### Media

Video# Must space-time be singular?

Ward StruyveAccording to Einsteinâ€™s theory of general relativity space-time singularities such as a big bang typically occur. It is believed that a quantum theory for gravity may eliminate such singularities. Whether this is indeed the case may of course depend on which approach to quantum gravity, for example the Wheeler-DeWitt theory or loop quantum gravity. But it may also depend on the approach to quantum mechanics itself, for example the standard quantum approach, consistent histories or Bohmian mechanics. For the case of mini-superspace models, it has been claimed in the context of standard quantum theory that the Wheeler-DeWitt theory does not eliminate the singularities, while loop quantum gravity does. However, the analysis is plagued by a number of conceptual problems: the measurement problem, the problem of time and the problem of what exactly it means to have a singularity. In my talk, I will explain the Bohmian approach to the Wheeler-DeWitt theory and loop quantum gravity and how this approach solves these conceptual problems. I will show for mini-superspace models that in the Wheeler-DeWitt theory the answer to the question of singularities depends on the wave function and the initial metric, and that in loop quantum gravity there are no singularities.