Séminaire

One of the big goals of today’s CMB experiments is to look for the faint signature of primordial gravitational waves in the B-mode polarization. Finding it would give us a unique window into the physics of the very early Universe and the Inflationary epoch.

Natural minerals, through their ability to record particle interactions over geological timescales, are emerging as a novel tool for astroparticle physics. The paleo-detector concept leverages the nanometer to micrometer-scale damage tracks left by nuclear recoils to search for rare events like dark matter and neutrinos. Our work takes a unique approach by treating the tracks from cosmic ray muons, typically a background for other paleo-detector studies, as the primary signal for probing the high-energy astrophysical history of our galaxy.

The Standard Model Higgs can be the inflaton, providing an attractively economical scenario. The core idea is simple, but there are complications both on the side of quantum corrections and gravity. I will discuss possibilities and problems due to such complications. In particular I will cover how the predictions of Higgs inflation depend on what is the correct formulation of general relativity: metric, Palatini or something else.

High-energy neutrino and γ-ray emission are expected from the Galactic plane, produced by interactions between cosmic rays and the interstellar medium or radiation fields. Recent LHAASO observations have detected diffuse γ-rays from the Galactic plane and an ultrahigh-energy γ-ray bubble (Cygnus Bubble) up to PeV energies, suggesting the possibility of neutrino emission. Using 7 years of publicly available IceCube track data with the full detector, we conducted searches for neutrino signals correlated with LHAASO diffuse Galactic γ-ray emission and Cygnus Bubble using a template method.

Understanding the complex transport of particles in turbulent plasmas is of great relevance in various fields. In astrophysics, the diffusive transport of high-energy particles is often described in an ensemble-averaged way, employing a transport equation that describes the time evolution of the particles distribution function in space and momentum. The standard transport equation can also be re-written into a set of stochastic differential equation.

Current cosmological data seem to point beyond the limits of quintessence for the behavior of dark energy accelerating the universe. This requires challenging physics such as modified gravity, interactions, or altered vacuum, in analogy with how non-Gaussianity in inflation requires physics beyond standard dynamics. We explore some possibilities.