Boundary driven waveguide arrays: Supratransmission and saddle-node bifurcation

In this report, we consider a semi-infinite discrete nonlinear Schr\"odinger equation driven at one edge by a driving force. The equation models the dynamics of coupled waveguide arrays. When the frequency of the forcing is in the allowed-band of the system, there will be a linear transmission of energy through the lattice. Yet, if the frequency is in the upper forbidden band, then there is a critical driving amplitude for a nonlinear tunneling, which is called supratransmission, of energy to occur. Here, we discuss mathematically the mechanism and the source of the supratransmission. By analyzing the existence and the stability of the rapidly decaying static discrete solitons of the system, we show rigorously that two of the static solitons emerge and disappear in a saddle-node bifurcation at a critical driving amplitude. One of the emerging solitons is always stable in its existence region and the other is always unstable. We argue that the critical amplitude for supratransmission is then the same as the critical driving amplitude of the saddle-node bifurcation. We consider as well the case of the forcing frequency in the lower forbidden band. It is discussed briefly that there is no supratransmission because in this case there is only one rapidly decaying static soliton that exists and is stable for any driving amplitude.Comment: Some figures are removed due to file size limi

Real fermionic symmetry in type II supergravity

It is known that the transformations of fermionic T-duality, derived from the worldsheet theory, generically transform real supergravity backgrounds to complex supergravity backgrounds. We consider the low-energy target space theory and show that the type II supergravity equations admit a symmetry that transforms the Ramond-Ramond fields and the dilaton. The transformations given by this symmetry involve Killing spinors and include the transformations of Berkovits and Maldacena. However, we show that they also allow real transformations.Comment: 30 pages; added comments and references. Corrected typo

Printable Nanoscopic Metamaterial Absorbers and Images with Diffraction-Limited Resolution

The fabrication of functional metamaterials with extreme feature resolution finds a host of applications such as the broad area of surface/light interaction. Non-planar features of such structures can significantly enhance their performance and tunability, but their facile generation remains a challenge. Here, we show that carefully designed out-of-plane nanopillars made of metal-dielectric composites integrated in a metal-dielectric-nanocomposite configuration, can absorb broadband light very effectively. We further demonstrate that electrohydrodynamic printing in a rapid nanodripping mode, is able to generate precise out-of-plane forests of such composite nanopillars with deposition resolutions at the diffraction limit on flat and non-flat substrates. The nanocomposite nature of the printed material allows the fine-tuning of the overall visible light absorption from complete absorption to complete reflection by simply tuning the pillar height. Almost perfect absorption (~95%) over the entire visible spectrum is achieved by a nanopillar forest covering only 6% of the printed area. Adjusting the height of individual pillar groups by design, we demonstrate on-demand control of the gray scale of a micrograph with a spatial resolution of 400 nm. These results constitute a significant step forward in ultra-high resolution facile fabrication of out-of-plane nanostructures, important to a broad palette of light design applications. nanostructures, important to a broad palette of light design applications

Дисфемизмы в арабском и русском языках и новые аспекты их формирования (на примере современных арабских СМИ)

This article considers dysphemism as a new linguistic phenomenon in the Arabic language, the development of ways of forming dysphemistic units and the effect of psychological, sociolinguistic, and social factors on this process. Our method is intellectual and we try forming dysphemistic units develop and new aspects appear in their formation. Results showed that dysphemisms are a poorly understood language phenomenon in ancient and modern Arabic footprints.Este artículo considera el disfemismo como un nuevo fenómeno lingüístico en el idioma árabe, el desarrollo de formas de formar unidades dishemísticas y el efecto de factores psicológicos, sociolingüísticos y sociales en este proceso. Nuestro método es intelectual e intentamos formar unidades disfemísticas para desarrollar y aparecen nuevos aspectos en su formación. Los resultados mostraron que los disfemismos son un fenómeno del lenguaje poco entendido en las huellas árabes antiguas y modernas.В этой статье дисфемизм рассматривается как новое языковое явление в арабском языке, разработка способов формирования дисфемистических единиц и влияние психологических, социолингвистических и социальных факторов на этот процесс. Наш метод интеллектуален, и мы стараемся формировать дисфемистические единицы, развиваться и в их формировании появляются новые аспекты. Результаты показали, что дисфемизмы являются плохо понятым языковым явлением в древних и современных арабских следах

Measuring intergranular force in granular media

A new method is proposed to measure intergranular forces in granular geomaterial from time-lapsehigh-resolution X-ray computed tomographyimaging using a grain trackingapproachand discrete element metho