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26/11/2026 09:00
Mots de bienvenue et organisation des Journées
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Thomas Chehab (Observatoire de la côte d'Azur, Laboratoire ARTEMIS)26/11/2026 09:30
Entangled Relativity is a non-linear reformulation of General Relativity that precludes the definition of a universe devoid of matter. In this framework, matter and spacetime are inseparably linked, in the literal sense that the gravitational dynamics cannot be defined independently of matter fields.
Despite its non-standard formulation, the phenomenology of General Relativity can be...
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26/11/2026 10:00
Ultralight bosons are well-motivated dark-matter candidates that can behave as coherent oscillating fields on Galactic scales. At the lower end of the mass spectrum, these oscillations can remain coherent for decades and leave detectable signatures in high-precision astrophysical observations. Binary pulsars are particularly powerful probes of such effects.
We investigate quadratically...
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Matthieu Dellavalle (ONERA - Office Nationale d'Études et de Recherches Aérospatiales)26/11/2026 11:00
General Relativity (GR) is the best description of gravity so far. In 2018, the MICROSCOPE mission tested its cornerstone, the Equivalence Principle (EP), with unprecedented precision, setting the current state-of-the-art upper limit on its validity. Yet, keeping on testing gravity at better precision is of crucial interest in the quest of a model that could explain Dark Matter, Dark Energy or...
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26/11/2026 11:30
A fifth fundamental force (as a deviation from Newtonian gravity) is predicted by several theories addressing, for instance, questions relative to the dark sector or the lack of a unified framework for General Relativity and the Standard Model. Probing the existence of a fifth force at the submicron scale is challenging because electromagnetic interactions (e.g., the Casimir-Polder potential...
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26/11/2026 12:00
Although compatible with General Relativity (GR), the dark Universe lacks experimental confirmation and support by the Standard Model (SM). Opposing darkness, extensions of GR face the successes of the latter. But photons, main messengers, are still read with the XIX Maxwell theory, although Quantum Electro-Dynamics (QED) requires non-linear corrections, e.g., photon-photon. Extended Theories...
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26/11/2026 13:30
Ultralight bosonic dark matter may induce oscillations of fundamental constants such as the fine-structure constant α and the proton-to-electron mass ratio μ, which can be searched for through precision spectroscopy. We present a molecular spectroscopy platform developed to search for such signals using the REFIMEVE optical frequency dissemination network. An ultrastable optical reference at...
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26/11/2026 14:00
Optical lattice clocks have progressed swiftly over the past decade, now outperforming state-of-the-art microwave clocks by more than two orders of magnitude in both stability and accuracy, reaching a level of control of the frequency of 18 digits or better. This opens up new applications in fundamental physics, astronomy and Earth science. In this context, LTE initiated the development of a...
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26/11/2026 14:30
The Grasse optical ground station (GRSM-7845) contributes to the International Laser Ranging Service (ILRS) by providing Satellite and Lunar Laser Ranging observations since 2009 with almost the same instrumental setup. If the current setup is still relevant for Lunar Laser Ranging (LLR), it does not allow to answer to the millimeter challenge required for the scientific applications in space...
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26/11/2026 15:30
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Karim Abd El Dayem (Observatoire de Paris (LESIA))26/11/2026 16:00
The orbits of S stars around the Galactic Center black hole, Sgr~A*, offer a unique opportunity to probe the relativistic regime of gravity and test the no-hair theorem. While the Schwarzschild precession has been detected with S2, the detection of spin-induced (Kerr) effects—Lense–Thirring and quadrupole moment terms—remains a major observational challenge. We aim to quantify the time needed...
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26/11/2026 16:30
The internal dynamics of a binary system can be affected by the passage of gravitational waves (GWs). This effect is significantly enhanced when the GW frequency is in resonance with the orbital frequency of the binary system. Recently, this phenomenon has been proposed as a novel approach to detecting GWs in the largely unexplored microhertz frequency band, using precise measurements of the...
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27/11/2026 09:00
The newly introduced Quantum Modified Inertia (QMI) framework is a relativistic theory of motion incorporating both upper and lower bounds on proper time. A mathematical consequence of these bounds is the emergence of corresponding upper and lower acceleration limits.
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Focusing on the lower bound, a characteristic minimum acceleration naturally emerges from the analysis. Applied to galactic... -
27/11/2026 09:30
We propose an innovative concept for a quantum gravimeter, where atoms prepared in a Heisenberg-limited state perform a single bounce on a mirror followed by a free fall. This quantum gravimeter produces a simple and robust interference pattern which should allow to measure the free-fall acceleration of atoms. The expected accuracy of the measurement is estimated using simulations and...
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Jérémie Vaubaillon (LTE, Observatoire de Paris)27/11/2026 10:00
Meteors are streaks of light appearing in the sky (a.k.a. shooting stars), produced by the high entry velocity of a meteoroid (rock in the interplanetary space) into our atmosphere. A meteor cluster involves several meteors following the same orbit, appearing at the same time. About 10 have been reported so far, although continuous meteor monitoring has been going on for more than 25 years...
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27/11/2026 11:00
The ILuRS is the new Moon references system proposed by the IAG/IAU WG 1.1.3 and adopted as a new product center by IERS in May 2026. I will introduce here the concepts and the associated definitions of ILuRs.
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27/11/2026 11:30
The New Astrometric Reduction of Old Observations (NAROO) program is dedicated to the measurement of astrophotographic plates and the analysis of old observations for scientific purposes. One of the main objectives is to provide accurate positional measurements of planets and satellites to improve our knowledge of their orbits and dynamics, and to infer the accuracy of the planet and satellite...
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27/11/2026 12:00
La connaissance de la rotation des satellites géodésiques est nécessaire ou utile pour de nombreuses applications, par exemple la modélisation de certaines perturbations du mouvement orbital (e.g. l’effet Yarkovsky) ou la synchronisation d’horloges distantes par lien laser via un satellite passif. L’étude de la dynamique de la rotation est également intéressante en soit. Nous avons développé...
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27/11/2026 13:30
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