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Walking lanes / walking lines: Bodily alignments and passing through doorways
No full textInternational audienceThere are very few studies that analyse the role of artefacts as shaping joint locomotion in public places. By video-recording pedestrians passing through doorways in a mall, we have observed how openings and doors contribute to mobile formations such as walking lanes or files. Doors play a major part as a focus for common direction. Doors occasion a modification of speed and a re-arrangement of spatial proximity between pedestrians during the process of passing through. We argue that mobile formats such as walking together in public places are based on culturally-methodic dynamics of bodily orientation to others. They are also based on a conjoint orientation to apertures that afford entry spaces to doors through which pedestrians wish to pass. Physical-artefactual boundaries such as doors, sidewalks and lanes play a major role in shaping joint locomotion. We would like to focus on a particular case of locomotion driven by artefacts: the passing through doors shaped by serial arrangements of pedestrians in a following/followed format. We treat this case of mobile formation as a specific genuine form of aggregate in its own right, distinct from side-by-side walking and other forms of mobile file
A posteriori closure of turbulence models: Are symmetries preserved?
No full textInternational audienceTurbulence modeling remains a longstanding challenge in fluid dynamics. Recent advances in data-driven methods have led to a surge of novel approaches aimed at addressing this problem. Thiswork builds upon our recent work [Phys. Rev. Fluids 10, 044602 (2025)], where we introduced anew closure for a shell model of turbulence using an a posteriori (or solver-in-the-loop) approach.Unlike most deep learning-based models, our method explicitly incorporates physical equationsinto the neural network framework, ensuring that the closure remains constrained by the underlyingphysics benefiting from enhanced stability and generalizability. In this paper, we further analyze thelearned closure, probing its capabilities and limitations. In particular, we look at joint probabilitydensity functions between resolved and unresolved variables, as well as the scale invariance ofmultipliers (ratios between adjacent shells) within the inertial range. Although our model excels inreproducing high-order statistical moments, it breaks this known symmetry near the cutoff, indicatinga fundamental limitation. We discuss the implications of these findings for subgrid-scale modeling in3D turbulence and outline directions for future research
L'impact du Contrat d'engagement jeune sur les trajectoires professionnelles des bénéficiaires
No full textCe rapport propose une analyse quantitative du programme « Contrat d’engagement jeune » (CEJ) mis en place en 2022, en remplacement du dispositif « Garantie jeune » (GJ) dans les Missions locales
Quantifying the Trade Impact of SPS and TBTs with Product-level Structural Gravity
No full textNon-tariff measures (NTMs), especially sanitary and phytosanitary (SPS) measures and technical barriers to trade (TBTs), have become crucial components of climate, industrial, and regulatory policy, impacting the majority of global trade. However, quantifying their effects on trade is challenging because NTMs are usually non-discriminatory and challenging to identify in standard gravity frameworks. Using a multistage structural gravity estimation strategy combined with a control-function correction for endogeneity, we estimate the trade elasticities and ad valorem equivalents of NTMs at the HS6 level for over 5,000 products. Our results reveal significant heterogeneity in NTM trade costs, especially in environmentally relevant sectors, such as clean technologies and electric vehicles. These estimates can inform regulatory impact assessments and general-equilibrium analyses of climate-aligned trade policies
Investigating the role of climate change in the 3 May 2025 Western Europe hailstorm using atmospheric analogues
No full textInternational audienceOn 3 May 2025, a severe hailstorm struck Paris and parts of western Europe, raising concerns about the influence of climate change. We analyze this event using ERA5 reanalysis and an analogue-based attribution framework. The synoptic setting involved a cut-off low and a surface cold front, occurring shortly after an early-season heatwave. We compare analogous patterns in past (1974–1999) and recent (1999–2024) climates to assess thermodynamic differences. Hail probability and size were estimated with two models: a logistic formulation based on convective available potential energy, wind shear, and convective precipitation, and a new model incorporating freezing-level height and 850 hPa temperature, designed for European hail environments. Both were calibrated with Ile-de-France observations and validated with independent data. Our findings show that present-day conditions favor higher hail probabilities and larger hailstones, suggesting anthropogenic warming has likely enhanced hailstorm intensity in the region
Near‐Inertial Wave Trapping Inside a Fine‐Scale Anticyclonic Eddy During the BioSWOT‐Med 2023 Cruise: Turbulence and Energy Flux
No full textInternational audienceAbstract Near‐inertial waves (NIWs) are an important source of turbulence for the ocean interior. Mesoscale anticyclonic eddies are known to facilitate their propagation at depth while trapping them. However, in situ observations have so far focused on large ( km radius), energetic eddies, whereas most of the ocean is populated by smaller, moderately energetic fine‐scale structures. Are these smaller structures efficient to trap NIWs and enhance turbulence? Here, we present in situ observations from the BioSWOT‐Med 2023 cruise addressing this issue by surveying a fine‐scale frontal area of the North Balearic front in the Mediterranean Sea, assisted by the first high‐resolution Sea Surface Height images of the new Surface Water and Ocean Topography (SWOT) satellite mission during its Calibration/Validation phase. We explore how fine scales modulate the evolution of turbulence below the mixed layer after experiencing two consecutive strong wind events. We show that turbulence remains low in the front and its cyclonic side, while being greatly enhanced in the anticyclonic side. The latter side is dominated by a fine‐scale anticyclone (12.8 km of radius, Rossby number of 0.5) that trapped NIWs, increasing turbulent dissipation level to several 10-8 W/kg . The NIW‐induced vertical kinetic energy flux reach up to 5.1 mW/m2 below the pycnocline and represent ~20 % of the wind power input into inertial motions, higher or similar to previous estimations outside and inside mesoscale anticyclones. Future work is needed to investigate whether these results extend to fine scales elsewhere in the world ocean, especially in regions with larger baroclinic Rossby radius of deformation
The Gerontocracy of Science: Attention Dynamics in the Age
No full text19 pages, 7 figuresScientific literature has been growing exponentially for decades, with publications from the last twenty years now comprising 60% of all academic output. While the impact of information overload on news and social-media consumption is well-documented, its consequences on scientific progress remain understudied. Here, we investigate how this rapid expansion affects the circulation and exploitation of scientific ideas. Unlike other cultural domains, science is experiencing a decline in the proportion of highly influential papers and a slower turnover in its canons. This results in the disproportionate persistence of established works, a phenomenon we term the ``gerontocratization of science''. To test whether hypergrowth drives this trend, we develop a generative citation model that incorporates random discovery, cumulative advantage, and exponential growth of the scientific literature. Our findings reveal that as scientific output expands exponentially, gerontocratization emerges and intensifies, reducing the influence of new research. Recognizing and understanding this mechanism is crucial for developing targeted strategies to sustain intellectual dynamism and ensure a balanced and healthy renewal of scientific knowledge
Intergenerational Mobility of Immigrants in 15 Destination Countries
No full textWe estimate intergenerational mobility of immigrants and their children in fifteen receiving countries. We document large income gaps for first-generation immigrants that diminish in the second generation. Around half of the second-generation gap can be explained by differences in parental income, with the remainder due to differential rates of absolute mobility. The daughters of immigrants enjoy higher absolute mobility than daughters of locals in most destinations, while immigrant sons primarily enjoy this advantage in countries with long histories of immigration. Cross-country differences in absolute mobility are not driven by parental country-of-origin, but instead by destination labor markets and immigration policy
Sampling from multi-modal distributions on Riemannian manifolds with training-free stochastic interpolants
No full textIn this paper, we propose a general methodology for sampling from un-normalized densities defined on Riemannian manifolds, with a particular focus on multi-modal targets that remain challenging for existing sampling methods. Inspired by the framework of diffusion models developed for generative modeling, we introduce a sampling algorithm based on the simulation of a non-equilibrium deterministic dynamics that transports an easy-to-sample noise distribution toward the target. At the marginal level, the induced density path follows a prescribed stochastic interpolant between the noise and target distributions, specifically constructed to respect the underlying Riemannian geometry. In contrast to related generative modeling approaches that rely on machine learning, our method is entirely training-free. It instead builds on iterative posterior sampling procedures using only standard Monte Carlo techniques, thereby extending recent diffusion-based sampling methodologies beyond the Euclidean setting. We complement our approach with a rigorous theoretical analysis and demonstrate its effectiveness on a range of multi-modal sampling problems, including high-dimensional and heavy-tailed examples
Initial Solution Sampling for the Variable Neighborhood Search Method : Fitness Landscapes Analysis
No full textInternational audienceInitial Solution Sampling for the Variable Neighborhood Search Method : Fitness Landscapes Analysi