Determine whether an ultralight two-form mass is natural in string compactifications

Determine whether the massive two-form fields arising in string-theoretic compactifications can naturally acquire ultralight masses while surviving the relevant orientifold projections, thereby establishing whether they provide viable ultraviolet realizations of axial-vector dark matter.

Background

Massive two-form fields are dual to massive axial vectors and arise in string-inspired constructions. A cited flux-compactification example provides a possible realization, but the paper identifies unresolved issues concerning the naturalness of the ultralight mass and whether the desired two-form remains in the physical spectrum after orientifolding.

References

It is not clear whether the mass can be naturally ultralight; furthermore, the desired two-form field is projected out in the orientifold.

— Ultralight Axial Dark Matter  (2609.10671 - Hook et al., 9 Sep 2026) in Section 5, paragraph “DM Production and UV Completions”