Analytic approximations to the spacetime of a critical gravitational collapse.

We present analytic expressions that approximate the behavior of the spacetime of a collapsing spherically symmetric scalar eld in the critical regime rst discovered by Choptuik. We nd that the critical region of spacetime can usefully be divided into a \quiescent" region and an \oscillatory" region, and a moving \transition edge" that separates the two regions. We nd that in each region the critical solution can be well approximated by a at spacetime scalar eld solution. A qualitative nonlinear matching of the solutions across the edge yields the right order of magnitude for the oscillations of the discretely self-similar critical solution found by Choptuik.