Is quantum unitarity lost in the Hawking evaporation of black holes
formed by collision of particles in a pure state? This long-standing
question may be simply studied in the context of three dimensional
gravity with a negative cosmological constant -- in this theory,
black holes can form by collision of conical defects
(so-called "point particles"). I will show how a large class
of three dimensional, supersymmetric conical defects can be realized
as dimensional reductions of non-singular solutions to the chiral,
*N*=4, 6-dimensional supergravity. This theory has
a dual description in terms of a bound state of D1 and D5 branes
compactified on K3. I will discuss how the point particles appear
as states in this dual theory, and how the process of collision to form
black holes can be modelled.

"*N*=2 quantum string scattering," Gordon Chalmers (Argonne),
Olaf Lechtenfeld, Bernd Niemeyer (Hannover U.).
hep-th/0007020

"Simplifying algebra in Feynman graphs, Part 1: Spinors,"
G. Chalmers, W. Siegel (SUNY, Stony Brook),
Phys. Rev. **D59** 045012, 1999,
hep-ph/9708251

"The selfdual sector of QCD amplitudes,"
G. Chalmers, W. Siegel (SUNY, Stony Brook),
Phys. Rev. **D54** 7628-7633, 1996,
hep-th/9606061

"One loop *N* gluon amplitutes with maximal helicity violation
via colinear limits," Zvi Bern, Gordon Chalmers (UCLA),
Lance Dixon (SLAC), David A. Kosower (Saclay),
Phys. Rev. Lett. **72** 2134-2137, 1994,
hep-ph/9312333

George T. Fleming ( gfleming@mps.ohio-state.edu ), last updated 05 October 2000.