to a routine use within the astronomical community in 5-10 years from now.Comment: 4 pages, 3 figures. Proceedings of the IAU Symposium 232 "The Scientific Requirements for Extremely Large Telescopes", eds. P. Whitelock, B. Leibundgut, and M. Dennefel