We apply to Michaelis-Menten kinetics an alternative approach to the study of Singularly Perturbed Differential Equations, that is based on the Renormalization Group (SPDERG). To this aim, we first rebuild the perturbation expansion for Michaelis-Menten kinetics, beyond the standard Quasi-Steady-State Approximation (sQSSA), determining the 2nd order contributions to the inner solutions, that ar...

The Dirac sea is calculated in an expansion around the light cone. The method is to analyze the perturbation expansion for the Dirac sea in position space. This leads to integrals over expressions containing distributions which are singular on the light cone. We derive asymptotic formulas for these “light cone integrals” in terms of line integrals over the external potential and its partial der...

A single-level quantum dot with Coulomb repulsion attached to two superconducting leads is studied via the perturbation expansion in the interaction strength. We use the Nambu formalism and the standard many-body diagrammatic representation of the impurity Green functions to formulate the Matsubara self-consistent perturbation expansion. We show that at zero temperature second order of the expa...

QCD perturbation theory at large orders with large renormalization scales in the large β 0 limit. Abstract. We examine the QCD perturbation series at large orders, for different values of the 'large β 0 renormalization scale'. It is found that if we let this scale grow exponentially with the order, the divergent series can be turned into an expansion that converges to the Borel integral, with a...

We present the result of a calculation of the next-to-leading correction to the Higgs propagator in the 1/N expansion, where the Higgs sector is treated as an O(N) symmetric σ-model. The results are compared with two-loop perturbation theory. The existing discrepancy between the lowest order of the 1/N expansion and perturbation theory is dramatically reduced by including the NLO in 1/N. We fin...