Abstract
The following results are proved for a system of Ising spins σi = ±1 in zero magnetic field coupled by a purely ferromagnetic interaction of the form −Σi<j Jijσiσj with Jij ≥ 0, for arbitrary crystal lattice and range of interaction: (1) The binary correlation functions 〈σkσl〉 are always nonnegative (〈 〉 denotes a thermal average). (2) For arbitrary i, j, k, and l, 〈σiσjσk σl〉 ≥ 〈σiσj〉 〈σkσl〉. Consequences of these results, in particular the second, are: (i) 〈σkσl〉 never decreases if any Jij is increased. (ii) If an Ising model with ferromagnetic interactions exhibits a long-range order, this long-range order increases if additional ferromagnetic interactions are added. This last fact may be used to prove the existence of long-range order in a large class of two- and three-dimensional Ising lattices with purely ferromagnetic interactions of bounded or unbounded range.
References
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Dates
Type | When |
---|---|
Created | 20 years, 7 months ago (Jan. 6, 2005, 3:06 p.m.) |
Deposited | 1 year, 6 months ago (Feb. 7, 2024, 4:49 p.m.) |
Indexed | 2 weeks, 3 days ago (Aug. 6, 2025, 9:01 a.m.) |
Issued | 58 years, 5 months ago (March 1, 1967) |
Published | 58 years, 5 months ago (March 1, 1967) |
Published Print | 58 years, 5 months ago (March 1, 1967) |
@article{Griffiths_1967, title={Correlations in Ising Ferromagnets. I}, volume={8}, ISSN={1089-7658}, url={http://dx.doi.org/10.1063/1.1705219}, DOI={10.1063/1.1705219}, number={3}, journal={Journal of Mathematical Physics}, publisher={AIP Publishing}, author={Griffiths, Robert B.}, year={1967}, month=mar, pages={478–483} }