Energy condition respecting warp drives: The role of spin in Einstein-Cartan theory

TL;DR

This paper explores how incorporating spin in Einstein-Cartan theory can enable warp drive spacetimes to respect energy conditions, reducing the need for exotic matter in theoretical faster-than-light travel models.

Contribution

It demonstrates that spin-induced torsion in Einstein-Cartan gravity allows for energy condition respecting warp drives, a novel approach in warp drive research.

Findings

Spin reduces energy condition violations in warp drives.

Limits on spin minimize matter requirements for warp drives.

Warp drives can be consistent with Einstein-Cartan theory without exotic matter.

Abstract

In this paper we study the so called "warp drive" spacetimes within the $U_{4}$ Riemann-Cartan manifolds of Einstein-Cartan theory. Specifically, the role that spin may play with respect to energy condition violation is considered. It turns out that with the addition of spin, the torsion terms in Einstein-Cartan gravity do allow for energy condition respecting warp drives. Limits are derived which minimize the amount of spin required in order to have a weak/null-energy condition respecting system. This is done both for the traditional Alcubierre warp drive as well as for the modified warp drive of Van Den Broeck which minimizes the amount of matter required for the drive. The ship itself is in a region of effectively vacuum and hence the torsion, which in Einstein-Cartan theory is localized in matter, does not affect the geodesic nature of the ship's trajectory. We also comment on the amount of spin and matter required in order for these conditions to hold.