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Event Analysis
No full textEvent analysis measures the impact of a given event (typically, an intervention) on one or more variables of interest, by comparing at a given point in time individuals who have already benefited from the intervention with others for whom this is not yet the case. This method of counterfactual analysis follows a logic similar to that of difference-in-differences
Wet foam coarsening: More than film permeability
No full textInternational audienceFoams with high liquid fractions, wet foams, are frequent in industrial applications. Understanding their stabilityis key to achieving control over foamy material design. Wet foams are difficult to study on ground as theyrapidly destabilise through gravity-driven drainage. Experiments in microgravity avoid this drainage and allowto isolate the foam coarsening process, where bubble size grows as gas transfers from smaller to larger bubbles.We have studied the impact of stabiliser chemistry on coarsening with various surfactants and a protein, andover a range of liquid fractions. We measure coarsening rates that vary by almost a factor ten depending onthe stabiliser. For moderately wet foams, we can rationalise the changing rates with surface tension and filmpermeability measured in independent experiments on ground. Once the foams become wetter and approach thevolume fraction of random close packing, other stabiliser effects become evident. Molecules which exhibit strongadhesion between bubbles modify foam structure with larger films, resulting in faster than predicted coarseningrates. If the surface permeability is very low, coarsening is also faster than predicted, as some of the gas transfersoutside of foam films. These results allow us to rationalise the multiple impacts of stabiliser chemistry on foamcoarsening
The conundrum challenges for Research Software and Research Data in Open Science
No full textInternational audienceAbstractThe Borgman's conundrum challenges [1] have been initially formulated concerning the difficulties to share Research Data: which Research Data might be shared, by whom, with whom, under what conditions, why, and to what effects.In our previous work, we have proposed a Research Software Definition [2] with a formulation that we have adapted in order to propose a Research Data definition [3,4]. We have thus constructed a framework to understand and to explain Research Software and Research Data in the Open Science context [5].This framework is constructed in three stages: definition, dissemination, and evaluation of these research outputs [2,3,4], and it is now completed with answers to the Borgman's conundrum challenges for Research Data [3] and for Research Software [6].In this talk we will present our answers to the Borgman's conundrum challenges, and we will explain the comparison methodologies that we have developed in order to construct and to complete this Open Science framework.It is our understanding that to provide correct and clear answers to the conundrum questions will have, as a consequence, the improvement of Research Software and Research Data sharing and dissemination practices, which, in turn, will enhance trustworthiness, correctness, rigor, reproducibility, reusability and transparency in the research endeavor.This FOSDEM'25 presentation follows and extends our previous talks at FOSDEM: [FOSDEM'21] Free/Open source Research Software production at the Gaspard-Monge Computer Science laboratory. Lessons learnt. https://archive.fosdem.org/2021/schedule/event/open_research_gaspard_monge/ [FOSDEM'22] On the dissemination/evaluation loop for Research Software. https://archive.fosdem.org/2022/schedule/event/open_research_cdur/ ReferencesBorgman, C.L. The conundrum of sharing research data. J Am Soc Inf Sci Tec 2012, 63, 1059–1078. https://doi.org/10.1002/asi.22634 Gomez-Diaz, T.; Recio, T. On the evaluation of research software: the CDUR procedure [version 2; peer review: 2 approved]. F1000Research 2019, 8 1353. https://doi.org/10.12688/f1000research.19994.2Gomez-Diaz, T.; Recio, T. Research Software vs. Research Data I: Towards a Research Data definition in the Open Science context. [version 2; peer review: 3 approved]. F1000Research 2022, 11 118. https://doi.org/10.12688/f1000research.78195.2 Gomez-Diaz, T.; Recio, T. Research Software vs. Research Data II: Protocols for Research Data dissemination and evaluation in the Open Science context. [version 2; peer review: 2 approved]. F1000Research 2022, 11 117. https://doi.org/10.12688/f1000research.78459.2 Gomez-Diaz, T.; Recio, T. Towards an Open Science definition as a political and legal framework: on the sharing and dissemination of research outputs. POLIS 2020, N. 19. https://doi.org/10.58944/yuro5734. Version 3, 2021, available at https://zenodo.org/doi/10.5281/zenodo.4577065 Gomez-Diaz, T.; Recio, T. The conundrum challenges for Research Software in Open Science, Computers, 2024, 13(11), 302. https://doi.org/10.3390/computers13110302</ol
Box complexes: At the crossroad of graph theory and topology
No full textInternational audienceVarious simplicial complexes can be associated with a graph. Box complexes form an important family of such simplicial complexes and are especially useful for providing lower bounds on the chromatic number of the graph via some of their topological properties. They provide thus a fascinating topic mixing topology and discrete mathematics. This paper is intended to provide an up-do-date survey on box complexes. It is based on classical results and recent findings from the literature, but also establishes new results improving our current understanding of the topic, and identifies several challenging open questions
Working in family firms
No full textInternational audienceFamily firms are ubiquitous in most countries. The differences in objectives, governance, and management styles between those firms and their non-family counterparts have several implications for the workforce, which scholars have only recently started to investigate. Family firms offer greater job security, employ different management practices, have a comparative advantage to avoid conflicts when employment relations are more hostile, and provide insurance to workers through implicit contracts when labor market regulation is limited. But all this also comes at a cost
New perspectives on Density-Matrix Embedding Theory
No full textQuantum embedding methods enable the study of large, strongly correlated quantum systems by (usually self-consistent) decomposition into computationally manageable subproblems, in the spirit of divide-and-conquer methods. Among these, Density Matrix Embedding Theory (DMET) is an efficient approach that enforces self-consistency at the level of one-particle reduced density matrices (1-RDMs), facilitating applications across diverse quantum systems. However, conventional DMET is constrained by the requirement that the global 1-RDM (low-level descriptor) be an orthogonal projector, limiting flexibility in bath construction and potentially impeding accuracy in strongly correlated regimes. In this work, we introduce a generalized DMET framework in which the low-level descriptor can be an arbitrary 1-RDM and the bath construction is based on optimizing a quantitative criterion related to the maximal disentanglement between different fragments. This yields an alternative yet controllable bath space construction for generic 1-RDMs, lifting a key limitation of conventional DMET. We demonstrate its consistency with conventional DMET in appropriate limits and exploring its implications for bath construction, downfolding (impurity Hamiltonian construction), low-level solvers, and adaptive fragmentation. We expect that this more flexible framework, which leads to several new variants of DMET, can improve the robustness and accuracy of DMET
Equilibrium with non-convex preferences: some insights
No full textWe study the existence of equilibrium when agents’ preferences may not beconvex. For some specific utility functions, we provide a necessary and sufficientcondition under which there exists an equilibrium. The standard approach cannot be directly applied to our examples because the demand correspondence of some agents is neither single-valued nor convex-valued
Livrable : Transports en commun, marche, vélo et micro-mobilité. Dix volets pour aménager des quartiers de gare du « quart d’heure » de la région Hauts-de-France, à l’échelle piétonnière et cyclable: Synthèse du projet de recherche doctorale à destination des décideurs
No full textThe growing interest in cycling and the rise of micromobility signal a profound shift in daily mobility patterns, driven by an increasing demand for multimodality and intermodality. This research underscores the pivotal role of integrating these diverse transport modes with public transit networks, offering an effective response to the challenges of first- and last-mile connectivity. Our findings reveal a strong potential for modal shift from private cars to intermodal solutions. This presents a dual opportunity: enhancing the appeal of transit while fostering more sustainable local mobility. To achieve this, these ten strategic areas aim to bridge urban planning and mobility by promoting a seamless synergy between a well-developed “bicycle system” and Transit-Oriented Development projects.This deliverable provides policymakers, urban planners, and transport operators with practical tools to fully integrate cycling into station neighborhoods. Through ten strategic recommendations, this policy brief outlines key actions to facilitate intermodal mobility and promote urban development that is not only transit-oriented but also designed to support proximity mobility, including walking and cycling.Le regain d’intérêt pour le vélo et l’émergence de la micro-mobilité témoignent d’une transformation profonde des pratiques de mobilité quotidienne, portée par une demande croissante d’intermodalité. La recherche menée met en relief le rôle clé de ces combinaisons modales diversifiées avec les réseaux de transport en commun, qui apparaissent comme une solution efficace aux défis des premiers et derniers kilomètres.Nos estimations révèlent un potentiel de report modal significatif de l’automobile vers ces pratiques intermodales. L’enjeu est double : renforcer l’attractivité des transports en commun tout en favorisant des déplacements de proximité plus sobres. À cette fin, ces dix volets contribuent à articuler urbanisme et mobilité en promouvant une synergie entre le développement d’un véritable « système vélo » et l’aménagement de territoires orientés vers les réseaux de transport en commun.Ce livrable vise à fournir aux décideurs, aménageurs et opérateurs de transport des outils pour intégrer pleinement le vélo et la micro-mobilité dans les quartiers de gare. Ce policy brief formule ainsi dix recommandations stratégiques pour créer des conditions favorables à la pratique intermodale et pour encourager un développement urbain à la fois orienté vers les transports en commun et soutenu par la marche, le vélo et la micro-mobilité
Scénarios économiques pour l'évaluation des risques financiers liés à la perte de biodiversité : Objectifs, Méthodes et Applications à la France et à l'objectif « zéro artificialisation nette »
No full textThe rapid and significant decline in biodiversity is expected to bring profound changes to our economies. Addressing this decline requires large-scale transformations in consumption and production patterns. Central banks are increasingly concerned about how financial risks could stem from both the damages induced by continued loss of biodiversity (‘physical risks') and the misalignment of firms and financial institutions with transition efforts to ‘halt and reverse' biodiversity loss (‘transition risks').This thesis analyses how to assess biodiversity-related financial risks, with a focus on the French context. It examines in particular how economic scenarios can be developed to assess these risks while adhering to a strong sustainability principle.The first part of the thesis focuses on both physical and transition biodiversity-related risks, drawing inspiration from existing methods in climate-related financial risk analysis. Chapter 1 analyses how stylised and applied Integrated Assessment Models (IAMs) - initially used to design global climate scenarios for stress tests - could contribute to designing similar scenarios representing the economic impacts of biodiversity loss and of the transition. It finds that stylised IAMs show significant impacts of biodiversity loss on GDP, although with no detail on transmission channels and some calibration issues. In contrast, applied IAMs focus on more detailed shocks, often linked with climate or land-use, but overlook many transmission channels of nature-related shocks to the macro-economy, and have features that tend to mitigate economic impacts. Chapter 2 presents a data-based analysis of the exposure of French financial institutions (FFIs) to biodiversity-related physical and transition risks, via the dependencies upon ecosystem services (physical risks) and the biodiversity footprint (transition risks) of the non-financial firms they finance. It finds that, in 2019, 42% of FFIs' security portfolio were linked to companies highly dependent on ecosystem services, while 30% were connected with companies with significant negative impacts on biodiversity. It also assesses the FFIs portfolio's biodiversity footprint and finds that it is equivalent to the complete loss of 130,000 km² of pristine nature.The second part of the thesis focuses on the possible ‘transition risks' associated with a key French biodiversity policy aimed at achieving 'No Net Land-Take' (NNLT) by 2050. Chapter 3 constructs a dataset tracking the use of built-up land (stock) and land-take (flow) by French economic sectors to evaluate the vulnerability of these sectors to the NNLT objective. It finds significant sectoral heterogeneity in land use, with sectors like Wholesale and Retail Trade and Manufacturing being prominent land-users. However, the latter may not necessarily be the most vulnerable to the NNLT regulation, in contrast to sectors such as Agriculture and Accommodation Services. Chapter 4 introduces a novel approach for assessing biodiversity transition financial risks through the concept of 'ecological debts.' This method values the misalignment between current biodiversity pressures (e.g. land-take) and policy goals (e.g. NNLT). Valuation is made in monetary terms using the cost of ecosystem restoration, which Chapter 5 computes for urban soil restoration. These also provide insights for future modelling of the economic impacts of the NNLT objective and quantifying investment needs.In conclusion, this thesis explores, constructs and applies a diversity of tools and methods at several scales to better apprehend biodiversity-related financial risks, with a particular focus on sector-level and data-driven approaches. It contributes to the literature on this emerging topic, and on the economics of the biodiversity transition.Le déclin rapide de la biodiversité pourrait entraîner des changements économiques profonds. Endiguer cette perte nécessite des transformations à grande échelle des modes de consommation et de production. Les banques centrales sont de plus en plus préoccupées par les risques financiers qui pourraient découler à la fois des dommages causés par la perte de biodiversité (« risques physiques ») et du décalage des entreprises et des institutions financières avec les politiques de transition nécessaire pour arrêter ce déclin (« risques de transition »).Cette thèse analyse les risques financiers liés à la biodiversité, en se concentrant sur le cas français. Elle examine en particulier la manière dont des scénarios économiques peuvent être développés pour évaluer ces risques tout en respectant un principe de durabilité forte.La première partie considère à la fois les risques physiques et de transition, et s'inspire des méthodes évaluant les risques financiers liés au climat. Le chapitre 1 analyse comment les modèles d'évaluation intégrée (IAM), utilisés initialement pour concevoir des scénarios mondiaux pour les stress-tests climatiques, pourraient être adaptés pour concevoir des scénarios analogues représentant les impacts économiques de la perte de biodiversité. On trouve que les IAM stylisés montrent des effets forts de la perte de biodiversité sur le PIB, mais ne détaillent pas les canaux de transmission et font face à des problèmes de calibration. Par contraste, les IAM appliqués représentent des chocs plus détaillés, souvent liés au climat ou à l'usage des terres, mais négligent de nombreux aspects par lesquels la perte de biodiversité pourrait affecter l'économie, et ont des caractéristiques atténuant les impacts économiques. Le chapitre 2 présente une analyse de l'exposition des institutions financières françaises (IFFs) aux risques physiques et de transition liés à la biodiversité, via l'évaluation des dépendances aux services écosystémiques (risques physiques) et de l'empreinte biodiversité (risques de transition) des entreprises qu'elles financent. En 2019, 42 % du portefeuille de titres des IFFs étaient liés à des entreprises fortement dépendantes des services écosystémiques, tandis que 30 % l'étaient à des entreprises ayant de forts impacts sur la biodiversité. L'empreinte biodiversité du portefeuille des IFFs équivaut à la perte totale de 130 000 km² de nature intacte.La deuxième partie se concentre sur les possibles risques de transition lié à une politique spécifique visant à atteindre « Zéro artificialisation nette » (ZAN) d'ici 2050. Pour évaluer la vulnérabilité de ces secteurs à cet objectif, le chapitre 3 construit un jeu de données sur l'usage de sols artificialisés (stock) et l'artificialisation des sols (flux) par les secteurs économiques français. Des secteurs comme le Commerce et l'Industrie manufacturière sont de grands utilisateurs de sols artificialisés, mais ne semblent pas les plus vulnérables au ZAN, contrairement à l'Agriculture ou aux Services d'Hébergement. Le chapitre 4 propose une approche novatrice pour évaluer les risques financiers de transition biodiversité, via l'usage du concept de « dettes écologiques ». Elle valorise l'écart entre les pressions actuelles sur la biodiversité (l'artificialisation des sols) et les objectifs politiques (le ZAN). La valorisation monétaire de cet écart est faite grâce au coût de restauration des écosystèmes, que le chapitre 5 calcule pour les sols urbains. Ces coûts fournissent aussi des pistes pour modéliser des impacts économiques de l'objectif ZAN et estimer des besoins d'investissements.Cette thèse explore, construit et applique une diversité d'outils et de méthodes à plusieurs échelles pour mieux appréhender les risques financiers liés à la biodiversité, en mettant particulièrement l'accent sur des approches sectorielles et les données. Elle contribue à la littérature sur ce sujet émergent, ainsi qu'à l'économie de la transition écologique
Is broader trading welfare improving for emission trading systems?
No full textInternational audienceEmission trading systems are cornerstone policies to reduce carbon emissions. Although economic intuition suggests that broader allowance trading should be welfare improving, this paper proves that view can be wrong. Under an increasingly popular type of emissions trading scheme — tradable performance standards (TPS), multiple narrow markets can decrease emissions relative to a single unified market, so that restricting trade does not always harm welfare. We show analytically that, when intensity benchmarks are heterogeneous within a sector, this result can hold even if the well-known “implicit output subsidy” does not impact total output. Finally, we provide evidence that this concern can be of high practical relevance. Using a general equilibrium model of China’s TPS for 2020–2030, we show that broader trading results in significantly higher emissions (up to 10%), and decreases welfare relative to narrower markets when the social cost of carbon exceeds $91/tCO