. According to a conformal bootstrap computation, these three dimensions are given by: This gives the following values of the critical exponents: Monte Carlo methods give compatible determinations: . See also Classical Heisenberg model Goldstone boson Ising model Potts model n-vector model Kosterlitz–Thouless transition Topological defect Superfluid film Sigma model Notes References Evgeny Demidov, Vortices in the XY model (2004) Further reading H. E. Stanley, Introduction to Phase Transitions and Critical Phenomena, (Oxford University Press, Oxford and New York 1971); H. Kleinert, Gauge Fields in Condensed Matter, Vol. I, " SUPERFLOW AND VORTEX LINES", pp. 1–742, Vol. II, "STRESSES AND DEFECTS", pp. 743–1456, World Scientific (Singapore, 1989); Paperback (also available online: Vol. I and Vol. II) External links real-time XY model WebGL simulation Interactive Monte Carlo simulation of the Ising, XY and Heisenberg models with 3D graphics (requires WebGL compatible browser) Lattice models