Pulses of chaos synchronization in coupled map chains with delayed transmission

Pulses of synchronization in chaotic coupled map lattices are discussed in the context of transmission of information. Synchronization and desynchronization propagate along the chain with different velocities which are calculated analytically from the spectrum of convective Lyapunov exponents. Since the front of synchronization travels slower than the front of desynchronization, the maximal possible chain length for which information can be transmitted by modulating the first unit of the chain is bounded.Comment: 4 pages, 6 figures, updated version as published in PR

Sublattice synchronization of chaotic networks with delayed couplings

Synchronization of chaotic units coupled by their time delayed variables are investigated analytically. A new type of cooperative behavior is found: sublattice synchronization. Although the units of one sublattice are not directly coupled to each other, they completely synchronize without time delay. The chaotic trajectories of different sublattices are only weakly correlated but not related by generalized synchronization. Nevertheless, the trajectory of one sublattice is predictable from the complete trajectory of the other one. The spectra of Lyapunov exponents are calculated analytically in the limit of infinite delay times, and phase diagrams are derived for different topologies

Non-Paraxial Accelerating Beams

We present the spatially accelerating solutions of the Maxwell equations. Such non-paraxial beams accelerate in a circular trajectory, thus generalizing the concept of Airy beams. For both TE and TM polarizations, the beams exhibit shape-preserving bending with sub-wavelength features, and the Poynting vector of the main lobe displays a turn of more than 90 degrees. We show that these accelerating beams are self-healing, analyze their properties, and compare to the paraxial Airy beams. Finally, we present the new family of periodic accelerating beams which can be constructed from our solutions

Bayesian Symbol Detection in Wireless Relay Networks via Likelihood-Free Inference

This paper presents a general stochastic model developed for a class of cooperative wireless relay networks, in which imperfect knowledge of the channel state information at the destination node is assumed. The framework incorporates multiple relay nodes operating under general known non-linear processing functions. When a non-linear relay function is considered, the likelihood function is generally intractable resulting in the maximum likelihood and the maximum a posteriori detectors not admitting closed form solutions. We illustrate our methodology to overcome this intractability under the example of a popular optimal non-linear relay function choice and demonstrate how our algorithms are capable of solving the previously intractable detection problem. Overcoming this intractability involves development of specialised Bayesian models. We develop three novel algorithms to perform detection for this Bayesian model, these include a Markov chain Monte Carlo Approximate Bayesian Computation (MCMC-ABC) approach; an Auxiliary Variable MCMC (MCMC-AV) approach; and a Suboptimal Exhaustive Search Zero Forcing (SES-ZF) approach. Finally, numerical examples comparing the symbol error rate (SER) performance versus signal to noise ratio (SNR) of the three detection algorithms are studied in simulated examples

Unusual interplay between copper-spin and vortex dynamics in slightly overdoped La{1.83}Sr{0.17}CuO{4}

Our inelastic neutron scattering experiments of the spin excitations in the slightly overdoped La{1.83}Sr{0.17}CuO{4} compound show that, under the application of a magnetic field of 5 Tesla, the low-temperature susceptibility undergoes a weight redistribution centered at the spin-gap energy. Furthermore, by comparing the temperature dependence of the neutron data with ac-susceptibility and magnetization measurements, we conclude that the filling in of the spin gap tracks the irreversibility/melting temperature rather than Tc2, which indicates an unusual interplay between the magnetic vortices and the spin excitations even in the slightly overdoped regime of high-temperature superconductors.Comment: 7 pages, including 5 figure

Engaging virtual agents

Embodied virtual assistants normally don’t engage the user emotionally. They fulfil their functions, e.g. as shopping assistants or virtual teachers, factually and emotionless. This way, they do not explore the full potential of the presence of an embodied character. In real life, the personality of the teacher or salesperson, their ability to involve and even to entertain is essential for their success. But how much of these “soft factors” can be translated into behaviour of virtual agents? Which kinds of virtual personalities are appropriate for which group, and in which context? We call virtual agents with engaging “soft skills” Engaging Virtual Agents. This paper presents a software platform employed for experimenting with soft skills and for creating different personalities of virtual agents. The focus of this platform is on authoring principles that facilitate the cooperation of content creators and computer scientists. We also present “Julie”, an example that was shortly concluded as part of a research project commissioned by SAP AG. Julie is a virtual sales assistant that employs actively emotional expressions and narrative techniques, in order to provide additional motivation for the customer to visit and to remain at the virtual shop

Ni-impurity effects on the superconducting gap of La2−x_{2-x}Srx_{x}CuO4_4 studied from the magnetic field and temperature dependence of the electronic specific heat

The magnetic field and temperature dependence of the electronic specific heat $C_{\rm el}$ have been systematically investigated in $\rm La_{2-{\it x}}Sr_{\it x}Cu_{1-{\it y}}Ni_{\it y}O_4$ (LSCNO) in order to study Ni-impurity effects on the superconducting (SC) gap. In LSCNO with $x$=0.15 and $y$=0.015, the value of $\gamma$ ($\equiv C_{\rm el}/T$) at $T$=0 K, $\gamma_0$, is enhanced under the magnetic field $H$ applied along the $\bm c$-axis. The increment of $\gamma_0$, $\Delta \gamma_0$, follows the Volovik relation $\Delta \gamma_0$=$A\sqrt{H}$, characteristic of the SC gap with line nodes, with prefactor $A$ similar to that of a pure sample. The $C_{\rm el}/T$ vs. $T$ curve under $H$=0 shows a d-wave-like SC anomaly with an abrupt increase at $T_{\rm c}$ and $T$-linear dependence at $T$$\ll$$T_{\rm c}$, although the $\gamma_0$-value in the $C_{\rm el}/T$ vs. $T$ curve increases with increasing Ni concentrations. Interestingly, as the SC part of $C_{\rm el}/T$, $C_{\rm el}/T$$-$$\gamma_0$$\equiv$$\gamma_{\rm s}$, decreases in LSCNO, $T_{\rm c}$ is reduced in proportion to the decrease of $\gamma_{\rm s}$. These findings can be explained phenomenologically by a simple model in which Ni impurities bring about strong pair breaking at the edges of the coherent nodal part of the Fermi surface but in the vicinity of the nodes of the SC gap. The reduction of the SC condensation energy $U_0$ in LSCNO, evaluated from $C_{\rm el}$ at $T$ {0.3em}\raisebox{0.4ex}{$<$} {-0.75em}\raisebox{-.7ex}{$\sim$} {0.3em}$T_{\rm c}$, is also understood by the same model.Comment: 7 pages, 6 figures, accepted in Phys. Rev.