Quantum Gravity at Strong Coupling and its Impact on Low Energy Physics

• Applicant: Dr. Max Wiesner
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 557478919

During the last ten years, much progress has been made in understanding the impact of quantum gravity on low-energy physics. In this context, many new techniques describing the low energy limits of theories of quantum gravity have been developed, for example, in the context of compactifications of string theory. However, most of these explicit results rely either on a weakly coupled UV completion or on the presence of enhanced supersymmetry such that a direct application of these techniques to quantum gravitational theories describing our Universe is not possible yet. To improve this situation, this project aims to develop methods to characterize the strong coupling dynamics of quantum gravitational theories with minimal or no supersymmetry to construct explicit realistic models beyond the confines of highly supersymmetric, perturbative string theory. In this context, our first goal is to work out the quantum geometry of the quasi-moduli space of four-dimensional theories with minimal supersymmetry at strong coupling. To that end, we will start from well-understood geometric compactifications of string-/F- and M-theory and exploit string dualities to compute explicit quantum corrections for these models. These corrections will be used to classify the strong coupling phases and the structure of singularities of this quasi-moduli space. The second objective is to determine the physical properties of the strong coupling phases of gravitational theories. To achieve this, we will initially analyze the spectrum of light, non-critical strings, and their excitations for theories with enhanced supersymmetry and subsequently extend these results to four-dimensional theories with minimal supersymmetry. To be able to describe effective theories of quantum gravity featuring a small cosmological constant, as a third goal, we aim to quantify the impact of a non-trivial space-time vacuum energy on the excitations of (non-)critical strings. To that end, we will combine worldsheet techniques with holographic methods to compute the spectrum of such excitations in supersymmetric Anti-de Sitter space. The fourth goal is to investigate the interplay between the dynamics of non-critical strings in the strong coupling regimes of quantum gravity and the effective low-energy physics. This will serve as a basis for computing scalar potentials and supersymmetry-breaking effects in the strong coupling regime of gravity. Finally, based on the results of the previous steps, we aim to identify candidates for low-energy theories derived from strong coupling regimes of quantum gravitational theories that exhibit a small cosmological constant and explore the implications of such models for observable physics.

• DFG Programme: Emmy Noether Independent Junior Research Groups