Adrien LOTY

PhD Student

Research group: String Theory


"Constraints on effective theories in quantum gravity"
Advisor : Guillaume Bossard

Research interests

Quantum gravity, effective theory, swampland

he low energy effective action in supergravity and string theories, as for any gravity theory, includes an infinity of irrelevant operators with arbitrary high numbers of derivatives. The Wilson coefficients for these operators are constrained by unitarity and analyticity. More recently, one more constraint has been proposed under the name of “weak gravity conjecture” that states that for any theory of quantum gravity including electromagnetism, there must exist a charged particule for which the electromagnetic repulsion dominates over the gravitational attraction. This conjecture sometimes implies more constraints on the Wilson coefficients in the effective action. One way to check these conjectures is to verify their validity in string theories, that are known to be consistent and to include gravity. One commonly says that an effective theory belongs to the “swampland” if this is not the effective theory of a string theory, or more generally if it cannot consistently describe quantum gravity.

In this thesis we propose to study the validity of these conjectures in some string and supergravity theories. Most of the checks in the literatures are restricted to the weak coupling limit, i.e. a tree level or one-loop in string theory. We shall extend these checks to couplings that are known non-perturbatively. More generally we shall concentrate on studying
– Bounds on the Wilson coefficients of irrelevant operators.
– Effects of irrelevant operators on extremal black holes.
– Instability of non-supersymmetric AdS vacua.


Bossard G, Loty A.
Saturating unitarity bounds at U-duality symmetric points.
Journal of High Energy Physics. 2023(10):110.
DOI: 10.1007/JHEP10(2023)110.


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