Talks

Various self-similar spherically symmetric spacetimes admit naked singularities, providing a challenge to the cosmic censorship hypothesis. However, it is not clear if the naked singularities are artefacts of the high degree of symmetry of the spacetimes, or if they are potentially generically present. To address this question, we consider perturbations of (various cases of) these spacetimes, focusing particularly on the behaviour of the perturbations as they impinge on the Cauchy horizon. We describe recent results on self-similar Lemaitre-Tolman-Bondi spacetime, indicating stability of scalar and odd parity perturbations, and instability of even parity perturbations.

Space and time are two of the universe's most fundamental elements. Relativity combines these two into the unified notion of space-time, but twistor theory goes beyond this replacing both by something entirely different, where the basic elements are the paths taken by particles of light or other particles without mass. Twistor theory has already found powerful applications in the field of high-energy physics. The creation of twistor theory was motivated with the hope that it would shed light on the foundations of quantum physics, a theory that puzzled even Einstein, particularly through the weird effects of quantum non-locality—the phenomenon whereby the behaviour of quantum particles can seem to have instantaneous effects over large distances. In this lecture, Prof. Penrose will describe a deep link between twistor theory and the simplest form of quantum non-locality and how the connection may be generalized in ways that provide a broader understanding of the phenomenon.