#paperOfTheDay is "1/n Expansion: Calculation of the exponent nu in the order 1/n^3 by the Conformal Bootstrap method" from 1982. This paper is the first computation of the third-order correction in 1/N of the critical exponent of phi^4 #QuantumFieldTheory They use the mapping of the theory to a sigma model, which has the advantage of making explicit the N-dependence of diagrams. Then, they use "conformal bootstrap" to determine the sought-after values. This method is quite clever: At the critical point, the theory is conformal. Therefore, one can essentially do a perturbation calculation around the conformal theory. This has the advantage that the functional dependence of propagators and vertices is under control (the full momentum dependence of these functions is infinitely complicated). My impression is that the Broadhurst-Kreimer "Hopf algebra" approach to solving Dyson-Schwinger equations is essentially a mathematical formulation of the same idea. To the best of my knowledge, this has never been discussed in the literature, probably because the BK formalism puts much emphasis on mathematical precision rather than intuition. #dailyPaperChallenge https://link.springer.com/article/10.1007/BF01015292