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Correlation function (statistical mechanics)
Additional recommended knowledge
Even in a disordered phase,spins at different positions are correlated. The alignment that would naturally arise as a result of the interaction between spins is destroyed by thermal effects. At high temperatures one sees an exponential correlation with the correlation function being given by,
where ξ is what is called the correlation length, r is the distance between spins and d is the dimension of the system. As the temperature is lowered, thermal disordering is lowered and the correlation length increases. In second order phase transitions, the correlation length diverges at the critical point, leading to a power law correlation, that is responsible for scaling, seen in these transitions. The power in the power law is independent of temperature. It is in fact universal, i.e found to be the same in a wide variety of systems.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Correlation_function_(statistical_mechanics)". A list of authors is available in Wikipedia.|