Description |
We study the classical non-linear O(2) sigma model with
a coupling beta and chemical potential mu on a 2+1 dimensional Euclidean lattice. In the conventional formulation this model suffers from a sign problem at
non-zero chemical potential and hence cannot be
studied with the Wolff cluster algorithm. However, when formulated in terms of world-line of particles, the sign problem is absent. The world-line formulation can be
studied very efficiently with the ``worm algorithm''. We use this algorithm to uncover the phase diagram in the (beta,mu) plane. In order to do this we develop finite size scaling relations and use them to extract the critical behaviour.
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