The fate of aerosols in open flows is relevant in a variety of physical contexts. Previous results are consistent with the assumption that such finite-size particles always escape in open chaotic advection. Here we show that a different behavior is possible. We analyze the dynamics of aerosols both in the absence and presence of gravitational effects, and both when the dynamics of the fluid particles is hyperbolic and nonhyperbolic. Permanent trapping of aerosols much heavier than the advecting fluid is shown to occur in all these cases. This phenomenon is determined by the occurrence of multiple vortices in the flow and is predicted to happen for realistic particle-fluid density ratios.

Experimental evidence of spatiotemporal antiphase dynamics is given for an extended system made of two liquid crystal slices that are optically coupled by two equal amplitude counterpropagating pumping beams. Theory and experiments carried out in a transverse one-dimensional configuration show that roll patterns are generated in each slice. These rolls are spatially in-phase or antiphase for a focusing or a defocusing nonlinearity type, respectively. These in-phase or antiphase dynamics remain robust even for complex spatiotemporal regimes such as dislocation regimes.

We investigate the dependence of the intensity of radiation due to high-harmonic generation as a function of the wavelength $\lambda$ of the fundamental driver field. Superimposed on a smooth power-law dependence observed previously, we find surprisingly strong and rapid fluctuations on a fine $\lambda$ scale. We identify the origin of these fluctuations in terms of quantum path interferences with up to five returning orbits significantly contributing.

We investigate the normal modes of a developable cone singularity as observed in a circular sheet supported by a rigid circular frame and pushed at its center. When the center of the sheet is in addition submitted to a sinusoidal forcing, two types of bending modes, named here rolling and tilt modes, are parametrically excited. The rolling mode is an angular oscillation of the concave sector of the developable cone structure. If the amplitude of vibration is high enough, the rolling mode amplitude increases dramatically giving rise to both a continuous rotation of the concave sector and a material angular displacement of the sheet, similar to that produced by a moving wrinkle in a carpet.

We present a numerical analysis of an incompressible decaying magnetohydrodynamic turbulence run on a grid of ${1536}^3$ points. The Taylor Reynolds number at the maximum of dissipation is $\approx 1100$, and the initial condition is a superposition of large-scale Arn’old-Beltrami-Childress flows and random noise at small scales, with no uniform magnetic field. The initial kinetic and magnetic energies are equal, with negligible correlation. The resulting energy spectrum is a combination of two components, each moderately resolved. Isotropy obtains in the large scales, with a spectral law compatible with the Iroshnikov-Kraichnan theory stemming from the weakening of nonlinear interactions due to Alfvén waves; scaling of structure functions confirms the non-Kolmogorovian nature of the flow in this range. At small scales, weak turbulence emerges with a $k_{\perp }^{-2}$ spectrum, the perpendicular direction referring to the local quasiuniform magnetic field.

We demonstrate experimentally that structural perturbations imposed on highly dispersive photonic crystal-based waveguides give rise to spectral features that bear signatures of Anderson localization. Sharp resonances with effective $Q$’s of over 30 000 are found in scattering spectra of disordered waveguides. The resonances are observed in a $\sim 20\mathrm{\text{−}}\mathrm{nm}$ bandwidth centered at the cutoff of slowly guided Bloch modes. The origin of the spectral features can be explained by the interference of coherently scattered electromagnetic waves which results in the formation of a narrow impurity (or localization) band populated with spectrally distinct quasistates. Standard photon localization criteria are fulfilled in the localization band.

We present measurements of the spatial intensity distribution of localized modes in a two-dimensional open microwave cavity randomly filled with cylindrical dielectric scatterers. We show that each of these modes displays a range of localization lengths, and we successfully relate the largest value to the measured leakage rate at the boundary. These results constitute unambiguous signatures of the existence of strongly localized electromagnetic modes in two-dimensionnal open random media.

The path integral for randomly forced incompressible fluids is shown to have an underlying Becchi-Rouet-Stora (BRS) symmetry as a consequence of Galilean invariance. This symmetry must be respected to have a consistent generating functional, free from both an overall infinite factor and spurious relations amongst correlation functions. We present a procedure for respecting this BRS symmetry, akin to gauge fixing in quantum field theory. Relations are derived between correlation functions of this gauge-fixed, BRS symmetric theory, analogous to the Slavnov-Taylor identities of quantum field theory.

We report the first experimental and theoretical demonstrations of in-band (or embedded) lattice solitons. Such solitons appear in trains, and their propagation constants reside inside the first Bloch band of a square lattice, different from all previously observed solitons. We show that these solitons bifurcate from Bloch modes at the interior high-symmetry $X$ points within the first band, where normal and anomalous diffractions coexist along two orthogonal directions. At high powers, the in-band soliton can move into the first band gap and turn into a gap soliton.

Nonlinear refraction spectroscopy measurements were performed in resonance with absorption lines in ${\mathrm{Nd}}^{3+}$ and ${\mathrm{Cr}}^{3+}$ doped crystals. The observed line shapes can be explained by the interference of resonant and nonresonant contributions to the nonlinear refractive index. These effects were fully discriminated using a pump and probe configuration, in which a dispersive line shape was observed on the top of a plateau that was attributed to the polarizability difference between excited and ground states ($\Delta \alpha$). A theoretical model was used to obtain $\Delta \alpha$ from the experimental data, and the results are in agreement with several previous experiments. Slow and fast light propagation are also discussed.

We study directed transport in a classical deterministic dissipative system. We consider the generic case of mixed phase space and show that large ratchet currents can be generated thanks to the presence, in the Hamiltonian limit, of transporting stability islands embedded in the chaotic sea. Because of the simultaneous presence of chaos and dissipation the stationary value of the current is independent of initial conditions, except for initial states with very small measure.

We put forward the concept of resonant, Rabi-like oscillatons and adiabatic transitions between confined light modes in properly modulated multimode waveguides. The phenomenon is shown to take place in both the linear and the nonlinear regimes. In addition, we find that the mode transitions occur not only in simple geometries, but also in complex confining multimode structures. The phenomenon is analogous to the familiar stimulated state transitions that occur in multilevel quantum systems.

We have developed a small, neutrally buoyant, wireless temperature sensor. Using a camera for optical tracking, we obtain simultaneous measurements of position and temperature of the sensor as it is carried along by the flow in Rayleigh-Bénard convection, at $\mathrm{Ra}\sim {10}^{10}$. We report on statistics of temperature, velocity, and heat transport in turbulent thermal convection. The motion of the sensor particle exhibits dynamics close to that of Lagrangian tracers in hydrodynamic turbulence. We also quantify heat transport in plumes, revealing self-similarity and extreme variations from plume to plume.

In this Letter, highly resolved measurements of the horizontal velocity inside the boundary layer of turbulent Rayleigh-Bénard convection are reported. They were performed in a cylindrical box with an aspect ratio $\Gamma =1.13$ which was filled with air with a Prandtl number $\mathrm{Pr}=0.7$. The horizontal velocity was measured along the central axis close to the cooling plate in a range of Rayleigh numbers between $\mathrm{Ra}={10}^{11}$ and $\mathrm{Ra}={10}^{12}$ using a two-dimensional laser Doppler velocimeter. We demonstrate that the profile of the mean velocity strongly differs from that of classical shear flows like the Blasius shape of a laminar flat plate boundary layer or a turbulent logarithmic velocity profile with standard coefficients.

We study a model of freely cooling inelastic granular gas in one dimension, with a restitution coefficient which approaches the elastic limit below a relative velocity scale $\delta$. While at early times ($t\ll {\delta }^{-1}$) the gas behaves as a completely inelastic sticky gas conforming to predictions of earlier studies, at late times ($t\gg {\delta }^{-1}$) it exhibits a new fluctuation-dominated phase ordering state. We find distinct scaling behavior for the (i) density distribution function, (ii) occupied and empty gap distribution functions, (iii) the density structure function, and (iv) the velocity structure function, as compared to the completely inelastic sticky gas. The spatial structure functions (iii) and (iv) violate the Porod law. Within a mean-field approximation, the exponents describing the structure functions are related to those describing the spatial gap distribution functions.

In this Letter we demonstrate Mie resonances mediated transport of light in randomly arranged, monodisperse dielectric spheres packed at high filling fractions. By means of both static and dynamic optical experiments we show resonant behavior in the key transport parameters and, in particular, we find that the energy transport velocity, which is lower than the group velocity, also displays a resonant behavior.

A wide variety of propagating disturbances in physical systems are described by equations whose solutions lack a sharp propagating front. We demonstrate that presence of particular nonlinearities may induce such fronts. To exemplify this idea, we study both dissipative $u_t+{\partial }_{x}f(u)=u_{xx}$ and dispersive $u_t+{\partial }_{x}f(u)+u_{xxx}=0$ patterns, and show that a weakly singular convection $f(u)=-u^{\alpha }+u^m$, $0<\alpha <1<m$, induces a sharp localization of fronts around the $u=0$ ground state. Notably, a sharp front also emerges in higher dimensional extensions: $u_t+{\partial }_x[f(u)+{\nabla }^{2}u]=0$ or in wave phenomena of the Boussinesq type: $Z_{tt}=\mathbf{\nabla }·[F_{*}(|\mathbf{\nabla }Z|)\mathbf{\nabla }Z]-{\nabla }^{4}Z$ where $F_{*}(\sigma )=C^2\sigma +f(\sigma )$.

We experimentally investigate the critical behavior of a phase transition between two topologically different turbulent states of electrohydrodynamic convection in nematic liquid crystals. The statistical properties of the observed spatiotemporal intermittency regimes are carefully determined, yielding a complete set of static critical exponents in full agreement with those defining the directed percolation class in $2+1$ dimensions. This constitutes the first clear and comprehensive experimental evidence of an absorbing phase transition in this prominent nonequilibrium universality class.

It was proposed that perfect invisibility cloaks can be constructed for hiding objects from electromagnetic illumination [J. B. Pendry, D. Schurig, and D. R. Smith, Science 312, 1780 (2006)]. The cylindrical cloaks experimentally demonstrated [D. Schurig et al., Science 314, 977 (2006)] and theoretically proposed [W. Cai et al., Nat. Photon. 1, 224 (2007)] have however simplified material parameters in order to facilitate easier realization as well as to avoid infinities in optical constants. Here we show that the cylindrical cloaks with simplified material parameters inherently allow the zeroth-order cylindrical wave to pass through the cloak as if the cloak is made of a homogeneous isotropic medium, and thus visible. To all high-order cylindrical waves, our numerical simulation suggests that the simplified cloak inherits some properties of the ideal cloak, but finite scatterings exist.

Previous studies of quantum delta-kicked rotors have found momentum probability distributions with a typical width (localization length $L$) characterized by fractional $\hslash$ scaling; i.e., $L\sim {\hslash }^{2/3}$ in regimes and phase-space regions close to “golden-ratio” cantori. In contrast, in typical chaotic regimes, the scaling is integer, $L\sim {\hslash }^{-1}$. Here we consider a generic variant of the kicked rotor, the random-pair-kicked particle, obtained by randomizing the phases every second kick; it has no Kol’mogorov-Arnol’d-Moser mixed-phase-space structures, such as golden-ratio cantori, at all. Our unexpected finding is that, over comparable phase-space regions, it also has fractional scaling, but $L\sim {\hslash }^{-2/3}$. A semiclassical analysis indicates that the ${\hslash }^{2/3}$ scaling here is of quantum origin and is not a signature of classical cantori.