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, abtract 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 — including across disciplinary boundaries.