Regensburg 2004 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.86: Poster

Donnerstag, 11. März 2004, 16:00–18:00, Poster D

Microcanonical entropy of classical spin systems with a continuous symmetry — •Andreas Richter, Michel Pleimling, and Alfred Hüller — Institut für Theoretische Physik I, Universität Erlangen-Nürnberg, D-91058 Erlangen

Critical phenomena of classical spin systems may be studied in many ways. In our approach we determine and analyse the microcanonical entropy S which is related to the density of states by S=k_B lnΩ, where k_B is the Boltzmann constant. Due to the huge amount of possible configurations it is in general impossible to calculate Ω exactly, even for systems of moderate size. The density of states can, however, be computed approximately from a numerical method using transition variables. Discrete classical systems, like the Ising or Potts model, were already studied with this method in the past [1,2]. We now extend this method to systems with continuous spins and apply it to the three-dimensional XY model. In addition, we discuss the determination of critical quantities directly from the numerically determined microcanonical entropy.

[1] A. Hüller, M. Pleimling, Int. J. Mod. Phys. C 13, 947 (2002)

[2] H. Behringer, J. Phys. A: Math. Gen 36, 8739 (2003)