Université Côte d'Azur

Water and land surfaces on a planet interact in particular ways with gases in the atmosphere and with radiation from the star. These interactions define the environments that prevail on the planet, some of which may be more amenable to prebiotic chemistry, some to the evolution of more complex life. This review article covers (i) the physical conditions that determine the ratio of land to sea on a rocky planet, (ii) how this ratio would affect climatic and biologic processes, and (iii) whether future astronomical observations might constrain this ratio on exoplanets. Water can be delivered in multiple ways to a growing rocky planet — and although we may not agree on the contribution of different mechanism(s) to Earth’s bulk water, hydrated building blocks and nebular ingassing could at least in principle supply several oceans’ worth. The water that planets can sequester over eons in their solid deep mantles is limited by the water concentration at water saturation of nominally anhydrous mantle minerals, being in sum likely less than 2000 ppm of the planet mass. Water is cycled between mantle and surface through outgassing and ingassing mechanisms that, while tightly linked to tectonics, do not necessarily require plate tectonics in every case. The actual water/land ratio at a given time then emerges from the balance between the volume of surface water on the one hand, and on the other hand, the shape of the planet (its ocean basin volume) that is carved out by dynamic topography, the petrologic evolution of continents, impact cratering, and other surface-sculpting processes. By leveraging the contrast in reflectance properties of water and land surfaces, spatially resolved 2D maps of Earth-as-an-exoplanet have been retrieved from models using real Earth observations, demonstrating that water/land ratios of rocky exoplanets may be determined from data delivered by large-aperture, high-contrast imaging telescopes in the future.

The purpose of this article is to show that an intrinsic noise with values in the space 𝒫(ℝ) of 1d probability measures may force uniqueness to first order mean field games. The structure of the noise is inspired from the earlier work (Delarue and Hammersley in Probab Theory Relat Fields 191(1–2):41–102, 2025) . It reads as a coloured Ornstein-Uhlenbeck process with reflection on the boundary of quantile functions on the 1d torus, with the elements of the latter playing the role of indices for the continuum of players underpinning the game. In Delarue and Hammersley (Probab Theory Relat Fields 191(1–2):41–102, 2025), the semi-group generated by the noise is shown to enjoy smoothing properties that become key in the study carried out here. Although the analysis is limited to the 1d setting, this is the first example of uniqueness forcing for generic mean field games set over an infinite dimensional set of probability measures and this may be one step forward towards a more systematic regularization by noise theory for mean field games.

Operationalizing social justice is challenged by the absence of a universal equity definition and inherent policy trade-offs. This study bridges theoretical social justice principles with operational decision-making by integrating four commonly discussed distributive justice theories—Utilitarianism, Rawls’ Egalitarianism, Prioritarianism, and Capabilitarian Sufficiency—into a bilevel bus frequency optimization model. It introduces linearized equity-oriented formulations to reflect the distinct distributive principles of these theories and proposes justice theory-driven equity metrics to evaluate distributive impacts using different ethical criteria. Using cumulative opportunity as a unit of distribution, the proposed frameworks and metrics are applied to Canberra’s southern suburbs. The results demonstrate that the choice of justice framework is not a neutral modelling decision but a normative one, with each framework producing distinct redistributive patterns and community-level trade-offs. This highlights the importance of aligning equity frameworks with policy objectives and governance contexts, as these choices ultimately shape public perception, political feasibility, and the long-term societal goals of transport investment.

Tsunami wave observations far from the coast remain challenging due to the logistics and cost of deploying and operating offshore instrumentation on a long-term basis with sufficient spatial coverage and density. Distributed Acoustic Sensing (DAS) on submarine fiber optic cables now enables real-time seafloor strain observations over distances exceeding 100 km at a relatively low cost. Here, we evaluate the potential contribution of DAS to tsunami warning by assessing theoretically the sensitivity required by a DAS instrument to record tsunami waves. Our analysis includes signals due to two effects induced by the hydrostatic pressure perturbations arising from tsunami waves: the Poisson’s effect of the submarine cable and the compliance effect of the seafloor. It also includes the effect of seafloor shear stresses and temperature transients induced by the horizontal fluid flow associated with tsunami waves. The analysis is supported by fully coupled 3-D physics-based simulations of earthquake rupture, seismo-acoustic waves and tsunami wave propagation. The strains from seismo-acoustic waves and static deformation near the earthquake source are orders of magnitude larger than the tsunami strain signal. We illustrate a data processing procedure to discern the tsunami signal. With enhanced low-frequency sensitivity on DAS interrogators (strain sensitivity ≈ 2×10 at mHz frequencies), we find that, on seafloor cables located above or near the earthquake source area, tsunamis are expected to be observable with a sufficient signal-to-noise ratio within a few minutes of the earthquake onset. These encouraging results pave the way towards faster tsunami warning enabled by seafloor DAS.

Alzheimer’s disease (AD) is the most common neurodegenerative disorder, affecting millions worldwide. The clinical presentation of AD is heterogenous and often complicated by the presence of multiple co-pathologies, which can overlap with features of other neurodegenerative disorders, underscoring the need for tools to aid accurate and timely diagnosis. Biomarkers for AD span multiple modalities and are being increasingly used in clinical settings to aid diagnosis, monitor disease progression, and assess eligibility and response to disease-modifying therapies. Here, we provide an overview of current clinical applications of fluid, imaging, and digital biomarkers for AD. We also discuss biomarkers under development and challenges associated with the implementation of these modalities in clinical settings.