Théorie

I will present cuHARM, a general relativistic radiation magnetohydrodynamic solver optimized to exploit exascale computing facilities. After describing the core numerical strategies enabling efficient calculation for multi-node and multi-GPU architectures, I will discuss how radiative cooling changes the dynamics of magnetically arrested accretion disks. In the second part of the talk, I will detail how radiation and its feedback on the dynamics are modeled. In cuHARM, the specific intensity is discretized in space and momentum, and is evolved through the solution of the radiative transfer equation via the discrete ordinate method. This approach eliminates the need for a closure relation and enables to resolve the anisotropy of the specific intensity. Finally, I will present the first results obtained for a radiative accretion disk operating at 0.1 times the Eddington luminosity.

Warm Inflation is a variant inflationary scenario where the inflaton field continuously dissipates its energy to a subdominant radiation bath during inflation. Among the many advantages that WI has over its more standard counterpart, which we will refer to as Cold Inflation, is that WI smoothly transits to a radiation dominated Universe post inflation without invoking the need of a reheating phase, dynamics of which is still quite unknown. The dissipation effects effective during Warm Inflation makes the dynamics of the inflation quite intricate. Even the simple graceful exit in Cold Inflation turns out to be not so simple in Warm Inflation. In this talk, we will do the background analysis of Warm Inflation and shed light on how Warm Inflation ends or gracefully exits. These graceful exit criteria also constrain the form of the potential and the dissipative coefficients that one may choose for their Warm Inflationary model. Moreover, it indicates whether Warm Inflation can at all exit to a radiation dominated epoch or not.

Cosmological correlators encode the signatures of the universe's evolution, and by measuring correlations in the late universe we infer the dynamics and contents of the universe. I will review some recent developments in the study of the structure of quantum field theory in curved spacetimes, and the computation of cosmological correlators.

The Alpha Magnetic Spectrometer (AMS) is a general purpose high energy particle detector, which was successfully deployed on the International Space Station on May 19, 2011. It conducts a unique, long-duration mission of fundamental physics research in space. To date, the detector has collected over 255 billion cosmic ray events. This talk presents the latest AMS measurements of cosmic ray elementary particles. The latest results up to the energies of few Tera-electronvolts reveal distinctive properties of particle fluxes and indicate the existence of a primary source of high-energy electrons and positrons, associated with either Dark Matter or an Astrophysical origin. AMS is poised to continue its mission through 2030, providing unique insights into the origins of cosmic ray matter and antimatter and exploring new physics phenomena within the cosmos.