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1. Seamless Parametrization in Penner Coordinates

   https://doi.org/10.1145/3658202  

   Capouellez, Ryan; Zorin, Denis (July 2024, ACM Transactions on Graphics)

   We introduce a conceptually simple and efficient algorithm for seamless parametrization, a key element in constructing quad layouts and texture charts on surfaces. More specifically, we consider the construction of parametrizations with prescribedholonomy signaturesi.e., a set of angles at singularities, and rotations along homology loops, preserving which is essential for constructing parametrizations following an input field, as well as for user control of the parametrization structure. Our algorithm performs exceptionally well on a large dataset based on Thingi10k [Zhou and Jacobson 2016], (16156 meshes) as well as on a challenging smaller dataset of [Myles et al. 2014], converging, on average, in 9 iterations. Although the algorithm lacks a formal mathematical guarantee, presented empirical evidence and the connections between convex optimization and closely related algorithms, suggest that a similar formulation can be found for this algorithm in the future. 

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2. Doubly heavy baryons in Born-Oppenheimer EFT

   https://doi.org/10.1051/epjconf/202225804003  

   Tarrús Castellà, Jaume (January 2022, EPJ Web of Conferences)

   Rothkopf, A.; Brambilla, N.; Andersen, J.O.; Kurkela, A.; Röhrich, D.; Tolos, L.; Tranberg, A.; Tywoniuk, K. (Ed.)

   We report on the recent progress on the computation of the doubly heavy baryon spectrum in effective field theory. The effective field theory is built upon the heavy-quark mass and adiabatic expansions. The potentials can be expressed as NRQCD Wilson loops with operator insertions. These are nonperturbative objects and so far only the one corresponding to the static potential has been computed with lattice QCD. We review the proposal for a parametrization of the potentials based in an interpolation between the shortand long-distance regimes. The long-distance description is obtained with a newly proposed Effective String Theory which coincides with the previous ones for pure gluodynamics but it is extended to contain a fermion field. We show the doubly heavy baryon spectrum with hyperfine contributions obtained using these parametrizations for the hyperfine potentials. 

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3. Cloud-based framework for inter-comparing submesoscale-permitting realistic ocean models

   https://doi.org/10.5194/gmd-15-5829-2022  

   Uchida, Takaya; Le Sommer, Julien; Stern, Charles; Abernathey, Ryan P.; Holdgraf, Chris; Albert, Aurélie; Brodeau, Laurent; Chassignet, Eric P.; Xu, Xiaobiao; Gula, Jonathan; et al (January 2022, Geoscientific Model Development)

   Abstract. With the increase in computational power, ocean models with kilometer-scale resolution have emerged over the last decade. These models have been used for quantifying the energetic exchanges between spatial scales, informing the design of eddy parametrizations, and preparing observing networks. The increase in resolution, however, has drastically increased the size of model outputs, making it difficult to transfer and analyze the data. It remains, nonetheless, of primary importance to assess more systematically the realism of these models. Here, we showcase a cloud-based analysis framework proposed by the Pangeo project that aims to tackle such distribution and analysis challenges. We analyze the output of eight submesoscale-permitting simulations, all on the cloud, for a crossover region of the upcoming Surface Water and Ocean Topography (SWOT) altimeter mission near the Gulf Stream separation. The cloud-based analysis framework (i) minimizes the cost of duplicating and storing ghost copies of data and (ii) allows for seamless sharing of analysis results amongst collaborators. We describe the framework and provide example analyses (e.g., sea-surface height variability, submesoscale vertical buoyancy fluxes, and comparison to predictions from the mixed-layer instability parametrization). Basin- to global-scale, submesoscale-permitting models are still at their early stage of development; their cost and carbon footprints are also rather large. It would, therefore, benefit the community to document the different model configurations for future best practices. We also argue that an emphasis on data analysis strategies would be crucial for improving the models themselves. 

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4. Global perspectives of the bulk electronic structure of URu ₂ Si ₂ from angle-resolved photoemission

   https://doi.org/10.1088/2516-1075/ac4315  

   Denlinger, J. D.; Kang, J-S; Dudy, L.; Allen, J. W.; Kim, Kyoo; Shim, J-H; Haule, K.; Sarrao, J. L.; Butch, N. P.; Maple, M. B. (January 2022, Electronic Structure)

   Abstract Previous high-resolution angle-resolved photoemission (ARPES) studies of URu₂Si₂have characterized the temperature-dependent behavior of narrow-band states close to the Fermi level (E_F) at low photon energies near the zone center, with an emphasis on electronic reconstruction due to Brillouin zone folding. A substantial challenge to a proper description is that these states interact with other hole-band states that are generally absent from bulk-sensitive soft x-ray ARPES measurements. Here we provide a more globalk-space context for the presence of such states and their relation to the bulk Fermi surface (FS) topology using synchrotron-based wide-angle and photon energy-dependent ARPES mapping of the electronic structure using photon energies intermediate between the low-energy regime and the high-energy soft x-ray regime. Small-spot spatial dependence,f-resonant photoemission, Si 2pcore-levels, x-ray polarization, surface-dosing modification, and theoretical surface slab calculations are employed to assist identification of bulk versus surface state character of theE_F-crossing bands and their relation to specific U- or Si-terminations of the cleaved surface. The bulk FS topology is critically compared to density functional theory (DFT) and to dynamical mean field theory calculations. In addition to clarifying some aspects of the previously measured high symmetry Γ,ZandXpoints, incommensurate 0.6a* nested Fermi-edge states located alongZ–N–Zare found to be distinctly different from the DFT FS prediction. The temperature evolution of these states aboveT_HO, combined with a more detailed theoretical investigation of this region, suggests a key role of theN-point in the hidden order transition. 

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5. Parametrization of Fluid Models for Electrical Breakdown of Nitrogen at Atmospheric Pressure

   https://doi.org/10.3390/plasma7030037  

   Dhali, Shirshak Kumar (September 2024, Plasma)

   In the transient phase of an atmospheric pressure discharge, the avalanche turns into a streamer discharge with time. Hydrodynamic fluid models are frequently used to describe the formation and propagation of streamers, where charge particle transport is dominated by the creation of space charge. The required electron transport data and rate coefficients for the fluid model are parameterized using the local mean energy approximation (LMEA) and the local field approximation (LFA). In atmospheric pressure applications, the excited species produced in the electrical discharge determine the subsequent conversion chemistry. We performed the fluid model simulation of streamers in nitrogen gas at atmospheric pressure using three different parametrizations for transport and electron excitation rate data. We present the spatial and temporal development of several macroscopic properties such as electron density and energy, and the electric field during the transient phase. The species production efficiency, which is important to understand the efficacy of any application of non-thermal plasmas, is also obtained for the three different parametrizations. Our results suggest that at atmospheric pressure, all three schemes predicted essentially the same macroscopic properties. Therefore, a lower-order method such as LFA, which does not require the solution of the energy conservation equation, should be adequate to determine streamer macroscopic properties to inform most plasma-assisted applications of nitrogen-containing gases at atmospheric pressure. 

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