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1. Suppression of indium clustering and quantum confined stark effect of InGaN LED on silicon (111)

   https://doi.org/10.1117/12.2506426  

   Liu, Richard; McCormick, Callan; Bayram, Can (March 2019, Gallium Nitride Materials and Devices XIV)

   Optical properties of InGaN/GaN multi-quantum-well (MQWs) grown on sapphire and on Si(111) are reported. The tensile strain in the MQW on Si is shown to be beneficial for indium incorporation and Quantum-confined Stark Effect reduction in the multi-quantum wells. Raman spectroscopy reveals compressive strains of -0.107% in MQW on sapphire and tensile strain of +0.088% in MQW on Si. Temperature-dependent photoluminescence shows in MQW on sapphire a strong (30 meV peak-to-peak) S-shaped wavelength shift with decreasing temperature (6 K to 300K), whereas MQW on Si luminescence wavelength is stable and red-shifts monotonically. Micro-photoluminescence mapping over 200 by 200 μm2 shows the emission wavelength spatial uniformity of MQW on Si is 2.6 times higher than MQW on sapphire, possibly due to a more uniform indium incorporation in the multi-quantum-wells as a result of the tensile strain in MQW on Si. A positive correlation between emission energy and intensity is observed in MQW on sapphire but not in those on Si. Despite the lower crystal quality of MQW on Si revealed by atomic force microscopy, it exhibits a higher internal quantum efficiency (IQE) than MQW on sapphire from 6 K to 250 K, and equalizes at 300 K. Overall, MQW on Si exhibits a high IQE, higher wavelength spatial uniformity and temperature stability, while providing a much more scalable platform than MQW on sapphire for next generation integrated photonics. 

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2. Bergman-Harmonic Functions on Classical Domains

   https://doi.org/10.1093/imrn/rnz260  

   Xiao, Ming (December 2019, International Mathematics Research Notices)

   Abstract We study Bergman-harmonic functions on classical domains from a new point of view in this paper. We first establish a boundary pluriharmonicity result for Bergman-harmonic functions on classical domains: a Bergman-harmonic function $$u$$ on a classical domain $$D$$ must be pluriharmonic on germs of complex manifolds in the boundary of $$D$$ if $$u$$ has some appropriate boundary regularity. Next we give a new characterization of pluriharmonicity on classical domains which may shed a new light on future study of Bergman-harmonic functions. We also prove characterization results for Bergman-harmonic functions on type I domains. 

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3. 1/f noise and anomalous scaling in Lévy noise-driven on–off intermittency

   https://doi.org/10.1088/1742-5468/acac71  

   van Kan, Adrian; Pétrélis, François (January 2023, Journal of Statistical Mechanics: Theory and Experiment)

   Abstract On–off intermittency occurs in nonequilibrium physical systems close to bifurcation points, and is characterised by an aperiodic switching between a large-amplitude ‘on’ state and a small-amplitude ‘off’ state. Lévy on–off intermittency is a recently introduced generalisation of on–off intermittency to multiplicative Lévy noise, which depends on a stability parameter α and a skewness parameter β . Here, we derive two novel results on Lévy on–off intermittency by leveraging known exact results on the first-passage time statistics of Lévy flights. First, we compute anomalous critical exponents explicitly as a function of arbitrary Lévy noise parameters ( α , β ) for the first time, by a heuristic method, extending previous results. The predictions are verified using numerical solutions of the fractional Fokker–Planck equation. Second, we derive the power spectrum S ( f ) of Lévy on–off intermittency, and show that it displays a power law S ( f ) ∝ f κ at low frequencies f , where κ ∈ ( − 1 , 0 ) depends on the noise parameters α , β . An explicit expression for κ is obtained in terms of ( α , β ) . The predictions are verified using long time series realisations of Lévy on–off intermittency. Our findings help shed light on instabilities subject to non-equilibrium, power-law-distributed fluctuations, emphasizing that their properties can differ starkly from the case of Gaussian fluctuations. 

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4. Scalable Riemann Solvers with the Discontinuous Galerkin Method for Hyperbolic Network Simulation

   https://doi.org/10.1145/3592979.3593421  

   Hamilton, Aidan; Qiu, Jing-Mei; Zhang, Hong (July 2023, Platform for Advanced Scientific Computing (PASC))

   We develop a set of highly efficient and effective computational algorithms and simulation tools for fluid simulations on a network. The mathematical models are a set of hyperbolic conservation laws on edges of a network, as well as coupling conditions on junctions of a network. For example, the shallow water system, together with flux balance and continuity conditions at river intersections, model water flows on a river network. The computationally accurate and robust discontinuous Galerkin methods, coupled with explicit strong stability preserving Runge-Kutta methods, are implemented for simulations on network edges. Meanwhile, linear and nonlinear scalable Riemann solvers are being developed and implemented at network vertices. These network simulations result in tools that are added to the existing PETSc and DMNetwork software libraries for the scientific community in general. Simulation results of a shallow water system on a Mississippi river network with over one billion network variables are performed on an extreme-scale computer using up to 8,192 processor with an optimal parallel efficiency. Further potential applications include traffic flow simulations on a highway network and blood flow simulations on a arterial network, among many others. 

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5. Embeddings Among Quantum Affine sl_n

   https://doi.org/10.1007/s10114-023-2073-2  

   Li, Yi Qiang (June 2023, Acta Mathematica Sinica, English Series)

   We establish an explicit embedding of a quantum affine sl_n into a quantum affine sl_{n+1} . This embedding serves as a common generalization of two natural, but seemingly unrelated embeddings, one on the quantum affine Schur algebra level and the other on the non-quantum level. The embedding on the quantum affine Schur algebras is used extensively in the analysis of canonical bases of quantum affine sl_n and gl_n. The embedding on the non-quantum level is used crucially in a work of Riche and Williamson on the study of modular representation theory of general linear groups over a finite field. The same embedding is also used in a work of Maksimau on the categorical representations of affine general linear algebras. We further provide a more natural compatibility statement of the em- bedding on the idempotent version with that on the quantum affine Schur algebra level. A gl_n-variant of the embedding is also established. 

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