Séminaire

Neutrino astronomy and oscillations: first results of the KM3NeT telescope

KM3NeT is a multi-purpose neutrino observatory under construction in the Mediterranean Sea. It is composed of two Cherenkov detectors with different designs: ORCA, a compact and dense detector optimised for the high-statistic measurement of atmospheric neutrino physics, and ARCA, instrumenting a cu- bic kilometre to catch fluxes of extraterrestrial neutrinos. The two detectors have a final configuration comprising 115 and 230 detection lines, respectively. With its modular layout, partial configurations of KM3NeT take data promptly upon deployment.

Microcausality without Lorentz invariance

I will describe how causality implies certain non-perturbative analyticity and exponential boundedness conditions on correlators of relativistic QFTs, in a mixed (t,k) representation. I will then discuss their implications for correlators in Lorentz-breaking backgrounds, including finite-density states and cosmological spacetimes, and show how they can be used to derive a positivity condition on inflationary theories. Along the way, I will compare with the case of S-matrix positivity in flat space Lorentz-invariant theories.

Probing dynamic masses of neutrinos using the Diffuse supernova neutrino background

Neutrino masses may have evolved dynamically throughout the history of the Universe, potentially leading to a mass spectrum distinct from the normal or inverted ordering observed today. While cosmological measurements constrain the total energy density of neutrinos, they are not directly sensitive to a dynamically changing mass ordering unless future surveys achieve exceptional precision in detecting the distinct imprints of each mass eigenstate on large-scale structures.

Dissipation and noise in effective field theories for cosmology

Dissipation and noise arise from the incomplete modelling of unknown environments through which light and gravitational waves propagate. In this talk, I will introduce a framework that extends effective field theories to account for these effects. I will highlight how symmetries, locality, and unitarity impose constraints on dissipation and noise. Finally, I will explore the resulting phenomenology in the early and late universe, with a focus on the potential observational signatures of these effects.

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 

Energy flow of λ in Hořava-Lifshitz cosmology

Hořava-Lifshitz gravity is  perturbatively renormalizable quantum gravity model candidate with an anisotropic UV-scaling between space and time. I would like to present a cosmological background analysis of the minimal projectable formulations of the theory, with particular focus on the running of the parameter λ with energy.

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.

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.
Séminaire