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Euclid Quick Data Release (Q1): From spectrograms to spectra: the SIR spectroscopic Processing Function
No full textInternational audienceThe Euclid space mission aims to investigate the nature of dark energy and dark matter by mapping the large-scale structure of the Universe. A key component of Euclid's observational strategy is slitless spectroscopy, conducted using the Near Infrared Spectrometer and Photometer (NISP). This technique enables the acquisition of large-scale spectroscopic data without the need for targeted apertures, allowing precise redshift measurements for millions of galaxies. These data are essential for Euclid's core science objectives, including the study of cosmic acceleration and the evolution of galaxy clustering, as well as enabling many non-cosmological investigations. This study presents the SIR processing function (PF), which is responsible for processing slitless spectroscopic data. The objective is to generate science-grade fully-calibrated one-dimensional spectra, ensuring high-quality spectroscopic data. The processing function relies on a source catalogue generated from photometric data, effectively corrects detector effects, subtracts cross-contaminations, minimizes self-contamination, calibrates wavelength and flux, and produces reliable spectra for later scientific use. The first Quick Data Release (Q1) of Euclid's spectroscopic data provides approximately three million validated spectra for sources observed in the red-grism mode from a selected portion of the Euclid Wide Survey. We find that wavelength accuracy and measured resolving power are within requirements, thanks to the excellent optical quality of the instrument. The SIR PF represents a significant step in processing slitless spectroscopic data for the Euclid mission. As the survey progresses, continued refinements and additional features will enhance its capabilities, supporting high-precision cosmological and astrophysical measurements
Scaling limits of solitons in the box-ball system
No full textInternational audienceWe study the space-time scaling limits of solitons in the box-ball system with random initial distribution. In particular, we show that any recentered tagged soliton converges to a Brownian motion in the diffusive space-time scale, and also prove the large deviation principle for the tagged soliton under certain shift-ergodic invariant distributions, including Bernoulli product measures and two-sided Markov distributions. Furthermore, in the diffusive space-time scaling, we show that two tagged solitons converge to the same Brownian motion even if they are macroscopically far apart
Graph functional dependencies: Analysis and translation to PG-schema
No full textInternational audienceOfficially published as an ISO/IEC standard in April 2024, the Graph Query Language (GQL) aims to establish itself as the standard language for querying graph data, much like SQL is for relational data. The graph database community has also recently introduced additional specifications, such as PG-Key and, later, PG-Schema, to define graph schemas and dependencies. At the same time, several proposals have emerged in the literature to express Functional Dependency constraints in graph data. Given the wide range of Graph Dependencies presented in the literature, the first contribution of this article is a survey of Graph Functional Dependencies in existing proposals, highlighting the most significant ones, their differences, and their relative expressiveness. In a second contribution, we align with the goals of the graph database community by proposing mappings to translate different kinds of Graph Functional Dependencies from the literature into PG-Schema-compliant dependencies. These mappings are implemented within a publicly available tool PG-FD, which to our knowledge, is the first solution capable of transforming Graph Dependencies into the PG-Schema standard while fully preserving their semantics
Plurals, mass nouns and reference: philosophical issues
No full textHow do plurals and mass nouns refer? What kind of logic should be used in order to account for the truth-conditions of the sentences they appear in? For linguists, first-order predicate logic is adequate, provided it is supplemented by a notion of mereological sum for plurals and for mass nouns. On the contrary, according to some philosophers, new logics must be used, plural logic for plurals and mass logic for mass nouns. We survey these debates in this entry.</div
Euclid Quick Data Release (Q1). A probabilistic classification of quenched galaxies
No full textInternational audienceInvestigating the drivers of the quenching of star formation in galaxies is key to understanding their evolution. The Euclid mission will provide rich spatial and spectral data from optical to infrared wavelengths for millions of galaxies, enabling precise measurements of their star formation histories. Using the first Euclid Quick Data Release (Q1), we developed a probabilistic classification framework, that combines the average specific star-formation rate () inferred over two timescales ( yr), to categorize galaxies as `Ageing' (secularly evolving), `Quenched' (recently halted star formation), or `Retired' (dominated by old stars). We validated this methodology using synthetic observations from the IllustrisTNG simulation. Two classification methods were employed: a probabilistic approach, integrating posterior distributions, and a model-driven method optimizing sample purity and completeness using IllustrisTNG. At and , we obtain Euclid class fractions of 68-72%, 8-17%, and 14-19% for Ageing, Quenched, and Retired populations, respectively, consistent with previous studies. The evolution with redshift shows increasing/decreasing fraction of Ageing/Retired galaxies. The fraction of quenched systems shows a weaker dependence on stellar mass and redshift, varying between 5% and 15%. We analysed the mass-size-metallicity relation for each population. Ageing galaxies generally exhibit disc morphologies and low metallicities. Retired galaxies show compact structures and enhanced chemical enrichment, while Quenched galaxies form an intermediate population, more compact and chemically evolved than Ageing systems. This work demonstrates Euclid's great potential for elucidating the physical nature of the quenching mechanisms that govern galaxy evolution
Plant diversity estimates of Mediterranean islands differ among biodiversity databases
No full textInternational audienceLarge‐scale biodiversity databases encompass three main types of data for plants, namely single species point occurrences, co‐occurrences in vegetation plots, and checklists for specific areas. Evidence shows that such data types exhibit specific biases, reporting different species assemblages at local scales. We used the Mediterranean Basin, a global biodiversity hotspot with more than 2200 islands larger than 0.01 km 2 , to compare island vascular plant diversity patterns emerging from occurrence data (Global Biodiversity Information Facility; GBIF), vegetation plots (European Vegetation Archive; EVA), and species checklists (Global Inventory of Flora and Traits; GIFT). We aggregated plant data at the island level and compared geographic coverage, inventory completeness, and taxonomic coverage among these data sources. The combined databases accounted for 8702 species distributed on 790 islands (35.6% of the target islands). Data availability increased from small (26.8%) over medium (75.7%) to large islands (100.0%). Spatial coverage of databases on a 30 × 30 km grid was high for GBIF (52.8%) and EVA (45.4%), and low for GIFT (21.7%). GIFT provided higher native and alien species richness values for most of the islands, whereas GBIF and EVA consistently missed a considerable fraction of the expected species richness. Taking GIFT as reference, GBIF, and to a lesser extent EVA, showed a positive bias towards perennial species and an underrepresentation of annuals. Despite their lower taxonomic coverage, GBIF and EVA data can complement our knowledge on Mediterranean islands' plant diversity, providing data for islands lacking plant inventories. Moreover, GBIF and EVA's large datasets can be used for investigating other levels of ecological organisation and modelling single species (GBIF) or population (EVA) trends over space and time. Finally, our results advocate for a coordinated effort to fill the knowledge gaps through data collection and digitisation, possibly integrating data collected by experts by means of citizen science initiatives
CO₂ Injection in Opalinus Clay at the Mont Terri CL-Experiment: Insights from Laboratory Experiments and Hydraulic-Geochemical Coupled Modeling
No full textInternational audienceCarbon capture and storage (CCS) projects raise fundamental questions beyond technical performance, including how injected CO₂ behaves in the subsurface over long-time scales, how reliable model predictions are, and how experimental observations and simulations can be meaningfully combined. Addressing these questions requires not only process-based physical understanding, but also transparent modeling workflows, experimental validation, and effective collaboration across disciplines and institutions. In this contribution, we use the ongoing CO₂ Long-term Periodic Injection Experiment (CL-Experiment) at the Mont Terri Rock Laboratory in Switzerland as a central case study to illustrate how such integrated understanding can be developed. The core of the work is a numerical benchmark modeling study of CO₂ injection into the Opalinus Clay formation, using a two-dimensional axisymmetric representation of the injection system to investigate hydraulic propagation and coupled geochemical processes over a 20-year period. The simulations assume a fully water-saturated domain and single-phase injection at 3 MPa, using artificial porewater containing dissolved CO₂ corresponding to a partial pressure of 2 MPa. As part of a benchmark study, international teams use different numerical codes. Evaluation of the results enables a transparent assessment of model assumptions, sensitivities, and limitations, as well as model verification.To gain insights into CO₂–water–rock interactions, laboratory experiments were conducted using crushed Opalinus Clay from the in-situ sandy facies field site in an open system under controlled CO₂ conditions. Differences and consistencies between laboratory observations and numerical simulations are explicitly examined, highlighting key parameters and controlling processes that influence both model behavior and experimental responses.This study integrates numerical benchmarking, laboratory experiments, and interdisciplinary collaboration as a learning process to improve understanding of CO₂ storage in clay formations. Continuum-scale modeling shows that the CO₂ plume remains confined within approximately 1 m of the injection zone over 20 years (based on a cutoff concentration of 10 mmol/L), while CO₂-induced carbonate dissolution causes localized porosity increases within about 5 cm of the injection zone. At the laboratory scale, modeling indicates that carbonate reactions are the dominant factor on the pH evolution. However, strong spatial mineralogical heterogeneity observed in the in-situ samples limits the applicability of homogeneous batch-scale representations. For the international benchmark exercise, effective coordination relied on a hierarchical benchmarking strategy in which model complexity was increased stepwise by progressively introducing key variables and parameters. Together, the results of this study demonstrate the strength of coordinated benchmarking initiatives, and continuous exchange across disciplines, tools, and teams
Annealing in variational inference mitigates mode collapse: A theoretical study on Gaussian mixtures
No full textInternational audienceMode collapse -the failure to capture one or more modes when targetting a multimodal distribution -is a central challenge in modern variational inference. In this work, we provide a mathematical analysis of annealing-based strategies for mitigating mode collapse in a tractable setting: learning a Gaussian mixture, where mode collapse is known to arise. Leveraging a low-dimensional summary statistics description, we precisely characterize the interplay between the initial temperature and the annealing rate, and derive a sharp formula for the probability of mode collapse. Our analysis shows that an appropriately chosen annealing scheme can robustly prevent mode collapse. Finally, we present numerical evidence that these theoretical trade-offs qualitatively extend to neural network-based models, Real-NVP normalizing flows, providing guidance for designing annealing strategies mitigating mode collapse in practical variational inference pipelines
Nonlinear Terahertz Electroluminescence from Dirac-Landau Polaritons
No full textInternational audienceWe report Dirac-Landau polaritons observed by terahertz (THz) magnetoreflectivity spectroscopy, demonstrating strong coupling between cyclotron transitions of two-dimensional (2D) Dirac fermions in HgTe quantum wells and optical cavity modes. Under pulsed electrical injection we observe efficient nonlinear electroluminescence, with a strongly out-of-equilibrium polariton distribution dominated by emission from the upper polariton branches. Model analysis of the bias-dependent emission intensity and spectral narrowing indicates a polariton occupancy per mode approaching unity, with a possible contribution from stimulated polariton emission in the spectral region of the upper anticrossing. These results open prospects toward Dirac-Landau polariton condensates and low-threshold, tunable THz polariton lasers based on cyclotron emission.</div
Multidisciplinary science funding is more than ever a planetary priority: Reflections from the Make Our Planet Great Again (MOPGA) program
No full textInternational audienceGlobal change poses “wicked problems” that have become ever more complex, pervasive, and damaging. Developing innovative solutions increasingly require diverse research approaches. The Franco-German Make Our Planet Great Again (MOPGA) program was designed to create a unique international network of top-level research, from fundamental to solution-oriented projects. MOPGA stands out from other large research initiatives by focusing not on a singular central research challenge but on facilitating multidisciplinary interactions between traditionally separated fields. MOPGA recognized that social, natural and engineering sciences share a unifying aim to address global change. In addition to addressing timely and innovative research questions within disciplines, MOPGA worked to improve communication across disciplines via annual meetings for all laureates and their research groups, scientific board exchanges, and public online seminars. Drawing on our MOPGA experiences, we discuss how such exchanges should be extended to meet the needs identified by the scientific community, international policy-makers, and regional stakeholders. In the current political landscape of scientific suppression and heightened mistrust in scientific expertise, the need for such bold, independent and collaborative scientific initiatives is greater than ever