Surface density Σ in units as a function of the radial coordinate, for the moment of time corresponding to t = 1500P₀. The perturber was initiated in the disk at t = 0. The solid curve is obtained from a direct two-dimensional simulation and from averaging over the azimuthal coordinate. The dashed curve is obtained from a numerical solution of Eq. (34), and the dot dashed curve gives the shape of the gap according to Eq. (47) with the constants F and C₋ obtained from a fit to the numerical solution of (34); see the text for more details.