Perturbative and non-perturbative Quantum Gravity

Gerard 't Hooft

Utrecht, Netherlands

December 1, 4:15pm


Quantum gravity can be Taylor expanded in powers of E^2 G, where E is
the energy scale of the interactions considered, and G is Newton's
constant in units where \hbar = c = 1. All terms are well-defined, except
for the fact that, at every order, new, freely adjustable parameters
appear. This means that gravity does not require deviations from standard
quantummechanical procedures at any finite order in E^2 G.
If, on the other hand, we wish a non-perturbative treatment, in cases where
E^2 G >~ 1, fundamentally new approaches are needed. My consistency
requirements are more stringent than what presently can be offered by
superstring theory and its relatives, supergravity and M-theory.
The issue of the interpretation of Quantum Mechanics cannot be avoided.

Return to Applied Math Colloquium home page