Title: "Spacetime Singularities of (2+1)-Dimensional Universe in Quantum Gravity"
General relativity (GR) predicts the existence of spacetime singularities,
where physically measurable quantities become infinite and the laws of
physics, including GR, break down. Occurrence of singularities are indeed
a generic feature of GR. This is so troubling that John A. Wheeler has
called this situation "...the greatest crisis of physics of all time."
Singularities predict the necessity of going beyond classical GR. Near the
singularities, where one expects curvature to enter the Plank regime, and
fluctuations of spacetime become significant, quantum gravity offers a
natural generalization. While we don't have a fully consistent, finite,
and tractable quantum theory of gravity, simplified models of quantum
gravity offer some hope. In (2+1)-dimensional gravity, one has black hole
and cosmological singularities, and there are finite and tractable quantum
theories of gravity. In this talk, I will use a cosmological model in
(2+1)-dimensional quantum gravity, and discus what we can learn about the
big bang/big crunch type singularities in this model. This model
simplifies the quantization, but still has many of the essential features
of the full theory.