Understand
We discuss some topics concerning rational approximations in Quantum Chromodynamics, especially those related with the mathematical theory of Pad\'e Approximants.
- We focus on two kind of problems: the first one related with meromorphic functions (inspired by the Large-Nc limit in QCD) where we explore the Minimal Hadronic Approximation through the extraction of Low-Energy Constants and Condensate parameters of a two-point Green's function; and the second one related with meromorphic functions of Stieltjes-type where we present a critical analysis to a unitarization process applied to the Linear Sigma Model and also and application of the Pad\'e Theory to the vacuum polarization function of a heavy quark.
- We also show the ability of these approximations when working with experimental data.
- Along these line, we make special emphasis on the reliability of that theory to control on systematic errors.