Simple Method to Make Asymptotic Series of Feynman Diagrams Converge
Simple Method to Make Asymptotic Series of Feynman Diagrams Converge
We show that, for two nontrivial $\ensuremath{\lambda}{\ensuremath{\varphi}}^{4}$ problems (the anharmonic oscillator and the Landau-Ginzburg hierarchical model), improved perturbative series can be obtained by cutting off the large field contributions. The modified series converge to values exponentially close to the exact ones. For $\ensuremath{\lambda}$ larger than some critical value, the method …