79 research outputs found
The sign problem and Abelian lattice duality
For a large class of Abelian lattice models with sign problems, including the
case of non-zero chemical potential, duality maps models with complex actions
into dual models with real actions. For extended regions of parameter space,
calculable for each model, duality resolves the sign problem for both analytic
methods and computer simulations. Explicit duality relations are given for
models for spin and gauge models based on Z(N) and U(1) symmetry groups. The
dual forms are generalizations of the Z(N) chiral clock model and the lattice
Frenkel-Kontorova model, respectively. From these equivalences, rich sets of
spatially-modulated phases are found in the strong-coupling region of the
original models.Comment: Latex, 7 pages, 1 figure. Presented at the 31st International
Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013,
Mainz, German
Approaches to the sign problem in lattice field theory
Quantum field theories (QFTs) at finite densities of matter generically
involve complex actions. Standard Monte-Carlo simulations based upon importance
sampling, which have been producing quantitative first principle results in
particle physics for almost fourty years, cannot be applied in this case.
Various strategies to overcome this so-called Sign Problem or Complex Action
Problem were proposed during the last thirty years. We here review the sign
problem in lattice field theories, focussing on two more recent methods:
Dualization to world-line type of representations and the density-of-states
approach.Comment: mini-review, 20 pages, 4 figure
Gauge and matter fields as surfaces and loops - an exploratory lattice study of the Z(3) Gauge-Higgs model
We discuss a representation of the Z(3) Gauge-Higgs lattice field theory at
finite density in terms of dual variables, i.e., loops of flux and surfaces. In
the dual representation the complex action problem of the conventional
formulation is resolved and Monte Carlo simulations at arbitrary chemical
potential become possible. A suitable algorithm based on plaquette occupation
numbers and link-fluxes is introduced and we analyze the model at zero
temperature and finite density both in the weak and strong coupling phases. We
show that at zero temperature the model has different first order phase
transitions as a function of the chemical potential both for the weak and
strong coupling phases. The exploratory study demonstrates that alternative
degrees of freedom may successfully be used for Monte Carlo simulations in
several systems with gauge and matter fields.Comment: Typos corrected and some statements refined. Final version to appear
in Phys. Rev.
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