Exploring an S-matrix for gravitational collapse

Understand

We analyze further a recently proposed S-matrix description of transplanckian scattering in the specific case of axisymmetric collisions of extended sources, where some of the original approximations are not necessary.

• We confirm the claim that such an approximate description appears to capture the essential features of (the quantum counterpart of) classical gravitational collapse.
• More specifically, the S-matrix develops singularities whose location in the sources' parameter space are consistent with (and numerically close to) the bounds coming from closed-trapped-surface collapse criteria.
• In the vicinity of the critical "lines" the phase of the elastic S-matrix exhibits a universal fractional-power behaviour reminiscent of Choptuik's scaling near critical collapse.