A common situation in theoretical physics is that analytic calculations are restricted to perturbation theory, which gives accurate results only at low orders and at weak coupling. Resummation methods such as Pade approximants or Borel resummation can improve perturbative calculations, but are often not reliable at strong coupling. In this talk, we introduce a new resummation method based on order-dependent reexpansions that incorporate explicit strong-coupling constraints from experiment or numerical computations. We show that for a zero-dimensional field-theory model the method converges quickly to the exact result. The method is then applied to the dilute Fermi gas in one and three dimensions, and we find that the obtained results compare very well with nonperturbative computations throughout the BCS region and beyond.
Online via ZOOM:
Meeting ID: 984 5733 2925
Peter Thirolf (LMU) / Norbert Kaiser (TUM)