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Étude géoarchéologique du système d’irrigation de Sarazm (IVe-IIIe millénaires av. n. è.). De la gestion de l’eau à la fabrique du paysage fluvial dans la moyenne vallée semi-aride et tectoniquement active du Zeravshan (Tadjikistan, Asie centrale).
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All-sky search for continuous gravitational-wave signals from unknown neutron stars in binary systems in the first part of the fourth LIGO-Virgo-KAGRA observing run
No full textInternational audienceWe present the results of a blind all-sky search for continuous gravitational-wave signals from neutron stars in binary systems using data from the first part of the fourth observing run (O4a) using LIGO detectors data. Rapidly rotating, non-axisymmetric neutron stars are expected to emit continuous gravitational waves, whose detection would significantly improve our understanding of the galactic neutron star population and matter under extreme conditions, while also providing valuable tests of general relativity. Neutron stars in binary systems likely constitute a substantial fraction of the unobserved galactic population and, due to potential mass accretion, may emit stronger gravitational-wave signals than their isolated counterparts. This search targets signals from neutron stars with frequencies in the 100-350 Hz range, with orbital periods between 7 and 15 days and projected semi-major axes between 5 and 15 light-seconds. The analysis employs the GPU-accelerated fasttracks pipeline. No credible astrophysical signals were identified, and, in the absence of a detection, we report search sensitivity estimates on the population of neutron stars in binary systems in the Milky Way
Cosmological and High Energy Physics implications from gravitational-wave background searches in LIGO-Virgo-KAGRA's O1-O4a runs
No full textInternational audienceWe search for gravitational-wave background signals produced by various early Universe processes in the Advanced LIGO O4a dataset, combined with the data from the earlier O1, O2, and O3 (LIGO-Virgo) runs. The absence of detectable signals enables powerful constraints on fundamental physics. We derive gravitational-wave background energy density upper limits from the O1-O4a data to constrain parameters associated with various possible processes in the early Universe: first-order phase transitions, cosmic strings, domain walls, stiff equation of state, axion inflation, second-order scalar perturbations, primordial black hole binaries, and parity violation. In our analyses, the presence of an astrophysical background produced by compact (black hole and neutron star) binary coalescences throughout the Universe is also considered. We address the implications for various cosmological and high energy physics models based on the obtained parameter constraints. We conclude that LIGO-Virgo data already yield significant constraints on numerous early Universe scenarios
Direct multi-model dark-matter search with gravitational-wave interferometers using data from the first part of the fourth LIGO-Virgo-KAGRA observing run
No full textInternational audienceGravitational-wave detectors can probe the existence of dark matter with exquisite sensitivity. Here, we perform a search for three kinds of dark matter -- dilatons (spin-0), dark photons (spin-1) and tensor bosons (spin-2) -- using three independent methods on the first part of the most recent data from the fourth observing run of LIGO--Virgo--KAGRA. Each form of dark matter could have interacted with different standard-model particles in the instruments, causing unique differential strains on the interferometers. While we do not find any evidence for a signal, we place the most stringent upper limits to-date on each of these models. For scalars with masses between eV that couple to photons or electrons, our constraints improve upon those from the third observing run by one order of magnitude, with the tightest limit of at a mass of . For vectors with masses between eV that couple to baryons, our constraints supersede those from MICROSCOPE and Eöt-Wash by one to two orders of magnitude, reaching a minimum of at a mass of eV. For tensors with masses of eV (the full mass range analyzed) that couple via a Yukawa interaction, our constraints surpass those from fifth-force experiments by four to five orders of magnitude, achieving a limit as low as at eV. Our results show that gravitational-wave interferometers have become frontiers for new physics and laboratories for direct multi-model dark-matter detection
Intuitions of mathematical curves in young children's drawings
No full textInternational audienceHow sophisticated is young children's comprehension of geometric lines, curves and patterns, and how can we probe it? We investigated early proto-mathematical intuitions by asking kindergarteners (N = 39, 25 girls, 66 months) and first-graders (N = 42, 20 girls, 76 months) to draw the prolongation of mathematical patterns. Children's drawings revealed an early yet partial understanding of key mathematical properties such as linearity, curvature, periodicity, and compositionality. These abilities were confirmed in a second task, where participants were asked to select the correct prolongation among six options, ruling out motor entrainment as an explanation for the drawing task. These findings highlight children's emerging intuitions of proto-mathematical concepts and underscore the potential of drawing as a powerful and concrete tool for assessing early mathematical reasoning
Precision Measurements of Atom-Dimer Interactions in a Uniform Planar Bose Gas
No full textCold quantum gases, when acted upon by electromagnetic fields, can give rise to samples where isolated atoms coexist with dimers or trimers, which raises the question of the interactions between these various constituents. Here we perform microwave photoassociation in a degenerate gas of Rb atoms to create weakly-bound dimers in their electronic ground state. From the density-induced shift of the photoassociation line, we measure the atom-dimer scattering length for the two least-bound states of the molecular potential. We also determine the complete energy diagram of one hyperfine manifold of the least-bound state, which we accurately reproduce with a simple model
Sociologie du travail créateur: [résumé des cours et travaux : 2021-2022]
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Words of Aspiration with Advice Granted to Ön Zhenpen Kunga, by Jamyang Khyentse Wangpo
No full textdbon gzhan phan kun dga’ la gnang ba’i zhal gdams smon tshig (B128) Jamyang Khyentse Wangpo Kabum, vol. 1 (ka), 359.1–359.5, Dzongsar, 2014
