Density Transport
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Related Articles from SNS
Reinforcement Learning for Flow-Matching Policies with Density Transport
Announce Type: new Abstract: We present an online reinforcement learning (RL) algorithm for fine-tuning flow-matching policies in continuous-control problems. Our key insight is to view RL-based policy improvement as a transport of action densities towards regions of high reward, which naturally aligns with the transport formulation of flow matching models. Prior methods either approximate the current or optimal policy distribution or resort to distillation, which introduces biased gradients...
A prognostic human brain network for diffuse midline glioma
Abstract Diffuse midline gliomas (DMGs) are near-universally lethal tumours of the childhood central nervous system1,2. In animal models, DMGs form brain-wide integrated networks through neuron-to-glioma synapses3,4,5,6 and glioma-to-glioma gap junctional coupling3. This extensive connectivity robustly promotes the growth and invasion of DMG3,4,5,6,7,8,9 and other glial malignancies10,11,12 through paracrine mechanisms and direct neuron-to-glioma synapses.
Conservative Charge and Current Deposition on Nonuniform 3D Cylindrical PIC Meshes with Residual Self-Field Diagnostics
arXiv:2606.09168v1 Announce Type: new Abstract: Particle-in-cell simulations on nonuniform cylindrical meshes require deposition schemes that respect cylindrical metrics while controlling numerical self-fields. This work develops cylindrical-volume-weighted charge and current deposition using nodal control volumes and swept-volume factors on logically structured stretched grids. Uniform-density and controlled-transport tests demonstrate accurate charge recovery, well-controlled...
Physics-Informed Modeling and Control of Emergent Behaviors in Robot Swarms
arXiv:2606.01597v1 Announce Type: new Abstract: Robot swarms can exhibit coherent collective behaviors through local perception, limited communication and decentralized decision-making, yet modeling and controlling such emergence remains challenging when behaviors unfold over multiple phases. Here we introduce PhySwarm, a physics-informed micro--macro framework that represents multi-stage swarm emergence as physically constrained density-field evolution coupled to executable robot motion. At...
Hidden meltwater found deep in Antarctic coastal waters reveals stronger climate impacts
June 5, 2026 feature Hidden meltwater found deep in Antarctic coastal waters reveals stronger climate impacts Hannah Bird Author Gaby Clark Scientific Editor Robert Egan Associate Editor Freshwater from melting Antarctic glaciers may be influencing the Southern Ocean in ways scientists have largely overlooked. New research, published in Frontiers in Marine Science, has found that glacial meltwater is not confined to the ocean's surface, as previously assumed, but can also be detected much...
Conservative Discrete Structure Stabilizes Autoregressive Rollouts in a 1D Drift Diffusion Poisson Benchmark
arXiv:2606.01366v1 Announce Type: cross Abstract: Learned plasma transport surrogates can match short horizon states while failing over long rollouts because charge accounting, density admissibility, and Poisson compatible field reconstruction are not enforced. We study this issue in a controlled nondimensional one dimensional drift diffusion Poisson benchmark with Dirichlet electrostatic potential boundaries and zero species wall fluxes. The benchmark is a conservation and rollout test, not...
Conservative Discrete Structure Stabilizes Autoregressive Rollouts in a 1D Drift Diffusion Poisson Benchmark
arXiv:2606.01366v1 Announce Type: new Abstract: Learned plasma transport surrogates can match short horizon states while failing over long rollouts because charge accounting, density admissibility, and Poisson compatible field reconstruction are not enforced. We study this issue in a controlled nondimensional one dimensional drift diffusion Poisson benchmark with Dirichlet electrostatic potential boundaries and zero species wall fluxes. The benchmark is a conservation and rollout test, not a...
Sharp-interface Simulations of Energetic Multiphase Flows with Large Density and Viscosity Ratios
arXiv:2606.02467v1 Announce Type: new Abstract: Flows with high density ratios, such as wave breaking and air entrainment in maritime applications, remain challenging to simulate due to their energetic and strongly nonlinear nature. In such regimes, maintaining numerical robustness is difficult when using the commonly adopted velocity-based formulation. The Consistent Mass-Momentum (CMOM) transport framework improves numerical robustness by enforcing fundamental physical properties, most...
Bridged SBI: Correcting Biased Low-Fidelity Posteriors for Cost-Efficient High-Fidelity Inference
arXiv:2606.09155v1 Announce Type: new Abstract: Accurate calibration of particle-based simulators is crucial for robotic earthwork simulation, but analytical calibration is challenging due to this task's highly nonlinear particle dynamics and the black-box nature of conventional simulators. Although simulation-based inference (SBI) can estimate posterior distributions over simulation parameters solely from forward simulations, applying SBI directly to high-fidelity (HF) particle simulators...
Meltwater transport and mixing layer growth near the ice--ocean interface
Announce Type: replace Abstract: Ice melting into saline water plays a fundamental role in the dynamics near the ice-ocean interface in polar oceans. The physics of ice melting involves a non-trivial interplay between thermodynamics at the interface, hydrodynamic transport in the bulk and the properties of the ambient ocean. The key control parameters are the density ratio $R_\rho$ proportional to the ambient ocean salinity and the Lewis number $Le = \kappa_T/\kappa_S$, which compares the...