On the icosahedron: from two to three dimensions

In his famous book, Felix Klein describes a complex variable for the quotients of the ordinary sphere by the finite groups of rotations and in particular for the most complex situation of the quotient by the symmetry group of the icosahedron. The purpose of this work and its sequels is to obtain similar results for the quotients of the three--dimensional sphere. Various properties of the group $SU(2)$ and of its representations are used to obtain explicit expressions for coordinates and the relations they satisfy.Comment: 8 page

Spinons as Composite Fermions

We show that gauge invariant composites in the fermionic realization of $SU(N)_1$ conformal field theory explicitly exhibit the holomorphic factorization of the corresponding WZW primaries. In the $SU(2)_1$ case we show that the holomorphic sector realizes the spinon $Y(sl_2)$ algebra, thus allowing the classification of the chiral Fock space in terms of semionic quasi-particle excitations created by the composite fermions.Comment: SU(N)_1 case included. Final version to appear in Mod. Phys. Lett. A. Latex, 13 page

Turbulent jet simulation using high-order DG methods for aeroacoustics analysis

In this work, a high-order discontinuous Galerkin (DG) method is used to perform a large-eddy simulation (LES) of a subsonic isothermal jet at high Reynolds number Re D = 10^6 on a fully un-structured mesh. Its radiated acoustic field is computed using the Ffowcs Williams and Hawkings formulation. In order to assess the accuracy of the DG method, the simulation results are compared to experimental measurements and a reference simulation based on a finite volume method. The comparisons are made on the flow quantities (mean, rms and spectra) and pressure far field (rms and spectra)

Phase Transitions in a Kinetic Flocking Model of Cucker-Smale Type

We consider a collective behavior model in which individuals try to imitate each others' velocity and have a preferred speed. We show that a phase change phenomenon takes place as diffusion decreases, bringing the system from a “disordered” to an “ordered” state. This effect is related to recently noticed phenomena for the diffusive Vicsek model. We also carry out numerical simulations of the system and give further details on the phase transition