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1. Evolution of superoscillations for spinning particles

   https://doi.org/10.1090/bproc/159  

   Colombo, Fabrizio; Pozzi, Elodie; Sabadini, Irene; Wick, Brett (April 2023, Proceedings of the American Mathematical Society, Series B)

   Superoscillating functions are band-limited functions that can oscillate faster than their fastest Fourier component. These functions appear in various fields of science and technology, in particular they were discovered in quantum mechanics in the context of weak values introduced by Y. Aharonov and collaborators. The evolution problem of superoscillatory functions as initial conditions for the Schrödinger equation is intensively studied nowadays and the supershift property of the solution of Schrödinger equation encodes the persistence of superoscillatory phenomenon during the evolution. In this paper, we prove that the evolution of a superoscillatory initial datum for spinning particles in a magnetic field has the supershift property. Our techniques are based on the exact propagator of spinning particles, the associated infinite order differential operators and their continuity on suitable spaces of entire functions with growth conditions. 

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2. Physics-informed reduced-order learning from the first principles for simulation of quantum nanostructures

   https://doi.org/10.1038/s41598-023-33330-9  

   Veresko, Martin; Cheng, Ming-Cheng (April 2023, Scientific Reports)

   Abstract Multi-dimensional direct numerical simulation (DNS) of the Schrödinger equation is needed for design and analysis of quantum nanostructures that offer numerous applications in biology, medicine, materials, electronic/photonic devices, etc. In large-scale nanostructures, extensive computational effort needed in DNS may become prohibitive due to the high degrees of freedom (DoF). This study employs a physics-based reduced-order learning algorithm, enabled by the first principles, for simulation of the Schrödinger equation to achieve high accuracy and efficiency. The proposed simulation methodology is applied to investigate two quantum-dot structures; one operates under external electric field, and the other is influenced by internal potential variation with periodic boundary conditions. The former is similar to typical operations of nanoelectronic devices, and the latter is of interest to simulation and design of nanostructures and materials, such as applications of density functional theory. In each structure, cases within and beyond training conditions are examined. Using the proposed methodology, a very accurate prediction can be realized with a reduction in the DoF by more than 3 orders of magnitude and in the computational time by 2 orders, compared to DNS. An accurate prediction beyond the training conditions, including higher external field and larger internal potential in untrained quantum states, is also achieved. Comparison is also carried out between the physics-based learning and Fourier-based plane-wave approaches for a periodic case. 

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3. Towards a density functional theory of molecular fragments. What is the shape of atoms in molecules?

   https://doi.org/http://dx.doi.org/10.18257/raccefyn.960  

   Chavez, Victor; Wasserman, Adam (March 2020, Revista de la Academia Colombiana de Ciencias Exactas Físicas y Naturales)

   In some sense, quantum mechanics solves all the problems in chemistry: The only thing one has to do is solve the Schrödinger equation for the molecules of interest. Unfortunately, the computational cost of solving this equation grows exponentially with the number of electrons and for more than ~100 electrons, it is impossible to solve it with chemical accuracy (~ 2 kcal/mol). The Kohn-Sham (KS) equations of density functional theory (DFT) allow us to reformulate the Schrödinger equation using the electronic probability density as the central variable without having to calculate the Schrödinger wave functions. The cost of solving the Kohn-Sham equations grows only as N3, where N is the number of electrons, which has led to the immense popularity of DFT in chemistry. Despite this popularity, even the most sophisticated approximations in KS-DFT result in errors that limit the use of methods based exclusively on the electronic density. By using fragment densities (as opposed to total densities) as the main variables, we discuss here how new methods can be developed that scale linearly with N while providing an appealing answer to the subtitle of the article: What is the shape of atoms in molecules 

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4. Emulation of Schrödinger dynamics with metamaterials

   https://doi.org/10.1016/j.scib.2025.02.032  

   Chen, Zhao-Xian; Song, Wan-Ge; He, Guang-Chen; Zhang, Xiao-Meng; Chen, Ze-Guo; Xu, Haitan; Prodan, Emil (April 2025, Science Bulletin)

   The exploration of metamaterials with artificial sub-wavelength structures has empowered researchers to engineer the propagation of classical waves, enabling advancements in areas such as imaging, sensing, communication, and energy harvesting. Concurrently, the investigation into topology and symmetry has not only unveiled valuable insights into fundamental physics, but also expanded our ability to manipu- late waves effectively. Combined with the remarkable flexibility and diversity of artificial metamaterials, these considerations have sparked a focused research interest. Notably, a class of structures capable of supporting topological propagation modes akin to the Schrödinger equation has been identified. Leveraging metamaterials to emulate Schrödinger dynamics has emerged as a promising avenue for robust wave manipulation and the exploration of quantum phenomena beyond the confines of electronic systems. Despite rapid progress in this burgeoning field, comprehensive summaries are scarce. Thus, this review aims to systematically consolidate recent advancements in classical wave physics based on a Schrödinger equation approach. This discourse initiates with an overview of quantum and classical wave descriptions, subsequently delving into the elucidation of numerous models realized across diverse experimental platforms, including photonic/phononic waveguides, acoustic cavities, and optomechanics. Finally, we address the challenges and prospects associated with emulating Schrödinger dynamics, underscoring the potential for groundbreaking developments in this captivating domain. 

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5. IMEX Runge-Kutta Parareal for Non-diffusive Equations

   https://doi.org/10.1007/978-3-030-75933-9_5  

   Buvoli, Tommaso; Minion, Michael (August 2021, Parallel-in-Time Integration Methods)

   Ong, B.; Schroder, J.; Shipton, J.; Friedhoff, S (Ed.)

   Parareal is a widely studied parallel-in-time method that can achieve meaningful speedup on certain problems. However, it is well known that the method typically performs poorly on non-diffusive equations. This paper analyzes linear stability and convergence for IMEX Runge-Kutta Parareal methods on non-diffusive equations. By combining standard linear stability analysis with a simple convergence analysis, we find that certain Parareal configurations can achieve parallel speedup on non-diffusive equations. These stable configurations possess low iteration counts, large block sizes, and a large number of processors. Numerical examples using the nonlinear Schrödinger equation demonstrate the analytical conclusions. 

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