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Extracting light-cone wave functions from covariant amplitudes: a detailed study in scalar field theory
No full textInternational audienceWe propose a conjectured formula that systematically maps covariant off-shell amplitudes to light-cone wave functions in scalar field theory. Through an explicit comparison at one-loop accuracy, we establish its equivalence to the light-cone perturbation theory series, thereby validating the conjecture at this order. Applying this formula, we efficiently re-derive wave functions from known covariant amplitudes, bypassing both the conceptual complexities of light-cone quantization and the technical challenges of perturbative calculations in this framework. In addition to simplifying computations, this approach opens new avenues for applications in gauge theories and deeper explorations of the fundamental equivalence between covariant and light-cone quantization
Global transport of stratospheric aerosol produced by Ruang eruption from EarthCARE ATLID, limb-viewing satellites and ground-based lidar observations
No full textInternational audienceThe Atmospheric LIDar (ATLID) instrument of the ESA’s Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) satellite mission launched in May 2024 provides high-resolution vertical profiling of aerosols and clouds at 355 nm. Fully operational since July 2024, ATLID has been witness to a significant perturbation of stratospheric aerosol budget following the eruptions of Ruang volcano (Indonesia) in late April 2024. Using ATLID together with limb-viewing satellite instruments (OMPS-LP and SAGE III), we quantify the stratospheric aerosol perturbation generated by the Ruang eruption and characterize the global transport of volcanic aerosols. To evaluate the ATLID performance in the stratosphere, its data are compared with collocated ground-based lidar observations at various locations in both hemispheres and overpass-coordinated balloon flights carrying AZOR backscatter sonde. The intercomparison with suborbital observations suggests excellent performance of ATLID in the stratosphere and proves its capacity to accurately resolve fine structures in the vertical distribution of stratospheric aerosols. Using various satellite observations, we show that Ruang’s eruptive sequence in April 2024 produced eruptive columns reaching 25 km altitude, and resulted in a doubling of the tropical stratospheric aerosol abundance for several months. The eruption timing in austral Fall and its high-altitude reach fostered efficient poleward transport into the southern extratropics during austral Winter 2024. By the time of the austral Fall 2025, the sulphate aerosols from Ruang have spread across the entire Southern hemisphere and were most probably entrained by the 2025 Antarctic polar vortex, potentially enhancing the polar stratospheric cloud occurrence
A comprehensive analysis of the decay
No full textInternational audienceAn analysis of the decay is presented using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 8.4 fb. The full set of -averaged and -asymmetric angular observables is determined in bins of the invariant mass squared of the dimuon system, as well as the branching fraction relative to the decay. For the first time, the full set of observables pertaining to the S-wave contribution to the final state are presented and consideration is given to effects arising from the mass of the muons. The measurements of the -averaged observables and the branching fractions continue to exhibit the pattern of tensions with the Standard Model predictions that have been seen in previous analyses that use part of the dataset considered in this study. The extracted -asymmetry observables show no significant deviations from zero
Modeling high dimensional point clouds with the spherical cluster model
No full textA parametric cluster model is a statistical model providing geometric insights onto the points defining a cluster. The spherical cluster model (SC) approximates a finite point set P ⊂ R d by a sphere S(c, r) as follows. Taking r as a fraction η ∈ (0, 1) (hyper-parameter) of the std deviation of distances between the center c and the data points, the cost of the SC model is the sum over all data points lying outside the sphere S of their power distance with respect to S. The center c of the SC model is the point minimizing this cost. Note that η = 0 yields the celebrated center of mass used in KMeans clustering. We make three contributions.First, we show fitting a spherical cluster yields a strictly convex but not smooth combinatorial optimization problem. Second, we present an exact solver using the Clarke gradient on a suitable stratified cell complex defined from an arrangement of hyper-spheres. Finally, we present experiments on a variety of datasets ranging in dimension from d = 9 to d = 10, 000, with two main observations. First, the exact algorithm is orders of magnitude faster than BFGS based heuristics for datasets of small/intermediate dimension and small values of η, and for high dimensional datasets (say d > 100) whatever the value of η. Second, the center of the SC model behave as a parameterized high-dimensional median.The SC model is of direct interest for high dimensional multivariate data analysis, and the application to the design of mixtures of SC will be reported in a companion paper
Machine-Learning Text Analysis of Intergenerational Mobility Perceptions in Germany, Sweden, and the United Kingdom
No full textResearch on intergenerational mobility has traditionally focused on objective markers of socioeconomic position. In this study, we argue that the subjective aspects of intergenerational mobility deserve greater attention and empirically explore what individuals report they compare when they gauge their intergenerational mobility trajectories. Drawing on representative survey data from Germany, Sweden, and the United Kingdom, as well as machine-learning-driven text analyses of open-ended survey responses, we reveal that, in addition to conventional measures of intergenerational mobility, such as education, occupational status, and income, individuals consider a diverse array of factors, including family life, home ownership, and lifestyle choices. Our findings highlight the heterogeneity of these comparisons across different countries, genders, and generations. We identify significant variations in the dimensions of intergenerational comparisons, such as the prominence of education in Sweden, the focus on housing in the United Kingdom, and the salience of freedom, opportunity, and lifestyle in Germany. Furthermore, gender differences reveal that females are more likely to emphasize education and family life, while males focus on income and occupational status. These insights provide a deeper understanding of the subjective dimensions of intergenerational mobility and contribute to ongoing debates in social stratification research and general social theory
First measurement of the decay-time-integrated asymmetry in decays
No full textInternational audienceA measurement of the flavour-untagged decay-time-integrated asymmetry in the flavour-specific decay , , is performed using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of , corresponding to a total integrated luminosity of . The asymmetry is measured in two meson decay modes, and . The combined result, , is consistent with the Standard Model expectation and provides a direct constraint on new physics in tree-level -hadron decays
Platform Information Provision: Evidence from an Online Auction Platform
No full textDigital platforms have reduced search costs, fostering niche product markets. However, these markets often suffer from limited and asymmetric information due to a lack of consumer feedback, risking market failure. This paper examines Catawiki's solution, where over 240 experts provide value estimates for rare collectibles being auctioned on a digital platform. Using data from 57,000 listings, we analyze the impact of these estimates on final prices and seller behavior. By leveraging both minimum and maximum expert estimates, we isolate the effect of increasing the maximum estimate while holding the minimum estimate fixed. Our findings indicate that higher expert estimates increase final bidden prices, suggesting buyer trust. Sellers also adjust their behavior by setting fewer reserve prices for items with high estimates, leading to more bids. Despite potential conflicts of interest stemming from the platform's dual role as matchmaker and advisor, our results show that expert estimates are influential even when potentially overinflated. This study underscores the critical role of platform-provided information in enhancing market efficiency
Reduced carbon outflow from a Floridian mangrove estuary up to two years after a hurricane
No full textInternational audienceMangrove ecosystems are our most carbon rich forests. They play a vital role in regulating carbon fluxes to the ocean (outwelling). These ecosystems are increasingly threatened by degradation. Here we present a 5-year long timeseries from 2014 to 2019 of dissolved organic and inorganic carbon outwelling from the Everglades National Park (Florida, US). The data includes a category 3-4 hurricane in 2017. Our results reveal a substantial and sustained decrease in both organic and inorganic carbon outwelling. Both remain low for up to two years following the hurricane. The mangrove estuarine contribution decreases compared to that of the marsh upstream. The proposed mechanisms are increased outwelling during the hurricane and extreme tree mortality limiting root respiration. With more intense hurricanes in the future, carbon outwelling risks being permanently lowered, which could alter the buffering capacity of coastal ocean acidification depending on the ratio of carbon dioxide within dissolved inorganic carbon
ClimarisQ: What can we learn from playing a game for climate education?
No full textInternational audienceClimarisQ is both a web and mobile game developed by the Institut Pierre-Simon Laplace to support climate change communication through interactive decision-making. This paper presents an exploratory evaluation of the game based on a post-play questionnaire completed by 77 users. Respondents rated ClimarisQ positively in terms of usability and scientific credibility. Self-reported outcomes indicate that the game supported reflection on the complexity, trade-offs, and uncertainty of climate-related decision-making, rather than the acquisition of factual knowledge, particularly among users with prior expertise. The respondent group was predominantly composed of educated and climate-aware adults, which limits generalization to other audiences. Beyond the questionnaire, the game has been tested in dozens of facilitated sessions with thousands of non-specialist participants, with consistently positive feedback. These results suggest that ClimarisQ can function as a complementary tool for climate education and outreach, especially when used in facilitated settings that encourage discussion and interpretation
Estimating the True Distribution of Data Collected with Randomized Response
No full textInternational audienceRandomized Response (RR) is a protocol designed to collect and analyze categorical data with local differential privacy guarantees. It has been used as a building block of mechanisms deployed by Big Tech companies to collect app or web users' data. Each user reports an automatic random alteration of their true value to the analytics server, which then estimates the histogram of the true unseen values of all users using a debiasing rule to compensate for the added randomness. A known issue is that the standard debiasing rule can yield a vector with negative values (which can not be interpreted as a histogram), and there is no consensus on the best fix. An elegant but slow solution is the Iterative Bayesian Update algorithm (IBU), which converges to the Maximum Likelihood Estimate (MLE) as the number of iterations goes to infinity. This paper bypasses IBU by providing a simple formula for the exact MLE of RR and compares it with other estimation methods experimentally to help practitioners decide which one to use