Global Asymptotics, the Swampland Conjectures, and Preheating of String Moduli

Abstract

While the cosmological implications of the Swampland Conjectures are usually discussed in the context of inflationary model building, they also have implications for the violent, non-adiabatic dynamics that can follow inflation or any displacement of string moduli. We study this question through the lens of self-resonant preheating, where we point out that two Swampland motivated structures play central roles. The first is the local curvature of the potential: the tachyonic branch of the refined de Sitter Conjecture singles out the kind of negative curvature that can drive tachyonic amplification. We show, however, that local curvature data is not enough; the large field asymptotics of the potential determines how the modulus samples the unstable region. Thus, plateaus, barriers, and runaways can lead to different resonance efficiencies; we study tachyonic resonance for bulk moduli in LVS and KKLT compactifications, as well as for typical blow-up moduli potentials and alpha-attractor models. The second Swampland motivated structure pertains to the tower of light states predicted by the Swampland Distance Conjecture. Modeling a finite subset of such states as an effective stochastic environment within which a string modulus preheats, we find that the light states mainly reshape existing resonance bands by smearing, shifting, and mildly seeding instabilities, rather than opening a robust new reheating channel. Our results suggest that Swampland physics affects preheating by controlling both the deterministic curvature structure of the potential as well as stochastic corrections from emergent light states.