Cosmological D-instantons and Cyclic Universes

TL;DR

This paper explores models of gravity coupled to hyperbolic sigma models, revealing smooth connections between cosmologies and D-instantons, leading to cyclic and bouncing universe scenarios.

Contribution

It demonstrates how smooth trajectories in augmented target space connect FLRW cosmologies to D-instantons, introducing novel cyclic and bouncing universe models.

Findings

Identified closed cyclic universes with endless big-bang to big-crunch cycles.

Discovered big-bounce universes where collapsing universes bounce into expanding ones.

Connected cosmological singularities with D-instanton phases through smooth trajectories.

Abstract

For models of gravity coupled to hyperbolic sigma models, such as the metric-scalar sector of IIB supergravity, we show how smooth trajectories in the `augmented target space' connect FLRW cosmologies to non-extremal D-instantons through a cosmological singularity. In particular, we find closed cyclic universes that undergo an endless sequence of big-bang to big-crunch cycles separated by instanton `phases'. We also find `big-bounce' universes in which a collapsing closed universe bounces off its cosmological singularity to become an open expanding universe.