Singularity in supercritical collapse of a spherical scalar field

We study the singularity created in the supercritical collapse of a spherical massless scalar field. We first model the geometry and the scalar field to be homogeneous, and find a generic solution (in terms of a formal series expansion) describing a monotonic, scalar curvature, strong spacelike singularity. We confront the predictions of this analytical model with the pointwise behavior of fully nonlinear and inhomogeneous numerical simulations, and find full compliance. We also study the phenomenology of the spatial structure of the singularity numerically. At asymptotically late advanced time the singularity approaches the Schwarzschild singularity, in addition to discrete points at finite advanced times, where the singularity is Schwarzschild-like. At other points the singularity is different from a Schwarzschild singularity due to the nonlinear scalar field. [S0556-2821(98)07116-1].