Non-singular bounce transitions in the multiverse

Understand

According to classical GR, negative-energy (AdS) bubbles in the multiverse terminate in big crunch singularities.

• It has been conjectured, however, that the fundamental theory may resolve these singularities and replace them by non-singular bounces.
• Here we explore possible dynamics of such bounces using a simple modification of the Friedmann equation, which ensures that the scale factor bounces when the matter density reaches some critical value $\rho_c$.
• This is combined with a simple scalar field `landscape', where the energy barriers between different vacua are small compared to $\rho_c$.