The evolution of a Friedmann-Robertson-Walker universe filled with a viscous simple fluid is analysed. At variance with other treatments the authors' approach complies with relativistic causality since dissipative signals travelling at superluminal speeds are forbidden. This is because use is made of the extended thermodynamics theory of irreversible processes instead of the conventional one. As a consequence some novel results arise. In particular, the initial de Sitter phase of the deflationary universe does not occur. Likewise, the generalized second law of thermodynamics is studied within this context.

A fully predictive Kinetic Collective Model using first principles phonon spectra and relaxation times is presented. Thermal conductivity values obtained for Si, Ge, C (diamond) and GaAs in a wide range of sizes and temperatures have good agreement with experimental data without the use of any fitting parameter. This validation of the model open the door to discuss how the precise combination of kinetic and collective contributions to heat transport could provide a useful framework to interpret recent complex experiments displaying non-Fourier behavior.

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Second sound is known as the thermal transport regime where heat is carried by temperature waves. Its experimental observation was previously restricted to a small number of materials, usually in rather narrow temperature windows. We show that it is possible to overcome these limitations by driving the system with a rapidly varying temperature field. High-frequency second sound is demonstrated in bulk natural Ge between 7 K and room temperature by studying the phase lag of the thermal response under a harmonic high-frequency external thermal excitation and addressing the relaxation time and the propagation velocity of the heat waves. These results provide a route to investigate the potential of wave-like heat transport in almost any material, opening opportunities to control heat through its oscillatory nature.

Brownian dynamics simulations were used to study the adhesion of hard spheres on a solid surface by taking the hydrodynamic interactions into account. Special attention was paid to analyze the configuration of the assembly of adsorbed particles. These results were compared to configurations generated by the extensively studied random sequential adsorption (RSA) model. In our case the adsorption probability for a particle is almost uniform over the entire available surface. This surprising result shows that RSA provides a good approximation to generate adsorbed particle configurations. (DRSA) [2], where the adsorbing particle is allowed to diffuse in three-dimensional space subject to hard sphere interactions with previously adsorbed ones. The DRSA leads to an increased adsorption probability for an incoming sphere in the close vicinity of an already attached one as compared to RSA. The DRSA distribution of adsorbed particles is thus different at a given coverage from its RSA counterpart except near saturation (jamming limit) [3]. However, since the diffusion coeKcient is taken constant, the DRSA seems to model a particle as moving in "dry water" [4]. This Letter is devoted to take hydrodynamic interactions into account and should thus represent a significant jump toward reality.The effect of the hydrodynamic interaction is to increase the frictional force experienced by a particle when it approaches another one or a fiat surface [5]. This kind of interaction between a sphere and a clean wall is well known, and its effect on the rate of adsorption has already been studied [6]. The main goal of this Letter is to investigate the inHuence of the hydrodynamic interactions between an adsorbing particle and (i) the already adsorbed ones, and (ii) the planar adsorbing surface, on the distribution of the particles on this surface. It will in particular be compared to RSA distributions in order to investigate the degree of accuracy of this simple and now well-known algorithm.The Brownian motion of a spherical particle is completely described by the friction tensor, which is in general position dependent and nonisotropic.In particular, the normal component of the friction tensor diverges when the separation between the particle and any solid surface vanishes due to lubrication forces. As a consequence, contact of the particles with the adsorbing surface is impossible in the absence of a strong attractive force, like the van der Waals attraction. The latter becomes strong enough at small separations to overcome the lubrication effects. In general van der Waals, hard core, and electrostatic forces also act between the particles. However, in this study we will solely consider, besides the hydrodynamic interactions, the different hard core repulsions, and the van