(3+1)-Dimensional Expanding Universe From a Lorentzian Matrix Model for Superstring Theory in (9+1)-Dimensions

Abstract

We study the Lorentzian version of the type IIB matrix model as a nonperturbative formulation of superstring theory in (9 + 1)-dimensions. Monte Carlo results show that not only space but also time emerges dynamically in this model. Furthermore, the realtime dynamics extracted from the matrices turns out to be remarkable: 3 out of 9 spatial directions start to expand at some critical time. This can be interpreted as the birth of our Universe.