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Beyond Stage IV: Quasar and Galaxy Clustering and the Fundamental Physics of the 2040s
No full textInternational audienceStage IV galaxy surveys (DESI, 4MOST, MOONS, Euclid) are establishing precision constraints on cosmological parameters through baryon acoustic oscillations and redshift-space distortions, yet fundamental questions on neutrino masses, inflationary physics, and the nature of gravity remain beyond their reach. We present a science case for next-generation wide-field spectroscopic surveys targeting with simultaneous observations of thousands of galaxies, quasars, and emission-line galaxies. Such surveys would deliver transformative advances: (i) cosmological constraints on absolute neutrino masses (), three times more stringent than Stage IV, enabling resolution of the neutrino mass hierarchy; (ii) detection of primordial non-Gaussianity at the level of , probing multi-field inflation; (iii) measurements of structure growth spanning cosmic time to constrain dark energy and test gravitational modifications. Achieving these goals requires revolutionary advances in spectroscopic multiplexing ( simultaneous spectra), sub- redshift precision at scale, and field-level inference techniques exploiting higher-order clustering statistics. We demonstrate that the proposed Wide-field Spectroscopic Telescope concept provides a technically feasible and scientifically compelling path to unlock the physics of neutrinos, inflation, and gravity that will remain inaccessible to Stage IV surveys
A Mnemonic Matrix Rule for (Split) Octonionic Multiplication and its Extension to the Cayley--Dickson Tower
No full textInternational audienceWe present a compact mnemonic device for computing the product of two (split) octonions written in Cayley--Dickson form q+l p with q,p in H. The rule appears as a simple (R+L) pattern of right-ordered and left-ordered (quaternionic) products inside a 2X2 quaternionic matrix model. The pattern extends verbatim to all algebras in the Cayley--Dickson tower, providing an efficient computational tool in non-associative settings. To our knowledge, this explicit ``(R+L)'' mnemonic does not appear in the classical literature on octonions or composition algebras
The Power of DESI for Photometric Redshift Calibration: A Case Study with KiDS-1000
No full textInternational audienceAccurate redshift estimates are a critical requirement for weak lensing surveys and one of the main uncertainties in constraints on dark energy and large-scale cosmic structure. In this paper, we study the potential to calibrate photometric redshift (photo-z) distributions for gravitational lensing using the Dark Energy Spectroscopic Instrument (DESI). Since beginning its science operations in 2021, DESI has collected more than 50 million redshifts, adding about one million monthly. In addition to its large-scale structure samples, DESI has also acquired over 256k high-quality spectroscopic redshifts (spec-zs) in the COSMOS and XMM and VVDS fields. This is already a factor of 3 larger than previous spec-z calibration compilations in these two regions. Here, we explore calibrating photo-zs for the subset of KiDS-1000 galaxies that fall into joint self-organizing map (SOM) cells overlapping the DESI COSMOS footprint using the DESI COSMOS observations. Estimating the redshift distribution in KiDS-1000 with the new DESI data, we find broad consistency with previously published results while also detecting differences in the mean redshift in some tomographic bins with an average shifts of Delta Mean(z) = -0.028 in the mean and Delta Median(z) = +0.011 in the median across tomographic bins. However, we also find that incompleteness per SOM cell, i.e., groups of galaxies with similar colors and magnitudes, can modify n(z) distributions. Finally, we comment on the fact that larger photometric catalogs, aligned with the DESI COSMOS and DESI XMM and VVDS footprints, would be needed to fully exploit the DESI dataset and would extend the coverage to nearly eight times the area of existing 9-band photometry
Du serment doctoral d'intégrité scientifique à un serment personnel : un atelier d'écriture et de réflexion sur la responsabilité et le rôle des scientifiques dans la société
No full textNous présentons un atelier de réflexion sur le serment doctoral d’intégrité scientifique et d’écriture d’un serment personnel, destiné aux doctorantes et doctorants, et plus généralement au personnel de la recherche. L’atelier est proposé depuis 2025 comme formation à l’éthique de la recherche dans quelques écoles doctorales en France. Avec un dispositif original, il permet d’examiner plusieurs aspects de la pratique et des enjeux sociaux-environnementaux de le Recherche : la responsabilité des scientifiques, l’engagement, le rôle des sciences dans l’anthropocène, la place de l’éthique et de l’intégrité dans la pratique du doctorat et des sciences en général
Validation of the DESI DR2 Ly BAO analysis using synthetic datasets
No full textInternational audienceThe second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI), containing data from the first three years of observations, doubles the number of Lyman- (Ly) forest spectra in DR1 and it provides the largest dataset of its kind. To ensure a robust validation of the Baryonic Acoustic Oscillation (BAO) analysis using Ly forests, we have made significant updates compared to DR1 to both the mocks and the analysis framework used in the validation. In particular, we present CoLoRe-QL, a new set of Ly mocks that use a quasi-linear input power spectrum to incorporate the non-linear broadening of the BAO peak. We have also increased the number of realisations used in the validation to 400, compared to the 150 realisations used in DR1. Finally, we present a detailed study of the impact of quasar redshift errors on the BAO measurement, and we compare different strategies to mask Damped Lyman- Absorbers (DLAs) in our spectra. The BAO measurement from the Ly dataset of DESI DR2 is presented in a companion publication
Search for Magnetic Monopoles with the Complete ANTARES Dataset
No full textInternational audienceThis study presents a novel search for magnetic monopoles using data collected over a 14 year period (2008-2022) by the ANTARES neutrino telescope. The interaction of magnetic monopoles with matter was modeled according to Kazama, Yang, and Goldhaber cross-section. Upper limits on the flux of magnetic monopoles are obtained for velocities both above and below the Cherenkov threshold. No events consistent with the passage of magnetic monopoles were detected, enabling the setting of an upper flux limit for relativistic magnetic monopoles of the order of
Proton beam-induced effects of platinum nanoparticles and their intracellular localization
No full textInternational audienceThis study investigates the effects of platinum nanoparticles (Pt NPs) on breast cancer cell lines (MCF7 and MDA-MB-231) under proton beam irradiation, with a focus on nanoparticle accumulation behavior, cytotoxicity and radiosensitization. Platinum NPs used in this research exhibited a uniform, flower-like morphology with an average size of 26.2 ± 3.9 nm and showed no agglomeration. Cytotoxicity assays revealed that Pt NPs induced time- and concentration-dependent decrease in cell viability, with significant toxic effects observed at concentrations ≥ 0.375 mM. Moreover, holotomographic imaging demonstrated dynamic nanoparticle accumulation in both cell lines, initially localizing at the membrane and progressively internalizing over time. Importantly, no specific accumulation site preference was detected. Quantitative analysis showed that Pt NP uptake by MCF7 cells was approximately twice that of MDA-MB-231 cells, with simulation models aligning closely with experimental data (86 % and 90 % fit, respectively). Proton irradiation studies indicated a marked radiosensitizing effect of Pt NPs, with cell viability reduced by up to 85 % at higher NP concentrations and radiation doses (10 Gy). These findings underscore the potential of flower-like Pt NPs as effective radiosensitizers in proton therapy, owing to their high cellular uptake, surface reactivity and cytotoxicity
TCT-based monitoring of LGAD radiation hardness for ATLAS-HGTD production
No full textInternational audienceProduction of the High Granularity Timing Detector for the ATLAS experiment at High Luminosity LHC requires over 21000 silicon sensors based on Low Gain Avalanche Diode (LGAD) technology. Their radiation hardness is monitored as a part of the production quality control. Dedicated test structures from each wafer are irradiated with neutrons and a fast and comprehensive characterization is required. We introduce a new test method based on Transient Current Technique (TCT) performed in the interface region of two LGAD devices. The measurement enables extraction of numerous sensor performance parameters, such as LGAD gain layer depletion voltage, LGAD gain dependence on bias voltage, sensor leakage current and effective interpad distance. Complementary capacitance-voltage measurements and charge collection measurements with 90Sr on the same samples have been performed to calibrate the TCT results in terms of charge collection and define acceptance criteria for wafer radiation hardness in the ATLAS-HGTD project
Probing the Cosmological Principle with CMB lensing and cosmic shear
No full textInternational audienceThe standard cosmological model assumes the Cosmological Principle. However, recent observations hint at possible violations of isotropy on large scales, possibly through late-time anisotropic expansion. Here we investigate the potential of cross-correlations between CMB lensing convergence and galaxy cosmic shear -modes as a novel probe of such late-time anisotropies. Our signal-to-noise forecasts reveal that information from the - cross-correlation is primarily contained on large angular scales (). We find that this cross-correlation for a Euclid-like galaxy survey is sensitive to anisotropy at the percent level. Making use of tomography yields a modest improvement of in detection power. Incorporating the galaxy - cross-correlations would further enhance these constraints
Disentangling Initial-State and Evolution Effects in Heavy-Ion Collisions Using EPOS and PHSD
No full textInternational audienceIn this study we examine the impact of the initial stage and dynamical evolution on final-state observables in heavy-ion collisions. For this goal we develop a novel approach, EPOSir+PHSDe, which employs EPOS initial conditions as the starting point for parton and hadron evolution within the PHSD microscopic transport approach. By examining the space-time evolution of matter in this model and comparing to EPOS (which starts with an S-matrix approach for parallel scatterings for the initial conditions and uses a hydrodynamic evolution for the quark-gluon plasma stage with the UrQMD as afterburner) and PHSD (which starts with primary high energy scattering realized via the LUND string model and continues with fully microscopic transport dynamics for strongly interacting partonic and hadronic matter), we identify the key differences in the final particle distributions among the three approaches. Our analysis focuses on rapidity, transverse momentum spectra, and flow harmonics for Au+Au collisions at the invariant energy of GeV. We find a dominant influence of dynamical evolution over the initial conditions on the final observables