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arXiv 2024年

作者： Barton, Brandon Sagal, Jacob Feeney, Sean Grattan, George Patnaik, Pratik Oganesyan, Vadim Carr, Lincoln D. Kapit, Eliot Quantum Engineering Program Colorado School of Mines 1523 Illinois St GoldenCO80401 United States Department of Applied Mathematics and Statistics Colorado School of Mines 1500 Illinois St GoldenCO80401 United States Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Department of Physics Colorado School of Mines 1523 Illinois St GoldenCO80401 United States Department of Computer Science Colorado School of Mines 1500 Illinois St GoldenCO80401 United States Department of Physics and Astronomy College of Staten Island City University of New York Staten IslandNY10314 United States Physics program and Initiative for the Theoretical Sciences The Graduate Center City University of New York New YorkNY10016 United States

In this work, we introduce a new iterative quantum algorithm, called Iterative Symphonic Tunneling for Satisfiability problems (IST-SAT), which solves quantum spin glass optimization problems using high-frequency oscillating transverse fields. IST-SAT operates as a sequence of iterations, in which bitstrings returned from one iteration are used to set spin-dependent phases in oscillating transverse fields in the next iteration. Over several iterations, the novel mechanism of the algorithm steers the system toward the problem ground state. We benchmark IST-SAT on sets of hard MAX-3-XORSAT problem instances with exact state vector simulation, and report polynomial speedups over trotterized adiabatic quantum computation (TAQC) and the best known semi-greedy classical algorithm. When IST-SAT is seeded with a sufficiently good initial approximation, the algorithm converges to exact solution(s) in a polynomial number of iterations. Our numerical results identify a critial Hamming radius(CHR), or quality of initial approximation, where the time-to-solution crosses from exponential to polynomial scaling in problem size. By combining IST-SAT with future classical or quantum approximation algorithms, larger gains may be achieved. The mechanism we present in this work thus presents a new path toward achieving quantum advantage in optimization. © 2024, CC BY.

关键词： Combinatorial optimization

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T-wave Inversion through Inhomogeneous Voltage Diffusion within the FK3V Cardiac Model

arXiv

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arXiv 2023年

作者： Angelaki, E. Lazarides, N. Barmparis, G.D. Kourakis, Ioannis Marketou, Maria E. Tsironis, G.P. Department of Physics Institute of Theoretical and Computational Physics University of Crete Heraklion Greece Harvard John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA United States Department of Mathematics Khalifa University of Science and Technology P.O. Box 127788 Abu Dhabi United Arab Emirates School of Medicine University of Crete Heraklion Greece Department of Cardiology Heraklion University Hospital Heraklion Greece

The heart beats due to the synchronized contraction of cardiomyocytes triggered by a periodic sequence of electrical signals called action potentials, which originate in the sinoatrial node and spread through the heart’s electrical system. A large body of work is devoted to modeling the propagation of the action potential and to reproducing reliably its shape and duration. Connection of computational modeling of cells to macroscopic phenomenological curves such as the electrocardiogram has been also intense, due to its clinical importance in analysing cardiovascular diseases. In this work we simulate the dynamics of action potential propagation using the three-variable Fenton-Karma model that can account for both normal and damaged cells through spatially inhomogeneous voltage diffusion coefficient. We monitor the action potential propagation in the cardiac tissue and calculate the pseudo-electrocardiogram that reproduces the R and T waves. The R wave amplitude varies according to a double exponential law as a function of the (spatially homogeneous, for an isotropic tissue) diffusion coefficient. The addition of spatial inhomogeneity in the diffusion coefficient by means of a defected region representing damaged cardiac cells, may result in T-wave inversion in the calculated pseudo-electrocardiogram. The transition from positive to negative polarity of the T-wave is analyzed as a function of the length and the depth of the defected region. © 2023, CC BY.

关键词： Electrocardiograms

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Antithetic Multilevel Methods for Elliptic and Hypo-Elliptic Diffusions with Applications

arXiv

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arXiv 2024年

作者： Iguchi, Yuga Jasra, Ajay Maama, Mohamed Beskos, Alexandros Department of Statistical Science University College London LondonWC1E 6BT United Kingdom School of Data Science The Chinese University of Hong Kong Shenzhen China Applied Mathematics and Computational Science Program Computer Electrical and Mathematical Sciences and Engineering Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia

In this paper we present a new antithetic multilevel Monte Carlo (MLMC) method for the estimation of expectations with respect to laws of diffusion processes that can be elliptic or hypo-elliptic. In particular, we consider the case where one has to resort to time discretization of the diffusion and numerical simulation of such schemes. Motivated by recent developments, we introduce a new MLMC estimator of expectations, which does not require simulation of intractable Lévy areas but has a weak error of order 2 and achieves the optimal computational complexity. We then show how this approach can be used in the context of the filtering problem associated to partially observed diffusions with discrete time observations. We illustrate with numerical simulations that our new approaches provide efficiency gains for several problems relative to some existing methods. © 2024, CC BY.

关键词： Diffusion

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Title: Robust Super-Moiré in Large Angle Single-Twist Bilayers

arXiv

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arXiv 2025年

作者： Li, Yanxing Shi, Chuqiao Zhang, Fan Liu, Xiaohui Xue, Yuan Ha, Viet-Anh Gao, Qiang Dong, Chengye Lin, Yu-Chuan Holtsman, Luke N. Morales-Durán, Nicolas Kim, Hyunsue Jiang, Yi Holbrook, Madisen Hone, James Barmak, Katayun Robinson, Joshua Li, Xiaoqin Giustino, Feliciano Khalaf, Eslam Han, Yimo Shih, Chih-Kang Department of Physics The University of Texas at Austin AustinTX United States Department of Materials Science and NanoEngineering Rice University HoustonTX United States Department of Physics Harvard University CambridgeMA United States Oden Institute for Computational Engineering and Sciences The University of Texas at Austin AustinTX United States Department of Materials Science and Engineering Pennsylvania State University University ParkPA United States Department of Materials Science and Engineering National Yang Ming Chiao Tung University Hsinchu Taiwan Department of Applied Physics and Applied Mathematics Columbia University New York CityNY United States Advanced Photon Source Argonne National Laboratory LemontIL United States Department of Mechanical Engineering Columbia University New York CityNY United States

Forming long wavelength moiré superlattices (MSL) at small-angle twist van der Waals (vdW) bilayers has been a key approach to creating moiré flat bands1–8. The small-angle twist, however, leads to strong lattice reconstruction, causing domain walls and moiré disorders, which pose considerable challenges in engineering such platforms6–10. At large twist angles, the rigid lattices render a more robust, but shorter wavelength MSL, making it difficult to engineer flat bands. Here, we depict a novel approach to tailoring robust super-moiré (SM) structures that combines the advantages of both small-twist and large-twist transition metal dichalcogenides (TMDs) bilayers using only a single twist angle near a commensurate angle. Structurally, we unveil the spontaneous formation of a periodic arrangement of three inequivalent commensurate moiré (CM) stacking, where the angle deviation from the commensurate angle can tune the periodicity. Electronically, we reveal a large set of van Hove singularities (VHSs) that indicate strong band hybridization, leading to flat bands near the valence band maximum. Our study paves the way for a new platform of robust SM bilayers with structural rigidity and controllable wavelength, extending the investigation of the interplay among band topology, quantum geometry, and moiré superconductivity to the large twist angle regime. Copyright © 2025, The Authors. All rights reserved.

关键词： Van der Waals forces

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Hyperbolic procrustes analysis using riemannian geometry 21

Hyperbolic procrustes analysis using riemannian geometry

引用

Proceedings of the 35th International Conference on Neural Information Processing Systems

作者： Ya-Wei Eileen Lin Yuval Kluger Ronen Talmon Viterbi Faculty of Electrical and Computer Engineering Technion Program in Applied Mathematics Yale University and Interdepartmental Program in Computational Biology and Bioinformatics Yale University and Department of Pathology Yale University

ISBN: (纸本)9781713845393

Label-free alignment between datasets collected at different times, locations, or by different instruments is a fundamental scientific task. Hyperbolic spaces have recently provided a fruitful foundation for the development of informative representations of hierarchical data. Here, we take a purely geometric approach for label-free alignment of hierarchical datasets and introduce hyperbolic Procrustes analysis (HPA). HPA consists of new implementations of the three prototypical Procrustes analysis components: translation, scaling, and rotation, based on the Riemannian geometry of the Lorentz model of hyperbolic space. We analyze the proposed components, highlighting their useful properties for alignment. The efficacy of HPA, its theoretical properties, stability and computational efficiency are demonstrated in simulations. In addition, we showcase its performance on three batch correction tasks involving gene expression and mass cytometry data. Specifically, we demonstrate high-quality unsupervised batch effect removal from data acquired at different sites and with different technologies that outperforms recent methods for label-free alignment in hyperbolic spaces.

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Probing the state of hydrogen in δ-AlOOH at mantle conditions with machine learning potential

arXiv

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arXiv 2023年

作者： Luo, Chenxing Sun, Yang Wentzcovitch, Renata M. Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Department of Physics and Astronomy Iowa State University AmesIA50011 United States Department of Earth and Environmental Sciences Columbia University New YorkNY10027 United States Lamont-Doherty Earth Observatory Columbia University PalisadesNY10964 United States Data Science Institute Columbia University New YorkNY10027 United States Center for Computational Quantum Physics Flatiron Institute New YorkNY10010 United States

Hydrous and nominally anhydrous minerals (NAMs) are a fundamental class of solids of enormous significance to geophysics. They are the water carriers in the deep geological water cycle and impact structural, elastic, plastic, and thermodynamic properties and phase relations in Earth's forming aggregates (rocks). They play a critical role in the geochemical and geophysical processes that shape the planet. Their complexity has prevented predictive calculations of their properties, but progress in materials simulations ushered by machine learning potentials is transforming this state of affairs. Here, we adopt a hybrid approach that combines deep learning potentials (DP) with the SCAN meta-GGA functional to simulate a prototypical hydrous system. We illustrate the success of this approach to simulate δ-AlOOH (δ), a phase capable of transporting water down to near the core-mantle boundary of the Earth (∼2,900 km depth and ∼135 GPa) in subducting slabs. A high-throughput sampling of phase space using molecular dynamics simulations with DP-potentials sheds light on the hydrogen-bond behavior and proton diffusion at geophysical conditions. These simulations provide a pathway for a deeper understanding of these crucial components that shape Earth's internal state. Copyright © 2023, The Authors. All rights reserved.

关键词： Molecular dynamics

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On the Backreaction of Dirac Matter in JT Gravity and SYK Model

arXiv

引用

arXiv 2023年

作者： Lau, Pak Hang Chris Ma, Chen-Te Murugan, Jeff Tezuka, Masaki Department of Physics Osaka University Osaka Toyonaka560-0043 Japan Department of Physics Kobe University Hyogo Kobe-shi657-8501 Japan Department of Physics and Astronomy Iowa State University AmesIA50011 United States Asia Pacific Center for Theoretical Physics Pohang University of Science and Technology Gyeongsangbuk-do Pohang37673 Korea Republic of The Laboratory for Quantum Gravity and Strings Department of Mathematics and Applied Mathematics University of Cape Town Private Bag Rondebosch7700 South Africa National Institute for Theoretical and Computational Sciences Private Bag X1 Matieland South Africa Department of Physics Kyoto University Kitashirakawa Sakyo-ku Kyoto606-8502 Japan

We model backreaction in AdS2 JT gravity via a proposed boundary dual Sachdev-Ye-Kitaev quantum dot coupled to Dirac fermion matter and study it from the perspective of quantum entanglement and chaos. The boundary effective action accounts for the backreaction through a linear coupling of the Dirac fermions to the Gaussian-random two-body Majorana interaction term in the low-energy limit. We calculate the time evolution of the entanglement entropy between graviton and Dirac fermion fields for a separable initial state and find that it initially increases and then saturates to a finite value. Moreover, in the limit of a large number of fermions, we find a maximally entangled state between the Majorana and Dirac fields in the saturation region, implying a transition of the von Neumann algebra of observables from type I to type II. This transition in turn indicates a loss of information in the holographically dual emergent spacetime. We corroborate these observations with a detailed numerical computation of the averaged nearest-neighbor gap ratio of the boundary spectrum and provide a useful complement to quantum entanglement studies of holography. Copyright © 2023, The Authors. All rights reserved.

关键词： Quantum entanglement

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Graph Neural Networks for Radiological/Nuclear Detection with Static Detector Networks

Graph Neural Networks for Radiological/Nuclear Detection wit...

引用

IEEE Symposium on Nuclear Science (NSS/MIC)

作者： M. D. Verlie D. T. Murnane A. Butko R. Cooper M. Kiran E. Rofors K. Vetter Department of Nuclear Engineering University of California Berkeley Berkeley California United Statesof America Applied Nuclear Physics Program Lawrence Berkeley National Laboratory (LBNL) Berkeley California United States of America Computational Research Division Lawrence Berkeley National Laboratory (LBNL) Berkeley California United States of America

To address the threat posed by the nefarious use of radiological/nuclear sources, there is a growing interest in deploying connected static detector networks in cities. Connected detector networks can have improved detection sensitivity over unconnected networks by using the correlations between detectors. We explore the use of graph neural networks (GNNs) to exploit such correlations in a minimal detector network of two nodes and one edge in downtown Chicago. We compare a GNN model with and without message passing, and find that the model with message passing performs significantly better (p = 0.03), suggesting that it is leveraging spatiotemporal relationships to improve detection performance. Future work includes assessing the performance of GNN models on larger detector networks and benchmarking them against existing algorithms.

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A robust alternating direction method of multipliers numerical scheme in a shape optimization setting for solving geometric inverse problems

arXiv

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arXiv 2023年

作者： Rabago, Julius Fergy Tiongson Hadri, Aissam Afraites, Lekbir Hendy, Ahmed S. Zaky, Mahmoud A. Faculty of Mathematics and Physics Institute of Science and Engineering Kanazawa University Kanazawa920-1192 Japan Université Ibn Zohr Faculté Polydisciplinaire Ouarzazate Morocco EMI FST Université Sultan Moulay Slimane Béni-Mellal Morocco Department of Computational Mathematics and Computer Science Institute of Natural Sciences and Mathematics Ural Federal University 19 Mira St. Ekaterinburg620002 Russia Department of Mathematics Faculty of Science Benha University Benha13511 Egypt Department of Mathematics and Statistics College of Science Imam Mohammad Ibn Saud Islamic University Riyadh Saudi Arabia Department of Applied Mathematics National Research Centre Dokki Cairo12622 Egypt

The alternating direction method of multipliers within a shape optimization framework is developed for solving geometric inverse problems, focusing on a cavity identification problem from the perspective of non-destructive testing and evaluation techniques. The rationale behind this method is to achieve more accurate detection of unknown inclusions with pronounced concavities, emphasizing the aspect of shape optimization. Several numerical results to illustrate the applicability and efficiency of the method are presented for various shape detection problems. These numerical experiments are conducted in both two- and three-dimensional settings, with a focus on cases involving noise-contaminated data. The main finding of the study is that the proposed method significantly outperforms conventional shape optimization methods in reconstructing unknown cavity shapes. © 2023, CC BY.

关键词： Inverse problems

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Inverted pin beams for robust long-range propagation through atmospheric turbulence

arXiv

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arXiv 2023年

作者： Droulias, Sotiris Loulakis, Michalis Papazoglou, Dimitris G. Tzortzakis, Stelios Chen, Zhigang Efremidis, Nikolaos K. Institute of Applied and Computational Mathematics FORTH Crete Heraklion70013 Greece Department of Digital Systems University of Piraeus Piraeus18534 Greece Institute of Electronic Structure and Laser Foundation for Research and Technology - Hellas P.O. Box 1527 Crete Heraklion71110 Greece Department of Materials Science and Technology University of Crete Crete Heraklion700 13 Greece MOE Key Laboratory of Weak-Light Nonlinear Photonics TEDA Applied Physics Institute School of Physics Nankai University Tianjin300457 China Collaborative Innovation Center of Extreme Optics Shanxi University Shanxi Taiyuan030006 China Department of Applied Mathematics University of Crete Heraklion71409 Greece

We introduce a new class of optical beams, which feature a spatial profile akin to an "inverted pin". In particular, we asymptotically find that close to the axis the transverse amplitude profile of such beams takes the form of a Bessel function with width that gradually increases during propagation. We examine numerically the behavior of such inverted pin beams in turbulent environments as measured via the scintillation index, and show that they outperform Gaussian beams (collimated and focused) as well as Bessel beams and regular pin beams, which are all optimized, especially in the moderate and strong fluctuation regimes. Copyright © 2023, The Authors. All rights reserved.

关键词： Gaussian beams

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