Théorie

Quantum gravity Induced Entanglement of Masses (QGEM) protocol

Understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. Along this line, a prime question is to find whether gravity is a quantum entity subject to the rules of quantum mechanics. It is fair to say that there are no feasible ideas yet to test the quantum coherent behaviour of gravity directly in a laboratory experiment. Here, I will introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator.

Euclidean Wormholes and Holography

Wormholes are exotic solutions of General Relativity that still challenge our physical intuition. In this talk I will first review and distinguish various types of wormholes along with their expected physical properties. I will then focus on asymptotically AdS wormhole solutions in the context of holography. I will explain how to compute correlation functions of local operators as well as non local observables such as correlation functions of Wilson loops on the distinct boundaries and discuss their behavior.

Stochastic formalism of cosmic inflation, with applications to the physics of primordial black holes. La soutenance HDR Vincent Vennin

Dear friends and colleagues,

It is my pleasure to invite you to my habilitation defense, which will take place on the 30th of June at 3pm. 

I will present my work on the stochastic formalism of cosmic inflation, with applications to the physics of primordial black holes (a short description follows below).

Due to the current covid-19 restrictions, unfortunately, only members of the jury will be allowed to be physically present. The defense will however be broadcasted online, via the BlackBoard Collaborate platform:

Free falling with a pulsar in a triple system 

Universality of free fall, famously depicted by Galileo's letting down various masses from the top of Pisa's tower, is a cornerstone of General Relativity to the extent that any alternative theory of gravity would almost certainly break that principle. This is why it is being tested by ever more sensitive experiments in the Solar system, such as the recent Microscope satellite.

The H0 tension and non-minimal couplings to gravity

Theoretical models that aim to solve the tension between local measurements of the Hubble constant H0 and its inference from CMB data  have to include a modification to the standard LCDM model around the time of matter-radiation equality. I propose that such an early-time modification consists in a scalar field non-minimally coupled to the Ricci scalar, which behaves effectively like a dark radiation component and induces a time evolution of the Newton constant G.

Vainshtein screening for slowly rotating stars 

We study the Vainshtein mechanism in the context of slowly rotating stars in scalar-tensor theories.
While the Vainshtein screening is well established for spherically symmetric spacetimes, we introduce a slow rotation of the source and examine its validity in the axi-symmetric case.
We solve for the frame-dragging function accounting for the slow rotation and show that the deviations from the general relativity (GR) solution are screened in the weak-field approximation, meaning the solution for the frame-dragging function is the same as GR to leading order.
This suggests that the Vainsh
Théorie