Ultralight bosons are compelling dark-matter candidates and arise in a variety of beyond-Standard-Model scenarios. These fields can tap energy and angular momentum from spinning black holes through a process known as "black hole superradiance", during which a macroscopic bosonic condensate develops around the black hole. Striking signatures of this phenomenon that have been studied over the past few years include for example: gaps in the spin-mass distribution of astrophysical black holes, the emission of continuous gravitational-wave signals and signatures in the gravitational waves emitted by binary black holes, opening the exciting possibility to search for extremely light particles using current and future observations of black holes and gravitational waves. In this talk I will give an overview of the status of this research program.

The MICROSCOPE mission allowed for an unprecedented precision on the test of the Weak Equivalence Principle (WEP). The WEP states that all bodies fall at the same rate, independently of their mass and composition, and is the cornerstone of General Relativity (GR). MICROSCOPE’s measurement concept relied on comparing the free fall of two test masses of different compositions as they orbited the Earth.

Beside testing GR’s foundation, it allowed us to shed light on modified gravity models involving the existence of a putative fifth force. For instance, the test of the equivalence principle in the Earth orbit sets constraints on long-range (of order a thousand kilometres and more) fifth force, while the interaction of MICROSCOPE’s test masses with each other provides clues on a shorter (of order 0.1 m) fifth force.

In this talk, I will first present the MICROSCOPE experiment and test of the WEP. I will then discuss how MICROSCOPE could set new constraints on fifth force models such as a Yukawa deviation from Newtonian gravity, a light dilaton and a chameleon field.

Bio:
2007 : thèse au CEA Saclay, “Les lentilles gravitationnelles faibles vers la cosmologie de haute précision”, sous la direction d’Alexandre Réfrégier
2008 – 2011 : postdoc au JPL et Caltech sur le weak lensing (phénoménologie et analyse de données)
2011 – 2012 : postdoc à l’ETH Zurich sur le weak lensing (analyse de données, simulations, Euclid)
2013 – présent : ingénieur-chercheur à l’ONERA (DPHY -- Département de Physique, Instrumentation, Environnement, Espace). Travail sur MICROSCOPE (segment sol et analyse de données) et concepts de tests de la gravitation dans l’espace.

Because of their weak interactions, neutrinos can traverse matter like no other known particle. These elusive messengers can therefore be turned into a new probe to investigate the structure and composition of the deep Earth.
In this seminar, I will present the different methodological approaches to neutrino tomography, focusing on recent efforts exploiting either the oscillation or the absorption of atmospheric neutrinos in the Earth. I will then describe how these methods can be used and combined to investigate open questions in deep-Earth science.
The advent of a new generation of large-scale atmospheric neutrino detectors such as KM3NeT and IceCube, and in the future HyperKamiokande and even DUNE,  might finally bring these ideas into a concrete possibility that can be investigated with real data. The seminar will conclude with a discussion of the expected performances of these detectors for neutrino tomography, while paving the way to a next-generation instrument fully optimised for Earth tomography.

Since summer 2019, the national computing center of the CNRS for high performance computing and artificial intelligence is hosting the supercomputer « Jean Zay ». With more than 1500 scalar CPU nodes and 600 accelerated GPU nodes the peak performance reaches 28 PFLOPs. This equipment is available for research communities, either private or academic, relying on extrem computing. Getting
hours to run on the supercomputer is free at the condition that results are published.
During this talk we will cover the important administrative steps to be able to use the machine then describe the  hardware and software environment. You will have all you need to get started on « Jean Zay ».

Myriam Peyrounette: CV

At CERN, we have recently become able to study atoms of antihydrogen - the antimatter equivalent of hydrogen.  The question to be addressed is fundamental and profound: “Do matter and antimatter obey the same laws of physics?”  The Standard Model requires that hydrogen and antihydrogen have the same spectrum. The possibility of applying the precision measurement techniques of atomic physics to an antimatter atom makes antihydrogen a very compelling testbed for fundamental symmetries such as CPT. I will discuss the latest developments in antihydrogen physics: observation of the first laser-driven transition (1S-2S)$^{1,2}$ observation of the antihydrogen hyperfine structure$^{3}$, observation of the Lyman-alpha transition$^{4}$, and laser cooling of trapped antihydrogen$^{5}$. To study antihydrogen, it must first be produced, trapped$^{6}$, and then held for long enough$^{7}$ to observe a transition - using very few anti-atoms.  I will illustrate the techniques necessary to achieve the latest milestones, and then consider the future of optical spectroscopy, as well as gravitational studies$^{8}$ with the brand-new ALPHA-g experiment.

1. Observation of the 1s-2s Transition in Trapped Antihydrogen, M Ahmadi et al., (ALPHA Collaboration) Nature 541, 506–510 (2017).
2 Characterization of the 1S-2S transition in antihydrogen, M Ahmadi et al., (ALPHA Collaboration), Nature 557, 71–75 (2018).
3, Observation of the hyperfine spectrum of antihydrogen, M Ahmadi et al., (ALPHA Collaboration) Nature 548, 66–69 (2017).
4. Observation of the 1S–2P Lyman-α transition in antihydrogen, M Ahmadi et al., (ALPHA Collaboration), Nature 561, 211–215 (2018).
5. Laser cooling of antihydrogen atoms, (ALPHA Collaboration), Nature 592, 35–42 (2021).
6. Andresen, G.B. et al., Trapped Antihydrogen, Nature, 468, 673 (2010).
7. Andresen, G. B. et al. Confinement of antihydrogen for 1,000 seconds. Nature Physics 7, 558 (2011).
8. Amole, C. et al., Description and first application of a new technique to measure the gravitational mass of antihydrogen, Nature Communications DOI: 10.1038/ncomms2787 (2013).