We investigate the classical and semiclassical instabilities of de Sitter space. Due to the
presence of a cosmological event horizon and its associated Hawking temperature, de Sitter …

The graviton propagator in a de Sitter background is found to be divergent. We show that as
a consequence of this divergence, de Sitter space is not a solution of the equations of …

The instabilities of quantum gravity are investigated using the path-integral formulation of
Einstein's theory. A brief review is given of the classical gravitational instabilities, as well as …

We examine the thermodynamic stability of large black holes in four-dimensional anti-de
Sitter space, and we demonstrate numerically that black holes which lack local …

This is my contribution to the Festschrift honoring Stephen Hawking on his 60th birthday.
Twenty-five years ago, Gibbons and Hawking laid out the semi-classical properties of de …

We consider degrees of freedom for a quantum de Sitter spacetime. The problem is studied
from both a Lorentzian and a Euclidean perspective. From a Lorentzian perspective, we …

The stability properties of Einstein theory with a cosmological constant Λ are investigated.
For Λ> 0, stability is established for small fluctuations, about the de Sitter background …

We investigate stability of the D-dimensional Reissner-Nordström-anti-de Sitter metrics as
solutions of the Einstein-Maxwell equations. We have shown that asymptotically anti-de …

We discuss some of the issues arising when considering asymptotically de Sitter space–
times and attempts to address them. Our development begins at the classical level where …

In this work we analyse the backreaction of a quantum field on a spherically symmetric black
hole geometry with an inner horizon, ie an internal boundary of the trapped region. We start …