April 24: Jean-Luc Lehners (Max Planck Institute, Potsdam)

Time: 2pm
Place: 2N36
Title: New Ekpyrotic Quantum Cosmology
Abstract: This talk will present recent results in the quest to construct a viable cosmological model devoid of singularities and infinities. More specifically: the no-boundary proposal provides a compelling theory for the initial conditions of our universe. In this context, the recently discovered ekpyrotic instantons describe the creation of a classically contacting universe out of nothing. One notable consequence is that the ekpyrotic attractor can explain how the universe became classical. However, up to now these instantons ended in a big crunch singularity. We show how this can be remedied by adding higher-derivative terms, allowing a smooth bounce into an expanding phase to take place. Remarkably, and although there is a non-trivial evolution during the bounce, the wavefunction of the universe is ``classical'' in a WKB sense just as much after the bounce as before. These new non-singular instantons can thus form the basis for a fully non-singular and calculable (ekpyrotic) history of the universe, from creation until now.