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Still Accelerating: Type Ia supernova cosmology is robust to host galaxy age evolution
No full textInternational audienceType Ia supernovae are a cornerstone of modern cosmology, providing first evidence for cosmic acceleration and new tests of dark energy. Son et al. 2025 (S25) claim a strong redshift evolution in standardized supernova luminosities driven by supernova progenitor age, with dramatic cosmological implications: rapidly evolving dark energy, decelerating expansion, and a tension with CDM. We show that the underpinning evidence required for this conclusion -- the supernova progenitor-age dependence, the redshift-dependent age difference, and their combined impact -- is either negligible or relies on effects already corrected for in modern supernova analyses. First, the S25 analysis omits the standard host-galaxy stellar mass correction that captures known environmental dependencies that also correlate with stellar age. Applying this correction to the S25 sample, we find no dependence of standardized supernova brightness on host age. Independent data also show no significant difference at low-redshift in standardized brightness between star-forming galaxies and several Gyr older quiescent galaxies of the same stellar mass. Second, the S25 scenario predicts strong redshift evolution of the host-mass effect. Data from the Dark Energy Survey supernova survey measure evolution of , consistent with zero and altering the dark-energy equation-of-state measurement () by 0.01 if included. Third, we demonstrate that the claimed ~Gyr progenitor age difference between nearby and distant supernovae is overstated by factors of three to five largely due to a conflation of host galaxy age with supernova progenitor age. We conclude that type~Ia supernova cosmology remains robust for current measurements of dark energy
On the relaxation towards mechanical equilibrium for two-pressure compressible flows
No full textWe introduce a symmetrization of a one-velocity two-pressures Baer-Nunziato type model for mixtures of barotropic compressible fluids. It allows us to justify the zero compaction viscosity limit and to recover a solution of the so-called Kapila model. On the other hand, the symmetrization highlights a pressure-induced stabilization mechanism which allows us to recover a global-in-time existence result for initial data close to constant states
Le bibliographisme de Flaubert: [Titre annoncé : Les recherches bibliographiques de Flaubert]
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The CO snow line favours strong clumping by the streaming instability in protoplanetary discs with porous grains
No full textInternational audienceContext: The radial drift and fragmentation of small dust grains in protoplanetary discs impedes their growth past centimetre sizes. Several mechanisms have been proposed to overcome these planet formation barriers, such as dust porosity or the streaming instability (SI), which is today regarded as the most promising mechanism to form planetesimals.Aims: Here, we examine whether the conditions for the SI to lead to strong clumping, the first step in planetesimal formation, are realised in protoplanetary discs containing porous grains.Methods: We used results from previous simulations of the evolution of porous grains subjected to growth, fragmentation, compaction and bouncing in protoplanetary discs. In the ensuing disc structures, we determined the regions where the dust-to-gas ratio exceeds the critical value for strong clumping found in simulations of the SI including external turbulence.Results: We find that the conditions for strong clumping are met within the first hundred thousand years in large regions of protoplanetary discs containing porous grains, provided that the CO snow line is taken into account. If the CO snow line is neglected, the conditions are met only very close to the inner disc edge early on, or over large areas well after 200,000 yr
Forecasting stock prices: Deep Learning and Full Order Book Dynamics
No full textInternational audienceThis paper examines the effectiveness of deep learning models in short-term stock price forecasting using full order book (FOB) data alongside traditional OHLCV features. Historical prices and order book data for 39 stocks over one month were collected, cleaned, and normalized to build three datasets. Convolutional Neural Network (CNN), Long Short-Term Memory (LSTM), and hybrid CNN-LSTM models were developed with optimized hyperparameters and trained to predict the next 100 five-minute intervals based on the preceding 100 intervals. Evaluation metrics included mean squared error, mean absolute error, and directional accuracy. Results show that the CNN-LSTM model combining OHLCV and FOB data outperforms other configurations, achieving the lowest prediction errors. Sensitivity analysis using Sobol indices indicates that aggregate liquidity variables and recent time steps are the most influential predictors. These findings demonstrate that integrating granular microstructure data significantly improves forecasting accuracy, providing valuable insights for the design of data-driven trading strategies that capitalize on short-term market dynamics
Experimental Demonstration of an IGCT/SiC PiN Diode Switching Cell Operating Without Any Turn-On Snubber
No full textInternational audienceIGCTs are attractive for high power, low-frequency converters such as HVdc MMCs because of their lower losses compared to IGBTs. However, a drawback of IGCTs is that they typically require an additional and bulky turn-on snubber circuit to limit their turn-on dI/dt. This limitation in current dynamics prevents destructive recovery from occurring in the diode of an IGCT/diode switching cell. Previous studies have shown the possibility of removing the snubber by setting strict limits to the operating range of the IGCT/Si-diode pair, which in practice strongly restrain the application of a snubberless IGCT submodule or switching cell.In this article, high-voltage, high-current, SiC PiN diodes are used successfully with IGCTs in a snubberless configuration up to 4 kV/500 A, and a comparison is made with IGCTs operating with Si PiN diodes. The IGCT turn-on behavior is analyzed, through the evaluation of the IGCT equivalent resistance during turn-on. The impact of very short reverse recovery (RR) is also investigated, with the observation and analysis of the shared voltage between the IGCT and the diode and its impact. It is found that SiC PiN diodes can operate with IGCTs without the limitations encountered with Si diodes and without requiring a turn-on snubber
The complexity of semidefinite programs for testing -block-positivity
No full textWe extend \cite{chen2025srkbp} by analyzing the complexity of the -block-positivity testing algorithm. In this paper, we investigate a symmetry reduction scheme based on rectangular shaped Young diagrams. Connecting the complexity to the dimensions of irreducible representations of , we derive an explicit formula for the complexity, which also clarifies why the semidefinite program hierarchy collapses in the case
Les conseils d'administration européens sous la pression des activistes
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Green Synthesis of MIL-53(Al)/Fe2O3 Core-Shell Composites Using PET-Derived Linker Source for Enhanced Orthophosphate Cleanup: Synthèse verte de composites cœur-coquille MIL-53(Al)/Fe2O3 utilisant une source de liaison dérivée du PET pour une purification améliorée de l'orthophosphate
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Magnetized dynamical black holes
No full textInternational audienceWe construct a novel exact solution of the Einstein-scalar-Maxwell equations describing a dynamical black hole immersed in an external, time-dependent electromagnetic field. Motivated by the need for more realistic analytical black hole models, our construction incorporates two key ingredients often neglected in exact solutions: a fully dynamical cosmological background and the non-perturbative backreaction of external electromagnetic fields. The compact object is obtained by dressing a Schwarzschild black hole with a radially and temporally dependent scalar field, yielding a time-dependent generalization of the Fisher-Janis-Newman-Winicour solution within the Fonarev framework. The external electromagnetic field is generated via a Lie point symmetry of the Einstein-scalar-Maxwell system, which exports the effect of a Harrison transformation to dynamical settings provided a spacelike Killing vector is present. The resulting spacetime combines a spherically symmetric dynamical horizon with an axisymmetric electromagnetic field and exhibits a rich asymptotic structure mixing Friedmann-Lemaître-Robertson-Walker and Levi-Civita geometries. We show that the time dependence of the configuration plays a crucial role in potentially cloaking curvature singularities, which would otherwise be generically naked in the stationary limit. We analyze the geometric and physical properties of the solution, including its asymptotic behavior, algebraic classification, and the structure of trapped surfaces defining the dynamical horizon. Possible implications for primordial black holes and some astrophysical applications, as well as extensions to higher dimensions, are also discussed