Abstract. We develop a formalism for the calculation of the flow of angular momentum carried by the fluctuating electromagnetic field within a cavity bounded by two flat anisotropic materials. By generalizing a procedure employed recently for the calculation of the Casimir force between arbitrary materials, we obtain an expression for the torque between anisotropic plates in terms of their reflection amplitude matrices. We evaluate the torque in 1D for ideal and realistic model materials.

We study, both experimentally and numerically, the Anderson localization phenomenon in flexural waves of a disordered elastic beam, which consists of a beam with randomly spaced notches. We found that the effect of the disorder on the system is stronger above a crossover frequency f c than below it. For a chosen value of disorder, we show that above f c the normal-mode wave functions are localized as occurs in disordered solids, while below f c the wave functions are partially and fully extended, but their dependence on the frequency is not governed by a monotonous relationship, as occurs in other classical and quantum systems. These findings were corroborated with the calculation of the participation ratio, the localization length and a level statistics. In particular, the nearest spacing distribution is obtained and analyzed with a suitable phenomenological expression, related to the level repulsion.

PACS 43.20.Fn -Scattering of acoustic waves PACS 24.30.Cz -Giant resonances PACS 43.40.At -Experimental and theoretical studies of vibrating systems Abstract -The doorway-state phenomenon has been observed in many quantum and classical undulatory systems when two oscillating systems are coupled, one that has a high level density and the other one a very low density. Up to now the systems analysed have in common that they are governed by second-order differential equations. In the present work it is shown that the doorway state mechanism also appears when dealing with flexural vibrations of elastic systems, which are governed by fourth-order differential equations. It should be mentioned that this phenomenon also emerges from the two coupled second-order differential Navier equations.

Liesegang pattern formations are widely spread in nature. In spite of a comparably simple experimental setup under laboratory conditions, a variety of spatio-temporal structures may arise. Presumably because of easier control of the experimental conditions, Liesegang pattern formation was mainly studied in gel systems during more than a century. Here we consider pattern formation in a gas phase, where beautiful but highly complex reaction-diffusion-convection dynamics are uncovered by means of a specific laser technique. A quantitative analysis reveals that two different, apparently independent processes, both highly correlated and synchronized across the extension of the reaction cloud, act on different time scales. Each of them imprints a different structure of salt precipitation at the tube walls.