Given a D-dimensional lattice Λ, per each lattice site j ∈ Λ there is a two-dimensional, unit-length vector sj = (cos θj, sin θj) See more

• The existence of the thermodynamic limit for the free energy and spin correlations were proved by Ginibre, extending to this case the See more

• Classical Heisenberg model
• Coulomb gas
• Goldstone boson
• Ising model See more

• real-time XY model WebGL simulation
• Interactive Monte Carlo simulation of the Ising, XY and Heisenberg models with 3D graphics (requires WebGL compatible browser) See more

As mentioned above in one dimension the XY model does not have a phase transition, while in two dimensions it has the See more

• H. E. Stanley, Introduction to Phase Transitions and Critical Phenomena, (Oxford University Press, Oxford and New York 1971);
• See more