Séminaire

Gravitational Wave Precision Observables and Waveforms from Scattering Amplitudes

In recent years, Scattering Amplitudes methods, developed for computations in relativistic Quantum Field Theories, have been applied to compute observables which are relevant for the generation of Gravitational Wave templates. In the first part of the talk, I will give a review of recent achievements. In the second part of the talk, I will talk about new attempts to compute gravitational waveforms directly from Amplitudes, their matching to classical results from General Relativity and ongoing developments.

Identifying supermassive binary black holes in blazar centers with a jet precession model

Abstract: Blazars are among the most powerful objects in the Universe. These active galactic nuclei launch a relativistic jet that is viewed under a small inclination angle from Earth. They are characterized by a high time variability along the whole electromagnetic spectrum, reaching from scales of minutes to years. Is the time period between such blazar flares declining, then they can be caused by jet precession in an inspiraling supermassive binary black hole at the blazar center.
 

Weyl-invariant Einstein-Cartan gravity: unifying the strong CP and hierarchy puzzles

 We show that the minimal Weyl-invariant Einstein-Cartan gravity in combination with the Standard Model of particle physics contains just one extra scalar degree of freedom (in addition to the graviton and the Standard Model fields) with the properties of an axion-like particle which can solve the strong CP-problem. The smallness of this particle's mass as well as of the cosmological constant is ensured by tiny values of the gauge coupling constants of the local Lorentz group.

Neutrino-neutrino interactions, entanglements, and flavor evolution

Neutrino-neutrino scatterings create entanglements between them which may affect their flavor evolution. Although insignificant in terrestrial settings, this phenomenon may be consequential in some astrophysical environments where neutrinos transport significant amount of energy and lepton number including core collapse supernova and neutron star mergers. The problem is equivalent to that of a many-body system away from equilibrium and presents significant challenges.

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.
Séminaire