Talks

Apart from Einstein, Paul Dirac was probably the greatest theoretical physicist of the twentieth century. Dirac, co-inventor of the most revolutionary theory for 150 years 'quantum mechanics' is now best known for conceiving of anti-matter in his head and also for his deeply eccentric behaviour. For him, the most important attribute of a fundamental theory was its mathematical beauty, an idea that he said was 'almost a religion' to him. In this talk, Farmelo will argue that this obsession originated in his early life and training as an engineer and mathematician. An examination of Dirac's character will show why he was sometimes called 'the strangest man' in the modern history of physics.

To study the continuum limit of a microscopic model of gravity we need microscopic observables that have a clear interpretation in terms of continuum geometry. In general the construction of such observables is notoriously difficult. In the model of causal dynamical triangulations (CDT) it is clear what the microscopic observables are, but at present the only known well-behaved observables with a continuum interpretation are spatial volumes. In this talk I will demonstrate what it takes to go beyond these by introducing the moduli as observables for CDT in 2+1 dimensions with spatial topology of the torus. Measurements of these observables using computer simulations provide valuable clues concerning the effective action describing CDT in the continuum. In particular I will present numerical evidence indicating that the effective kinetic term is well described by a modified Wheeler-De Witt metric like the one appearing in Horava-Lifshitz gravity.

Paul Dirac has been called ‘the first truly modern theoretical physicist’. In the latter part of his life, he was obsessed by the idea that the fundamental laws of nature must have mathematical beauty. This was ‘almost a religion to him’, he said. In this talk, I shall trace the origins of his fascination with this idea (going back to his school education) and question the account he gave of his contribution to quantum mechanics and field theory, which he often said emerged from his aesthetic perspective. I shall also give some insights into the extraordinary character of this man, whom Niels Bohr called ‘the strangest man’ who ever visited his Institute in Copenhagen.