Emergent strings from infinite distance limits

A bstract As a refinement of the Swampland Distance Conjecture, we propose that quantum gravitational theory in an infinite distance limit its moduli space either decompactifies, or reduces to asymptotically tensionless, weakly coupled string theory. We support our claim by classifying, as special cases, behaviour M-Theory and Type IIA compactifications on Calabi-Yau three-folds at distances Kähler space. The analysis comprises three parts: first classify possible limits classical three-fold. Each such finite volume is characterized universal fibration structure, for which generic fiber shrinking elliptic curve, K3 surface, Abelian surface. In second part focus investigate nature towers massless states arise from branes wrapped fibers. Depending classes fibrations are considered, obtain decompactification F-Theory, with unique heterotic II string, respectively. latter probes dual D-manifold general non-geometric. addition intrinsic excitations, M2-branes along non-contractible curves become light correspond further wrapping winding modes tensionless string. third analysis, consider show effects obstruct taking only not involves K3-fibrations scale gives rise emergent