Vol 104, No 9 (2016)

The work presents a mechanism of spiral wave initiation due to the specific boundary conditions on a border of cardiac tissue defect. There are known scenarios when anatomical or functional defects in cardiac tissue may provoke the spiral wave origination, including unidirectional blockage while passing through the narrow gates, bent over critical curvature wave fronts, inhomogeneous recovery of the tissue, etc. We show a new scenario of spiral wave breakup on a small defect, which is unexcitable but permeable for ionic currents supporting the excitation wave. It was believed that such defects stabilize the rotating wave; however, as shown, instead of stabilizing it leads to the spiral breakup and subsequent multiplication of the rotating waves.

This article is based on renormalization analysis by using the single dressed gluon (SDG) approximation. This model is used to measure the coupling constant in perturbative as well as in the nonperturbative part of the QCD theory. We employ the event shape observables 〈B_T〉, 〈B_W〉, 〈1 − T〉, 〈C〉, and 〈ρ〉. By fitting both Monte Carlo and the real data with SDG, we find the mean values \({\alpha _S}\left( {{M_{{Z^0}}}} \right)\) = (0.1215 ± 0.0030) GeV and ν = (1.2685 ± 0.0173) GeV in the perturbative and nonperturbative regions, respectively. Our results are consistent with those obtained from other experiments at different energies. We explain all these features in this paper.

The type-II Weyl and type-II Dirac fermions may emerge behind the event horizon of black holes. Correspondingly, the black hole can be simulated by creation of the region with overtilted Weyl or Dirac cones. The filling of the electronic states inside the “black hole” is accompanied by Hawking radiation. The Hawking temperature in the Weyl semimetals can reach the room temperature, if the black hole region is sufficiently small, and thus the effective gravity at the horizon is large.

Longitudinal waves in microcavities emerging because of spatial dispersion are investigated. It is shown that longitudinal modes similar to whispering-gallery modes exist in microcavities of this kind. These longitudinal modes should exist in metal microcavities in the vicinity of the plasma frequency.

The mechanism of synchronized acceleration of ions by slow intense laser light is studied in application to available low-density targets of a new generation, which open prospects for experimental detection of a new effect of acceleration of protons.

Recent measurements of the conductivity of nanoperforated graphene are interpreted in terms of edges states existing near the edge of each nanohole. The perimetric quantization of edge states should result in the formation of a quasi-equidistant ladder of quasistationary energy levels. Dirac fermions filling this ladder rotate about each nanohole in the direction determined by the valley index. It is shown that the irradiation of this system by circularly polarized terahertz radiation leads to a resonance in absorption in one of the valleys. The magnitude of absorption at the resonance frequency can be controlled by means of gate voltage.

The effect of the magnetic field on the generation of an electric current in a two-dimensional electronic ratchet is theoretically studied. Mechanisms of the formation of magnetically induced photocurrent are proposed for a structure with a two-dimensional electron gas (quantum well, graphene, or topological insulator) with a lateral asymmetric superlattice consisting of metallic strips on the external surface of the structure. The ratchet with the spatially oscillating magnetic field generated by the ferromagnetic lattice, as well as the nonmagnetic ratchet placed in the uniform magnetic field both classically weak and strong quantizing, is considered. It is established that the ratio of the amplitude of the magnetic oscillations of photocurrent to the ratchet photocurrent in zero field can exceed two orders of magnitude.