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Des bouteilles à la mer : un contrat pour le commerce transatlantique du vin au XVIe siècle
No full textInternational audienceL'Europe médiévale avait vécu adossée à un mur, l'Atlantique » 1 , écrivait Jean Hilaire dans son Introduction historique au droit commercial. C'est à la toute fin du XVᵉ siècle que ce mur tombe et que les océans s'imposent comme les grands protagonistes du commerce proto-global. C'est donc au XVIᵉ siècle que le commerce transatlantique se développe, reliant l'Europe aux Amériques grâce à d'imposants convois de vaisseaux transportant des grandes quantités de marchandises 2 . Ce phénomène bouleverse profondément l'économie et le droit, introduisant des transformations majeures et rapides.En particulier, ce dynamisme économique influence profondément les pratiques contractuelles des marchands. Les structures conventionnelles évoluent en réponse aux nouvelles réalités commerciales, modifiant les dispositifs actuels des engagements entre les parties prenantes 3 . Toutefois, ce ne sont pas uniquement les grands marchands qui bénéficient de cette effervescence. Une grande partie de la population andalouse participe activement à ces nouvelles opportunités commerciales, encouragée par l'expansion des échanges avec les Indes et les perspectives économiques qui en découlent.Séville, en tant que port fluvial détenant le monopole des échanges transatlantiques 4 , voit son commerce avec les Amériques croître de manière exponentielle 5 . À la route atlantique Séville-Veracruz 6 , après la conquête des Philippines au XVIᵉ siècle, l'Espagne ajoute une route maritime de la Chine au port de Manille et de là au port d'Acapulco sur la côte ouest du Mexique : il s'agit de la Nao de China (la route de Chine) 7 par laquelle les marchandises étaient expédiées depuis l'Est au Mexique et puis repartaient pour Séville 8 . Cette expansion engendre une vague d'initiatives</div
Nuclear operations with a high penetration of renewables: the case of France
No full textNuclear and intermittent renewables (wind and solar) are generally regarded as the only scalable technologies producing low-carbon electricity. However, the extent to which these technologies can co-exist in a reliable power system depends on whether nuclear units can adjust their operations to renewable output fluctuations. Using hourly data from the French power system, we find that nuclear units are operated quite flexibly, and that the foregone energy production due to "load following" actions (relative to the counterfactual of operating at full capacity during load following events) is currently limited. However, we find that an additional load following event is associated with a slightly higher likelihood of a unit failure. We also find that unit-level minimum output constraints are binding more frequently as system-wide renewable generation increases, especially so for units most exposed to solar generation. In 2024, hours during which available nuclear flexibility was exhausted are associated with non-positive hourly day-ahead prices
Au moins aussi inquiétant que la perspective d’un conflit ouvert avec les Etats-Unis, la soumission tranquille du Canada et de certains Européens à la Chine
No full textInternational audienceLa reconfiguration du monde sur le plan stratégique, l'avenir de la France face à la Chine et les Etats-Uni
Extracting quantum field theory dynamics from an approximate ground state
No full textWe develop a linear-programming method to extract dynamical information from static ground-state correlators in quantum field theory. We recast the K¨all´en–Lehmann inversion as a convex optimization problem, in a spirit similar to the recent approach of Lawrence [2408.11766]. This produces robust estimates of the smeared spectral density, the real-time propagator, and the mass gap directly from an approximate equal-time two-point function, and simultaneously yields an a posteriori lower bound on the correlation-function error. We test the method on the 1 + 1-dimensional ϕ4 model, using a variational approximation to the vacuum—relativistic continuous matrix product states—that provides accurate correlators in the continuum and thermodynamic limits. The resulting mass gaps agree with renormalized Hamiltonian truncation and Borel-resummed perturbation theory across a wide range of couplings, demonstrating that accurate dynamical data can berecovered from a single equal-time slice
Search for long-lived particles using displaced vertices of oppositely charged leptons in 140 fb of pp collisions at TeV with the ATLAS detector
No full textInternational audienceA search is presented for long-lived particles decaying into an oppositely charged lepton pair, , , or , that form a vertex within the inner tracking system of the ATLAS detector at the Large Hadron Collider, displaced from the primary proton-proton interaction region. The analysis uses the 140 fb of Run-2 data collected at TeV by the ATLAS experiment in 2015-2018. The results of the analysis are interpreted in the context of three benchmark models covering masses from 0.1 to 2.2 TeV and a range of mean proper lifetimes times the speed of light from 1 to 10000 mm. The first model is a generic boson pair-produced by a new heavy scalar, with the decaying into lepton pairs. The remaining two models are -parity violating supersymmetric models in which the lightest neutralino decays into (, ). The models differ by the mode of production of the , which can be produced via the decay of pairs of gluinos or of pairs of charginos and neutralinos (, , or ). Although each benchmark sample includes pair-produced LLPs, only a single vertex is required to be reconstructed. No dilepton displaced vertex candidate is observed and the results are presented as upper limits on the production cross-sections. This analysis sets leading limits on the production cross-sections for multiple models, including parameter space that has never been directly probed
Optimising Density Computations in Probabilistic Programs via Automatic Loop Vectorisation
No full textInternational audienceProbabilistic programming languages (PPLs) are a popular tool for high-level modelling across many !elds. They provide a range of algorithms for probabilistic inference, which analyse models by learning their parameters from a dataset or estimating their posterior distributions. However, probabilistic inference is known to be very costly. One of the bottlenecks of probabilistic inference stems from the iteration over entries of a large dataset or a long series of random samples. Vectorisation can mitigate this cost, but manual vectorisation is error-prone, and existing automatic techniques are often ad-hoc and limited, unable to handle general repetition structures, such as nested loops and loops with data-dependent control "ow, without signi!cant user intervention. To address this bottleneck, we propose a sound and e#ective method for automatically vectorising loops in probabilistic programs. Our method achieves high throughput using speculative parallel execution of loop iterations, while preserving the semantics of the original loop through a !xed-point check. We formalise our method as a translation from an imperative PPL into a lower-level target language with primitives geared towards vectorisation. We implemented our method for the Pyro PPL and evaluated it on a range of probabilistic models. Our experiments show signi!cant performance gains against an existing vectorisation baseline, achieving 1.1-6→ speedups and reducing GPU memory usage in many cases. Unlike the baseline, which is limited to a subset of models, our method e#ectively handled all the tested models
When Less is More: Approximating the Quantum Geometric Tensor with Block Structures
No full textThe natural gradient is central in neural quantum states optimizations but it is limited by the cost of computing and inverting the quantum geometric tensor, the quantum analogue of the Fisher information matrix. We introduce a block-diagonal quantum geometric tensor that partitions the metric by network layers, analogous to block-structured Fisher methods such as K-FAC. This layer-wise approximation preserves essential curvature while removing noisy cross-layer correlations, improving conditioning and scalability. Experiments on Heisenberg and frustrated - models show faster convergence, lower energy, and improved stability
MaskCaptioner: Learning to Jointly Segment and Caption Object Trajectories in Videos
No full textInternational audienceDense Video Object Captioning (DVOC) is the task of jointly detecting, tracking, and captioning object trajectories in a video, requiring the ability to understand spatio-temporal details and describe them in natural language. Due to the complexity of the task and the high cost associated with manual annotation, previous approaches resort to disjoint training strategies, potentially leading to suboptimal performance. To circumvent this issue, we propose to generate captions about spatio-temporally localized entities leveraging a stateof-the-art VLM. By extending the LVIS and LV-VIS datasets with our synthetic captions (LVISCap and LV-VISCap), we train MaskCaptioner, an endto-end model capable of jointly detecting, segmenting, tracking and captioning object trajectories. Moreover, with pretraining on LVISCap and LV-VISCap, MaskCaptioner achieves state-of-the-art DVOC results on three existing benchmarks, VidSTG, VLN and BenSMOT. The datasets and code are available at https://www.gabriel.fiastre.fr/maskcaptioner/
Tissue stress measurements with Bayesian Inversion Stress Microscopy
No full textCells within biological tissue are constantly subjected to dynamic mechanical forces. Measuring the internal stress of tissues has proven crucial for our understanding of the role of mechanical forces in fundamental biological processes like morphogenesis, collective migration, cell division or cell elimination and death. Previously, we have introduced Bayesian Inversion Stress Microscopy (BISM), which is relying on measuring cell-generated traction forces in vitro and has proven particularly useful to measure absolute stresses in confined cell monolayers. We further demonstrate the applicability and robustness of BISM across various experimental settings with different boundary conditions, ranging from confined tissues of arbitrary shape to monolayers composed of different cell types. Importantly, BISM does not require assumptions on cell rheology. Therefore, it36 pages, 12 figure
Du serment doctoral d'intégrité scientifique à un serment personnel : un atelier d'écriture et de réflexion sur la responsabilité et le rôle des scientifiques dans la société
No full textNous présentons un atelier de réflexion sur le serment doctoral d’intégrité scientifique et d’écriture d’un serment personnel, destiné aux doctorantes et doctorants, et plus généralement au personnel de la recherche. L’atelier est proposé depuis 2025 comme formation à l’éthique de la recherche dans quelques écoles doctorales en France. Avec un dispositif original, il permet d’examiner plusieurs aspects de la pratique et des enjeux sociaux-environnementaux de le Recherche : la responsabilité des scientifiques, l’engagement, le rôle des sciences dans l’anthropocène, la place de l’éthique et de l’intégrité dans la pratique du doctorat et des sciences en général