Extrapolating the precision of the Hypergeometric Resummation to Strong couplings with application to the $\mathcal{PT-}$Symmetric $i\phi^{3}$ Field Theory

Abstract

In PRL 115, 143001 (2015), H. Mera et al. developed a new simple but precise Hypergeometric Resummation technique. In this work, we suggest to obtain half of the parameters of the Hypergeometric function from the strong coupling expansion of the physical quantity. Since these parameters are taking now their exact values they can improve the precision of the technique for the whole range of the coupling values. The second order approximant $\,_{2}F_{1}$ of the algorithm is applied to resum the perturbation series of the ground state energy of the $\mathcal{PT-}$symmetric $(i\phi^{3})_{0+1}$ field theory. It gives accurate results compared to exact calculations from the literature specially for very large coupling values. The $\mathcal{PT-}$ symmetry breaking of the Yang-Lee model has been investigated where third, fourth and fifth orders were able to get very accurate results when compared to other resummation methods involving $150$ orders. The critical exponent $\nu$ of the $O(4)$-symmetric model in three dimensions has been precisely obtained using only first order of perturbation series as input. The algorithm can be extended easily to accommodate any order of perturbation series in using the generalized Hypergeometric function $\,_{k+1}F_{k}$ as it shares the same analytic properties with $\,_{2}F_{1}$.