Publication : t18/142

Abstract:
We use type I string models with supersymmetry broken by compactification (`a la Scherk-Schwarz) in order to test the weak gravity conjecture in the presence of runaway potentials in a perturbative string theory setting. For a finite value of the supersymmetry breaking radius there is a runaway potential, which is the only possibility if one accepts the non-existence of de Sitter vacua. Although the weak gravity conjecture is valid in the decompactification limit, for fixed values of the radius we show that there are short-ranged attractive D1 brane-brane interactions, which would naively imply formation of bound states and potential black hole remnants and therefore a violation of the weak gravity conjecture. We argue however that at one-loop level the effective tension of the branes decreases such that there is a long-ranged repulsive force, which should come from higher-loops. Our conclusion is that the weak gravity conjecture should be respected provided that we accept a small number of black-hole remnants and if the string coupling $g_s$ is not extremely small.