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Les lieux nommés d’après Marceline Desbordes-Valmore
No full textNational audienceVoies de circulation, établissements scolaires, bibliothèques, salles de spectacle, une trentaine de lieux en France sont nommés d’après Marceline Desbordes-Valmore. Ces choix de dénomination correspondent à des logiques variées : hommages à l’enfant du pays, liens avec l’itinéraire de la poète et avec son œuvre, dénominations en série dans des quartiers aux noms de poètes. Une comparaison avec les autres poètes françaises montre une évolution du nombre d’odonymes relatifs à Marceline Desbordes-Valmore similaire à celle de Lucie Delarue-Mardrus. Avec une quinzaine d’odonymes chacune, elles sont devancées par Louise Labé et plusieurs poètes du XXe siècle, ainsi que par d’autres femmes connues pour d’autres activités que la poésie, la reine Marguerite de Valois et l’écrivaine et militante Louise Michel
A stable local commuting projector and optimal hp approximation estimates in H(curl)
No full textInternational audienceWe design an operator from the infinite-dimensional Sobolev space H(curl) to its finite-dimensional subspace formed by the Nédélec piecewise polynomials on a tetrahedral mesh that has the following properties: 1) it is defined over the entire H(curl), including boundary conditions imposed on a part of the boundary; 2) it is defined locally in a neighborhood of each mesh element; 3) it is based on simple piecewise polynomial projections; 4) it is stable in the L2-norm, up to data oscillation; 5) it has optimal (local-best) approximation properties; 6) it satisfies the commuting property with its sibling operator on H(div); 7) it is a projector, i.e., it leaves intact objects that are already in the Nédélec piecewise polynomial space. This operator can be used in various parts of numerical analysis related to the H(curl) space. We in particular employ it here to establish the two following results: i) equivalence of global-best, tangential-trace-and curl-constrained, and local-best, unconstrained approximations in H(curl) including data oscillation terms; and ii) fully h- and p- (mesh-size- and polynomial-degree-) optimal approximation bounds valid under the minimal Sobolev regularity only requested elementwise. As a result of independent interest, we also prove a p-robust equivalence of curl-constrained and unconstrained best-approximations on a single tetrahedron in the H(curl)setting, including hp data oscillation terms
Moral Force: Leaders' Actions and Public Health Compliance in Crisis
No full textCharismatic leaders shape public sentiment but may weaken institutions by prioritizing personal appeal over trust in government. During the COVID-19 pandemic, the Mexican president disregarded stay-at-home guidelines. We assess the impact on social distancing using granular mobility and electoral data. Applying a dynamic difference-in-difference design and leveraging the timing of social distancing announcements and presidential support, we find increased mobility in pro-president areas, leading to 38% more COVID-19 cases and 21% more deaths. Our findings suggest the president's example, rather than partisan differences, drove these effects
Does Feasibility Explain the Unequal Development of Working From Home?
No full textUsing rich historical surveys on job tasks and advanced machine learning techniques, we study which jobs can be moved from the office to home over three decades in France.The share of jobs that can be done from home has increased steadily from 14% in 1991 to 45% in 2021. At the same time, actual Working From Home (WFH) remained limited to less than one fifth of its full potential before the Covid-19 crisis and is still below it in 2021.The growth of WFH is largely unrelated to the evolution of job tasks, implying that the main obstacles to WFH have not been technical constraints. Low-skilled employees in particular have jobs that have long been largely teleworkable but they were barely teleworking before the Covid-19 crisis and remained still below 50% of their full potential during it. This pattern is not explained by differences in workers' desire to telework. It implies that the well-known large inequality in access to WFH along the earnings distribution cannot be attributed only to feasibility constraints and is potentially inefficient.</p
Food Waste: You Can't Always Want What You Get
No full textFood waste constitutes a significant economic inefficiency and should therefore be a central policy issue. While in low-income countries food waste is often associated with poor harvesting, storage and transportation conditions, in middle-and high-income countries consumers' behavior is considered to be the main driver of this problem. The general aim of our paper is to contribute to the understanding of food waste. We focus on household food waste and the economic mechanisms behind it. We propose a stylized model in which food waste appears as an economic decision of households. Our framework of "rational food waste" relies primarily on consumer behavioural biases, which could be further encouraged by aggressive pricing strategies such as quantity discounts
Fast mesoscopic model of plasticity in polycrystals to compute probabilistic S-N curves in high cycle fatigue
No full textInternational audienceHigh cycle fatigue in polycrystals is mostly governed by deterministic laws such as crystal plasticity, but also depends on probabilistic properties, such as random defects and crystallographic and morphological textures, which result in significant scatter of fatigue lifetime at the macroscopic scale. Thus, modeling fatigue phenomena so that the probabilistic density function of failure is anticipated, would be useful especially for very high cycle fatigue involving up to 10^9 cycles. To do so, the grain structure with crystal orientations should be considered in full field computations, which usually involve prohibitive computation cost therefore hindering numerical exploration of statistical distribution of fatigue failures.This paper therefore consists in developing a very fast full field mesoscopic model of polycrystals subjected to crystal plasticity during cyclic loading based on energy minimization techniques. As a result, the uniform plastic slip in each grain is obtained in the form of a relatively simple recursive formula, which guarantees short computation time even for very high cycle fatigue. The proposed approach has been validated against a classical crystal plasticity finite element model in 2D, and satisfying agreement is observed. In addition the model has be applied in combination with classical fatigue criteria to rapidly compute the fatigue lifetime and then derive probabilistic S-N curves, hence creating a substantial link between crystallographic and morphological textures on the one hand, and fatigue lifetime estimations on the other hand
Rapports sociaux et possibles spatiaux : Les travailleuses du care rémunéré dans les quartiers
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Évaluation de risque des dérivés climatiques liés au marché de l'énergie.
No full textWith the increasing demand for climate risk transfer financial tools, climate derivatives have gained considerable popularity among both researchers and practitioners. This thesis contributes to deepening the understanding of the risk related to temperature and energy based derivatives.In Chapter 1, we develop a new stochastic volatility model for the average daily temperature that is a natural extension of the Ornstein-Uhlenbeck model proposed by Benth and Benth. This model allows to be more conservative regarding extreme events while keeping tractability. We give a method based on Conditional Least Squares to estimate the parameters on daily data and estimate our model on eight major European cities. We then show how to calculate efficiently the average payoff of weather derivatives both by Monte-Carlo and Fourier transform techniques. This new model allows to better assess the risk related to temperature volatility.In Chapter 2, we focus on quanto derivatives. We develop a coupled model for day-ahead electricity prices and average daily temperature which allows to model quanto weather and energy derivatives. These products are quickly spreading as they enable to hedge against both volumetric and price risks. Electricity day-ahead prices and average daily temperatures are modelled through non homogeneous Ornstein-Uhlenbeck processes driven by a Brownian motion and a Normal Inverse Gaussian Lévy process, which allows to include dependence between them. A Conditional Least Square method is developed to estimate the different parameters of the model and used on real data. Then, explicit and semi-explicit formulas are obtained for derivatives including quanto options and compared with Monte Carlo simulations. Last, we develop explicit formulas to hedge statically single and double sided quanto options by a portfolio of electricity options and temperature options (CDD or HDD).All in all, this study contributes to the establishment of a mathematical framework to better understand risk related to temperature and energy derivatives while answering to both business and research challenges.Face à une demande croissante d'outils financiers permettant de transférer du risque climatique, les dérivés climatiques ont connu un essor important parmi les chercheurs et les professionnels. Cette thèse contribue à l'approfondissement des techniques d'évaluation de risques des produits dérivés liés à la température. Dans le Chapitre 1, nous développons un nouveau modèle de volatilité stochastique pour la température journalière moyenne. Ce modèle constitue un élargissement du modèle classique d'Ornstein-Uhlenbeck proposé par Benth et Benth. Il nous permet d'être plus conservateur en ce qui concerne les événements extrêmes tout en conservant des méthodes de calcul numérique efficaces. Nous estimons les paramètres du modèle à partir de la méthode des moindres carrés conditionnels sur une base de données incluant huit grandes villes européennes. Nous montrons ensuite comment obtenir efficacement la distribution des paiements des dérivés par des techniques de Monte-Carlo et de transformée de Fourier. Ce nouveau modèle permet de mieux capter le risque lié à la volatilité de la température. Dans le Chapitre 2, nous nous concentrons sur les dérivés hybrides, appelés quantos, et liant prix de l'électricité et température moyenne journalière. Ces produits connaissent un grand succès puisqu'ils permettent de se couvrir à la fois contre les risques volumétriques et les risques de prix. Nous développons un modèle couplé. Les sous-jacents sont modélisés par des processus d'Ornstein-Uhlenbeck non homogènes entraînés par un mouvement Brownien et un processus de Lévy Normal Inverse Gaussien, permettant d'inclure la dépendance entre eux. Une méthode des moindres carrés conditionnels est développée pour estimer les différents paramètres du modèle et appliquée sur des données réelles. Ensuite, nous développons des formules explicites et semi-explicites les espérances de paiements des dérivés, y compris les options quantos. Ces résultats sont comparés à des simulations de Monte Carlo. Enfin, nous développons des formules explicites pour couvrir statiquement les options quantos simples et doubles par un portefeuille d'options d'électricité et d'options de température (CDD ou HDD).Dans l'ensemble, cette étude contribue à l'établissement d'un cadre mathématique permettant de mieux comprendre le risque lié aux dérivés de température et d'énergie tout en répondant aux problématiques des professionnels et de la recherche
Big hits in export growth
No full textInternational audienceThis paper identifies export accelerations at the country pair-product level that are large enough to drive aggregate export growth in the medium run. In a sample of 100 countries, these export “big hits” are rare, less than 2 percent of all export spells, yet account for over two-thirds of export growth in a given country. The paper then explores their microfoundations using matched customs-census firm-level data for France. We find that typically, two firms are sufficient to generate a big hit and these firms’ access to external financing is key to their ability to drive export success. Moreover, big hits spread within firms across destinations and products. Our results offer new evidence on the granularity of export growth by linking micro-level entrepreneurial decisions with country-level export outcomes
Can affirmative action policies be inefficiently persistent?
No full textInternational audienceWe develop a dynamic model where successive, decentralized policy makers must decide whether to implement affirmative action policies aimed at improving the performance of future generations of a targeted group. Employers do not perfectly observe if a worker benefited from affirmative action, but take that possibility into account, resulting in the devaluation of the worker’s credentials and an associated feeling of injustice. We establish that, in equilibrium, affirmative action is implemented perpetually by benevolent policy makers, despite the feeling of injustice that eventually dominates the anticipated benefits. This contrasts with the first best, which requires affirmative action to be temporary