{"slug":"wilson-1971","title":"Wilson 1971 — Renormalization Group and Critical Phenomena","body":"## The Source\n\nWilson, K.G. \"Renormalization Group and Critical Phenomena. I.\" *Physical Review B* 4(9), 3174–3183 (1971). DOI: 10.1103/PhysRevB.4.3174.\n\nWilson, K.G. \"Renormalization Group and Critical Phenomena. II.\" *Physical Review B* 4(9), 3184–3205 (1971). DOI: 10.1103/PhysRevB.4.3184.\n\n## The Claim\n\nAt criticality, correlation length shoots to infinity. The system forgets its atoms. Symmetry alone picks the numbers.\n\n## The Context\n\n1971. Cornell. Magnets, fluids, and alloys share the same exponents. Landau's theory fails. Experiments defy prediction. Wilson takes Kadanoff's block-spin idea and builds the machine. Coarse-graining erases the small. The large survives.\n\n## The Evidence\n\nWilson writes the renormalization group as a flow. Repeated rescaling drives the Hamiltonian toward fixed points. At those points, ξ → ∞. Finite scales wash away. Critical exponents emerge as eigenvalues. Part I maps Kadanoff scaling to field theory. Part II runs the phase-space cell analysis. The epsilon expansion debuts. The numbers match experiment.\n\n## The Convergence\n\nThis instantiates **C05 — Criticality** and **C10 — Scale Invariance**.\n\nWilson proves that criticality and scale invariance are one face. No characteristic scale means power laws. The same exponents rule magnets, fluids, and sandpiles. The renormalization group is the bridge. It links Bak's avalanches [SOURCE:bak-1987|type:empirical] to fractal geometry to metabolic scaling. One engine. Many bodies.\n\nGRAIN scores this edge at convergence strength 8. Four fields. Four methods. Same statistics.\n\n## The Honest Limits\n\nWilson addresses equilibrium. He does not touch self-organized criticality. Bak's sandpiles find criticality alone. Wilson needs a dial.\n\nThe epsilon expansion lives near four dimensions. Low dimensions break it. The Kosterlitz-Thouless transition escapes his net.\n\nWilson gives math. He does not give the why. Why do brains, markets, and quakes sit near criticality? That waits for Beggs, Kauffman, and GRAIN.\n\nRival: power laws are fitting artifacts. Log-log plots make them appear. Finite systems show cutoff effects. Pure scaling is an idealization.\n\n## The Receipt\n\n> \"At criticality, correlation length ξ → ∞; the system becomes scale-invariant.\"\n\nThis is Wilson's core payload. The Hamiltonian flows to H* under rescaling. Microscopic details vanish. Different systems land on the same fixed point. Same exponents. Same numbers. That is the proof.\n\n## Related Sources\n\n- [Bak, Tang & Wiesenfeld — Self-Organized Criticality (1987)](/articles/bak-1987): Wilson's math meets systems that tune themselves.\n- [Schrödinger 1944 — What Is Life?](/articles/schrodinger-1944): Physics crosses into biology. Wilson's machinery follows.\n- [Noether 1918 — Invariante Variationsprobleme](/articles/noether-1918): Symmetry begets conservation. Wilson's fixed points inherit this law.\n- [Wiener 1948 — Cybernetics](/articles/wiener-1948): Feedback and control. The engineering cousin to scaling.\n- [Barabási & Albert 1999 — Scale-Free Networks](/articles/barabasi-1999): Power laws in links. Wilson's math in graph space.\n- [Prigogine 1977 — Dissipative Structures](/articles/prigogine-1977): Non-equilibrium order. The thermodynamic cousin to criticality.\n","register":"source","tags":["source","grain","convergence","wilson"],"style":{},"claims":[{"id":"c1","text":"At criticality, correlation length ξ diverges to infinity, rendering the system scale-invariant.","tier":"system","source_ids":["s1","s2"]},{"id":"c2","text":"The renormalization group describes critical phenomena as a flow of Hamiltonians under repeated rescaling toward fixed points.","tier":"system","source_ids":["s1","s2"]},{"id":"c3","text":"Critical exponents emerge as eigenvalues of the linearized renormalization group at fixed points.","tier":"system","source_ids":["s1","s2"]},{"id":"c4","text":"The same critical exponents govern magnets, fluids, and alloys — universality across different physical systems.","tier":"system","source_ids":["s1","s2"]},{"id":"c5","text":"Wilson's epsilon expansion near four dimensions yields quantitative predictions matching experimental measurements.","tier":"system","source_ids":["s1","s2"]},{"id":"c6","text":"Wilson's framework addresses equilibrium critical phenomena but does not encompass self-organized criticality.","tier":"system","source_ids":["s1","s2"]},{"id":"c7","text":"The epsilon expansion breaks down in low dimensions, failing to capture phenomena such as the Kosterlitz-Thouless transition.","tier":"system","source_ids":["s1","s2"]}],"sources":[{"id":"s1","type":"primary","url":"https://doi.org/10.1103/PhysRevB.4.3174","title":"Wilson, K.G. \"Renormalization Group and Critical Phenomena. I.\" Physical Review B 4(9), 3174–3183 (1971).","quote":"At criticality, correlation length ξ → ∞; the system becomes scale-invariant.","summary":"Introduces the renormalization group as a flow of Hamiltonians under rescaling, mapping Kadanoff's block-spin idea to quantum field theory.","claim_ids":["c1","c2","c3","c4","c5"]},{"id":"s2","type":"primary","url":"https://doi.org/10.1103/PhysRevB.4.3184","title":"Wilson, K.G. \"Renormalization Group and Critical Phenomena. II.\" Physical Review B 4(9), 3184–3205 (1971).","quote":"","summary":"Develops the phase-space cell analysis and introduces the epsilon expansion, providing quantitative predictions for critical exponents.","claim_ids":["c1","c2","c3","c4","c5"]},{"id":"s3","type":"adjacent","url":"https://miscsubjects.com/articles/bak-1987","title":"Bak, Tang & Wiesenfeld — Self-Organized Criticality (1987)","quote":"","summary":"Empirical and theoretical work on systems that spontaneously tune themselves to criticality without external parameter adjustment.","claim_ids":["c6"]},{"id":"s4","type":"rival","url":"","title":"Rival frame: Power-law fitting artifacts and finite-size effects","quote":"Log-log plots make them appear. Finite systems show cutoff effects. Pure scaling is an idealization.","summary":"Challenges whether observed critical scaling is genuine or an artifact of log-log plotting and finite-size effects in real systems.","claim_ids":[]}],"prov":{"model":"manual","action":"write"}}