Square vortex solitons with a large angular momentum

We show the existence of square shaped optical vortices with a large value of the angular momentum hosted in finite size laser beams which propagate in nonlinear media with a cubic-quintic nonlinearity. The light profiles take the form of rings with sharp boundaries and variable sizes depending on the power carried. Our stability analysis shows that these light distributions remain stable when propagate, probably for unlimited values of the angular momentum, provided the hosting beam is wide enough. This happens if the peak amplitude approaches a critical value which only depends on the nonlinear refractive index of the material. A variational approach allows us to calculate the main parameters involved. Our results add extra support to the concept of surface tension of light beams that can be considered as a trace of the existence of a liquid of light.Comment: 6 pages, 6 figures, submitted to Phys. Rev.

Twisted speckle entities inside wavefront reversal mirrors

The previously unknown property of the optical speckle pattern reported. The interference of a speckle with an oppositely moving phase-conjugated speckle wave produces a randomly distributed ensemble of a twisted entities (ropes) surrounding optical vortex lines. These entities appear in a wide range of randomly chosen speckle parameters inside the phase-conjugating mirrors regardless to an internal physical mechanism of the wavefront reversal. These numerically generated interference patterns are relevant to a Brillouin $\bf PC$-mirrors and to a four-wave mixing $\bf PC$-mirrors based upon laser trapped ultracold atomic cloud.Comment: 4 pages,3 figures, Accepted to Physical Review

Electron detachment from negative ions in bichromatic laser field

Negative ion detachment in two-colour laser field is considered within the recent modification of Keldysh model which makes it quantitatively reliable. The general approach is illustrated by calculation of angular differential detachment rates, partial rates for particular ATD (Above Threshold Detachment) channels and total detachment rates for H$^-$ ion in bichromatic field with 1:2 frequency ratio. Both perturbative and strong field regimes are examined. Polar asymmetry and phase effects are quantitatively characterized with some new features revealed. Phase effects are found to result in a huge anisotropy factor $\sim 10^3$ in the electron angular distribution in the perturbative regime.Comment: 13 pages, 8 figures in separate files which are not incorporated in the latex file of the pape

Para a questão de avaliar a credibilidade da empresa por bancos comerciais russos

Credit in the economy plays a double role, since it is a source of development for organizations (acquisition of fixed assets, modernization and reconstruction of production, launching of new projects, as well as the replacement of working capital) and an instrument for the generation of income for the bank and, in general, its main activity. To analyze the differences in the industry, we selected 30 companies. On the basis of its financial statements, we calculate the liquidity indices, the profitability of sales and the turnover of accounts payable and accounts receivable. The results showed that the reliability and financial stability of the clients reduce the bank risks, help the bank to obtain a higher income. It is considered that the bank deals not only with high-level customers: there are also customers among them who experience financial difficulties due to inadequate production organization, poor market research or poorly chosen strategy. The ability to correctly identify the client's capabilities, recognize their strengths and weaknesses is an important task for credit institutions. Therefore, these analytical indicators allow to objectively evaluate the creditworthiness of the borrower. However, in addition to the analysis of the financial ratios, it is necessary to evaluate the quality parameters, that is, analyze the client's credit history, the period of his service in the bank, the quality of the administration, his dependence on the suppliers and customers, and credit security.El crédito en la economía desempeña un doble papel, ya que es una fuente de desarrollo para las organizaciones (adquisición de activos fijos, modernización y reconstrucción de la producción, lanzamiento de nuevos proyectos, así como la reposición del capital de trabajo) y un instrumento para la generación de ingresos para el banco y, en general, su actividad principal. Para analizar las diferencias de la industria, seleccionamos 30 empresas. Sobre la base de sus estados contables (financieros), calculamos los índices de liquidez, la rentabilidad de las ventas y el volumen de negocios de las cuentas por pagar y las cuentas por cobrar. Los resultados demostraron que la confiabilidad y la estabilidad financiera de los clientes reducen los riesgos bancarios, ayudan al banco a obtener un ingreso más alto. Se considera que el banco trata no solo con los clientes de alto nivel: también hay clientes entre ellos que experimentan dificultades financieras debido a una producción inadecuada organización, pobre investigación de mercado o una estrategia mal elegida. La capacidad de identificar correctamente las capacidades del cliente, reconocer sus fortalezas y debilidades es una tarea importante para las instituciones de crédito. Por lo tanto, estos indicadores analíticos permiten evaluar objetivamente la solvencia crediticia del prestatario. Sin embargo, además del análisis de los ratios financieros, es necesario evaluar los parámetros de calidad, es decir, analizar el historial crediticio del cliente, elperíodo de su servicio en el banco, la calidad de la administración, su dependencia de los proveedores y clientes, y seguridad crediticia.O crédito na economia desempenha um papel duplo, uma vez que é uma fonte de desenvolvimento para as organizações (aquisição de ativos fixos, modernização e reconstrução da produção, lançamento de novos projetos, bem como a substituição do capital de giro) e um instrumento para a geração de renda para o banco e, em geral, sua principal atividade. Para analisar as diferenças na indústria, selecionamos 30 empresas. Com base em suas demonstrações financeiras, calculamos os índices de liquidez, a rentabilidade das vendas e o giro das contas a pagar e contas a receber. Os resultados mostraram que a confiabilidade e a estabilidade financeira dos clientes reduzem os riscos bancários, ajudando o banco a obter uma receita maior. Considera-se que o banco lida não apenas com clientes de alto nível: há também clientes entre eles que enfrentam dificuldades financeiras devido à organização inadequada da produção, pesquisa de mercado deficiente ou estratégia mal escolhida. A capacidade de identificar corretamente as capacidades do cliente, reconhecer seus pontos fortes e fracos é uma tarefa importante para as instituições de crédito. Portanto, esses indicadores analíticos permitem avaliar objetivamente a qualidade de crédito do tomador de empréstimo. No entanto, além da análise dos índices financeiros, é necessário avaliar os parâmetros de qualidade, ou seja, analisar o histórico de crédito do cliente, o período de seu atendimento no banco, a qualidade da administração, sua dependência dos fornecedores e clientes e segurança de crédito

Creation, doubling, and splitting, of vortices in intracavity second harmonic generation

We demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate, and become anisotropic, as the resonator is tuned across resonance

INNOVATIVE APPROACH IN PREPARING STUDENTS OF TECHNICAL UNIVERSITIES

В статье поднимается вопрос о специфики подхода к обучению в технических вузах с применением инновационных методик. Предложены инновационные решения, позволяющие улучшить качество образованияThe article raises the question of the specifics of the approach to training in technical universities. The proposed innovative solutions to improve the quality of educatio

Laser in the axial electric field as a tool to search for P-, T- invariance violation

We consider rotation of polarization plane of the laser light when a gas laser is placed in a longitudinal electric field (10~kV/cm). It is shown that residual anisotropy of the laser cavity 10^{-6} and the sensitivity to the angle of polarization plane rotation about 10^{-11} -10^{-12} rad allows one to measure an electron EDM with the sensitivity about 10^{-30} e cm.Comment: 12 page

Polarization-dependent transformation of a paraxial beam upon reflection and refraction: a real-space approach

We analyze the paraxial beam transformation upon reflection and refraction at a plane boundary. In contrast to the usual approach dealing with the beam angular spectrum, we apply the continuity conditions to explicit spatial representations of the electric and magnetic fields on both sides of the boundary. It is shown that the polarization-dependent distortions of the beam trajectory (in particular, the "longitudinal" Goos-H\"anchen shift and the "lateral" Imbert-Fedorov shift of the beam center of gravity) are directly connected to the incident beam longitudinal component and appear due to its transformation at the boundary.Comment: 10 pages, 1 figure. Formulae (32), (33), footnote 2 and Ref. 27 are added, some sentences are correcte

Adiabatic Theory of Electron Detachment from Negative Ions in Two-Color Laser Field

Negative ion detachment in bichromatic laser field is considered within the adiabatic theory. The latter represents a recent modification of the famous Keldysh model for multiphoton ionization which makes it quantitatively reliable. We calculate angular differential detachment rates, partial rates for particular ATD (Above Threshold Detachment) channels and total detachment rates for the Hydrogen ion in a bichromatic field with 1:3 frequency ratio and various phase differences. Reliability of the present, extremely simple approach is testified by comparison with much more elaborate earlier calculations.Comment: 22 pages, 6 Postscript figure