Talk:Mermin–Wagner theorem
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In the Heisenberg model example, the infinite magnetization is only an artifact of using the linear approximation. Maliz 21:12, 12 November 2006 (UTC)
The section on the Heisenberg model needs rewriting, but I am not an expert on the Heisenberg model. Maliz 21:23, 12 November 2006 (UTC)
[edit] For an expert on the Mermin-Wagner theorem please ask ...
... one of the authors (Herbert Wagner) himself; he is in Munich at the LMU university. You can also ask Patrick Bruno at the Max-Planck Institute at Halle, Germany. The present article seems rather good. -- 132.199.38.104 12:01, 12 October 2007 (UTC)
[edit] Kosterlitz-Thouless transition
I don't understand the statement in the "Kosterlitz-Thouless transition" section that there can be an ordered phase without spontaneous symmetry breaking. Does this refer to a trivial (e.g. s = 0) ordered phase (which is not admissible for any systems where the spin has fixed magnitude)? How can there be an ordered phase which isn't killed by fluctuations? Woodford 07:04, 3 December 2007 (UTC)
- That was at best a poor wording of the situation. The XY model at low (nozero) temperature has quasi-long-range order (rational decay of correlations, so infinite range correlations in a certain sense) but this isn't an ordered phase as would generally be understood, trivial or otherwise. Rafaelgr (talk) 22:49, 8 February 2008 (UTC)
