Talk:Quantum phase transition

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What does "Such quantum phase transitions can be phase transition or continuous" mean? I guess it is a typo. What should it say?

[edit] what is so "quantum" about a QPT?

I fail to see in what sense quantum effects are relevant for a QPT. Take a classical antiferromagnetic spin lattice, for example: why shouldn't there be a zero temperature phase transition when the external magnetic field is varied? There is a well-defined (possibly degenerate) classical ground state, and its energy might change in a non-analytic way under variation of the magnetic field.

Also, the statement "A classical system does not have entropy at zero temperature" also applies in the quantum case since a pure state has vanishing entropy. - Saibod 11:05, 31 August 2007 (UTC)