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Can the whole not merely be the sum of its parts? How do collective patterns appear?
Could three molecules of water form ice?
Could higher-level abilities be created from interacting AI agents?
The notion of complexity pertains to systems in which somewhat unexpected properties emerge from the interplay of a sufficiently large number of entities — be they particles, living cells, artificial neurons, organisms, people, abstract agents... or even a mixture of some (or all!) of these.
Statistical physics has been the first branch of science to try and model in a mathematical manner such systems, focusing especially on the subtle and often elusive passage from the micro/individual level to the macro/collective level. This lecture course explores further how the mindset of statistical physics can provide fertile ground for the analysis and modelling of complexity, across disciplinary boundaries.
The seminar takes place on Wednesdays at 1:30pm in the lecture room Conf IV room. It is held in alternation with the physics department’s colloquium. The list is updated often.
Les enseignements dispensés à l’ENS s’adressent aux meilleurs étudiantes et étudiants issus des CPGE ou universités françaises et internationales, à partir d’un niveau bac+2, commençant leurs études à l’ENS avec la troisième année de licence (L3) ou en master première année (M1) ou master deuxième année (M2), ou au niveau doctorat. Il est donc possible de rejoindre nos cursus à ces différentes étapes. Chaque année d’étude est structurée en semestres sauf en doctorat.
The main goal of the course is to study the light-matter interaction at the fundamental level where one two-level system interacts with a single mode of the electromagnetic field.
The lecture will first present the fundamental concept of cavity quantum electrodynamics (Jaynes–Cummings model, resonant and dispersive interaction, Schrödinger cat states of light) and then moves to the more recent developments of circuit QED.
This course deals with transfers in complex fluids, which are ubiquitous processes in everyday life and industrial applications, as well as in geological or biological systems. Different types of transfers will be examined : first, drying and dissolution and, in a second part, wetting of a solid surface. The specificities of the drying of complex fluids will be highlighted, and associated phenomena such as glass transition, Marangoni effects, etc. will be described quantitatively in the light of recent literature. The mechanisms of the reverse process of dissolution will also be detailed. Then, starting from the description of the wetting of a solid by a simple liquid, we will see how introducing complexity in this multiphase problem (viscoelasticity, surface-volume exchanges, intermediate characteristic length scale, activity…) modifies the contact between media. The related challenges posed in industrial applications will also be detailed.