The underlying idea is the idea of fixed points (aka spectra, diagonalizations, embedding, invariants, braids). By fixed point I mean something like the "Lawvere's fixed point theorem".
<a href="https://ncatlab.org/nlab/show/Lawvere%27s+fixed+point+theorem" rel="nofollow">https://ncatlab.org/nlab/show/Lawvere%27s+fixed+point+theore...</a><p>I have a linkdump on this<p><a href="https://github.com/adamnemecek/adjoint" rel="nofollow">https://github.com/adamnemecek/adjoint</a><p>I also have a discord <a href="https://discord.gg/mr9TAhpyBW" rel="nofollow">https://discord.gg/mr9TAhpyBW</a>
I knew Craige Schensted left his mark on the subject; I had no idea his wife (Irene Verona Schensted) had written a book about it! (well, I think it's about it; it's not on libgen...)