Fermion bag approach to the sign problem in strongly coupled lattice QED with Wilson fermions - High Energy Physics - LatticeReport as inadecuate




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Abstract: We explore the sign problem in strongly coupled lattice QED with one flavorof Wilson fermions in four dimensions using the fermion bag formulation. Weconstruct rules to compute the weight of a fermion bag and show that eventhough the fermions are confined into bosons, fermion bags with negativeweights do exist. By classifying fermion bags as either simple or complex, wefind numerical evidence that complex bags with positive and negative weightscome with almost equal probabilities and this leads to a severe sign problem.On the other hand simple bags mostly have a positive weight. Since the complexbags almost cancel each other, we suggest that eliminating them from thepartition function may be a good approximation. This modified partitionfunction suffers only from a mild sign problem. We also find a simpler modelwhich does not suffer from any sign problem and may still be a goodapproximation at small and intermediate values of the hopping parameter. Wealso prove that when the hopping parameter is strictly infinite all fermionbags are non-negative.



Author: Shailesh Chandrasekharan, Anyi Li

Source: https://arxiv.org/



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