I will describe fluctuations in systems of active particles. In particular, we consider the active work, which measures how far the local self-forcing of active particles translates into real motion. The probability distribution of the time-averaged active work has a characteristic form, which is related to the presence of two dynamical phase transitions. One transition involves phase separation and the other involves collective motion where rotational symmetry is broken and all particles move in the same direction. These results can be used to understand instabilities of the system in the face of particular kinds of "control forces'.

Directed assembly of advanced materials in soft condensed matter provides a fascinating tool for producing a new generation of technological applications that combine several properties and may respond to external conditions. In particular, ordered fluids offer the potential for many innovative applications based on the directed assembly of particles because of their unique properties. In this talk, I will present an overview of the methods we have used to engineer topological defects within liquid crystals and at their interfaces. Then, I will explain how liquid crystal defects can be used to develop new mechanisms for the assembly of colloidal particles. Finally, I will discuss how these assemblies will offer essential insights for novel applications in different technological fields.

$T^3$ in Grande Ourse*

Rupert will entertain us with possible explanations of the
${\mathbf b \mathbf \to \mathbf s}$ anomalies at one-loop:
Indications of lepton flavour universality violation in ${\mathbf b
\mathbf \to \mathbf s}$ transitions at LHCb present one of the
most statistically significant departures from the SM in recent years. I will summarise these observations and review the EFT techniques used to describe them. I will motivate and discuss explanations involving effects induced by new physics at loop level and assess the viability of such solutions given the various important constraints.
This will initially be in an EFT context, before moving to specific simplified models. Finally, I will turn to complementary tests of this new physics.

*tea/coffee/biscuits break around 4pm

Colloidal suspensions are ubiquitous in our daily life. Micrometric particles dispersed in a solvent are indeed present in common liquids such as paints, inks or even food products. We will discuss the properties of those colloidal suspensions from their liquid phase to solid deposits after drying.
First, colloidal suspensions exhibit a wide range of rheological behaviors from shear-thinning to yield stress fluids. We will focus on the shear-thickening transition when dense suspensions experience a dramatic increase in viscosity above a critical shear-stress. By changing the physico-chemistry of the particles, we can tune this rheological transition and thus understand the interactions involved in this behavior.
Increasing concentration can also be noticed during drying when solvent evaporates: particles finally form a solid deposit. After drying, a drop of a colloidal suspension leads to a variety of patterns from coffee-stain to more homogeneous coatings in paintings. We will discuss the effect of the initial concentration of particles on the drying pattern and on the subsequent mechanical instabilities.
Finally, after the whole drying of the colloidal suspension, coatings are achieved. Depending of the nature of the particles, we can tune the wettability of the substrate up to superhydrophobic solid. We will briefly discuss how such a water-repellent substrate can allow levitation of liquids.

Recent data on b->c ℓ nu and b→sℓℓ transitions exhibit an interesting pattern of deviations from Standard Model expectations, hinting at the violation of lepton flavour universality. I will recall the current situation for the various observables of interest. I will discuss the theoretical approaches used to determine the Standard Model predictions for these observables and some of their shortcomings, before explaining how the observed deviations can be analysed in a model-independent framework. I will then briefly discuss some of the simplified New Physics models used to explain the deviations observed.

Complete understanding of cell mechanics requires probing also the mechanical properties of individual proteins, filaments, and molecular complexes, since these provide structural stability and mechanical flexibility to the living cell. Moreover, the dynamical response of biological systems at the nano- and microscales span over several orders of magnitude in time. Thus, access to a wide range of length and time scales is required to decipher the molecular determinants of cell mechanics. High-speed atomic force microscopy (HS-AFM) is a unique technology allowing subsecond, nanometric imaging[1]. We have adapted HS-AFM to perform high-speed force spectroscopy (HS-FS) probing protein unfolding and receptor/ligand unbinding up to the velocity of molecular dynamics simulations[2–5]. This combination provides atomistic understanding of biomolecular processes based on experimental results. Our recent results revealed heterogeneous and rate dependent unfolding and unbinding pathways on different biomolecules. We have also developed high-frequency microrheology (HFMR) to probe the mechanics of cells at high frequencies, up to 100 kHz[6]. We report the viscoelastic response of different cell types and upon cytoskeletal drug treatments. At a few microsecond timescales, cells exhibit rich viscoelastic responses that depend on the state of the cytoskeleton and on the cell type. Mechanical measurements over the widest dynamic range provide mechanistic understanding of molecular and cellular mechanics allowing direct evaluation of theoretical predictions.

References
[1] T. Ando, N. Kodera, E. Takai, D. Maruyama, K. Saito, A. Toda, A high-speed atomic force microscope for studying biological macromolecules, Proceedings of the National Academy of Sciences. 98 (2001) 12468–12472. doi:10.1073/pnas.211400898.
[2] F. Rico, L. Gonzalez, I. Casuso, M. Puig-Vidal, S. Scheuring, High-Speed Force Spectroscopy Unfolds Titin at the Velocity of Molecular Dynamics Simulations, Science. 342 (2013) 741–743.
[3] F. Sumbul, A. Marchesi, H. Takahashi, S. Scheuring, F. Rico, High-Speed Force Spectroscopy for Single Protein Unfolding, in: Y.L. Lyubchenko (Ed.), Nanoscale Imaging: Methods and Protocols, Springer New York, New York, NY, 2018: pp. 243–264.
[4] H. Takahashi, F. Rico, C. Chipot, S. Scheuring, α-Helix Unwinding as Force Buffer in Spectrins, ACS Nano. 12 (2018) 2719–2727.
[5] F. Rico, A. Russek, L. González, H. Grubmüller, S. Scheuring, Heterogeneous and rate-dependent streptavidin–biotin unbinding revealed by high-speed force spectroscopy and atomistic simulations, PNAS. 116 (2019) 6594–6601.
[6] A. Rigato, A. Miyagi, S. Scheuring, F. Rico, High-frequency microrheology reveals cytoskeleton dynamics in living cells, Nat Phys. 13 (2017) 771–775.