J. Phys. II France
Volume 5, Numéro 3, March 1995
Page(s) 427 - 436
DOI: 10.1051/jp2:1995142
J. Phys. II France 5 (1995) 427-436

Monte Carlo Simulation of the Hedgehog Defect Core in Spin Systems

C. Chiccoli1, P. Pasini1, F. Semeria1, T.J. Sluckin2 and C. Zannoni3

1  INFN Sezione di Bologna, Via Irnerio 46, 40126 Bologna, Italy
2  Department of Mathematics, The University, Southampton SO9 5NH, England
3  Dipartimento di Chimica Fisica ed Inorganica, Università, Viale Risorgimento 4, 40136 Bologna, Italy

(Received 17 June 1994, revised 26 September 1994, accepted 21 November 1994)

The core structures of hedgehog point disclinations in Heisenberg magnets and Lebwohl-Lasher nematic liquid crystals have been investigated by Monte Carlo simulation. We find qualitative agreement with the theoretical predictions of Schopohl and Sluckin that the magnetic defects have smaller cores. We also find some evidence for the picture of Penzen-stadler and Trebin in which spherical symmetry of the nematic hedgehog core is broken, and the core region can be considered as a disclination line of index 1/2. Finally we make some general comments about the significance of our results in the context of other recent theoretical speculations.

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