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Certified to Stay ? Long-Run Experimental Evidence on Land Formalization and Widows’ Tenure Security in Benin
No full textIn settings where women's land rights are informal, the death of a husband can severely limit a widow's access to land and her ability to remain in her home -- especially in the absence of a male heir. This paper examines whether large-scale land formalization programs can improve widows' land access. Using data from a randomized controlled trial in rural Benin, the analysis finds that widows in villages with land formalization are more likely to stay in their homes four years after the program, with the strongest effects among those without a male heir. The paper identifies two key mechanisms: enhanced community recognition of women's land rights and greater decision-making power over land resources. These findings highlight the potential of land formalization to strengthen women's tenure security and promote their long-term economic stability in similar settings
Rigorous numerical computation of the Stokes multipliers for linear differential equations with single level one
No full textWe describe a practical algorithm for computing the Stokes multipliers of a linear differential equation with polynomial coefficients at an irregular singular point of single level one. The algorithm follows a classical approach based on Borel summation and numerical ODE solving, but avoids a large amount of redundant work compared to a direct implementation. It applies to differential equations of arbitrary order, with no genericity assumption, and is suited to high-precision computations. In addition, we present an open-source implementation of this algorithm in the SageMath computer algebra system and illustrate its use with several examples. Our implementation supports arbitrary-precision computations and automatically provides rigorous error bounds. The article assumes minimal prior knowledge of the asymptotic theory of meromorphic differential equations and provides an elementary introduction to the linear Stokes phenomenon that may be of independent interest
Morphology of ice structures induced by a freezing rivulet
No full textWe investigate the solidification of a water rivulet flowing over a cold inclined substrate and the resulting formation of three-dimensional ice structures. Using a controlled hydraulic and thermal setup, combined with spatiotemporal phase-shifting profilometry and infrared thermography, we characterize both the transient evolution and the final morphology of the ice. We show that a typical experiment proceeds through three stages: formation of a straight ice ridge that stabilizes the rivulet, destabilization and lateral excursions of the flow leading to rapid transverse spreading of the ice structure, and progressive thickening and smoothing of the ice block. Across a wide range of flow rates, inclinations and thermal conditions, the final morphology comprises an upstream triangular lateral envelope, followed by a downstream region of nearly constant width once the substrate edges are reached. Infrared measurements reveal that the rivulet residence time on the substrate follows a Gaussian distribution in the azimuthal angle, implying that the central region of the structure is visited far more frequently than its lateral edges. Focusing on the domain where the height has converged at the end of the experiments, we develop a two-dimensional theoretical model that couples a hydrodynamic model for the rivulet geometry with heat transport in both liquid and solid phases. In the large Péclet number limit, the model predicts an exponential increase of the stationary ice height along the flow direction and it shows an excellent agreement with the experimental height field. We further show how the combination of the stationary height profile and the non-uniform residence time distribution controls the angular convergence of the ice cross-sections.</div
A year-long observational analysis of atmospheric trace gases and particulate matter in Kathmandu
No full textInternational audienceKathmandu Valley is one of the most densely populated cities in Nepal, facing significant air quality challenges. This study presents a comprehensive analysis based on twelve months of continuous air quality measurement data collected at the Khumaltar Air Quality Monitoring Station (ICIMOD AQMS), which is located in the southern part of the Kathmandu Valley. The study investigates particulate matter (PM10, PM2.5 , PMC (PM10-PM2.5)) alongside trace gases (O3, NOx, SO2, and CO), focuses on their seasonal, diurnal variations, interspecies correlations, potential sources, and the impact of regional atmospheric transport. The results reveal that the annual PM2.5 concentration (49 µg m-3) largely exceeds the WHO air quality guideline of 5 µg m -3 . Pollutant concentrations show clear seasonal variation, with peaks during the winter and pre-monsoon seasons, and a noticeable decline during the monsoon. A strong correlation (r = 0.82, p = 0.00) between PM2.5 and NOx indicates that fossil fuel combustion is a dominant source of fine particulate pollution. During the pre-monsoon season, O3 concentrations occasionally exceed 100 ppb (8-hr running average), with seasonal diurnal concentration observed close to 90 ppb in the afternoon. The study found that temperature and relative humidity significantly influence coarse PM levels, with a strong negative correlation (r = -0.89, p = 0.00) between coarse PM and the relative humidity, suggesting less resuspension under moist conditions. Furthermore, this study highlights the severe air pollution in the Kathmandu Valley throughout the year, driven primarily by local emissions, with regional atmospheric transport further contributing to poor air qualit
Separation rates for the detection of synchronization of interacting point processes in a mean field frame. Application to neuroscience.
No full textInternational audiencePermutation tests have been proposed by Albert et al. (2015) to detect dependence between point processes, modeling in particular spike trains, that is the time occurrences of action potentials emitted by neurons. Our present work focuses on exhibiting a criterion on the separation rate to ensure that the Type II errors of these tests are controlled non asymptotically. This criterion is then discussed in two major models in neuroscience: the jittering Poisson model and Hawkes processes having components interacting in a mean field frame and evolving in stationary regime. For both models, we obtain a lower bound of the size of the sample necessary to detect the dependency between two neurons
Self-interacting approximation to McKean-Vlasov long-time limit: a Markov chain Monte Carlo method
No full textInternational audienceFor a certain class of McKean-Vlasov processes, we introduce proxy processes that substitute the mean-field interaction with self-interaction, employing a weighted occupation measure. Our study encompasses two key achievements. First, we demonstrate the ergodicity of the self-interacting dynamics, under broad conditions, by applying the reflection coupling method. Second, in scenarios where the drifts are negative intrinsic gradients of convex mean-field potential functionals, we use entropy and functional inequalities to demonstrate that the stationary measures of the self-interacting processes approximate the invariant measures of the corresponding McKean-Vlasov processes. As an application, we show how to learn the optimal weights of a two-layer neural network by training a single neuron
A strong-weak duality for the 1d long-range Ising model
No full textInternational audienceWe investigate the one-dimensional Ising model with long-range interactions decaying as . In the critical regime, for , this system realizes a family of nontrivial one-dimensional conformal field theories (CFTs), whose data vary continuously with . For s>1 the model has instead no phase transition at finite temperature, as in the short-range case. In the standard field-theoretic description, involving a generalized free field with quartic interactions, the critical model is weakly coupled near but strongly coupled in the vicinity of the short-range crossover at . We introduce a dual formulation that becomes weakly coupled as . Precisely at , the dual description becomes an exactly solvable conformal boundary condition of the two-dimensional free scalar. We present a detailed study of the dual model and demonstrate its effectiveness by computing perturbatively the CFT data near , up to next-to-next-to-leading order in , by two independent approaches: (i) standard renormalization of our dual field-theoretic description and (ii) the analytic conformal bootstrap. The two methods yield complete agreement
Search for b hadron decays to long-lived particles in the CMS endcap muon detectors
No full textInternational audienceA search for long-lived particles originating from the decay of b hadrons produced in proton-proton collisions with a center-of-mass energy of 13 TeV at the LHC is presented. The analysis is performed on a data set recorded in 2018, corresponding to an integrated luminosity of 41.6 fb. Interactions of the long-lived particles in the CMS endcap muon system would create hadronic or electromagnetic showers, producing clusters of detector hits. Selected events contain at least one such high-multiplicity cluster in the muon endcaps and require the presence of a displaced muon. The most stringent upper limits to date on the branching fraction (B K), where the long-lived particle decays to a pair of hadrons, are obtained for masses of 0.33.0 GeV and mean proper decay lengths in the range of 1500 cm
Search for heavy neutral leptons in decays to positrons
No full textInternational audienceA search for heavy neutral lepton () production in in-flight decays using data collected by the NA62 experiment at CERN in 2017-2024 is reported. Upper limits for the extended neutrino mixing matrix element are established at the level of for heavy neutral leptons with mass in the range 95-126 and lifetime exceeding 50 ns
First observation of violation and measurement of polarization in decays
No full textInternational audienceAn amplitude analysis of the decay is performed in the mass regions and , using collision data recorded with the LHCb detector corresponding to an integrated luminosity of . The polarization fractions and asymmetries for decays are measured. Violation of the symmetry in the decay is observed for the first time, with a significance exceeding nine standard deviations. The asymmetry is measured to be and the -averaged longitudinal polarization fraction of . The measurements help to shed light on the polarization puzzle of mesons decaying to two vector mesons