paper

Universal Magnetic Fluctuations with a Field Induced Length Scale

arXiv:cond-mat/0102283 · doi:10.1103/PhysRevE.64.036111

Abstract

We calculate the probability density function for the order parameter fluctuations in the low temperature phase of the 2D-XY model of magnetism near the line of critical points. A finite correlation length, ξ, is introduced with a small magnetic field, h, and an accurate expression for ξ(h) is developed by treating non-linear contributions to the field energy using a Hartree approximation. We find analytically a series of universal non-Gaussian distributions with a finite size scaling form and present a Gumbel-like function that gives the PDF to an excellent approximation. We propose the Gumbel exponent, a(h), as an indirect measure of the length scale of correlations in a wide range of complex systems.

7 pages, 4 figures, 1 table. To appear in Phys. Rev. E

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