{"title":"Multisymplecticity in finite element exterior calculus","authors":"Ari Stern, Enrico Zampa","doi":"arxiv-2312.03657","DOIUrl":"https://doi.org/arxiv-2312.03657","url":null,"abstract":"We consider the application of finite element exterior calculus (FEEC)\u0000methods to a class of canonical Hamiltonian PDE systems involving differential\u0000forms. Solutions to these systems satisfy a local multisymplectic conservation\u0000law, which generalizes the more familiar symplectic conservation law for\u0000Hamiltonian systems of ODEs, and which is connected with physically-important\u0000reciprocity phenomena, such as Lorentz reciprocity in electromagnetics. We\u0000characterize hybrid FEEC methods whose numerical traces satisfy a version of\u0000the multisymplectic conservation law, and we apply this characterization to\u0000several specific classes of FEEC methods, including conforming\u0000Arnold-Falk-Winther-type methods and various hybridizable discontinuous\u0000Galerkin (HDG) methods. Interestingly, the HDG-type and other nonconforming\u0000methods are shown, in general, to be multisymplectic in a stronger sense than\u0000the conforming FEEC methods. This substantially generalizes previous work of\u0000McLachlan and Stern [Found. Comput. Math., 20 (2020), pp. 35-69] on the more\u0000restricted class of canonical Hamiltonian PDEs in the de Donder-Weyl \"grad-div\"\u0000form.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138553686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Energy-consistent integration of mechanical systems based on Livens principle","authors":"Philipp L. Kinon, Peter Betsch","doi":"arxiv-2312.02825","DOIUrl":"https://doi.org/arxiv-2312.02825","url":null,"abstract":"In this work we make us of Livens principle (sometimes also referred to as\u0000Hamilton-Pontryagin principle) in order to obtain a novel structure-preserving\u0000integrator for mechanical systems. In contrast to the canonical Hamiltonian\u0000equations of motion, the Euler-Lagrange equations pertaining to Livens\u0000principle circumvent the need to invert the mass matrix. This is an essential\u0000advantage with respect to singular mass matrices, which can yield severe\u0000difficulties for the modelling and simulation of multibody systems. Moreover,\u0000Livens principle unifies both Lagrangian and Hamiltonian viewpoints on\u0000mechanics. Additionally, the present framework avoids the need to set up the\u0000system's Hamiltonian. The novel scheme algorithmically conserves a general\u0000energy function and aims at the preservation of momentum maps corresponding to\u0000symmetries of the system. We present an extension to mechanical systems subject\u0000to holonomic constraints. The performance of the newly devised method is\u0000studied in representative examples.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alina Chertock, Alexander Kurganov, Michael Redle, Vladimir Zeitlin
{"title":"Divergence-Free Flux Globalization Based Well-Balanced Path-Conservative Central-Upwind Schemes for Rotating Shallow Water Magnetohydrodynamics","authors":"Alina Chertock, Alexander Kurganov, Michael Redle, Vladimir Zeitlin","doi":"arxiv-2312.02881","DOIUrl":"https://doi.org/arxiv-2312.02881","url":null,"abstract":"We develop a new second-order flux globalization based path-conservative\u0000central-upwind (PCCU) scheme for rotating shallow water magnetohydrodynamic\u0000equations. The new scheme is designed not only to maintain the divergence-free\u0000constraint of the magnetic field at the discrete level but also to satisfy the\u0000well-balanced (WB) property by exactly preserving some physically relevant\u0000steady states of the underlying system. The locally divergence-free constraint\u0000of the magnetic field is enforced by following the method recently introduced\u0000in [A. Chertock, A. Kurganov, M. Redle, and K. Wu, ArXiv preprint (2022),\u0000arXiv:2212.02682]: we consider a Godunov-Powell modified version of the studied\u0000system, introduce additional equations by spatially differentiating the\u0000magnetic field equations, and modify the reconstruction procedures for magnetic\u0000field variables. The WB property is ensured by implementing a flux\u0000globalization approach within the PCCU scheme, leading to a method capable of\u0000preserving both still- and moving-water equilibria exactly. In addition to\u0000provably achieving both the WB and divergence-free properties, the new method\u0000is implemented on an unstaggered grid and does not require any (approximate)\u0000Riemann problem solvers. The performance of the proposed method is demonstrated\u0000in several numerical experiments that confirm the lack of spurious\u0000oscillations, robustness, and high resolution of the obtained results.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Japan K. Patel, Barry D. Ganapol, Martha M. Matuszak
{"title":"Assessing Nonlinear Diffusion Acceleration for Boltzmann Fokker Planck Equation in Slab Geometry","authors":"Japan K. Patel, Barry D. Ganapol, Martha M. Matuszak","doi":"arxiv-2312.02930","DOIUrl":"https://doi.org/arxiv-2312.02930","url":null,"abstract":"The convergence of Boltzmann Fokker Planck solution can become arbitrarily\u0000slow with iterative procedures like source iteration. This paper derives and\u0000investigates a nonlinear diffusion acceleration scheme for the solution of the\u0000Boltzmann Fokker Planck equation in slab geometry. This method is a\u0000conventional high order low order scheme with a traditional\u0000diffusion-plus-drift low-order system. The method, however, differs from the\u0000earlier variants as the definition of the low order equation, which is adjusted\u0000according to the zeroth and first moments of the Boltzmann Fokker Planck\u0000equation. For the problems considered, we observe that the NDA-accelerated\u0000solution follows the unaccelerated well and provides roughly an order of\u0000magnitude savings in iteration count and runtime compared to source iteration.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Inexact linear solves in the low-rank ADI iteration for large Sylvester equations","authors":"Patrick Kürschner","doi":"arxiv-2312.02891","DOIUrl":"https://doi.org/arxiv-2312.02891","url":null,"abstract":"We consider the low-rank alternating directions implicit (ADI) iteration for\u0000approximately solving large-scale algebraic Sylvester equations. Inside every\u0000iteration step of this iterative process a pair of linear systems of equations\u0000has to be solved. We investigate the situation when those inner linear systems\u0000are solved inexactly by an iterative methods such as, for example,\u0000preconditioned Krylov subspace methods. The main contribution of this work are\u0000thresholds for the required accuracies regarding the inner linear systems which\u0000dictate when the employed inner Krylov subspace methods can be safely\u0000terminated. The goal is to save computational effort by solving the inner\u0000linear system as inaccurate as possible without endangering the functionality\u0000of the low-rank Sylvester-ADI method. Ideally, the inexact ADI method mimics\u0000the convergence behaviour of the more expensive exact ADI method, where the\u0000linear systems are solved directly. Alongside the theoretical results, also\u0000strategies for an actual practical implementation of the stopping criteria are\u0000developed. Numerical experiments confirm the effectiveness of the proposed\u0000strategies.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Higher-order FEM and CIP-FEM for Helmholtz equation with high wave number and perfectly matched layer truncation","authors":"Yonglin Li, Haijun Wu","doi":"arxiv-2312.02476","DOIUrl":"https://doi.org/arxiv-2312.02476","url":null,"abstract":"The high-frequency Helmholtz equation on the entire space is truncated into a\u0000bounded domain using the perfectly matched layer (PML) technique and\u0000subsequently, discretized by the higher-order finite element method (FEM) and\u0000the continuous interior penalty finite element method (CIP-FEM). By formulating\u0000an elliptic problem involving a linear combination of a finite number of\u0000eigenfunctions related to the PML differential operator, a wave-number-explicit\u0000decomposition lemma is proved for the PML problem, which implies that the PML\u0000solution can be decomposed into a non-oscillating elliptic part and an\u0000oscillating but analytic part. The preasymptotic error estimates in the energy\u0000norm for both the $p$-th order CIP-FEM and FEM are proved to be $C_1(kh)^p +\u0000C_2k(kh)^{2p} +C_3 E^{rm PML}$ under the mesh condition that $k^{2p+1}h^{2p}$\u0000is sufficiently small, where $k$ is the wave number, $h$ is the mesh size, and\u0000$E^{rm PML}$ is the PML truncation error which is exponentially small. In\u0000particular, the dependences of coefficients $C_j~(j=1,2)$ on the source $f$ are\u0000improved. Numerical experiments are presented to validate the theoretical\u0000findings, illustrating that the higher-order CIP-FEM can greatly reduce the\u0000pollution errors.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carles Domingo-Enrich, Jiequn Han, Brandon Amos, Joan Bruna, Ricky T. Q. Chen
{"title":"Stochastic Optimal Control Matching","authors":"Carles Domingo-Enrich, Jiequn Han, Brandon Amos, Joan Bruna, Ricky T. Q. Chen","doi":"arxiv-2312.02027","DOIUrl":"https://doi.org/arxiv-2312.02027","url":null,"abstract":"Stochastic optimal control, which has the goal of driving the behavior of\u0000noisy systems, is broadly applicable in science, engineering and artificial\u0000intelligence. Our work introduces Stochastic Optimal Control Matching (SOCM), a\u0000novel Iterative Diffusion Optimization (IDO) technique for stochastic optimal\u0000control that stems from the same philosophy as the conditional score matching\u0000loss for diffusion models. That is, the control is learned via a least squares\u0000problem by trying to fit a matching vector field. The training loss, which is\u0000closely connected to the cross-entropy loss, is optimized with respect to both\u0000the control function and a family of reparameterization matrices which appear\u0000in the matching vector field. The optimization with respect to the\u0000reparameterization matrices aims at minimizing the variance of the matching\u0000vector field. Experimentally, our algorithm achieves lower error than all the\u0000existing IDO techniques for stochastic optimal control for four different\u0000control settings. The key idea underlying SOCM is the path-wise\u0000reparameterization trick, a novel technique that is of independent interest,\u0000e.g., for generative modeling.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Coverage Explorer: Coverage-guided Test Generation for Cyber Physical Systems","authors":"Sanaz Sheikhi, Stanley Bak","doi":"arxiv-2312.02313","DOIUrl":"https://doi.org/arxiv-2312.02313","url":null,"abstract":"Given the safety-critical functions of autonomous cyber-physical systems\u0000(CPS) across diverse domains, testing these systems is essential. While\u0000conventional software and hardware testing methodologies offer partial\u0000insights, they frequently do not provide adequate coverage in a CPS. In this\u0000study, we introduce a testing framework designed to systematically formulate\u0000test cases, effectively exploring the state space of CPS. This framework\u0000introduces a coverage-centric sampling technique, coupled with a cluster-based\u0000methodology for training a surrogate model. The framework then uses model\u0000predictive control within the surrogate model to generates test cases tailored\u0000to CPS specifications. To evaluate the efficacy of the framework, we applied it\u0000on several benchmarks, spanning from a kinematic car to systems like an\u0000unmanned aircraft collision avoidance system (ACAS XU) and automatic\u0000transmission system. Comparative analyses were conducted against alternative\u0000test generation strategies, including randomized testing, as well as\u0000falsification using S-TaLiRo.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Axisymmetric Virtual Elements For Problems of Elasticity and Plasticity","authors":"Louie L. Yaw","doi":"arxiv-2312.01559","DOIUrl":"https://doi.org/arxiv-2312.01559","url":null,"abstract":"The virtual element method (VEM) allows discretization of elasticity and\u0000plasticity problems with polygons in 2D and polyhedrals in 3D. The polygons\u0000(and polyhedrals) can have an arbitrary number of sides and can be concave or\u0000convex. These features, among others, are attractive for meshing complex\u0000geometries. However, to the author's knowledge axisymmetric virtual elements\u0000have not appeared before in the literature. Hence, in this work a novel first\u0000order consistent axisymmetric virtual element method is applied to problems of\u0000elasticity and plasticity. The VEM specific implementation details and\u0000adjustments needed to solve axisymmetric simulations are presented.\u0000Representative benchmark problems including pressure vessels and circular\u0000plates are illustrated. Examples also show that problems of near\u0000incompressibility are solved successfully. Consequently, this research\u0000demonstrates that the axisymmetric VEM formulation successfully solves certain\u0000classes of solid mechanics problems. The work concludes with a discussion of\u0000results for the current formulation and future research directions.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Patrick Buchfink, Silke Glas, Bernard Haasdonk, Benjamin Unger
{"title":"Model Reduction on Manifolds: A differential geometric framework","authors":"Patrick Buchfink, Silke Glas, Bernard Haasdonk, Benjamin Unger","doi":"arxiv-2312.01963","DOIUrl":"https://doi.org/arxiv-2312.01963","url":null,"abstract":"Using nonlinear projections and preserving structure in model order reduction\u0000(MOR) are currently active research fields. In this paper, we provide a novel\u0000differential geometric framework for model reduction on smooth manifolds, which\u0000emphasizes the geometric nature of the objects involved. The crucial ingredient\u0000is the construction of an embedding for the low-dimensional submanifold and a\u0000compatible reduction map, for which we discuss several options. Our general\u0000framework allows capturing and generalizing several existing MOR techniques,\u0000such as structure preservation for Lagrangian- or Hamiltonian dynamics, and\u0000using nonlinear projections that are, for instance, relevant in\u0000transport-dominated problems. The joint abstraction can be used to derive\u0000shared theoretical properties for different methods, such as an exact\u0000reproduction result. To connect our framework to existing work in the field, we\u0000demonstrate that various techniques for data-driven construction of nonlinear\u0000projections can be included in our framework.","PeriodicalId":501061,"journal":{"name":"arXiv - CS - Numerical Analysis","volume":" 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138494238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}