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Idealized modeling of stratospheric aerosol injection deployment scenarios with two non-cooperative actors
No full textInternational audienceThis code is the version of https://github.com/OB-IPSL/two-actor-SRM used in the article by Määttänen et al. (2025) in Environmental Science: Atmospheres of the Royal Society of Chemistry (A. Määttänen, F. Ravetta, J. Bureau, T. Lurton and O. Boucher, Environ. Sci.: Atmos., 2026, DOI: 10.1039/D5EA00022J. The article investigates solar radiation management scenarios of two non-cooperative actors deploying stratospheric aerosol injection (SAI) through idealized experiments. The repository includes the codes for a four-box Energy Balance Model capable of predicting hemispheric temperatures and monsoon precipitation and the coupled PI-controller. A short README is included
Existence and orbital stability proofs of traveling wave solutions on an infinite strip for the suspension bridge equation
No full textIn this paper, we present a computer-assisted approach for constructively proving the existence of traveling wave solutions of the suspension bridge equation on the infinite strip Ω = R × (-d2, d2). Using a meticulous Fourier analysis, we derive a quantifiable approximate inverse A for the Jacobian DF(ū) of the PDE at an approximate traveling wave solution ū. Such approximate objects are obtained thanks to Fourier coefficient sequences and operators, arising from Fourier series expansions on a rectangle Ω0 = (-d1, d1) × (-d2, d2) for large d1. In particular, the challenging exponential nonlinearity of the equation is tackled using a rigorous control of the aliasing error when computing related Fourier coefficients. This allows to establish a Newton-Kantorovich approach, from which the existence of a true traveling wave solution of the PDE can be proven in a vicinity of ū. We successfully apply such a methodology in the case of the suspension bridge equation and prove the existence of multiple traveling wave solutions on Ω. Finally, given a proven solution ũ, a Fourier series approximation on Ω0 allows us to accurately enclose the spectrum of DF(ũ). Such a tight control provides the number of negative eigenvalues, which in turn, allows us to conclude about the orbital (in)stability of the traveling wave.</div
Stability analysis and long-time convergence of a partial differential equation model of two-phase ageing
No full textRecent biological evidence suggests the presence of a two-phase ageing process in several species. We introduce a system of two age-structured partial differential equations (PDE) representing two phases of ageing of a wild population. The model includes a coupling of both equations through birth and transition between phases and non-linearities due to competition. We show the existence, positivity and uniqueness of weak solutions in a general setting. For a simplified system of ordinary differential equations (ODE), we show existence and uniqueness of a strictly positive steady state attracting all trajectories. We study another simplification, a coupled PDE-ODE model, for which we prove existence, uniqueness and local asymptotic stability of a strictly positive steady state. Under further assumptions, but without assuming weak non-linearities, we show the global asymptotic stability of that steady state. The uniqueness of steady states and absence of oscillations in these systems show that the proportion of individuals in each phase at equilibrium is a unique feature of the model. This paves the way to ecological applications as the experimental measure of such a proportion could help gain some insight on the health of a wild population
On the Consistency and Performance of the Iterative Bayesian Update
No full textFor many social, scientific, and commercial purposes, it is often important to estimate the distribution of the users' data regarding a sensitive attribute, e.g. their ages, locations, etc. To allow this estimation while protecting the users' privacy, every user applies a local privacy protection mechanism that releases a noisy (sanitized) version of her/his original datum to the data collector; then the original distribution is estimated using one of the known methods, such as the matrix inversion (INV), RAPPOR's estimator, and the iterative Bayesian update (IBU). Unlike the other estimators, the consistency of IBU, i.e. the convergence of its estimate to the real distribution as the amount of noisy data grows, has been either ignored or incorrectly proved in the literature. In this article, we use the fact that IBU is a maximum likelihood estimator to prove that IBU is consistent. We also show, through experiments on real datasets, that IBU significantly outperforms the other methods when the users' data are sanitized by geometric, Laplace, and exponential mechanisms, whereas it is comparable to the other methods in the case of the k-RR and RAPPOR mechanisms. Finally, we consider the case when the alphabet of the sensitive data is infinite and we show a technique that allows IBU to operate in this case too.</div
Irradiation-resistant heterostructures based on monolayer MoS 2
No full textInternational audienceMonolayer molybdenum disulfide is a semiconducting 2D material presenting very appealing characteristics for its incorporation into electronic flexible devices. At present, atomic vacancies in its structure are known to significantly affect its properties. Nonetheless, the effects of electron irradiation on it are still under investigation. In this work, the structural, electronic, and optical properties of monolayer molybdenum disulfide are studied before and after electron irradiation. By analyzing samples either obtained via a mechanical exfoliation process or grown via chemical vapor deposition, we show that following irradiation no significant change is present. This result indicates a strong resistance to the effect of electron irradiation at energies able to induce the formation of sulfur vacancies. By comparing our results to the current literature, we hypothesize that previously reported effects of electron irradiation are either due to the formation of molybdenum vacancies or to ionization of the electronic shell of this material. The presented results help to shed light on the role of atomic vacancies on the properties of this 2D material from a fundamental point of view and on its usage in extreme environment applications
A posteriori closure of turbulence models: Are symmetries preserved?
No full textInternational audienceTurbulence modeling remains a longstanding challenge in fluid dynamics. Recent advances in data-driven methods have led to a surge of novel approaches aimed at addressing this problem. Thiswork builds upon our recent work [Phys. Rev. Fluids 10, 044602 (2025)], where we introduced anew closure for a shell model of turbulence using an a posteriori (or solver-in-the-loop) approach.Unlike most deep learning-based models, our method explicitly incorporates physical equationsinto the neural network framework, ensuring that the closure remains constrained by the underlyingphysics benefiting from enhanced stability and generalizability. In this paper, we further analyze thelearned closure, probing its capabilities and limitations. In particular, we look at joint probabilitydensity functions between resolved and unresolved variables, as well as the scale invariance ofmultipliers (ratios between adjacent shells) within the inertial range. Although our model excels inreproducing high-order statistical moments, it breaks this known symmetry near the cutoff, indicatinga fundamental limitation. We discuss the implications of these findings for subgrid-scale modeling in3D turbulence and outline directions for future research
Modeling the risks within the protocol Aave, with an application to portfolio allocation
No full textDecentralized Finance (DeFi) lending and borrowing protocols enable investors to take leveraged long and short positions on digital assets without centralized intermediaries, but expose them to a distinctive form of risk: on-chain liquidation triggered by debt and collateral value fluctuations. In this work, we provide a detailed formalization of Aave's lending, borrowing, and liquidation mechanisms, grounded in the protocol's open-source implementation. In doing so, we propose a mathematical modeling of the risk of liquidation, including some stochastic approximations with the purpose of efficient analysis, with different applications. Among them, portfolio optimization problem
Fermi-LAT 16-year Source List
No full textInternational audienceThe current Fermi-LAT source catalog (4FGL-DR4: 7194 sources over 14 years) was built incrementally from the 8-year catalog. In a survey mission like Fermi, data accumulate on each source over time, so after 16 years (reached in August 2024) and twice the data for the original 4FGL sources we have more precise localization (by 24% on average). It is thus time to generate a new original catalog, which implies, beyond adding the sources newly detectable after two more years, changing the existing source names (derived from their coordinates) and reviewing the associations. We present an early 16-year list (FL16Y) of 7220 sources, which relocalizes all sources and improves a few aspects of the catalog analysis, but still uses the same model of interstellar diffuse emission as 4FGL-DR4
Programmes linéaires en nombre entiers pour la recherche de puissances de circuits Hamiltoniens
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Polarization measurement of and baryons in Ne collisions at GeV
No full textInternational audienceThe first measurement of the polarization of charm baryons by the LHCb experiment recorded in fixed-target mode is presented. The polarization of baryons is studied in collisions of protons, at an energy of 2.51 TeV, incident on a gaseous target of neon, at a nucleon-nucleon center-of-mass energy of GeV. The world's first measurement of separate-charge polarizations for and baryons is performed, determining where the first uncertainty is statistical and the second systematic. The polarization is also measured in intervals of baryon transverse momentum and the Feynman- variable