Quantum Corrections and the Swampland

In this thesis, we investigate the role of quantum corrections for certain Swampland constraints. In the first part of the talk we analyse the effect of D-brane instanton corrections in the vicinity of classical infinite distance singularities in the hypermultiplet moduli space of Calabi—Yau compactifications of type IIB string theory in the context of the Swampland Distance Conjecture. We will show that due to the instantons these classical infinite distance singularities are not part of the quantum moduli space and that at the quantum level the residual infinite distance limits necessarily correspond to weak coupling limits for asymptotically tensionless strings. 

In  the second part of the talk we then discuss perturbative corrections in F-theory compactifications with N=1 supersymmetry. Here we find a similar obstruction to classical infinite distance limits and in the context of the Weak Gravity Conjecture show that the quantum corrections also have a non-trivial effect on the charge-to-mass ratio of excitations of a tensionless heterotic string. Taking into account loop corrections to the mass of the string excitations, we propose a 1-loop correction of the extremality bound in F-theory.

In the final part of the talk we then present a systematic analysis of F-theory flux vacua at large complex structure. We provide general expressions for the vacua conditions for an arbitrary number of moduli including polynomial corrections to the leading superpotential. Imposing tadpole cancellation we then argue that there exist two families of vacua for which full moduli stabilisation can be achieved if certain corrections are included. For one of these families we show that the on-shell value of the tadpole is independent of the dimension of the field space in tension with a recently proposed Swampland constraint.