Description
In the context of phenomenological modified gravity, Starobinsky inflation is considered one of the most successful inflationary models. However, from a fundamental physics perspective, it faces a significant naturalness challenge. Compatibility with cosmological observations requires a remarkably strong hierarchy: the $R^2$ term must be extremely large, while higher-order corrections must be strictly suppressed.
In my Master’s thesis, I investigate whether such a hierarchy can emerge dynamically from the renormalization group flow within a UV-complete theory of gravity. This question is addressed within the framework of Asymptotic Safety. Since operators beyond quadratic order correspond to irrelevant directions, their coefficients are fundamentally determined by the ultraviolet dynamics.
The results indicate that these higher-order contributions are generically not suppressed along ultraviolet-complete trajectories, barring extreme fine-tuning or pushing the scale of quantum gravity to trans-Planckian values. This reveals a structural tension between quantum consistency and observational viability. Consequently, as a purely gravitational phenomenon, Starobinsky inflation appears structurally unnatural.
| Field of study | Quantum Physics |
|---|---|
| Supervisor | Alessia Benedetta Platania |