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From Spin Ladders to the 2-d O(3) Model at Non-Zero Density

S. Chandrasekharan·B. Scarlet·U. -J. Wiese
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Abstract

The numerical simulation of various field theories at non-zero chemical potential suffers from severe complex action problems. In particular, QCD at non-zero quark density can presently not be simulated for that reason. A similar complex action problem arises in the 2-d O(3) model -- a toy model for QCD. Here we construct the 2-d O(3) model at non-zero density via dimensional reduction of an antiferromagnetic quantum spin ladder in a magnetic field. The complex action problem of the 2-d O(3) model manifests itself as a sign problem of the ladder system. This sign problem is solved completely with a meron-cluster algorithm.

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S. Chandrasekharan, B. Scarlet, U. -J. Wiese. 2001-10-29. From Spin Ladders to the 2-d O(3) Model at Non-Zero Density. https://doi.org/10.1016/s0010-4655(02)00311-9

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