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Lagrangian duality in mixed integer optimization is a useful framework for problems decomposition and for producing tight lower bounds to the optimal objective, but in contrast to the convex counterpart, it is generally unable to produce…

Optimization and Control · Mathematics 2014-11-10 Robin Vujanic , Peyman Mohajerin Esfahani , Paul Goulart , Sebastien Mariethoz , Manfred Morari

Two triangular factorizations of the deformation gradient tensor are studied. The first, termed the Lagrangian formulation, consists of an upper-triangular stretch premultiplied by a rotation tensor. The second, termed the Eulerian…

Classical Physics · Physics 2020-03-16 Alan D. Freed , Shahla Zamani , Laszlo Szabo , John D. Clayton

We analyze an axisymmetric magnetohydrodynamics configuration, describing the morphology of a purely differentially rotating thin plasma disk, in which linear and non-linear perturbations are triggered associated with microscopic magnetic…

Solar and Stellar Astrophysics · Physics 2018-10-02 Giovanni Montani , Mariachiara Rizzo , Nakia Carlevaro

We consider nodal-based Lagrangian interpolations for the finite element approximation of the Maxwell eigenvalue problem. The first approach introduced is a standard Galerkin method on Powell-Sabin meshes, which has recently been shown to…

Numerical Analysis · Mathematics 2023-04-04 Daniele Boffi , Ramon Codina , Önder Türk

In the early stages of a protoplanetary disk, when its mass is a significant fraction of its star's, turbulence generated by gravitational instability (GI) should feature significantly in the disk's evolution. At the same time, the disk may…

Earth and Planetary Astrophysics · Physics 2020-03-25 Hongping Deng , Lucio Mayer , Henrik Latter

We present global 3D MHD simulations of geometrically thin but unstratified accretion disks in which a near Keplerian disk rotates between two bounding regions with initial rotation profiles that are stable to the MRI. The inner region…

Astrophysics · Physics 2015-05-27 Adriane Steinacker , John C. B. Papaloizou

Magnetized disk winds and wind-driven accretion are an essential and intensively studied dispersion mechanism of protoplanetary disks. However, the stability of these mechanisms has yet to be adequately examined. This paper employs…

Earth and Planetary Astrophysics · Physics 2024-07-04 Lile Wang , Sheng Xu , Zhenyu Wang , Min Fang , Jeremy Goodman

Our understanding of the process through which magnetic fields reached their observed strengths in present-day galaxies remains incomplete. One of the advocated solutions is a turbulent dynamo mechanism that rapidly amplifies weak magnetic…

Astrophysics of Galaxies · Physics 2022-05-04 Sergio Martin-Alvarez , Julien Devriendt , Adrianne Slyz , Debora Sijacki , Mark L. A. Richardson , Harley Katz

Hydrodynamic simulations of planet-disk interactions often show material accumulation near the co-orbital Lagrange points $L_4$ and $L_5$ -- features that may correspond to observed crescents in protoplanetary disks. Intriguingly, these…

Earth and Planetary Astrophysics · Physics 2025-05-14 Agustin Heron , Cristobal Petrovich , Pablo Benítez-Llambay , Juan Garrido-Deutelmoser

The magnetorotational instability (MRI) is an important process in sufficiently ionized accretion disks, as it can create turbulence that acts as an effective viscosity, mediating angular momentum transport. Due to its local nature, it is…

Earth and Planetary Astrophysics · Physics 2023-09-28 Oliver Zier , Volker Springel

The paper outlines novel variational technique for finding microstructures of optimal multimaterial composites, bounds of composites properties, and multimaterial optimal designs. The translation method that is used for the exact…

Optimization and Control · Mathematics 2014-03-10 Andrej Cherkaev

A Lagrangian numerical scheme for solving nonlinear degenerate Fokker-Planck equations in space dimensions $d\ge2$ is presented. It applies to a large class of nonlinear diffusion equations, whose dynamics are driven by internal energies…

Numerical Analysis · Mathematics 2018-06-18 José A. Carrillo , Bertram Düring , Daniel Matthes , David S. McCormick

We propose two closely--related Lagrangian numerical methods for the simulation of physical processes involving advection, reaction and diffusion. The methods are intended to be used in settings where the flow is nearly incompressible and…

Computational Physics · Physics 2018-03-14 Francesco Paparella , Marina Popolizio

Recently, we developed a pair of meshless finite-volume Lagrangian methods for hydrodynamics: the 'meshless finite mass' (MFM) and 'meshless finite volume' (MFV) methods. These capture advantages of both smoothed-particle hydrodynamics…

Instrumentation and Methods for Astrophysics · Physics 2015-12-15 Philip F. Hopkins , Matthias J. Raives

This review article summarizes two decades of laboratory research aimed at understanding the dynamics of accretion disks, with particular emphasis on magnetohydrodynamic experiments involving liquid metals and plasmas. First, the…

Solar and Stellar Astrophysics · Physics 2024-12-18 Christophe Gissinger

This paper presents numerical simulations of metal machining processes with Eulerian and Total Lagrangian Smoothed Particle Hydrodynamics (SPH). Being a mesh-free method, SPH can conveniently handle large deformation and material…

Computational Engineering, Finance, and Science · Computer Science 2019-04-05 Md Rushdie Ibne Islam , Ankur Bansal , Chong Peng

For integrable systems in the sense of multidimensional consistency (MDC) we can consider the Lagrangian as a form, which is closed on solutions of the equations of motion. For 2-dimensional systems, described by partial difference…

Exactly Solvable and Integrable Systems · Physics 2018-05-04 Sarah B. Lobb , Frank W. Nijhoff

Global disk simulations provide a powerful tool for investigating accretion and the underlying magnetohydrodynamic turbulence driven by the magneto-rotational instability (MRI). Using them to predict accurately quantities such as stress,…

Instrumentation and Methods for Astrophysics · Physics 2015-06-16 John F. Hawley , Sherwood A. Richers , Xiaoyue Guan , Julian H. Krolik

A unified, Bayesian inference of midplane electron temperature and density profiles using both Thompson scattering (TS) and interferometric data is presented. Beyond the Bayesian nature of the analysis, novel features of the inference are…

Plasma Physics · Physics 2015-06-12 G. T. von Nessi , M. J. Hole

Mechanical contact between solids is almost exclusively modeled in Lagrangian frameworks. While these frameworks have been developed extensively and applied successfully to numerous contact problems, they generally require complex…

Soft Condensed Matter · Physics 2024-12-20 Flavio Lorez , Mohit Pundir , David S. Kammer