Exceptionnally the colloquium is opened to all students of the Physics Department. Detecting gravitational waves required 4 decades of experimental effort to reach a sensitivity at the h~10-21 level, corresponding to mirror displacements below 10-18 m. I will review this "noise hunting" effort and give some details about the recent observation of 2 black hole mergers. Apart from classical noise (seismic noise, thermal noise...), it was realized as soon as in the late 70s that quantum fluctuations of the light field were responsible for the Standard Quantum Limit, a sensitivity limit that second-generation gravitational-wave interferometers will reach once they operate at their design sensitivity. A number of ideas have been considered to beat the SQL: squeezed states of the light field, tailoring the optical response function or taking advantage of the mirror mechanical response to radiation pressure. I will present the first experimental demonstrations of such ideas, either on suspended interferometers or table-top experiments. I will also discuss how recent progress in micro/nanomechanics has allowed the emergence of the new field of quantum optomechanics, which addresses the quantum aspects of both the light field and the mechanical resonator. This new field is very promising both for the study of the foundations og quantum mechanics (quantum states and decoherence of macroscopic objects...) and for quantum information. I will present a few typical recent experiments.

Globular proteins are amphiphiles and adsorb to hydrophobic interfaces. Their propensity to change their conformation upon adsorption and to self associate within the interfacial film results in interfacial visco-elasticity and favors foam stabilisation. How is the variability in protein structural and physico-chemical properties reflected in their interfacial behavior? Within the interfacial films, the local protein concentration may reach several hundreds of grams per liter: what can we learn about the interfacial behaviour by studying the structure and osmotic pressure of highly concentrated bulk solutions?

For inertial granular flow near jamming, nearly all of the energy dissipation is due to frictional sliding, rather than inelastic collisions. However, collisions nevertheless send acoustic waves through the system, acting as a source of mechanical noise. Despite its tiny amplitude, we show that this noise controls the scaling of kinetic quantities. A corollary is that, for these quantities, there is no rigid limit. We argue that mechanical noise may be crucial to understand S-shape flow curves and flow instability in slow, inertial granular flow.

Potential CNRS candidate

Over the past two decades enormous achievements have been made to measure fundamental properties of neutrinos but there still are many unknowns. In this talk I briefly review three experimental perspectives that will be able to provide more insight into the still unknown neutrino properties. These experiments are DUNE as a long baseline oscillation experiment, NEXT as a neutrinoless double beta decay experiment and in the context of the LHC experiments what could be determined with respect to neutrinos in connection with electroweak physics.

To measure the last unknown $3\nu$ oscillation parameter ($\delta$), several long baseline neutrino experiments have been designed or proposed. Recently it has been shown that turning on neutral-current Non-Standard Interactions (NSI) of neutrinos with matter can induce degeneracies that may even hinder the proposed state-of-the-art DUNE long baseline experiment from measuring the value of $\delta$. We study how the result of the proposed MOMENT experiment with a baseline of 150 km and $200~{\rm MeV}<E_\nu<600~{\rm MeV}$ can help to solve the degeneracy induced by NSI and determine the true value of $\delta$. We also investigate the effects of charged-current NSIs at the source and at the detector in the simulated data for DUNE, while neglecting the neutral-current NSI at the propagation. We study the effects of NSI on the simultaneous measurements of $\theta_{23}$ and $\delta$ in DUNE. We also find the potential of DUNE to constrain the relevant charged-current NSI parameters.

Entanglement entropy is a valuable tool for characterizing the correlation structure of quantum field theories. When applied to gauge theories, subtleties arise which prevent the factorization of the Hilbert space underlying the notion of entanglement entropy. Borrowing techniques from extended topological field theories, I introduce a new definition of entanglement entropy for both Abelian and non–Abelian gauge theories. I will then relate this construction to earlier proposals and argue that it brings these closer to each other. I will also point out that different definitions of entanglement entropies can be related to choices of (squeezed) vacuum states and excitations there upon. Time allowing, I will briefly discuss aspects more closely related to topics in quantum gravity.

Despite its impressive success, the standard model (SM) of particle physics does not account for all experimental observations.
Then, the SM should not be viewed as an ultraviolet complete theory, trather as an effective description of a more fundamental theory and new physics should be introduced. In this presentation, I will follow two different approaches to new physics.
In the first one, the SM is extended by only a few new fermions, which are a common prediction of most well-motivated beyond the SM theories. The main purpose will be to identify the effect of these new fermions in light of the recent Higgs coupling measurements. The focus will be on loop-induced Higgs decays and I will show that some mechanisms allow the $h\gamma\gamma$ channel to remain SM-like as experimentally observed, while a strong departure is possible in the $h\gamma Z$ channel.
In the second part of the presentation, I will focus on composite Higgs models that aim to solve the hierarchy problem of the EW scale: the Higgs appears naturally light because it emerges as a pseudo-Nambu Goldstone boson of a spontaneously broken global symmetry.
While up to now, most of the literature considered an effective approach to the non-perturbative composite dynamics, I will rather present one well-defined ultraviolet-complete realisation.
Within the Nambu and Jona-Lasinio framework (based on the 1/N expansion), I will in particular present the spectrum of the lightest composite resonances that could be observed in the near future at the LHC.