Orientifold Planes, Type I Wilson Lines and Non-BPS D-branes

TL;DR

This paper investigates the existence and consistency of certain orientifold planes in string theory, proposing that O6~-planes are possible in massive IIA theory, while O7~- and O8~-planes are not, and explores their relation to non-BPS D-branes.

Contribution

It resolves a longstanding puzzle by demonstrating the conditions under which specific orientifold planes can exist in massive IIA string theory.

Findings

O6~-planes are possible in massive IIA with odd cosmological constant

O7~- and O8~-planes are not allowed in this framework

Relations between orientifold planes and non-BPS D-branes are clarified

Abstract

There is a longstanding puzzle concerned with the existence of Op~-planes with p>=6, which are orientifold p-planes of negative charge with stuck Dp-branes. We study the consistency of configurations with various orientifold planes and propose a resolution to this puzzle. It is argued that O6~-planes are possible in massive IIA theory with odd cosmological constant, while O7~-planes and O8~-planes are not allowed. Various relations between orientifold planes and non-BPS D-branes are also addressed.