OBSERVERS IN QUANTUM GRAVITY
The Observer in Cosmology: joint work with Feraz Azhar
We review conceptual issues about the role of the observer, i.e. the various ways in which the process of observation contributes to the scope, and indeed content, of physical knowledge: especially in cosmology, both classical and quantum. We proceed in three stages. First, we discuss the role of the observer, independently of the details of physics, whether classical or quantum. Second, we discuss the role of the observer in classical physics, especially classical cosmology: i.e. in a cosmology for a classical (not quantum) world. Thus this second stage considers issues about selection effects. Third, we discuss the role of the observer in quantum physics in general: and especially in quantum cosmology. Here we focus attention on the research programme of Hartle, Hawking and Hertog, especially the relation of their proposed no-boundary state to inflation, and to selection effects.