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A Prototype Hybrid Mode Cavity for Heterodyne Axion Detection
No full textInternational audienceIn the heterodyne approach to axion detection, axion dark matter induces transitions between two modes of a microwave cavity, resulting in a parametrically enhanced signal power. We describe the fabrication and characterization of a prototype normal conducting cavity specifically optimized for heterodyne detection. Corrugations on the cavity walls support linearly polarized hybrid modes which maximize the signal power while strongly suppressing noise. We demonstrate tuning mechanisms which allow one mode's frequency to be scanned across a 4 MHz range, while suppressing cross-coupling noise by at least 80 dB. A future superconducting cavity with identical geometry to our prototype would have the potential to probe orders of magnitude beyond astrophysical bounds
Measurements of differential cross-sections of production in the dilepton channel in collisions at = 13 TeV using the ATLAS detector
No full textInternational audienceAt the Large Hadron Collider, the final state is expected to be dominated by production with a contribution from single-top processes. Differential cross-sections for production in the dilepton decay channel are measured at the particle level as a function of various kinematic variables. The analysis is based on data from proton-proton collisions at a centre-of-mass energy of TeV, recorded by the ATLAS detector at the Large Hadron Collider over the period from 2015 to 2018, corresponding to an integrated luminosity of 140 fb. Measurements are performed within the fiducial phase-space defined by the presence of two -jets and one electron and one muon of opposite charges. The differential cross-sections are corrected for detector effects and unfolded to the particle level. Results are compared with predictions from Monte Carlo event generators at next-to-leading order in perturbative quantum chromodynamics. These measurements provide valuable constraints on the modelling of production and the interference between doubly resonant and singly resonant production
The effects of the spin and quadrupole moment of SgrA* on the orbits of S stars
No full textInternational audienceMeasuring the astrometric and spectroscopic data of stars orbiting the central black hole in our galaxy (Sgr A*) offers a promising way to measure relativistic effects. In principle, the "no-hair" theorem can be tested at the Galactic Center by monitoring the orbital precession of S-stars due to the angular momentum (spin) and quadrupole moment of Sgr A*. Closer-in stars, more strongly affected by the black hole's rotation, may be required. GRAVITY+ could detect such stars that are currently too faint for GRAVITY. We aim to analytically and numerically characterize orbital reorientations induced by spin-related effects of Sgr A* up to the second post-Newtonian (2PN) order. We use the two-timescale method to derive the 2PN analytical expressions of the secular evolution of the orbital parameters that are related to the observer. To study the interaction between the orbital and spin orientations, we introduce observer-independent quantities that offer insight into the Kerr geometry. We also use the post-Newtonian code OOGRE to simulate hypothetical stars orbiting closer to Sgr A*, where spin and quadrupole effects are stronger. This enables comparison with our analytical predictions. We exhibit three orbital-timescale precession rates that encode the in-plane pericenter shift and the out-of-plane redirection of the osculating ellipse. We provide the 2PN expressions of these precession rates and express the orbit-integrated associated angular shifts of the pericenter and of the ellipse axes. We relate these orbital-timescale precession rates to the secular-timescale precession of the orbital angular momentum around the black hole spin axis. We consider that the theoretical insight we provide in this article will be useful in constraining the spin effect of Sgr A* with GRAVITY+ observations
Neutrino non-radiative decay in matter: constraints and prospects
No full textInternational audienceNeutrinos, being massive, can decay. A heavier neutrino could decay into a lighter one and a massless scalar or pseudoscalar boson, such as the Majoron. Two-body non-radiative decay could occur in dense matter, such as in the inner dense regions of a core-collapse supernova. We first derive novel bounds on neutrino-Majoron couplings using the spectral distortions induced by neutrino non-radiative two-body decay in matter, and two-dimensional likelihood analyses of the 24 events from SN1987A. We then explore the prospects of neutrino-Majoron couplings from a future galactic core-collapse supernova, leaving either a neutron star or a black-hole. To this aim, we use information from detailed one-dimensional supernova simulations. We consider the supernova neutrino signal associated with inverse-beta decay in the upcoming JUNO and Hyper-Kamiokande detectors, with neutrino-argon scattering in DUNE, or with coherent neutrino-nucleus scattering in the DARWIN experiment. In a full 3 framework, based on the spectral distortions induced by neutrino decay in matter, we perform two-dimensional likelihood analyses and provide prospects for the limits on neutrino-Majoron couplings. Our results show that the observation of a future supernova will significantly improve on the current bounds, in particular from SN1987A and neutrinoless double-beta decay. Finally, we explore the impact of neutrino decay in matter on the diffuse supernova neutrino background formed by past supernova explosions. We show for the first time that the effects on black-hole contributions are important and modify the DSNB number of events by several tens of percent in Hyper-Kamiokande
SKA-Low simulations for a cosmic dawn/epoch of reionisation deep field
No full textInternational audienceWe present a realistic simulation of an SKA-Low cosmic dawn/epoch of reionisation (CD/EoR) observation, which can be used to further the development of foreground-mitigation approaches. The simulation corresponds to a deep (1000 h) integration pointing over the 106 MHz-196 MHz frequency range. The sky components include the CD/EoR signal, extragalactic foreground emission featuring strong (over 5 Jy at 150 MHz) out-of-field sources and in-field sources down to 1 microJy at 150 MHz, and Galactic emission from the GSM2016 model complemented with small-scales structure beyond its native deg resolution from a magneto-hydrodynamic simulation of the interstellar medium. Modeled errors include a partial de-mixing of the out-of-field sources, direction-dependent calibration errors leading to residual ionospheric effects, and direction-independent gain calibration errors, on top of thermal noise. Simulated observations are delivered as visibilities as well as imaging products with natural weighting. The true, uncorrupted, CD/EoR signal is also delivered, to allow an assessment of the efficacy of foreground-mitigation approaches. The codes used to generate these simulations are also delivered, so that new simulated datasets can be produced. This simulation has been the basis for the SKA Science Data Challenge 3a (SDC3a), which addressed foreground removal
Ergodicity of some stochastic Fokker-Planck equations with additive common noise
No full textInternational audienceIn this paper we consider stochastic Fokker-Planck Partial Differential Equations (PDEs), obtained as the mean-field limit of weakly interacting particle systems subjected to both independent (or idiosyncratic) and common Brownian noises. We provide sufficient conditions under which the deterministic counterpart of the Fokker-Planck equation, which corresponds to particle systems that are just subjected to independent noises, has several invariant measures, but for which the stochastic version admits a unique invariant measure under the presence of the additive common noise. The very difficulty comes from the fact that the common noise is just of finite dimension while the state variable, which should be seen as the conditional marginal law of the system given the common noise, lives in a space of infinite dimension. In this context, our result holds true if, in addition to standard confining properties, the mean field interaction term forces the system to be attracted by its conditional mean given the common noise and the intensity of the idiosyncratic noise is small
Across ancient oceans: Eocene dispersal routes of Asian terrestrial mammals to Europe, Afro-Arabia and South America
No full textInternational audienceDuring the middle and late Eocene, Asian terrestrial mammals dispersed to Europe, while primates and rodents dispersed across the 500-to-2000 km wide Neotethys Ocean and the 1500-to-2000 km wide Atlantic Ocean to colonize Afro-Arabia and South America. This study explores how these mammals have achieved such remarkable and enigmatic dispersals. We present high-resolution paleogeographic models for the middle to late Eocene based on updated plate kinematic reconstructions, paleo-bathymetry and paleo-topography data. With this, we evaluate landmass configurations and connectivity that may have facilitated faunal exchanges from Asia toward Europe, Afro-Arabia, and South America and discuss dispersal mechanisms between these biogeographic provinces. Our reconstructions reveal that during the Bartonian (~40–38 Ma), an overland dispersal corridor between Asia and Balkanatolia became available to terrestrial mammals and acted as a pivotal pathway for Asian faunas dispersing toward western Europe and Afro-Arabia. We identified two Balkanatolian island-hopping routes across the Western Neotethys potentially enabling the dispersal of small-bodied Asian primates, rodents and artiodactyls to Afro-Arabia. Alternatively, these taxa may have rafted across the Central Neotethys. By ~34 Ma, Balkanatolia fully connected with Western Europe, opening a southern “Grande Coupure” route for Asian faunas. In the Atlantic, we identify long-distance rafting as the most plausible mechanism for the 40–34 Ma transoceanic dispersal of the Asian-originated primates and rodents from Afro-Arabia to South America despite the likely presence of sparse islands along the Walvis Ridge and the Rio Grande Rise
Brief communication: Intercomparison study reveals pathways for improving the representation of sea-ice biogeochemistry in models
No full textInternational audienceSea-ice biogeochemical models are key to understanding polar marine ecosystems. We present an intercomparison of six one-dimensional sea-ice biogeochemical models, assessing their ability to simulate algal phenology and nutrient dynamics by comparing them with sea-ice physical-biogeochemical data collected during the N-ICE2015 expedition. While no model fully captured observed bloom dynamics without tuning, adjustments improved biomass simulations but had a limited impact on nutrient representation. Variability in tuning strategies underscores key knowledge gaps and the need for further model development in more harmonised ways. Our findings can inform future efforts to enhance the reliability and predictive capacity of sea-ice biogeochemical models.</div
The black-chinned tilapia Sarotherodon melanotheron, a model for environmental genomics and aquaculture resilience in the Western African's context of climate change
No full textInternational audienceThe euryhaline black-chinned tilapia (Sarotherodon melanotheron, Rüppell, 1852) has long been recognised as a valuable local resource in West African aquaculture and artisanal fisheries. Its production contributes to food security, the local economy and farmer’s incomes. Initial research on this species focused on understanding its biology and ecology in the field and in controlled conditions, and then on evaluating and improving practices to increase local production. More recently, the scope of this research has expanded to include investigations integrating molecular approaches in wild populations, such as population genetics and genomics studies, as well as ecophysiological and functional transcriptomics. Additionally, issues related to climate change have been incorporated. In the range of the black-chinned tilapia, the increase in salinity observed in so-called ‘inverse estuaries’ in Senegal, where hypersaline conditions of up to 130 psu may prevail throughout the year, has attracted significant attention. Even for a euryhaline species such as S. melanotheron, such conditions impose substantial energetic costs, resulting in observed phenotypic and adaptive changes to the fish’s biological and life-history traits. Salinity is a major issue in tilapia aquaculture. Improved production could be achieved by selecting strains from populations that are tolerant to salinity, or by hybridising with less tolerant tilapia species that demonstrate better growth performance. This study reviews and summarises knowledge acquired on S. melanotheron over several decades, paying particular attention to the northern subspecies, S. m. heudelotii. Current research limitations consist of: (i) the status of the species itself, comprising subspecies that are still too poorly characterized; (ii) the interaction between salinity and other parameters, particularly hypoxia; (iii) the impact of climate change on the entire species range, involving multiple environmental parameters in Western Africa; and (iv) limited access to resources in Africa, hindering local and regional development
ORKM: An R package for online multi-view data clustering
No full textInternational audienceWe propose a package called ORKM, which implements the ORKMC (Online Regularized K-Means Clustering) method for handling online multi-view or single-view data, which named ORKMeans function in the package incorporates a regularization term to address multi-view clustering problems with online updates. ORKM computes classification results, cluster center matrices, and view-specific weights for multi-view datasets. It also supports branching multi/single-view data by converting the online RKMC algorithm into an offline version, referred to as RKMC (Regularized K-Means Clustering) realized by function RKMeans. We demonstrate the package’s functionality through simulations and real-world data analyses, comparing it with other methods and related R packages. Overall, ORKM exhibits stable performance and effective clustering result