Centre for Particle Theory Colloquia: Causal sets as the deep structure of spacetime
25 February 2003 16:00 in CLC 202
"One approach to solving the problem of quantum gravity (reconciling and extending General Relativity and Quantum Theory) is based on the causal set hypothesis, which states that the deep, quantum structure of spacetime is discrete and is what is known in mathematics as a ``partial order'' or ``poset'', a kind of extended family tree. Causal set theory has now reached a stage at which questions of phenomenology are beginning to be addressed. This talk will introduce the basic concepts and motivations behind the hypothesis and address some of the latest developments which include: (i) an apparently confirmed order of magnitude prediction for the cosmological constant, the only prediction made in any proposed theory of quantum gravity that has been subsequently verified by observation; (ii) a classical stochastic causal set dynamics which is the most general consistent with the discrete analogs of general covariance and classical causality; (iii) the formulation of a ``cosmic renormalization group'' which indicates how one might in principle solve some of the ``large number puzzles'' of cosmology without recourse to post-quantum-era inflation; and (iv) a rigorous characterisation of the ``observables'' (or ``physical questions'') of causal set cosmology, at least in the classical case.
Coffee and biscuits at 15:30 in CM 211 (Maths Coffee Room).