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arXiv · 2604.00525

Strong-coupling expansion and two-point Pad\'e approximation for lattice $\phi^4$ field theory

Yuanran Zhu·Efekan Kökcü·Chao Yang
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Abstract

Reliable approximations for correlation functions at intermediate and strong coupling remain hard to obtain for general quantum field theories. Perturbative expansions are often asymptotic or have a finite radius of convergence, which limits their applicability beyond weak coupling. Here we combine weak- and strong-coupling expansions and propose to use two-point Pad\'e schemes to construct approximants. For lattice $\phi^4$ theory, we show that this two-point interpolation strategy yields accurate global approximations to the two-point correlation function across broad coupling regimes and compares favorably with standard one-point resummation methods. We also provide heuristic explanations for the observed convergence behavior and discuss the practical range of validity of the approach.

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Yuanran Zhu, Efekan Kökcü, Chao Yang. 2026-04-01. Strong-coupling expansion and two-point Pad\'e approximation for lattice $\phi^4$ field theory. https://arxiv.org/abs/2604.00525

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