Quantum Gravity

The search for a quantum theory of the gravitational field is one of the great
open problems in theoretical physics. This book presents a self-contained discussion
of the concepts, methods and applications that can be expected in such a theory. The
two main approaches to its construction -- the direct quantisation of Einstein's
general theory of relativity and string theory -- are covered. Whereas the first
attempts to construct a viable theory for the gravitational field alone,string
theory assumes that a quantum theory of gravity will be achieved only through a
unification of all the interactions. However, both employ the general method of
quantization of constrained systems, which is described together with illustrative
examples relevant for quantum gravity. There is adetailed presentation of the main
approaches employed in quantum general relativity: path-integral quantization, the
background-field method and canonical quantum gravity in the metric, connection and
loop formulations. The discussion of string theory centres around its
quantum-gravitational aspects and the comparison with quantum general relativity.
Physical applications discussed at length include the quantization of black holes,
quantum cosmology, the indications of a discrete structure ofspacetime, and the
origin of irreversibility.The second edition will add some sections on topical
issues. These include loop quantum cosmology, dynamical triangulation,
renormalization-group approach, primordial black holes, and information-loss problem
for black holes. The second edition will also contain some pedagogical
extensions.This book will be of interest to researchers and students working in
relativity and gravitation, cosmology, quantum field theory and related topics. It
will also be of interest to mathematicians and philosophers of science.