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arXiv:2610.10171

Vortex screening and the fate of the BKT transition with long-range couplings

Guido Giachetti

Published Oct 7, 2026• 0 citations
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Abstract

The stability of the Berezinskii--Kosterlitz--Thouless phase against long-range interactions remains an open problem. We address this question in the two-dimensional XY model with couplings decaying as $r^{-2-σ}$, by developing a real-space renormalization-group treatment near the Gaussian manifold of quasi-long-range ordered (QLRO) states. We retain the full many-body vortex interaction and show that, at leading order in the fugacity, screening by small vortex--antivortex pairs preserves its Gaussian-average representation without an expansion in the long-range coupling. Including spin waves perturbatively then yields a local stability criterion: a stable QLRO interval exists only for $σ>7/4$. We also investigate a Wilson--Fisher-like fixed point at finite coupling for $σ<7/4$, for which the retained flow predicts $ν^{-1}\sim\sqrt{7/4-σ}$ as it merges with the Gaussian line.

DOI
10.48550/arxiv.2610.10171

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