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Flow equation solution for the weak to strong-coupling crossover in the sine-Gordon model

Stefan Kehrein
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Abstract

A continuous sequence of infinitesimal unitary transformations, combined with an operator product expansion for vertex operators, is used to diagonalize the quantum sine-Gordon model for 2 pi < beta^2 < infinity. The leading order of this approximation already gives very accurate results for the single-particle gap in the strong-coupling phase. This approach can be understood as an extension of perturbative scaling theory since it links weak to strong-coupling behavior in a systematic expansion. The approach should also be useful for other strong-coupling problems that can be formulated in terms of vertex operators.

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Stefan Kehrein. 1999-12-15. Flow equation solution for the weak to strong-coupling crossover in the sine-Gordon model. https://doi.org/10.1103/physrevlett.83.4914

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