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We present and test a new numerical method to determine second-order Lagrangian displacement fields in the context of modified gravity (MG) theories. We start from the extension of Lagrangian Perturbation Theory to a class of MG models that…

Cosmology and Nongalactic Astrophysics · Physics 2020-03-04 Chiara Moretti , Simone Mozzon , Pierluigi Monaco , Emiliano Munari , Marco Baldi

A collision-based hybrid method for the discrete ordinates approximation of the multigroup neutron transport equation is developed for two-dimensional time-dependent problems. At each time step, this algorithm splits the neutron transport…

Computational Physics · Physics 2025-02-17 Ben Whewell , Ryan G. McClarren

A weighted, semi-discrete, fast optimal transport (OT) algorithm for reconstructing the Lagrangian positions of proto-halos from their evolved Eulerian positions is presented. The algorithm makes use of a mass estimate of the biased tracers…

Cosmology and Nongalactic Astrophysics · Physics 2023-01-10 Farnik Nikakhtar , Ravi K. Sheth , Bruno Lévy , Roya Mohayaee

In this work, we introduce a fast numerical algorithm to solve the time-dependent radiative transport equation (RTE). Our method uses the integral formulation of RTE and applies the treecode algorithm to reduce the computational complexity…

Numerical Analysis · Mathematics 2020-01-29 Hongkai Zhao , Yimin Zhong

In this paper, we extend the operator-split asymptotic-preserving, semi-Lagrangian algorithm for time dependent anisotropic heat transport equation proposed in [Chac\'on et al., JCP, 272, 719-746, 2014] to use a fully implicit time…

Plasma Physics · Physics 2024-04-16 O. Koshkarov , L. Chacon

We address key challenges in long-horizon embodied exploration and navigation by proposing a new object transport task and a novel modular framework for temporally extended navigation. Our first contribution is the design of a novel…

Computer Vision and Pattern Recognition · Computer Science 2022-10-31 Sriram Narayanan , Dinesh Jayaraman , Manmohan Chandraker

A significant drawback of Lagrangian (particle-tracking) reactive transport models has been their inability to properly simulate interactions between solid and liquid chemical phases, such as dissolution and precipitation reactions. This…

We consider optimal transport based distributionally robust optimization (DRO) problems with locally strongly convex transport cost functions and affine decision rules. Under conventional convexity assumptions on the underlying loss…

Optimization and Control · Mathematics 2021-04-27 Jose Blanchet , Karthyek Murthy , Fan Zhang

In this paper, a green transportation location problem is considered with uncertain demand parameter. Increasing robustness influences the number of trucks for sending goods and products, and consequently, makes the air pollution enhance.…

Optimization and Control · Mathematics 2019-01-08 Ali Rouhani , Mahdi Bashiri , Rashed Sahraeian

In this paper, a hybrid Lagrangian-Eulerian topology optimization (LETO) method is proposed to solve the elastic force equilibrium with the Material Point Method (MPM). LETO transfers density information from freely movable Lagrangian…

Computational Physics · Physics 2021-04-14 Yue Li , Xuan Li , Minchen Li , Yixin Zhu , Bo Zhu , Chenfanfu Jiang

In this work, we develop a numerically tractable trajectory optimization problem for rest-to-rest attitude transfers with CMG-driven spacecraft. First, we adapt a specialized dynamical model which avoids many of the numerical challenges…

Optimization and Control · Mathematics 2022-11-07 Thomas L. Dearing , John Hauser , Christopher Petersen , Marco M. Nicotra , Xudong Chen

Monte Carlo statistical ray-tracing methods are commonly employed to simulate carrier transport in nanostructured materials. In the case of a large degree of nanostructuring and under linear response (small driving fields), these…

Mesoscale and Nanoscale Physics · Physics 2023-02-09 Pankaj Priyadarshi , Neophytos Neophytou

A novel hybrid Monte Carlo transport scheme is demonstrated in a scene with solar illumination, scattering and absorbing 2D atmosphere, a textured reflecting mountain, and a small detector located in the sky (mounted on a satellite or a…

Mathematical Physics · Physics 2015-05-28 Guillaume Bal , Anthony Davis , Ian Langmore

For a given Lagrangian $L:[0,T]\times M\times M^\ast\rightarrow \mathbb{R}_+$ and probability measures $\mu\in\mathcal{P}(M^\ast)$, $\nu\in \mathcal{P}(M)$, we introduce the stochastic ballistic transportation problems…

Analysis of PDEs · Mathematics 2017-12-04 Alistair Barton , Nassif Ghoussoub

We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-09 Emiliano Munari , Pierluigi Monaco , Jun Koda , Francisco-Shu Kitaura , Emiliano Sefusatti , Stefano Borgani

We consider the problem of estimating parameters in large-scale weakly nonlinear inverse problems for which the underlying governing equations is a linear, time-dependent, parabolic partial differential equation. A major challenge in…

Numerical Analysis · Mathematics 2016-05-04 Tania Bakhos , Arvind K. Saibaba , Peter K. Kitanidis

Dose calculations in proton therapy require the fast and accurate solution of a high-dimensional transport equation for a large number of (pencil) beams with different energies and directions. Deterministically solving this transport…

Numerical Analysis · Mathematics 2025-08-07 Pia Stammer , Niklas Wahl , Jonas Kusch , Danny Lathouwers

A new Monte-Carlo algorithm for calculating time-dependent radiative-transfer under the assumption of LTE is presented. Unlike flux-limited diffusion the method is polychromatic, includes scattering, and is able to treat the optically thick…

Solar and Stellar Astrophysics · Physics 2015-05-28 Tim J. Harries

This paper presents hybrid numerical techniques for solving the Boltzmann transport equation formulated by means of low-order equations for angular moments of the angular flux. The moment equations are derived by the projection operator…

Numerical Analysis · Mathematics 2025-08-06 Vincent N. Novellino , Dmitriy Y. Anistratov

The development of fast numerical methods for multilevel radiative transfer (RT) applications often leads to important breakthroughs in astrophysics, because they allow the investigation of problems that could not be properly tackled using…

Astrophysics · Physics 2009-11-11 A. Asensio Ramos , J. Trujillo Bueno