Inhomogeneous dusty universes and their deceleration

Exact results stemming directly from Einstein equations imply that inhomogeneous universes endowed with vanishing pressure density can only decelerate, unless the energy density of the universe becomes negative. Recent proposals seem to argue that inhomogeneous (but isotropic) space–times, filled only with incoherent matter, may turn into accelerated universes for sufficiently late times. To scrutinize these scenarios, fully inhomogeneous Einstein equations are discussed in the synchronous system. In a dust-dominated universe, the inhomogeneous generalization of the deceleration parameter is always positive semi-definite implying that no acceleration takes place.     

Vortex glass and vortex liquid in oscillatory media

We study the disordered, multispiral solutions of two-dimensional oscillatory media for parameter values at which the single-spiral/vortex solution is fully stable. Using the complex Ginzburg-Landau (CGLE) equation, we show that these states, heretofore believed to be static, actually evolve extremely slowly. This is achieved via a reduction of the CGLE to the evolution of the sole vortex coordinates. This true defect-mediated turbulence occurs in two distinct phases, a vortex liquid characterized by normal diffusion of spirals, and a slowly relaxing, intermittent, "vortex glass."     

Numerical description of the edge mode at the beveled extremity of a plate

This paper deals with the reflection of a two-dimensional harmonic Lamb wave at the beveled end of a plate. The existence of a resonant edge mode is described by a numerical model. It is proved that the edge mode is the resonance of different complex modes. The behavior of this mode as a function of the bevel angle is studied. Its amplitude decreases and its resonance frequency shifts as the bevel angle decreases from 90 to 85 deg. An unexpected strong variation of the repartition of the reflected energy is linked to this phenomenon.     

Langevin description of critical phenomena with two symmetric absorbing states

On the basis of general considerations, we propose a Langevin equation accounting for critical phenomena occurring in the presence of two symmetric absorbing states. We study its phase diagram by mean-field arguments and direct numerical integration in physical dimensions. Our findings fully account for and clarify the intricate picture known so far from the aggregation of partial results obtained with microscopic models. We argue that the direct transition from disorder to one of two absorbing states is best described as a (generalized) voter critical point and show that it can be split into an Ising and a directed percolation transition in dimensions larger than one.     

Inelastic collision term in dilute magnetic alloys

The collision term derived by Kohn and Luttinger [1] to describe elastic scattering to third order in the potential is generalized to include inelastic processes for a system of conduction electrons interacting with localized spins. This result is obtained by using the Kadanoff and Baym [6] derivation of the Boltzmann equation.     

Über eine Synthese des angulären Di(cyclobuteno)benzols

On a Synthesis of the angular Di(cyclobuteno)benzol In the course of our studies aimed at better understanding the Mills-Nixon effect, we have also prepared the angular di(cyclobuteno)benzene ( 1 ), the synthesis of which has been recently described by another group [3]. Our completely different and essentially simpler synthetic approach will be pointed out. A special pyrolysis apparatus is designed.     

New access to lipo-chitooligosaccharide nodulation factors

Sulfonated and non-sulfonated lipo-chitooligosaccharides involved in Sinorhizobium meliloti-legume symbiosis are efficiently obtained on a multi mg scale by a 2-step procedure combining biotechnological and chemical approaches.