S-Duality at the Black Hole Threshold in Gravitational Collapse

Douglas M. Eardley
(doug@itp.ucsb.edu)

Eric W. Hirschmann
(ehirsch@dolphin.physics.ucsb.edu)

James H. Horne
(jhh20@damtp.cam.ac.uk)

Comments: 8 pages of latex/revtex; 1 figure, available uuencoded in gr-qc archive, or by anonymous ftp to ftp.itp.ucsb.edu as file /figures/nsf-itp-95-15.eps

Report-no: Physical Review D52, R5793-R5797 (1995) NSF-ITP-95-15, DAMTP-R95/27, gr-qc/950541

We study gravitational collapse of the axion/dilaton field in classical low energy string theory, at the threshold for black hole formation. A new critical solution is derived that is spherically symmetric and continuously self-similar. The universal scaling and echoing behavior discovered by Choptuik in gravitational collapse appear in a somewhat different form. In particular, echoing takes the form of SL(2,R) rotations (cf. S-duality). The collapse leaves behind an outgoing pulse of axion/dilaton radiation, with nearly but not exactly flat spacetime within it.