Séminaire

New post-Newtonian results for compact binaries in general relativity and scalar-tensor theories

In the first part of my talk, I give an overview of some recent results concerning the two-body problem in general relativity at high post-Newtonian (PN) order. I will present the energy flux at 4.5PN order, the equations of motion at 4.5PN order, and the memory contributions to the 3.5PN order waveform. In particular, I will discuss some subtleties about the definition of the center-of-mass frame, and its relevance to the comparison with second-order self-force (2SF) results.

Black holes with electroweak hair

We construct static and axially symmetric magnetically charged hairy black holes in the gravity-coupled 
Weinberg-Salam theory.  Large black holes merge with the Reissner-Nordstr\"om (RN) family, 
while the small ones are extremal and support a hair in the form of a ring-shaped electroweak condensate 
carrying superconducting W-currents and up to $22\%$ of the total magnetic charge. 
The extremal solutions are asymptotically  RN with a  mass {\it below} the total charge, $M<|Q|$,  due to 

Black holes and the integrability of extended body dynamics

In general relativity, freely-falling test objects follow geodesics of the background spacetime in which they live. In a sense, this feature is a mere rephrasing of Einstein’s equivalence principle. In 1968, Brandon Carter showed that the geodesic motion of objects orbiting a Kerr black hole was integrable, in the sense of Hamiltonian mechanics, by discovering a fourth constant of motion that now bears his name. This “universality” of geodesic free fall is, however, but an approximation: In general, two different bodies will follow two distinct paths, depending on how they spin and deform.

Spectroscopic surveys: DESI, DESI-2, Spec-S5

The DESI experiment will put tight constraints on the dark energy with the observation of more than 40 million spectroscopic redshifts, mostly at z < 2. It started its Main Survey in May, 2021, making it the first Stage-IV cosmological experiment to go on-sky. Cosmological analysis of the Y1 data acquisition were made public in Apr. 2024, and the Y3 data acquisition is done. I will present the DESI survey current status, along with the proposed extension of operations. I will then present the DESI-2 and Spec-S5 experiments.

Latest Results of the Diffuse Supernova Neutrino Background Search in Gadolinium-loaded Super-Kamiokande

The Diffuse Supernova Neutrino Background (DSNB) is the collection of neutrinos emitted from all past core-collapse supernovae, and it has yet to be detected experimentally. An observation of the DSNB can probe the star formation history of the universe, the fraction of black hole-forming supernovae, and even novel neutrino physics phenomena. At present, the Super-Kamiokande (SK) water Cherenkov detector is the most sensitive experiment to detect the DSNB.

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