Extended Wannier ridge model versus R-matrix treatment for double photoionization of helium

We revisit the well known extended Wannier ridge model (EWRM) by comparing its results with those of the novel ab initio hyperspherical R-matrix appro ach with semiclassical outgoing waves for the double photoionization of hel ium. We establish that acceleration gauge is the proper gauge to use within the EWRM. For this gauge, the results obtained with the two methods coinci de throughout the low-energy domain where the dynamics is concentrated abou t the ridge.