Séminaire

Backreaction and Cosmic Butterflies: what simulations can tell us about inflation

The small-scale physics of inflation can leave unique observational signatures in the gravitational wave background and may also generate primordial black holes as a dark matter candidate. These phenomena often involve a significant enhancement of inflationary fluctuations, potentially leading to the breakdown of standard perturbation theory. In this talk, I will discuss how lattice simulations provide a crucial tool for addressing these challenges.

Effective field theory reproducing the MOND phenomenology based on a non-Abelian Yang-Mills graviphoton

Motivated by the phenomenology of MOND, we propose a theory based on a fundamental non Abelian Yang-Mills gauge field with gravitational coupling constant (a "graviphoton") emerging in a regime of weak acceleration, i.e. below the MOND acceleration scale. Using the formalism of the effective field theory and invoking a mechanism of gravitational polarization of the dark matter medium, we show that generic solutions of this theory reproduce the deep MOND limit without having to introduce in an ad hoc way an arbitrary function in the action.

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.

Séminaire