Speaker
Description
By describing the properties of one quantum system relative to another (treated as a quantum reference frame), we can construct a relational picture of physics that reduces or eliminates reliance on idealised background structures such as classical coordinates. When applied to time, this relational approach offers a compelling resolution of the "problem of time" in canonical approaches to quantum gravity. I will give a brief introduction to arguably the most famous approach to relational dynamics -- the Page-Wootters formalism -- and describe our investigations into: a) the modelling of causal relations in the formalism; b) the appearance of non-unitary evolution due to interactions between clock and system; c) the physical consequences of describing systems relative to periodic clocks. Each topic highlights the importance of distinguishing between structures on the kinematic (non-symmetric) and physical (symmetric) Hilbert spaces.
