Strong-coupling expansion and two-point Pad\'e approximation for lattice $\phi^4$ field theory
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 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.
Keywords
Cite
@article{arxiv.2604.00525,
title = {Strong-coupling expansion and two-point Pad\'e approximation for lattice $\phi^4$ field theory},
author = {Yuanran Zhu and Efekan Kökcü and Chao Yang},
journal= {arXiv preprint arXiv:2604.00525},
year = {2026}
}