Astronomy - 't Hooft The Black Hole Interpretation Of String Theory.pdf

Nuclear Physics B335 (1990) 138-154
North-Holland
THE BLACK HOLE INTERPRETATION OF STRING THEORY
G. 't HOOFT
Institutefor Theoretical Physics, Princetonplein 5, . Box 80006,
3508 TA Utrecht, herlands
Received 7 September 1989
For scattering processes in which both s and t are significantly larger than the Planck mass
we have string theory on the one hand, and on the other hand the physics of black hole formation
and decay. Both these descriptions are as yet ill understood. It is argued in this paper that a lot of
insight is to be gained by insisting that black holes and strings should be "unified" . Just like string
theory, the horizon of a black hole is governed by some conformal operator algebra on a
two-dimensional surface, where the in- and out-going particles are represented as vertex insertions,
so here we have a starting point for a unified description . Only the "physical picture" is very
different . Rather than a quantized string, a black hole is seen to be a classical statistical ensemble
defined on a membrane, its horizon. The former requires a minkowskian surface ; the latter a
euclidean one. These two are known to be related by a Wick rotation . We stress that black holes
are as fundamental as strings, so the two pictures really plementary.
1. Introduction
The black hole interpretation of strings has been highlighted by the author at
various occasions in conferences and summer schools [1], but received remarkably
little attention. Because we think the observations made are absolutely crucial for a
proper understanding of both black holes and strings, those results that are basically
new are presented here.
(Super)string theory, as it stands, suffers from a couple of very fundamental
weaknesses. It is now ing more and more clear that these are standing in the
way of a good understanding of what precisely the purported fundamental laws of
nature are. Now such statements should not be regarded as cri