Mobility of solitons in one-dimensional lattices with the cubic-quintic nonlinearity

We investigate mobility regimes for localized modes in the discrete nonlinear Schr\"{o}dinger (DNLS) equation with the cubic-quintic onsite terms. Using the variational approximation (VA), the largest soliton's total power admitting progressive motion of kicked discrete solitons is predicted, by comparing the effective kinetic energy with the respective Peierls-Nabarro (PN) potential barrier. The prediction is novel for the DNLS model with the cubic-only nonlinearity too, demonstrating a reasonable agreement with numerical findings. Small self-focusing quintic term quickly suppresses the mobility. In the case of the competition between the cubic self-focusing and quintic self-defocusing terms, we identify parameter regions where odd and even fundamental modes exchange their stability, involving intermediate asymmetric modes. In this case, stable solitons can be set in motion by kicking, so as to let them pass the PN barrier. Unstable solitons spontaneously start oscillatory or progressive motion, if they are located, respectively, below or above a mobility threshold. Collisions between moving discrete solitons, at the competing nonlinearities frame, are studied too.Comment: 12 pages, 15 figure

Spatial rogue waves in photorefractive SBN crystals

We report on the excitation of large-amplitude waves, with a probability of around 1% of total peaks, on a photorefractive SBN crystal by using a simple experimental setup at room temperature. We excite the system using a narrow Gaussian beam and observe different dynamical regimes tailored by the value and time rate of an applied voltage. We identify two main dynamical regimes: a caustic one for energy spreading and a speckling one for peak emergence. Our observations are well described by a two-dimensional Schr\"odinger model with saturable local nonlinearity.Comment: 4 pages, 4 figure

Dissipative vortex solitons in 2D-lattices

We report the existence of stable symmetric vortex-type solutions for two-dimensional nonlinear discrete dissipative systems governed by a cubic-quintic complex Ginzburg-Landau equation. We construct a whole family of vortex solitons with a topological charge S = 1. Surprisingly, the dynamical evolution of unstable solutions of this family does not alter significantly their profile, instead their phase distribution completely changes. They transform into two-charges swirl-vortex solitons. We dynamically excite this novel structure showing its experimental feasibility.Comment: 4 pages, 20 figure

Introduction: Building word image, a new arena for architectural history

The study of word-image relationships is one of the most innovative and cross-disciplinary fields to have emerged in the humanities over the last decades. This special collection of Architectural Histories opens up this area to architectural history by exploring the rising coexistence of the graphic and the verbal in the public dissemination of architecture in the 19th and early 20th centuries. Originating from a conference session at the Third International Meeting of the European Architectural History Network in Turin, June 2014, this selection of articles also presents the foundation for an EAHN Interest Group on Word & Image, which will help to define this new arena. Even if word-image relationships are, so far, rarely identified as a specific topic within our discipline, as architectural historians we already investigate them across periods, territories and subjects. The purpose of this collection is to make this a subject per se by examining descriptions and illustrations of buildings in printed and publicly disseminated media such as newspapers, journals, pamphlets, books, manuscripts or catalogues. We hope that the papers in this special collection of Architectural Histories will encourage architectural historians of all fields to question the interplay between buildings, words and images afresh, thus building a new understanding of the verbal and visual presence of architecture

Direct measurements of the magnetocaloric effect in pulsed magnetic fields: The example of the Heusler alloy Ni50_{50}Mn35_{35}In15_{15}

We have studied the magnetocaloric effect (MCE) in the shape-memory Heusler alloy Ni$_{50}$Mn$_{35}$In$_{15}$ by direct measurements in pulsed magnetic fields up to 6 and 20 T. The results in 6 T are compared with data obtained from heat-capacity experiments. We find a saturation of the inverse MCE, related to the first-order martensitic transition, with a maximum adiabatic temperature change of $\Delta T_{ad} = -7$ K at 250 K and a conventional field-dependent MCE near the second-order ferromagnetic transition in the austenitic phase. The pulsed magnetic field data allow for an analysis of the temperature response of the sample to the magnetic field on a time scale of $\sim 10$ to 100 ms which is on the order of typical operation frequencies (10 to 100 Hz) of magnetocaloric cooling devices. Our results disclose that in shape-memory alloys the different contributions to the MCE and hysteresis effects around the martensitic transition have to be carefully considered for future cooling applications.Comment: 5 pages, 4 figure

Nonequilibrium dynamics of a stochastic model of anomalous heat transport: numerical analysis

We study heat transport in a chain of harmonic oscillators with random elastic collisions between nearest-neighbours. The equations of motion of the covariance matrix are numerically solved for free and fixed boundary conditions. In the thermodynamic limit, the shape of the temperature profile and the value of the stationary heat flux depend on the choice of boundary conditions. For free boundary conditions, they also depend on the coupling strength with the heat baths. Moreover, we find a strong violation of local equilibrium at the chain edges that determine two boundary layers of size $\sqrt{N}$ (where $N$ is the chain length), that are characterized by a different scaling behaviour from the bulk. Finally, we investigate the relaxation towards the stationary state, finding two long time scales: the first corresponds to the relaxation of the hydrodynamic modes; the second is a manifestation of the finiteness of the system.Comment: Submitted to Journal of Physics A, Mathematical and Theoretica

Memory Effects in Nonequilibrium Transport for Deterministic Hamiltonian Systems

We consider nonequilibrium transport in a simple chain of identical mechanical cells in which particles move around. In each cell, there is a rotating disc, with which these particles interact, and this is the only interaction in the model. It was shown in \cite{eckmann-young} that when the cells are weakly coupled, to a good approximation, the jump rates of particles and the energy-exchange rates from cell to cell follow linear profiles. Here, we refine that study by analyzing higher-order effects which are induced by the presence of external gradients for situations in which memory effects, typical of Hamiltonian dynamics, cannot be neglected. For the steady state we propose a set of balance equations for the particle number and energy in terms of the reflection probabilities of the cell and solve it phenomenologically. Using this approximate theory we explain how these asymmetries affect various aspects of heat and particle transport in systems of the general type described above and obtain in the infinite volume limit the deviation from the theory in \cite{eckmann-young} to first-order. We verify our assumptions with extensive numerical simulations.Comment: Several change

First experimental evidence for quantum echoes in scattering systems

A self-pulsing effect termed quantum echoes has been observed in experiments with an open superconducting and a normal conducting microwave billiard whose geometry provides soft chaos, i.e. a mixed phase space portrait with a large stable island. For such systems a periodic response to an incoming pulse has been predicted. Its period has been associated to the degree of development of a horseshoe describing the topology of the classical dynamics. The experiments confirm this picture and reveal the topological information.Comment: RevTex 4.0, 5 eps-figure

A non-perturbative renormalization group study of the stochastic Navier--Stokes equation

We study the renormalization group flow of the average action of the stochastic Navier--Stokes equation with power-law forcing. Using Galilean invariance we introduce a non-perturbative approximation adapted to the zero frequency sector of the theory in the parametric range of the H\"older exponent $4-2\,\varepsilon$ of the forcing where real-space local interactions are relevant. In any spatial dimension $d$, we observe the convergence of the resulting renormalization group flow to a unique fixed point which yields a kinetic energy spectrum scaling in agreement with canonical dimension analysis. Kolmogorov's -5/3 law is, thus, recovered for $\varepsilon=2$ as also predicted by perturbative renormalization. At variance with the perturbative prediction, the -5/3 law emerges in the presence of a \emph{saturation} in the $\varepsilon$-dependence of the scaling dimension of the eddy diffusivity at $\varepsilon=3/2$ when, according to perturbative renormalization, the velocity field becomes infra-red relevant.Comment: RevTeX, 18 pages, 5 figures. Minor changes and new discussion

A stochastic model of anomalous heat transport: analytical solution of the steady state

We consider a one-dimensional harmonic crystal with conservative noise, in contact with two stochastic Langevin heat baths at different temperatures. The noise term consists of collisions between neighbouring oscillators that exchange their momenta, with a rate $\gamma$. The stationary equations for the covariance matrix are exactly solved in the thermodynamic limit ($N\to\infty$). In particular, we derive an analytical expression for the temperature profile, which turns out to be independent of $\gamma$. Moreover, we obtain an exact expression for the leading term of the energy current, which scales as $1/\sqrt{\gamma N}$. Our theoretical results are finally found to be consistent with the numerical solutions of the covariance matrix for finite $N$.Comment: Minor changes in the text. To appear in Journal of Physics