This idea shows up in essentially all scientific fields. It’s the idea of adjointness. Together with norm, they give you the idea of fixed points, (invariants,

This idea shows up in essentially all scientific fields. It’s the idea of adjointness. Together with norm, they give you the idea of fixed points, (invariants, spectra, embeddings, braids etc).I'm Lawvere's fixed point theorem is I think the best formulation of the idea https://ncatlab.org/nlab/show/Lawvere%27s+fixed+point+theorem https://ncatlab.org/nlab/show/Lawvere%27s+fixed+point+theore... I've been putting together a brain dump on the topic https://github.com/adamnemecek/adjoint/ https://github.com/adamnemecek/adjoint/ Join the discord https://discord.gg/mr9TAhpyBW https://discord.gg/mr9TAhpyBW