We present a critical analysis of Padé-based methods for the unitarization of low energy amplitudes. We show that the use of certain Padé Approximants to describe the resonance region may lead to inaccurate determinations. In particular, we find that in the Linear Sigma Model the unitarization of the low energy amplitude through the inverse amplitude method produces essentially incorrect result...

Padé approximant methods are applied to the known terms of the DRED β-function for N = 1 supersymmetric SU(3) Yang-Mills theory. Each of the [N |M ] approximants with N + M ≤ 4, M 6= 0 constructed from this series exhibits a positive pole which precedes any zeros of the approximant, consistent with the same infrared-attractor pole behaviour known to characterize the exact NSVZ β-function. A sim...

We present a prediction for the four loop β-function for SQCD based on the method

We revisit the problem of calculating amplitude at infinity for class functions with power-law behavior by means a resummation procedure based on truncated series small variables. Iterative Borel summation is applied employing Padé approximants “odd” and “even” types modified to satisfy power-law. The odd approximations are conventional asymptotically equivalent an number terms in series. Even ...

We improve the class of indices for which normality takes place in a Nikishin system and apply this in Hermite-Padé approximation of such systems of functions.

A detailed analysis to the [1,2] Padé approximation to the ππ scattering 2–loop amplitudes in chiral perturbation theory is made.