We investigate the dynamics of a gas of noninteracting particlelike soliton waves, demonstrating that phase transitions originate from their collective behavior. This is predicted by solving exactly the nonlinear equations and by employing methods of the statistical mechanics of chaos. In particular, we show that a suitable free energy undergoes a metamorphosis as the input excitation is increased, thereby developing a first-order phase transition whose measurable manifestation is the formation of shock waves. This demonstrates that even the simplest phase-space dynamics, involving independent (uncoupled) degrees of freedom, can sustain critical phenomena.

At moderate values of the surface Peclet number and the dimensionless gas constant, a surfactant-covered, isolated drop that is initially spherical can undergo large deformations and eventually break in inertialess gravitational motion. A long, thin filament forms, extending from the trailing edge of the drop, with a breakup mechanism that is similar to tip streaming. In the range of parameters studied, the emitted drop has an equivalent spherical radius between 0.01 to 0.03 of the original drop radius and an interfacial tension from 0.2 to 0.6 of the clean-interface value.

The elastic coupling between the $a\mathrm{\text{−}}{\mathrm{SiO}}_2$ spheres composing opal films brings forth three-dimensional periodic structures which besides a photonic stop band are predicted to also exhibit complete phononic band gaps. The influence of elastic crystal vibrations on the photonic band structure has been studied by injection of coherent hypersonic wave packets generated in a metal transducer by subpicosecond laser pulses. These studies show that light with energies close to the photonic band gap can be efficiently modulated by hypersonic waves.

We numerically demonstrate so-far undescribed features in ionization and high harmonic generation from bound states with nonvanishing electronic angular momentum. The states’ modified response to a strong laser pulse can be exploited for novel measurement and pulse production schemes. It is shown that angularly asymmetric tunneling from the states can be mapped onto variations of high harmonic intensities and that near-circularly polarized isolated attosecond extreme ultraviolet or x-ray pulses can be produced.

Dynamic forces between a $50\mu \mathrm{m}$ radius bubble driven towards and from a mica plate using an atomic force microscope in electrolyte and in surfactant exhibit different hydrodynamic boundary conditions at the bubble surface. In added surfactant, the forces are consistent with the no-slip boundary condition at the mica and bubble surfaces. With no surfactant, a new boundary condition that accounts for the transport of trace surface impurities explains variations of dynamic forces at different speeds and provides a direct connection between dynamic forces and surface transport effects at the air-water interface.

We discuss a quantum system coupled to the environment, composed of an open array of billiards (dots) in series. Beside pointer states occurring in individual dots, we observe sets of robust states which arise only in the array. We define these new states as bipartite pointer states, since they cannot be described in terms of simple linear combinations of robust single-dot states. The classical existence of bipartite pointer states is confirmed by comparing the quantum-mechanical and classical results. The ability of the robust states to create “offspring” indicates that quantum Darwinism is in action.

The collective phase response to a macroscopic external perturbation of a population of interacting nonlinear elements exhibiting collective oscillations is formulated for the case of globally coupled oscillators. The macroscopic phase sensitivity is derived from the microscopic phase sensitivity of the constituent oscillators by a two-step phase reduction. We apply this result to quantify the stability of the macroscopic common-noise-induced synchronization of two uncoupled populations of oscillators undergoing coherent collective oscillations.

We report on the first observation of topologically stable spatially localized multivortex solitons generated in optically induced hexagonal photonic lattices. We demonstrate that topological stabilization of such nonlinear localized states can be achieved through self-trapping of truncated two-dimensional Bloch waves and confirm our experimental results by numerical simulations of the beam propagation in weakly deformed lattice potentials in anisotropic photorefractive media.

Using molecular dynamics simulations and analytics, we find that strain waves of terahertz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. By considering $\mathrm{AlN}/\mathrm{GaN}$ heterostructures, we show that the radiation is of detectable amplitude and contains sufficient information to determine the time dependence of the strain wave with potentially subpicosecond, nearly atomic time and space resolution. We demonstrate this phenomenon within the context of high amplitude terahertz frequency strain waves that spontaneously form at the front of shock waves in GaN crystals.

A fully printed Veselago-Pendry lens (isotropic $n=-1$, ${\epsilon }_r=-1$, ${\mu }_r=-1$) is presented which is based on transmission-line metamaterials. The lens is constructed in a parallel-plate environment at 1.569 GHz and without any embedded sources and achieves a resolution better than the diffraction limit (full width half power of $0.235\lambda$). Because the lens is low loss ($<0.3\mathrm{dB}$ per unit cell), the focused fields are dominated by the evanescent components which dictates that subwavelength tightening of the beam is achieved only in the transverse and not the longitudinal direction. The demonstrated lens is quarter-wavelength thick thus allowing ample “working distance” between the subject/image and the lens.

Water-in-oil microdroplets within fluidic channels have the potential to serve as isolated reaction compartments for monitoring real-time dynamics with high efficiency and repeatability. Droplets, usually generated from aqueous and oil solutions using standard microfluidic formats, can be produced at frequencies in excess of 1 kHz. Although mixing within such microdroplets is normally enhanced by chaotic advection, the mixing pattern from droplet to droplet is almost identical and reproducible in form. Herein, we demonstrate that fluorescence lifetime imaging can be used to reconstruct mixing patterns within a droplet with a time resolution of $5\mu \mathrm{s}$.

A complete landscape is presented of the acoustic transmission properties of subwavelength apertures (slits and holes). First, we study the emergence of Fabry-Perot resonances in single apertures. When these apertures are placed in a periodic fashion, a new type of transmission resonance appears in the spectrum. We demonstrate that this resonance stems from the excitation of an acoustic guided wave that runs along the plate, which hybridizes strongly with the Fabry-Perot resonances associated with waveguide modes in single apertures. A detailed discussion of the similarities and differences with the electromagnetic case is also given.

We describe a way to generate subdiffraction light spots that can be moved over a surface without resorting to near-field manipulation, nonlinear effects, or negative index materials. We use a periodically patterned substrate that converted efficiently, through scattering, the impinging propagative waves into evanescent ones. Then we optimize the wave front of the incident propagative beam so that the grating-scattered evanescent waves interfere constructively at the focal point. Numerical simulations show that focus spots as small as one-sixth of a wavelength can be obtained at any point on the substrate. One foreseen application is high resolution surface imaging.

We report on spatiotemporal behavior of self-adapted dielectric liquid columns generated and sustained by light radiation pressure. We show that single- or multivalued liquid column diameter depends on the excitation light beam. When the beam diameter is sufficiently small, we observe a well-defined stationary column diameter. In contrast, at a larger beam diameter, the liquid column experiences complex spatiotemporal dynamics whose statistical analysis evidences an underlying multistable structure. Experimental observations are all supported by a full electromagnetic model that accounts for the wave guiding properties of the liquid column viewed as a step-index liquid-core liquid-cladding optical fiber having an optically tunable core diameter.

A novel method to set highly accurate initial conditions has been designed in the context of shock tube experiments for the Richtmyer-Meshkov instability study. Stereolithography has been used to design the membrane supports which initially materialize the gaseous interface. The visualizations of both heavy-light and light-heavy sinusoidal interfaces were carried out with laser sheet diagnostics. Experiments are in very good agreement with theory and simulations for the heavy-light case, but probably due to the membrane effects, quickly deviate from them in the light-heavy configuration.

We present a collection of eight data sets from state-of-the-art experiments and numerical simulations on turbulent velocity statistics along particle trajectories obtained in different flows with Reynolds numbers in the range $R_{\lambda }\in [120:740]$. Lagrangian structure functions from all data sets are found to collapse onto each other on a wide range of time lags, pointing towards the existence of a universal behavior, within present statistical convergence, and calling for a unified theoretical description. Parisi-Frisch multifractal theory, suitably extended to the dissipative scales and to the Lagrangian domain, is found to capture the intermittency of velocity statistics over the whole three decades of temporal scales investigated here.

From the measurement of a reflection spectrum of an open microwave cavity, the poles of the scattering matrix in the complex plane have been determined. The resonances have been extracted by means of the harmonic inversion method. By this, it became possible to resolve the resonances in a regime where the linewidths exceed the mean level spacing up to a factor of 10, a value inaccessible in experiments up to now. The obtained experimental distributions of linewidths were found to be in perfect agreement with predictions from random matrix theory when wall absorption and fluctuations caused by couplings to additional channels are considered.

The effect of preferential concentration of heavy particles in a homogeneous stably stratified turbulent flow is studied by means of direct numerical simulations. Particle distributions show different clustering patterns in horizontal and vertical directions, thereby representing the anisotropy of the flow. Preferential concentration in stably stratified turbulence can be quantified using 2D and 3D radial distribution functions and the correlation dimension ${\mathcal{D}}_2$. With increasing stratification strength, the effect of preferential concentration decreases. Furthermore, it is found that in stably stratified turbulence preferential accumulation is enhanced when gravitational forces act on heavy particles.

We present a shear instability, which can be triggered in compressible fluids with density-dependent viscosity at shear rates above critical. The instability mechanism is generic: It is based on density-dependent viscosity, compressibility, as well as flow two-(three-)dimensionality that provides coupling between streamwise and transversal velocity components and density variations. The only factor stabilizing the instability is fluid elasticity. The corresponding eigenvalue problem for a plane Couette flow is solved analytically in the limiting cases of large and small wave numbers.

We generated a series of harmonics in a xenon gas jet inside a cavity seeded by pulses from a Ti:sapphire mode-locked laser with a repetition rate of 10.8 MHz. Harmonics up to 19th order at 43 nm were observed with plateau harmonics at the $\mu \mathrm{W}$ power level. An elaborate dispersion compensation scheme and the use of a moderate repetition rate allowed for this significant improvement in output power of the plateau harmonics of 4 orders of magnitude over previous results. With this power level and repetition rate, high-resolution spectroscopy in the extreme ultraviolet region becomes conceivable. An interesting target would be the $1S\mathrm{\text{−}}2S$ transition in hydrogenlike ${\mathrm{He}}^{+}$ at 60 nm.