On the K-point in moduli space

Journal article

We study a class of infinite-distance loci, referred to as K-points, in one-parameter complex-structure moduli spaces of type IIB string theory compactified on Calabi-Yau manifolds. We show that around K-points the effective four-dimensional supergravity exhibits certain unusual properties. The two most prominent being that the leading order dependence of the prepotential on the gauge couplings is non-perturbative and that the leading gauge kinetic terms in the action vanish when evaluated on an anti self-dual graviphoton background. These properties are shared with the conifold locus in moduli space, rather than the large complex-structure locus. The conifold locus is well-known to arise from integrating out a charged BPS state, and so the similarities suggest that the K-point also arises from integrating out a BPS state. We develop such an interpretation, finding that it corresponds to a BPS state which is extremely light, whose mass in Planck units is doubly-exponentially small in the distance to the K-point. The state behaves as if it had complex charges, or as if it couples to the self-dual and anti self-dual parts of the graviphoton differently. Assuming such an integrating-out scenario is indeed the correct physics for the K-point, we discuss the implications for our understanding of infinite distances in moduli space and for the Swampland Distance Conjecture.

Authors: Hattab, J; Palti, E; Quirant, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Volume: 2026
• Issue: 3
• Pages: 228
• Publication date: 2026-03-24
• DOI: 10.1007/jhep03(2026)228
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English
• Keywords: Moduli of algebraic curves; Moduli space; Effective action; Supergravity; Moduli; String theory; Gauge theory; Conifold; Locus (genetics)