Bound States in the Continuum and Fano Resonances in the Dirac Cone Spectrum

We consider light scattering by two dimensional arrays of high-index dielectric spheres arranged into the triangular lattice. It is demonstrated that in the case a triple degeneracy of resonant leaky modes in the Gamma-point the scattering spectra exhibit a complicated picture of Fano resonances with extremely narrow line-width. The Fan features are explained through coupled mode theory for a Dirac cone spectrum as a signature of optical bound states in the continuum (BIC). It is found that the standing wave in-Gamma BIC induces a ring of off-Gamma BICs due to different scaling laws for real and imaginary parts of the resonant eigenfrequencies in the Dirac cone spectrum. A quantitative theory of the spectra is proposed

Signatures of Quantum Chaos and fermionization in the incoherent transport of bosonic carriers in the Bose-Hubbard chain

We analyse the stationary current of Bose particles across the Bose-Hubbard chain connected to a battery, focusing on the effect of inter-particle interactions. It is shown that the current magnitude drastically decreases as the strength of inter-particle interactions exceeds the critical value which marks the transition to quantum chaos in the Bose-Hubbard Hamiltonian. We found that this transition is well reflected in the non-equilibrium many-body density matrix of the system. Namely, the level-spacing distribution for eigenvalues of the density matrix changes from Poisson to Wigner-Dyson distributions. With the further increase of the interaction strength, the Wigner-Dyson spectrum statistics changes back to the Poisson statistics which now marks fermionization of the bosonic particles. With respect to the stationary current, this leads to the counter-intuitive dependence of the current magnitude on the particle number.Comment: 5 pages, 5 figure

Difficulties in assessing the added value created by enterprises of the oil and gas sector of the Russian Federation

The article considers the relevance of the problem of assessing the gross value added created by enterprises belonging to the oil and gas sector of the Russian Federation. There is no unified system of statistical indicators in the world that determine the boundaries and characterize the economy of the oil and gas complexes of the countries of the world. The World Bank’s calculation of the share of oil rents in the gross domestic product of the Russian Federation has adopted as one of the simple indicators for assessing the role of the oil and gas complex in the country’s economy. It has been noted that the oil rent is reflected only as a part of the primary income arising from the extraction of oil and gas, their processing, transportation and further use. The expediency of taking into account the entire value chain created in the oil and gas sector of the economy has been justified. The methodological difficulties of a number of interrelated problems have been highlighted in detail: measuring the added value created by service sector enterprises related to the oil and gas sector; complexly organization of production structures (vertically integrated companies); transfer pricing in the oil and gas industry; reflecting taxes and subsidies on products of the oil and gas sector. The conclusion has been made about the expediency of calculating the share of the oil and gas sector in the gross domestic product of the Russian Federation

Approaches to measuring production performance enterprises in the oil and gas sector of the Russian Federation based on statistical reporting

The article highlights approaches to calculating indicators characterising the production activities of oil and gas enterprises in the Russian Federation on the basis of the Federal State Statistics Service’s reports. The production activities structure’s heterogeneity has been noted. The issues of reassessing the importance of core and ancillary economic activities in the oil and gas sector are raised. The importance of assessing the intersectoral redistribution of value added is pointed out. Prospects for the performance assessment development of output, intermediate consumption and value added are highlighted an outlook by enterprise group analysis. The principles and criteria for assigning enterprises to the group are indicated. The output indicators of the largest companies in the oil and gas sector of the Russian Federation are considered. A methodology for step-by-step calculating the output, intermediate consumption and value added indicators for large enterprises is provided. The authors concluded that calculating the indicators of output, intermediate consumption and value added for the factor models construction is expediency