Tootfinder

Study of the Turbulent/Non-turbulent Interface of Zero-Pressure-Gradient Turbulent Boundary Layer Using the Uniform Momentum Zone Concept
Bihai Sun, Callum Atkinson, Julio Soria
https://arxiv.org/abs/2505.23589

Study of the Turbulent/Non-turbulent Interface of Zero-Pressure-Gradient Turbulent Boundary Layer Using the Uniform Momentum Zone Concept
This paper investigates the turbulent--non-turbulent interface (TNTI) in a zero-pressure-gradient turbulent boundary layer (ZPG-TBL) using a novel, threshold-free method based on the uniform momentum zone (UMZ) concept. Requiring only planar streamwise velocity data, the method is directly applicable to experimental PIV and ensures consistent TNTI detection across simulations and experiments. Its performance is demonstrated using DNS data at $Re_τ= 1,000 - 2,000$. The TNTI height scales with t…

Fully nonlinear parabolic fixed transmission problems
David Jesus, Mar\'ia Soria-Carro
https://arxiv.org/abs/2507.19277 https://arxiv.org/pdf/2507.1927…

Fully nonlinear parabolic fixed transmission problems
We consider transmission problems for parabolic equations governed by distinct fully nonlinear operators on each side of a time-dependent interface. We prove that if the interface is $C^{1,α}$, in the parabolic sense, then viscosity solutions are piecewise $C^{1,α}$ up to the interface. As byproducts, we obtain a new ABP-Krylov-Tso estimate, and establish existence, uniqueness, a comparison principle, and regularity results for the flat interface problem.

Studying propagating turbulent structures in the near wake of a sphere using Hilbert proper orthogonal decomposition
Shaun Davey, Callum Atkinson, Julio Soria
https://arxiv.org/abs/2507.19167

Studying propagating turbulent structures in the near wake of a sphere using Hilbert proper orthogonal decomposition
Turbulent flows, despite their apparent randomness, exhibit coherent structures that underpin their dynamics. Proper orthogonal decomposition (POD) has been widely used to extract these structures from experimental data. While periodic features like vortex shedding can be identified using POD mode pairs when periodicity dominates the flow, detecting such structures in complex flows is more challenging. The Hilbert proper orthogonal decomposition (HPOD) addresses this by applying POD to the anal…

Einstein Probe Discovery of EP J182730.0-095633: A New Black Hole X-ray Binary Candidate in Faint Outburst?
Huaqing Cheng, Qingchang Zhao, L. Tao, H. Feng, F. Coti Zelati, H. W. Pan, A. L. Wang, Y. N. Wang, M. Y. Ge, A. Rau, A. Marino, L. Zhang, W. J. Zhang, F. Carotenuto, L. Ji, C. C. Jin, D. Y. Li, B. F. Liu, Y. Liu, E. L. Qiao, N. Rea, R. Soria, S. Wang, Z. Yan, W. Yuan, B. Zhang, G. B. Zhang, S. N. Zhang, W. D. Zhang, A. Beardmore, J. S. Bright, X. L. Chen, Z. Fan, S. Y. Fu, J. P. …

Einstein Probe Discovery of EP J182730.0-095633: A New Black Hole X-ray Binary Candidate in Faint Outburst?
Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts exhibiting peak X-ray luminosities $L_{\rm X}\lesssim10^{36}~{\rm erg~s^{-1}}$, likely due to the previous lack of sensitive, wide-field monitoring instruments in the X-ray band. In this Letter, we present the discovery of an intriguing X-ray transient, EP J182…

Four ages of rotating stars in the rotation--activity relationship and gyrochronology
Huiqin Yang, Jifeng Liu, Roberto Soria, Federico Spada, Song Wang, Xiangsong Fang, Xue Li
https://arxiv.org/abs/2506.07383

Four ages of rotating stars in the rotation--activity relationship and gyrochronology
Both of gyrochronology and the rotation-activity relationship are standard techniques to determine the evolution phase.The mismatch in the definition of the evolutionary phases has so far raised many issues in physics and mathematics and hampered the understanding of how the internal dynamo processes affect the observable properties.To address this problem, we seek a unified scheme that shows a one-to-one mapping from gyrochronology to the rotation--activity relationship.We obtained the chromos…

Investigation of the effects of superhydrophobic surface treatment on the dynamics of the flow in the near wake of a sphere using spatial dynamic mode decomposition
Shaun Davey, Callum Atkinson, Julio Soria
https://arxiv.org/abs/2507.17091

Investigation of the effects of superhydrophobic surface treatment on the dynamics of the flow in the near wake of a sphere using spatial dynamic mode decomposition
Viscous drag results from the fluid at a surface having zero relative velocity, a phenomenon known as the no-slip condition. Superhydrophobic surfaces, when submerged in water, trap a layer of air in their surface texture, partially replacing the liquid-solid interface with a liquid-gas interface. This air layer, called the plastron, results in partial slip at the surface, thereby reducing the viscous drag. In turbulent flows, large fluctuations in pressure and velocity can deplete or completel…

Best bounds for the dual Hardy operator minus identity on decreasing functions
Achraf Ben Said, Gord Sinnamon
https://arxiv.org/abs/2507.02290 https://

Best bounds for the dual Hardy operator minus identity on decreasing functions
The distance from the identity operator $I$ to $H^*$, the dual of the Hardy averaging operator, is studied on the cone of nonnegative, nonincreasing functions in Lebesgue space. The exact value is obtained. Optimal lower bounds are also given for difference, $H^*-I$, of these two operators acting on the same cone. A positive answer is given to a conjecture made in ``The norm of Hardy-type oscillation operators in the discrete and continuous settings'' by A. Ben Said, S. Boza, and J. Soria. Prep…