Robust moir\'e flatbands within a broad band-offset

Photonic analogs of the moir\'e superlattices mediated by interlayer electromagnetic coupling are expected to give rise to rich phenomena such as nontrivial flatband topology. Here we propose and demonstrate a scheme to tune the flatbands in a bilayer moir\'e superlattice by employing the band-offset. The band-offset is changed by fixing the bands of one slab but shifting that of the other slab, which is realized by changing the thickness of latter slab. Our results show that the band-offset tuning not only makes a few flatbands emerge and disappear, but also leads to two sets of robustly formed flatbands. These robust flatbands form either at the AA-stack site or at the AB-stack site, enabling the construction of a tunable, high-quality, and doubly-resonant single-cell superlattice. Moreover, we develop a diagrammatic model to give an intuitive insight into the formation of the robust flatbands. Our work demonstrates a simple yet efficient way to design and control complex moir\'e flatbands, providing new opportunities to utilize photonic moir\'e superlattices for advanced light-matter interaction including lasing and nonlinear harmonic generation.Comment: 5 pages, 5 figure

Phase diagram for coherent vortex formation in the two-dimensional inviscid fluid in circular geometries

We calculate the equilibrium states of a two-dimensional inviscid fluid in disk and annular geometries using the mean field equations that respect all conservation laws of the Euler equations. Axisymmetric vorticity distributions and their bifurcations to asymmetric solutions are calculated for a wide range of system parameters. Approximate zero-temperature compact vortices are also constructed and compared to symmetric states. From these results, the parameter ranges leading to the formation of a coherent vortex by the long time evolution from given initial conditions can be predicted without knowledge of the intervening dynamics. Applications to models of Jupiter’s great red spot and experiments on one-component plasmas in a magnetic field are discussed

Complete phase diagram for coherent vortex formation in a two-dimensional inviscid fluid in an annulus

By calculating the two-dimensional solutions and the second-order bifurcation analysis of the mean field equations of a two-dimensional ideal fluid, we are able to complete the phase diagram of coherent vortex formation in an annulus, which we have partially calculated in a previous paper [Phys. Rev. E 50, 2022 (1994)]. The complete phase diagram demonstrates the advantage of the statistical mechanics approach to determine the final equilibrium directly from the initial condition

Statistical two-vortex equilibrium and vortex merger

Two-vortex solutions from the mean field equations respecting all conservation laws of the Euler equations in two dimensions are calculated in a unit disk. These states are compared to symmetric and off-center single-vortex solutions. A thermodynamic stability analysis is used to determine their stability and a critical separation for stable two-vortex states is found from the crossover to instability. This could explain the merging critical ratios observed in numerical simulations and experiments

Controllable nonlinear propagation of partially incoherent Airy beams

The self-accelerating beams such as the Airy beam show great potentials in many applications including optical manipulation, imaging and communication. However, their superior features during linear propagation could be easily corrupted by optical nonlinearity or spatial incoherence individually. Here we investigate how the interaction of spatial incoherence and nonlinear propagation affect the beam quality of Airy beam, and find that the two destroying factors can in fact balance each other. Our results show that the influence of coherence and nonlinearity on the propagation of PIABs can be formulated as two exponential functions that have factors of opposite signs. With appropriate spatial coherence length, the PIABs not only resist the corruption of beam profile caused by self-focusing nonlinearity, but also exhibits less anomalous diffraction caused by the self-defocusing nonlinearity. Our work provides deep insight into how to maintain the beam quality of self-accelerating Airy beams by exploiting the interaction between partially incoherence and optical nonlinearity. Our results may bring about new possibilities for optimizing partially incoherent structured field and developing related applications such as optical communication, incoherent imaging and optical manipulations.Comment: 11pages,6 figure

Caustic analysis of partially coherent self-accelerating beams: Investigating self-healing property

We employed caustic theory to analyze the propagation dynamics of partially coherent self-accelerating beams such as self-healing of partially coherent Airy beams. Our findings revealed that as the spatial coherence decreases, the self-healing ability of beams increases. This result have been demonstrated both in simulation and experiment. This is an innovative application of the caustic theory to the field of partially coherent structured beams, and provides a comprehensive understanding of self-healing property. Our results have significant implications for practical applications of partially coherent beams in fields such as optical communication, encryption, and imaging.Comment: 9 pages, 4 figure

Non-linear Rheology of Lyotropic Lamellar Phases

この論文は国立情報学研究所の電子図書館事業により電子化されました。研究会報告スメクティック液晶やリオトロピック系のラメラ相のような一次元周期構造を有する系のレオロジーを議論する。我々は転位ループの運動が散逸に寄与すると仮定し、そのダイナミクスを考察することにより、ずり速度と応力の関係を与えるスケーリング則を導いた。さらに非イオン界面活性剤(C_E_5)水溶液におけるラメラ相のレオロジー測定を行い、理論的な予測の検証を行った。その結果、予測に近いスケーリング則を確認するとともに、ずり速度の揺らぎが平均のずり速度に比例するという興味深い現象を発見した

Spatiotemporal Scan and Age-Period-Cohort Analysis of Hepatitis C Virus in Henan, China: 2005–2012

Background: Studies have shown that hepatitis C virus (HCV) infection increased during the past decades in China. However, little evidence is available on when, where, and who were infected with HCV. There are gaps in knowledge on the epidemiological burden and evolution of the HCV epidemic in China. Methods: Data on HCV cases were collected by the disease surveillance system from 2005 to 2012 to explore the epidemic in Henan province. Spatiotemporal scan statistics and age-period-cohort (APC) model were used to examine the effects of age, period, birth cohort, and spatiotemporal clustering. Results: 177,171 HCV cases were reported in Henan province between 2005 and 2012. APC modelling showed that the HCV reported rates significantly increased in people aged > 50 years. A moderate increase in HCV reported rates was observed for females aged about 25 years. HCV reported rates increased over the study period. Infection rates were greatest among people born between 1960 and 1980. People born around 1970 had the highest relative risk of HCV infection. Women born between 1960 and 1980 had a five-fold increase in HCV infection rates compared to men, for the same birth cohort. Spatiotemporal mapping showed major clustering of cases in northern Henan, which probably evolved much earlier than other areas in the province. Conclusions: Spatiotemporal mapping and APC methods are useful to help delineate the evolution of the HCV epidemic. Birth cohort should be part of the criteria screening programmes for HCV in order to identify those at highest risk of infection and unaware of their status. As Henan is unique in the transmission route for HCV, these methods should be used in other high burden provinces to help identify subpopulations at risk