Counterflow around a cylinder
Matheus P. Severino, Leandro F. Souza, Elmer M. Gennaro, Daniel Rodr\'iguez, Fernando F. Fachini
https://arxiv.org/abs/2602.22022 https://arxiv.org/pdf/2602.22022 https://arxiv.org/html/2602.22022
arXiv:2602.22022v1 Announce Type: new
Abstract: The incompressible flow around a circular cylinder, positioned at the center of an unconfined planar counterflow, is studied by means of numerical solutions of the conservation equations and linear stability analysis. The flow is completely defined by the Reynolds number ($\Rey$) -- based on the cylinder radius, the strain rate defining the counterflow, and the kinematic viscosity. For very low values of $\Rey$, the flow is steady, two-dimensional, and fully attached to the cylinder wall. Increasing $\Rey$ above $\Rey_s \approx 16.86$, the flow separates, giving rise to two symmetric, counter-rotating recirculation regions on each side of the cylinder. Further increasing $\Rey$ leads to a progressive enlargement of the recirculation regions and the appearance of multiple recirculation centers, akin to Moffatt eddies. However, the convective acceleration imposed by the counterflow limits their size. An oscillatory mode becomes linearly unstable for $\Rey_{c} \approx 4146$. This mode gives rise to a sinuous meandering of the wake flow, on each side of the cylinder, being analogous to the well-known von K\'arm\'an instability. The frequency of this mode is directly proportional to the strain rate defining the counterflow.
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Spectroscopy of $^4$He at 0.25 ppt Uncertainty and Improved Alpha-Helion Charge-Radius Difference Determination
K. Steinebach, J. C. J. Koelemeij, H. L. Bethlem, K. S. E. Eikema
https://arxiv.org/abs/2601.19444
Does Order Matter : Connecting The Law of Robustness to Robust Generalization
Himadri Mandal, Vishnu Varadarajan, Jaee Ponde, Aritra Das, Mihir More, Debayan Gupta
https://arxiv.org/abs/2602.20971 https://arxiv.org/pdf/2602.20971 https://arxiv.org/html/2602.20971
arXiv:2602.20971v1 Announce Type: new
Abstract: Bubeck and Sellke (2021) pose as an open problem the connection between the law of robustness and robust generalization. The law of robustness states that overparameterization is necessary for models to interpolate robustly; in particular, robust interpolation requires the learned function to be Lipschitz. Robust generalization asks whether small robust training loss implies small robust test loss. We resolve this problem by explicitly connecting the two for arbitrary data distributions. Specifically, we introduce a nontrivial notion of robust generalization error and convert it into a lower bound on the expected Rademacher complexity of the induced robust loss class. Our bounds recover the $\Omega(n^{1/d})$ regime of Wu et al.\ (2023) and show that, up to constants, robust generalization does not change the order of the Lipschitz constant required for smooth interpolation. We conduct experiments to probe the predicted scaling with dataset size and model capacity, testing whether empirical behavior aligns more closely with the predictions of Bubeck and Sellke (2021) or Wu et al.\ (2023). For MNIST, we find that the lower-bound Lipschitz constant scales on the order predicted by Wu et al.\ (2023). Informally, to obtain low robust generalization error, the Lipschitz constant must lie in a range that we bound, and the allowable perturbation radius is linked to the Lipschitz scale.
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FLUKA-Based Optimization of Muon Production Target Design for a Muon Collider Demonstrator
Ruaa Al-Harthy
https://arxiv.org/abs/2602.16672 https://arxiv.org/pdf/2602.16672 https://arxiv.org/html/2602.16672
arXiv:2602.16672v1 Announce Type: new
Abstract: This study investigates how target geometry and material influence pion and muon production from an 8 GeV proton beam, in support of target-system design for a muon collider demonstrator. A 2 m long, 0.7 m radius solenoid with a 5 T peak magnetic field is used to capture secondary particles, with the target positioned at its center. We examine how variations in target radius, length, and material affect secondary-beam yield and emittance at the solenoid exit. In parallel, we evaluate temperature rise within the target to assess material limitations and guide future work on thermal and structural survivability. The results provide initial intuition for optimizing both particle yield and target durability in muon collider front-end systems.
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cloudflare writes “We’ve designed our change propagation to involve blast radius protection. With these protections in place, a highstate failure becomes a signal, rather than a customer-impacting event.”
Portland under siege by fascists, a 5 block radius saturated by chemical irritants after a non-violent march from City Hall, Americans stand their ground (Oregon - date unknown)
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