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DY: Dynamik und Statistische Physik

DY 35: Critical phenomena and phase transitions I

DY 35.5: Talk

Wednesday, March 26, 2003, 15:30–15:45, G\"OR/229

Critical exponents from a cluster molecular field approximation — •Hans Behringer, Michel Pleimling, and Alfred Hüller — Institut für Theoretische Physik I, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen

Cluster molecular field approximations such as the Bethe scheme lead to a substantial improvement of the simple Weiss treatment of spin systems. In our approach the Bethe approximation is systematically enhanced by inserting increasing clusters of spins in a magnetised background and treating the statistical mechanics of the clusters exactly. Finite size scaling relations and methods using effective exponents to extract the true critical exponents of the infinite system are discussed and tested for various Ising and Potts models. Reliable values of the critical quantities are obtained from small system sizes.

H. Behringer, M. Pleimling, and A. Hüller, to appear in Eur. Phys. J. B, cond-mat/0210099