Localization properties of third sound were studied experimentally in one-dimensional random lattices. Transmission spectra were measured and compared with those in periodic, Fibonacci, and Thue-Morse lattices. Not only the resonant transmission but also the phase-velocity renormalization of third sound was observed in the random lattices.

In connection with recent vibrationally excited sand-heaping observations we performed a series of experiments dealing with 2D compact triangular packings of monodisperse metallic beads under vibration. We report for the first time the observation of spontaneous heaping and associated convections for this system. We establish the mechanical conditions leading to this phenomenon and the domain of occurrence. We identify the microscopical mechanism to be a block-slip motion generated by the walls and we show that the heaping dynamics obeys a ln(t) law.

A new kind of instability is predicted for a system involving activator and inhibitor kinetics in a reactive flow. It is shown that a differential flow of activator and inhibitor, achievable, e.g., by selectively binding one component to a support, can destabilize the spatially homogeneous state of the system in a similar way as differential diffusivity does in the case of the Turing instability. The differential-flow-induced chemical instability is of the traveling-wave type. It is free from the restrictions of the Turning instability on the diffusion coefficients and can thus be expected to occur in a wide variety of physical, chemical, biological, and sociobiological systems.

A novel type of traveling-wave attractor is found in coupled-map lattices. Attractors with different velocities coexist, which are coded by the asymmetry of the wave form. Admissible velocities for the attractors form a series of bands. The velocity is proportional to the winding number of phase slips. If the wavelength and the system size do not match, the wave is modulated by low-dimensional chaos, which leads to spontaneous velocity switching by frustration or reverse transmission of chaotic modulation.

A quasimirrorless laser is shown to exhibit large interferences between macroscopic quantum states when submitted to weak external magnetic fields. Such a device is shown to have potentialities as a high signal-to-noise ratio vectorial magnetometer, especially because of its sensitivity to the mean value of the longitudinal magnetic field and its fast response to magnetic field variations. The behavior of the laser magnetometer is in good agreement with theory.

We discuss the explicit dependence of the final trajectory on initial conditions for randomly driven nonlinear dynamical systems which are stopped and restarted with random velocities at regular intervals (a Brownian-type motion). We find a transtion from chaotic behavior for long intervals between stops to nonchaotic behavior for short intervals between stops. For short intervals, the Lyapunov exponent is related to the thermal average square force due to the potential. The consequences for ‘‘hybrid molecular-dynamics Monte Carlo’’ sampling methods are discussed.

We present an experimental study of resonance frequencies of a diphasic medium that consists of diethyl ether containing vapor bubbles. We show that the liquid-vapor transfers affect the sound velocity and attenuation so that the usual liquid-gas effective-medium theory is in error at low frequency. The measurements of resonance frequency and attenuation can be used to estimate the vapor volume fraction and the bubble diameter. At high sound amplitude the shape of the resonance curves shows nonlinear effects, and acoustic bistability is observed.

The Kolmogorov relation for the third-order moments of the velocity differences is generalized for the case of statistically steady turbulence and applied to the Bénard convection problem. The predicted temperature and velocity spectra are ${\mathit{E}}_{\mathit{T}}$≊${\mathit{k}}^{\mathrm{-}7/5}$ and E≊${\mathit{k}}^{\mathrm{-}11/5}$, respectively. At the smaller scales, in the dissipation range of the temperature fluctuations, the Kolmogorov range where most of the energy is dissipated is predicted. The new set of scaling exponents, which can be observed in the experiments in the small-aspect-ratio convection cells, is derived.

We show that optical image-bearing beams manifest a generalized version of Berry’s phase. This topological phase results in a rotation, equal to Berry’s phase (with an opposite sign), of an arbitrary input optical image. Our method of measuring this phase applies to coherent as well as incoherent illumination, and thus is demonstrated experimentally using an incandescent light bulb. Furthermore, this is one of a few cases where a phase property of an ensemble of ‘‘particles’’ is unique, regardless of their energies, momenta, and spins.

We show experimentally that the output light of a single-mode semiconductor laser is changed into chaotic light after passage through a narrow spectral filter. Simple linear filtering allows us to distinguish between different statistical models of laser phase noise. The experimental results agree with the phase-diffusion model.

An investigation of the nonlinear dispersive equations of continuum mechanics reveals localized standing-wave solutions that are domain walls between regions of different wave number. These states can appear even when the dispersion law is a single-valued function of the wave number. In addition, we calculate solutions for kinks in cutoff and noncutoff modes, as well as cutoff breather solitons.

We present an experimental study of thermal plumes growing in Hele-Shaw cells which shows the existence of new objects, analogous to Saffman-Taylor fingers, for which the thermal boundary layer plays the role of the interface. The theoretical analysis reveals the underlying selection mechanism, which is provided by heat diffusion.

The energy cascade in both hydrodynamic and hydromagnetic Boussinesq convection is investigated at large Rayleigh numbers, using a scalar model for turbulence. Depending on the relative importance of direct and inverse transfer, either we observe classical Kolmogorov ${\mathit{k}}^{\mathrm{-}5/3}$ spectra or, if there is a strong inverse transfer of kinetic energy, we find a ${\mathit{k}}^{\mathrm{-}7/5}$ spectrum for the temperature fluctuation and a ${\mathit{k}}^{\mathrm{-}11/5}$ spectrum for the kinetic energy (Bolgiano-Obukhov scaling). We derive dissipative cutoff wave numbers that are consistent with these spectra.

New types of nonlinear evolution equations are derived that describe finite-amplitude surface gravity waves on a two-dimensional incompressible and inviscid fluid of finite depth. The novelty is as follows: (a) The equation can be expressed as a single equation with respect to the surface elevation, and (b) the expansion is in a steepness parameter and does not involve other approximations such as long waves or shallow water. Both the shallow- and deep-water limits of the equations are discussed.

A new method for nonlinear polychromatic resonant stimulation of conservative nonlinear oscillators is introduced. As an example we consider a Morse potential that serves as a model for the HF molecule. Numerical results show that a large energy transfer to such a conservative oscillator is possible under optimal stimulation with small driving fields. This makes selective excitation of specific modes possible. The classically determined optimal force was also applied to the corresponding quantum system, with similar results in energy transfer and dissociation.

Laboratory experiments on plane channel flow with a streamwise-periodic array of cylinders reveal a bifurcation from two-dimensional traveling waves to three-dimensional spanwise standing waves. The standing waves select a wave number that is independent of the wave number imposed initially by time-periodic disturbances. The stable tertiary flow stands in contrast with most open flows where instability develops directly to turbulence.

Atomistic simulations of a strong shock wave in a hard-sphere gas are analyzed in terms of thermodynamic forces and fluxes. Evidence is provided that the Burnett corrections to the heat flux significantly improve the agreement with the computed values over the Navier-Stokes predictions in the shock-front region.

The hydrodynamics of polymer solutions is modeled using a newly developed, thermodynamically consistent, generalized bracket formulation. This continuum thermodynamic development clarifies the connection between the physical assumptions introduced in previous models by Helfand and Fredrickson, Onuki, Doi, and Milner and the final governing equations. A quantitative description of the coupling between elastic stresses and concentration changes as well as the modeling of interphases is provided. The resulting equations describe the same phenomenology as the previous works; however, they are quantitatively different.

A class of exact large-amplitude traveling-wave solutions to the nonlinear Vlasov-Maxwell equations describing a one-dimensional collisionless magnetized plasma is obtained. These waves are complementary to the electrostatic Bernstein-Greene-Kruskal modes and can be classified as nonlinear fast electromagnetic waves and (slow) electromagnetic whistler waves. The wave characteristics are discussed for the case of a trapped-particle distribution function.

Nonlinear bound-free x-ray-absorption processes in an intense monochromatic x-ray radiation field such as an x-ray laser are investigated by using a collisional-radiative model. Above a threshold of the x-ray intensity, gain of stimulated free-bound emission is induced by strong photoionization. The wavelength of the stimulated free-bound emission is longer than that of the incident x rays, leading to a down-conversion of the frequency.