Goedel's Universe in a Supertube Shroud

TL;DR

The paper shows that certain supersymmetric Goedel-like universes are not valid string theory solutions due to instabilities caused by supertube configurations, but alternative stable solutions resembling Goedel universes can be constructed.

Contribution

It demonstrates the incompatibility of some supersymmetric Goedel universes with string theory and constructs stable, modified solutions with similar local properties.

Findings

Certain supersymmetric Goedel universes are unstable in string theory.

Supertubes wrapping closed timelike curves develop negative kinetic modes.

Stable solutions resembling Goedel universes can be achieved with domain walls.

Abstract

We demonstrate that certain supersymmetric Goedel-like universe solutions of supergravity are not solutions of string theory. This is achieved by realizing that supertubes are BPS states in these spaces, and under certain conditions, when wrapping closed timelike curves, some world-volume modes develop negative kinetic terms. Since these universes are homogeneous, this instability takes place everywhere in space-time. We also construct a family of supergravity solutions which locally look like the Goedel universe inside a domain wall made out of supertubes, but have very different asymptotic structure. One can adjust the volume inside the domain wall so there will be no closed timelike curves, and then those spaces seem like perfectly good string backgrounds.