May 16: Andreas Albrecht (UCDavis)
Title: Origin of probabilities and their application to the multiverse: Toward a resolution of cosmological measure problems
Place: DRL 4N12
Increasing observational support for cosmic inflation motivates further scrutiny of the challenging open questions related to multiverse theories such as eternal inflation. Page and others have argued that such theories only make sense if classical probabilities are introduced separately from the quantum ones. I argue using simple models that all successful practical uses of probabilities originate in quantum fluctuations in the microscopic physical world around us, often propagated to macroscopic scales. Thus I claim there is no physically verified fully classical theory of probability. I comment on the general implications of this view, and specifically question the application of classical probability theory to cosmology in cases where key questions are known to have no quantum answer. I argue that the ideas developed here may offer a way out of the notorious measure problems of eternal inflation.