Smearing orientifolds in flux compactifications can be OK

TL;DR

This paper constructs explicit supergravity solutions with localized O6 planes in flux compactifications, demonstrating the validity of smearing approximations and exploring exotic geometries outside the supergravity regime.

Contribution

It provides explicit supergravity solutions with localized O6 planes and analyzes the validity of smearing approximations in flux compactifications.

Findings

Smeared solutions approximate localized ones in large volume/weak coupling limits

An exotic solution with boundary disappearance upon backreaction

Some solutions lie outside the supergravity approximation

Abstract

We present explicit examples of supergravity solutions corresponding to backreacting localised (non-intersecting) O6 planes in flux reductions of massive IIA supergravity and address some criticism towards the very existence of such solutions. We verify in detail how the smeared orientifold solution becomes a good approximation to the localised solution in the large volume/weak coupling limit, as expected. We also find an exotic solution where prior to backreaction the internal space has a boundary and when backreaction is included the boundary disappears and the space closes off. The exotic example is however outside of the supergravity approximation everywhere.