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arXiv · 1711.00042

Spin models in complex magnetic fields: a hard sign problem

Philippe de Forcrand·Tobias Rindlisbacher
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Abstract

Coupling spin models to complex external fields can give rise to interesting phenomena like zeroes of the partition function (Lee-Yang zeroes, edge singularities) or oscillating propagators. Unfortunately, it usually also leads to a severe sign problem that can be overcome only in special cases; if the partition function has zeroes, the sign problem is even representation-independent at these points. In this study, we couple the N-state Potts model in different ways to a complex external magnetic field and discuss the above mentioned phenomena and their relations based on analytic calculations (1D) and results obtained using a modified cluster algorithm (general D) that in many cases either cures or at least drastically reduces the sign-problem induced by the complex external field.

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Philippe de Forcrand, Tobias Rindlisbacher. 2017-10-31. Spin models in complex magnetic fields: a hard sign problem. https://doi.org/10.1051/epjconf%2F201817507026

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