Archive ouverte de Sorbonne Université
Not a member yet
324019 research outputs found
Sort by
Étude comparative de phénomènes linguistiques complexes en restitution orale et écrite
No full textInternational audienc
Effect of local environment on Ly line profile in DESI/ODIN LAEs
No full textInternational audienceLyman-Alpha Emitters (LAEs) are star-forming galaxies with significant Ly emission and are often used as tracers of large-scale structure at high redshift. We explore the relationship between the Ly line profile and environmental density with spectroscopy from the Dark Energy Spectroscopic Instrument (DESI) of LAEs selected with narrow-band photometry through the One-hundred-deg DECam Imaging in Narrowbands (ODIN) survey. We use LAE surface density maps in the N419 (z 2.45) and N501 (z 3.12) narrow bands to probe the relationship between local environmental density and the Ly line profile. In both narrow bands, we stack the LAE spectra in bins of environmental density and inside and outside of protocluster regions. The N501 data shows 15% higher Ly line luminosity for galaxies in protoclusters, suggesting increased star formation in these regions. However, the line luminosity is not appreciably greater in protocluster galaxies in the N419 band, suggesting a potential redshift evolution of this effect. The shape of the line profile itself does not vary with environmental density, suggesting that line shape changes are caused by local effects independent of a galaxy's environment. These data indicate a potential relationship between LAE local environmental density, ionized gas distribution, and Ly line luminosity
Recommender system in X inadvertently profiles ideological positions of users
No full textStudies on recommendations in social media have mainly analyzed the quality of recommended items (e.g., their diversity or biases) and the impact of recommendation policies (e.g., in comparison with purely chronological policies). We use a data donation program, collecting more than 2.5 million friend recommendations made to 682 volunteers on X over a year, to study instead how real-world recommenders learn, represent and process political and social attributes of users inside the so-called black boxes of AI systems. Using publicly available knowledge on the architecture of the recommender, we inferred the positions of recommended users in its embedding space. Leveraging ideology scaling calibrated with political survey data, we analyzed the political position of users in our study (N=26,509 among volunteers and recommended contacts) among several attributes, including age and gender. Our results show that the platform's recommender system produces a spatial ordering of users that is highly correlated with their Left-Right positions (Pearson rho=0.887, p-value < 0.0001), and that cannot be explained by socio-demographic attributes. These results open new possibilities for studying the interaction between human and AI systems. They also raise important questions linked to the legal definition of algorithmic profiling in data privacy regulation by blurring the line between active and passive profiling. We explore new constrained recommendation methods enabled by our results, limiting the political information in the recommender as a potential tool for privacy compliance capable of preserving recommendation relevance
Measurement of differential -channel single top (anti)quark production cross-sections at 13 TeV with the ATLAS detector
No full textInternational audienceThe production of single top quarks and top antiquarks via the -channel exchange of a virtual boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The full Run 2 data sample recorded with the ATLAS detector in the years 2015-2018 is used, corresponding to an integrated luminosity of 140 fb. The absolute and normalised production cross-sections are measured differentially as a function of the transverse momentum and absolute rapidity of the top quark and top antiquark. In addition, the ratio of top quark to top antiquark production cross-sections is measured. The measured distributions are compared with next-to-leading-order quantum chromodynamics predictions obtained with different combinations of matrix-element generators, parton-shower programs and proton parton distribution functions, as well as to next-to-next-to-leading-order calculations. Overall, good agreement is observed between the measurements and the theoretical predictions. For most measured distributions, the sensitivity to differences between the predictions is limited by the systematic uncertainties in the measurement. The measured differential distributions are also interpreted in an effective field theory approach to constrain the Wilson-Coefficient associated with a four-quark operator. The interpretation accounts for the effect of the selection efficiency, which is altered significantly by non-zero contributions from
Gender differences in audience participation at infectious disease and microbiology conferences: a prospective observational study
No full textInternational audienceObjectivesIn medicine, women constitute a large proportion of the workforce but remain underrepresented in senior positions. Scientific conferences, critical for career advancement, reflect these inequities, with prior studies documenting gender gaps in invited speakers. However, less attention has been given to audience engagement, such as asking questions or making comments, which also enhances professional visibility. This study investigates gender differences in audience participation at infectious disease and clinical microbiology conferences, examining their prevalence, contextual variation, and potential structural drivers.MethodsThis prospective observational study recorded audience participations during national and international infectious disease and clinical microbiology conferences (October 2023–October 2024). Consortium members documented eligible sessions with traditional presentation–discussion formats, noting gender, role, and type of participation. Statistical analyses compared observed gender proportions with attendee distributions and examined factors associated with women's participation.ResultsA total of 298 sessions from 24 conferences were analysed, comprising 1873 audience participations. Women delivered 47.8% of presentations (n = 487/1018; 95% CI, 44.8–50.9%) but accounted for only 36.4% of participations (n = 681/1873; 95% CI, 34.2–38.5%), significantly fewer than men both in absolute terms and relative to their representation among attendees (p < 0.001). Multivariable analysis showed women were more likely to intervene when at least one moderator was female (OR = 1.44; 95% CI, 1.02–2.04%; p 0.037), with a stronger effect when all moderators were women (OR = 2.12; 95% CI, 1.40–3.24%; p < 0.001), and when the first question was asked by a woman (OR = 1.35; 95% CI, 1.00–1.81%; p 0.046).ConclusionOur findings highlight actionable levers to advance equity. Addressing participation gaps and raising awareness of gender disparities are essential to foster inclusive visibility, empower women, and strengthen scientific innovation
Molecule-driven control of the magnetic anisotropy of surface-functionalized maghemite nanoparticles
No full textInternational audienceUsing cobalt(II) complexes and a simple coordination reaction at the surface of maghemite nanoparticles, a molecule-driven control of the effective magnetic anisotropy can be achieved. This functionalisation strategy is explored for nanoparticles ranging from 4 to 8 nm and performed in soft conditions and aqueous media. It preserves colloidal stability and permits an acute control of the magnetic properties with an increase of the blocking temperature and of the coercive field values. This effect is correlated to the quantity of complexes coordinated at the surface and the increase of the surface anisotropy of the nanoparticles. Magnetometry studies show that the effective magnetic anisotropy constant, Keff, can be modulated from 32 to 168 kJ.m -3 , and with a few kJ.m -3 accuracy
Precision Measurements of Atom-Dimer Interactions in a Uniform Planar Bose Gas
No full textCold quantum gases, when acted upon by electromagnetic fields, can give rise to samples where isolated atoms coexist with dimers or trimers, which raises the question of the interactions between these various constituents. Here we perform microwave photoassociation in a degenerate gas of Rb atoms to create weakly-bound dimers in their electronic ground state. From the density-induced shift of the photoassociation line, we measure the atom-dimer scattering length for the two least-bound states of the molecular potential. We also determine the complete energy diagram of one hyperfine manifold of the least-bound state, which we accurately reproduce with a simple model
Attributable mortality of ICU-acquired bloodstream infections: Impact of the source, causative micro-organism, resistance profile and antimicrobial therapy
No full textInternational audienc
The Wishart–Rosenzweig–Porter random matrix ensemble
No full textInternational audienceIn recent years, the Rosenzweig–Porter (RP) ensemble, obtained by adding a diagonal matrix with independent and identically distributed elements to a Gaussian random matrix, has been widely used as a minimal model for the emergence of fractal eigenstates in complex many-body systems. A key open question concerns the robustness of its phase diagram when the assumption of independent and uncorrelated entries is relaxed—an assumption that simplifies its analysis but is generally violated in realistic quantum systems. In this work, we take a first step in this direction by considering a deformed Wishart (rather than Gaussian) random matrix, which we dub the ‘Wishart–RP’ ensemble. Using perturbation theory, as well as the cavity and replica methods and the Dyson Brownian motion approach, we characterize its phase diagram and localization properties. Remarkably, we show that the level compressibility, which quantifies spectral correlations in the fractal phase, coincides with that of the Gaussian RP model, thereby extending the universality conjectured in Venturelli et al (2023 SciPost Phys. 14 110) beyond the fully uncorrelated setting. We confirm our results with numerical tests
A Note on k-NN Gating in RAG
No full textWe develop a statistical proxy framework for retrieval-augmented generation (RAG), designed to formalize how a language model (LM) should balance its own predictions with retrieved evidence. For each query x, the system combines a frozen base model q0 (· x) with a k-nearest neighbor retriever r (k ) (· x) through a measurable gate k(x). A retrieval-trust weight wfact (x) quantifies the geometric reliability of the retrieved neighborhood and penalizes retrieval in low-trust regions. We derive the Bayes-optimal per-query gate and analyze its effect on a discordance-based hallucination criterion that captures disagreements between LM predictions and retrieved evidence. We further show that this discordance admits a deterministic asymptotic limit governedsolely by the structural agreement (or disagreement) between the Bayes rule and the LM. To account for distribution mismatch between queries and memory, we introduce a hybrid geometric-semantic model combining covariate deformation and label corruption. Overall, this note provides a principled statistical foundation for factuality-oriented RAG systems