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McCullough Henry posted an update 10 hours, 19 minutes ago
A high-intensity laser beam propagating through a dense plasma drives a strong current that robustly sustains a strong quasistatic azimuthal magnetic field. Hormones agonist The laser field efficiently accelerates electrons in such a field that confines the transverse motion and deflects the electrons in the forward direction. Its advantage is a threshold rather than resonant behavior, accelerating electrons to high energies for sufficiently strong laser-driven currents. We study the electron dynamics via a test-electron model, specifically deriving the corresponding critical current density. We confirm the model’s predictions by numerical simulations, indicating energy gains two orders of magnitude higher than achievable without the magnetic field.A polydispersed mixture of granular materials composed of different-sized particles segregates whenever it undergoes external actions such as shear. Predicting and controlling segregation pose a challenging problem of industrial interest. One of the most frequent and important causes of segregation is interparticle percolation that occurs when small particles fall down through the voids between large particles as a result of local shear in the presence of a gravitational field. In this paper, we present a theoretical model to predict the percolation velocity in sheared systems, and we validate it experimentally. The experiments were carried out in simple shear conditions. This type of flow was achieved in a shear box which allowed the quantitative study of particle percolation under constant shear conditions. The granular material inside the box was a binary mixture of cohesionless spheres differing only in size. The experiments allowed us to quantify the percolation speed for different size ratios and different shear rates. The collected data confirmed the validity of the proposed theoretical model; the latter can be implemented in a continuum framework to simulate more complex phenomena and geometries.Many living systems use assemblies of soft and slender structures whose deflections allow them to mechanically probe their immediate environment. In this work, we study the collective response of artificial soft hair assemblies to a shear flow by imaging their deflections. At all hair densities, the deflection is found to be proportional to the local shear stress with a proportionality factor that decreases with density. The measured collective stiffening of hairs is modeled both with a microscopic elastohydrodynamic model that takes into account long-range hydrodynamic hair-hair interactions and a phenomenological model that treats the hair assemblies as an effective porous medium. While the microscopic model is in reasonable agreement with the experiments at low hair density, the phenomenological model is found to be predictive across the entire density range.We study the time dependence of the local persistence probability during a nonstationary time evolution in the disordered contact process in d=1, 2, and 3 dimensions. We present a method for calculating the persistence with the strong-disorder renormalization group (SDRG) technique, which we then apply at the critical point analytically for d=1 and numerically for d=2,3. According to the results, the average persistence decays at late times as an inverse power of the logarithm of time, with a universal dimension-dependent generalized exponent. For d=1, the distribution of sample-dependent local persistence is shown to be characterized by a universal limit distribution of effective persistence exponents. Using a phenomenological approach of rare-region effects in the active phase, we obtain a nonuniversal algebraic decay of the average persistence for d=1 and enhanced power laws for d>1. As an exception, for randomly diluted lattices, the algebraic decay remains valid for d>1, which is explained by the contribution of dangling ends. Results on the time dependence of average persistence are confirmed by Monte Carlo simulations. We also prove the equivalence of the persistence with a return probability, a valuable tool for the argumentations.Today’s society faces widening disagreement and conflicts among constituents with incompatible views. Escalated views and opinions are seen not only in radical ideology or extremism but also in many other scenes of our everyday life. Here we show that widening disagreement among groups may be linked to the advancement of information communication technology by analyzing a mathematical model of population dynamics in a continuous opinion space. We adopted the interaction kernel approach to model enhancement of people’s information-gathering ability and introduced a generalized nonlocal gradient as individuals’ perception kernel. We found that the characteristic distance between population peaks becomes greater as the wider range of opinions becomes available to individuals or the more attention is attracted to opinions distant from theirs. These findings may provide a possible explanation for why disagreement is growing in today’s increasingly interconnected society, without attributing its cause only to specific individuals or events.A walker is a macroscopic coupling of a droplet and a capillary wave field that exhibits several quantumlike properties. In 2009, Eddi et al. [Phys. Rev. Lett. 102, 240401 (2009)PRLTAO0031-900710.1103/PhysRevLett.102.240401] showed that walkers may cross a submerged barrier in an unpredictable manner and named this behavior “unpredictable walker tunneling.” In quantum mechanics, tunneling is one of the simplest arrangements where similar unpredictability occurs. In this paper, we investigate how unpredictability can be unveiled for walkers through an experimental study of walker tunneling with precision. We refine both time and position measurements to take into account the fast bouncing dynamics of the system. Tunneling is shown to be unpredictable until a distance of 2.6 mm from the barrier center, where we observe the separation of reflected and transmitted trajectories in the position-velocity phase-space. The unpredictability is unlikely to be attributable to either uncertainty in the initial conditions or to the noise in the experiment.