Clay weekly context brief for the Physics category (ISO week 2026-W28). Clay tracks publications from the Physics feed list. Below are recent items from this category, each with its source and a short description of what the publication covers when one is available in the source feed. Recent publications: 1. Defect Localization by Vanishing Deviatoric Stress in Active Nematics Source: physics.flu-dyn (Fluid Dynamics) Link: https://arxiv.org/abs/2606.17595 Collective stress generation in cellular monolayers is a key phenomenological process governing coordinated migration and emergent multicellular dynamics. 2. Verification of the Outer Space Treaty with Cosmic Protons Source: physics.soc-ph (Physics and Society) Link: https://arxiv.org/abs/2512.20016 The Outer Space Treaty (OST) was opened to signatures in 1967, and since then 117 countries, including China, the United States, Russia, have become part of it. 3. Global Magnetohydrodynamic Simulations of Monster Shocks in Neutron Star Magnetospheres Source: physics.plasm-ph (Plasma Physics) Link: https://arxiv.org/abs/2602.21290 Waves launched from the neutron star surface or inner magnetosphere propagate through the magnetosphere as small perturbations, but can grow relative to the background magnetic field and steepen into ``monster shocks'' -- ultra-relativistic magnetized shocks which can power high-energy emission. 4. Plasma-state metasurfaces for ultra-intensive field manipulation Source: physics.optics (Optics) Link: https://arxiv.org/abs/2505.15567 High-power lasers offer ultrahigh intensities for plasma interactions, but they lack advanced techniques to control the properties of the fields, because no optical elements could withstand their high intensities. 5. Variational matrix product states for combinatorial optimization Source: physics.comp-ph (Computational Physics) Link: https://arxiv.org/abs/2512.20613 To compute approximate solutions for combinatorial optimization problems, we describe variational methods based on the product state (PS) and matrix product state (MPS) ans\"{a}tze. 6. An advanced undergraduate derivation of acceleration thermality Source: physics.class-ph (Classical Physics) Link: https://arxiv.org/abs/2607.08184 The thermal radioactivity of beta-decay photons, described by a 1D Planck distribution, can be modeled as classical radiation emitted by an accelerated electron. 7. Autonomous heterogeneous catalyst discovery with a self-evolving multi-agent digital twin Source: physics.chem-ph (Chemical Physics) Link: https://arxiv.org/abs/2606.05050 Theoretical heterogeneous catalysis promises rapid catalyst discovery, yet computational and machine-learning predictions often deviate from experiment and stay confined to narrow material families, for want of a faithful, condition-aware catalytic simulator. 8. Amplification at Equilibrium: Structural and Thermodynamic Limitations, and Implementation Source: physics.bio-ph (Biological Physics) Link: https://arxiv.org/abs/2604.04285 Amplifying weak molecular signals is essential in both natural and engineered biochemical systems. 9. Broadband Rydberg Atomic Microwave Sensing with 44.6$\,$MHz Instantaneous Bandwidth Source: physics.atom-ph (Atomic Physics) Link: https://arxiv.org/abs/2606.25555 Rydberg atoms have become a promising novel type of microwave sensor due to their excellent physical properties -- broad frequency coverage and large electric dipole moments. 10. Understanding surface potential dynamics of passivated perovskites via Kelvin Probe Force Microscopy Source: physics.app-ph (Applied Physics) Link: https://arxiv.org/abs/2607.07221 Molecular passivation has become central to reducing photovoltage losses in metal-halide perovskite solar cells, but its electronic action is still often inferred from device-level metrics rather than directly resolved at the nanoscale. 11. Evaluating the Generalizability of Foundation Models for Extreme Environmental Events: Case Study of California Wildfire PM2.5 Source: physics.ao-ph (Atmospheric and Oceanic Physics) Link: https://arxiv.org/abs/2607.07951 Wildfire smoke events produce extreme PM$_{2.5}$ concentrations that pose severe public health risks, yet forecasting rare, hazardous-level spikes remains a fundamental challenge. 12. Development of a Silicon-Based Ultra-Fast X-Ray Beam Size Monitor for SuperKEKB Source: physics.acc-ph (Accelerator Physics) Link: https://arxiv.org/abs/2607.08205 We present the development of a silicon-based ultra-fast X-ray beam size monitor (SiXRM) for SuperKEKB. 13. Approaching the optimal closure: equivariance, inductive bias, and Reynolds-number generalization in data-driven LES Source: physics.flu-dyn (Fluid Dynamics) Link: https://arxiv.org/abs/2603.05325 Data-driven closures for large-eddy simulation (LES) are commonly built to respect the symmetries of the Navier--Stokes equations, on the premise that this improves accuracy and generalization. 14. Using covariance of node states to design early warning signals for network dynamics Source: physics.soc-ph (Physics and Society) Link: https://arxiv.org/abs/2505.15982 Real-life systems often experience regime shifts. 15. The gravitational stratification of multifluid and multispecies plasma Source: physics.plasm-ph (Plasma Physics) Link: https://arxiv.org/abs/2601.05321 Context. 16. Inverse-designed release-free optomechanical crystal with high photon-phonon coupling Source: physics.optics (Optics) Link: https://arxiv.org/abs/2605.03910 Interactions between light and mechanics provide a powerful interface between optical and microwave-frequency signals, with applications spanning classical signal processing and quantum technologies. 17. Scaling WaterLily.jl with MPI and an improved geometric multigrid solver Source: physics.comp-ph (Computational Physics) Link: https://arxiv.org/abs/2607.07687 We present recent performance-oriented developments in WaterLily, a scale-resolving incompressible flow solver written in pure Julia that runs seamlessly on CPUs and GPUs of any vendor. 18. Economised path integrals Source: physics.chem-ph (Chemical Physics) Link: https://arxiv.org/abs/2607.06414 The Hessian of the ring polymer spring potential in the standard Trotter path integral is a $P\times P$ symmetric circulant matrix with a centroid eigenvalue of zero. 19. A stochastic agent-based extension of the GSM2 model for particle therapy: cell-cycle dynamics, dose-rate dependence, and fractionation effects Source: physics.bio-ph (Biological Physics) Link: https://arxiv.org/abs/2604.27630 Accurately linking microscopic energy deposition from ionizing radiation to emergent biological outcomes remains a central challenge in radiobiological modelling, particularly when stochastic damage induction, cell-cycle dynamics, and spatial organisation within irradiated tissues must be treated explicitly and consistently across scales. 20. Determination of atomic number density in MEMS vapor cells via single-pass absorption spectroscopy (SPAS) Source: physics.atom-ph (Atomic Physics) Link: https://arxiv.org/abs/2511.00526 Micro-electro-mechanical systems (MEMS)-based (chip-scale) alkali vapor cells are key components in emerging quantum technologies, where device performance critically depends on the atomic number density. 21. Spatiotemporal Optical Vortices From All-Dielectric Bilayer Metagratings Source: physics.app-ph (Applied Physics) Link: https://arxiv.org/abs/2603.02837 Spatiotemporal optical vortices (STOVs) carry transverse orbital angular momentum within the space-time domain, rendering them powerful tools for constructing high-dimensional and quantum optical fields. Sources in this brief: physics.acc-ph (Accelerator Physics); physics.ao-ph (Atmospheric and Oceanic Physics); physics.app-ph (Applied Physics); physics.atom-ph (Atomic Physics); physics.bio-ph (Biological Physics); physics.chem-ph (Chemical Physics); physics.class-ph (Classical Physics); physics.comp-ph (Computational Physics); physics.flu-dyn (Fluid Dynamics); physics.optics (Optics); physics.plasm-ph (Plasma Physics); physics.soc-ph (Physics and Society). Selected 21 of 85 available items for this weekly brief.