Séminaire des jeunes chercheurs du CPHT

The CPHT Young Researchers Seminar will be held on Wednesday October 1st, in Room Louis Michel, at 2PM.

Arthur Klause, on An introduction to modern Wilsonian renormalization
The Wilsonian renormalization group equations provide a powerful framework for rigorously analyzing renormalizability and triviality in scalar field theories under various approximations. The perturbative renormalizability of the Euclidean scalar $\phi^4$ theory was established long ago, and more recently, its triviality has been proven in the mean-field approximation using non-perturbative methods. We will present the perturbative renormalizability and perturbative triviality of Euclidean scalar field theories with an interaction term of odd power greater than or equal to 6. In the Wilsonian renormalization group framework, such interaction terms naturally emerge in the effective Lagrangian when evolving from a bare phi^4 theory. We show that under natural renormalization conditions, the theory remains renormalizable and a bare perturbatively nontrivial theory. However, we demonstrate that certain alternative renormalization schemes can spoil the nontriviality that has been highlighted, underlining the renormalization scheme dependence of the theory's fate.

Victor Chabirand, The Wonderland of Carrollian physics: Exotic limit of the Poincaré group:
In this talk, we will first motivate the study of Carrollian physics. We will briefly introduce the holographic principle, which states that gravity is dual to a CFT living on the boundary of spacetime. Applied to asymptotically flat spacetimes, the dual theory should exhibit Carrollian symmetry. We will therefore study the Carroll group in an intrinsic manner. It can be viewed as the opposite limit to the Galilei group, with the speed of light taken to zero. In this strange wonderland, we will attempt to reconstruct classical mechanics, electromagnetism, statistical physics, and quantum mechanics. Our approach will be non-standard, even within the Carrollian community. This investigation will be fun, but it will also reveal important insights about ordinary Galilean physics. We will see that the Galilean limit is in fact a two-parameter limit, and not simply a low-speed limit. We will also see that there exist two Galilean electromagnetic theories, and we will establish the Lévy-Leblond equation describing a Galilean spin-1/2 particle.

The seminar will be followed by a high tea.