Resonance- and Chaos-Assisted Tunneling

We consider dynamical tunneling between two symmetry-related regular islands that are separated in phase space by a chaotic sea. Such tunneling processes are dominantly governed by nonlinear resonances, which induce a coupling mechanism between ``regular'' quantum states within and ``chaotic'' states outside the islands. By means of a random matrix ansatz for the chaotic part of the Hamiltonian, one can show that the corresponding coupling matrix element directly determines the level splitting between the symmetric and the antisymmetric eigenstates of the pair of islands. We show in detail how this matrix element can be expressed in terms of elementary classical quantities that are associated with the resonance. The validity of this theory is demonstrated with the kicked Harper model.Comment: 25 pages, 5 figure

Nonlinear surface waves in left-handed materials

We study both linear and nonlinear surface waves localized at the interface separating a left-handed medium (i.e. the medium with both negative dielectric permittivity and negative magnetic permeability) and a conventional (or right-handed) dielectric medium. We demonstrate that the interface can support both TE- and TM-polarized surface waves - surface polaritons, and we study their properties. We describe the intensity-dependent properties of nonlinear surface waves in three different cases, i.e. when both the LH and RH media are nonlinear and when either of the media is nonlinear. In the case when both media are nonlinear, we find two types of nonlinear surface waves, one with the maximum amplitude at the interface, and the other one with two humps. In the case when one medium is nonlinear, only one type of surface wave exists, which has the maximum electric field at the interface, unlike waves in right-handed materials where the surface-wave maximum is usually shifted into a self-focussing nonlinear medium. We discus the possibility of tuning the wave group velocity in both the linear and nonlinear cases, and show that group-velocity dispersion, which leads to pulse broadening, can be balanced by the nonlinearity of the media, so resulting in soliton propagation.Comment: 9 pages, 10 figure

Precise determination of the conductivity exponent of 3D percolation using exact numerical renormalization

PACS. 05.50.+q Lattice theory and statistics (Ising, Potts, etc.) - 05.70.-a Thermodynamics,

Evaluating ablation and environmental impact of giant anthropogenic snow patches (Yuzhno-Sakhalinsk, Russia)

International audienceSystematic snow disposal from street cleaning operations may create large anthropogenic snow/ice bodies. Such man-made cryospheric objects may be considered as complex geophysical interfaces between the atmosphere, landscape, soils and hydrosphere. Urban snow patches not only produce large amounts of meltwater (and therefore a risk of flooding), but also serve as multiphase chemical reactors due to highly polluted mixture of snow/ice with various materials and water inclusions. However, the exact roles of snow patches in the environment and the factors driving their temporal evolution remain unclear. They are nevertheless of major importance for informed decision making and sustainable disposal operations. Here we present the results of a 4-year monitoring program concerning two artificial snow patches near the town of Yuzhno-Sakhalinsk (Russia) and the results of numerical modeling inferring the main corresponding processes, i.e. melting and water discharges. The temperature-based index method proved adequate to assess the evolution of the two snow patches. Constant ablation factors of about 0.45-0.58 and 0.27-0.31 cm w.e. d(-1) degrees C-1, respectively, were found to be appropriate for a first order approximation of snow patch melt dynamics. However, twice lower melt rates were found for one of the two closely located snow patches. This suggests that other factors, such as debris content, likely play a role. This difference in melting can be accounted for by modulating the ablation factor according to debris properties. In terms of peak daily water discharge, snow patch melting produces about 5-15 cm w.e. per day, comparable to rain rates during regional typhoons. This study represents a starting point that should be followed by a more detailed monitoring program and the application of a more complex numerical model of snow disposal sites, to allow optimization of their maintenance. For example, marginal melting or the combined influence of debris and soils on surface runoff should be further investigated. Moreover, better constrained and formulated chemical processes will allow a more reliable estimate of the local environmental impact of regular snow disposal

Compact-2D FDTD for Waveguides Including Materials with Negative Dielectric Permittivity, Magnetic Permeability and Refractive Index

An efficient compact-2D finite-difference time-domain method is presented for the numerical analysis of guided modes in waveguides that may include negative dielectric permittivity, negative magnetic permeability and negative refractive index materials. Both complex variable and real variable methods are given. The method is demonstrated for the analysis of channel-plasmon-polariton guided modes in triangular groves on a metal surface. The presented method can be used for a range of waveguide problems that were previously unsolvable analytically, due to complex geometries, or numerically, due to computational requirements of conventional three-dimensional finite-difference time-domain methods. A 3-dimensional finite-difference time-domain algorithm that also allows analysis in the presence of bound or free electric and equivalent magnetic charges is presented and an example negative refraction demonstrates the method