Natural solution to the naturalness problem: The universe does fine-tuning
Year: 2015
Type: article
Abstract: We propose a new mechanism to solve the fine-tuning problem. We start from a multi-local action |$S=\sum _{i}c_{i}S_{i}+\sum _{i,j}c_{i,j}S_{i}S_{j}+\sum _{i,j,k}c_{i,j,k}S_{i}S_{j}S_{k}+\cdots $|, where the |$S_{i}$|'s are ordinary local actions. Then, the partition function of this system is given by |$Z=\int d\overrightarrow {\lambda } f\big (\overrightarrow {\lambda }\big )\langle f|T\exp \left (-i\int _{0}^{+\infty }dt\hat {H} (\overrightarrow {\lambda };a_{cl}(t))\right )|i\rangle $|, where |$\overrightarrow {\lambda }$| represents the parameters of the system whose Hamiltonian is given by |$\hat {H}(\overrightarrow {\lambda };a_{cl}(t))$|, |$a_{cl}(t)$| is the radius of the universe determined by the Friedman equation, and |$f\big (\overrightarrow {\lambda }\big )$|, which is determined by |$S$|, is a smooth function of |$\overrightarrow {\lambda }$|. If a value of |$\overrightarrow {\lambda }$|, |$\overrightarrow {\lambda }_{0}$|, dominates in the integral, we can interpret that the parameters are dynamically tuned to |$\overrightarrow {\lambda }_{0}$|. We show that this indeed happens in some realistic systems. In particular, we consider the strong CP problem, the multiple point criticality principle, and the cosmological constant problem. It is interesting that these different phenomena can be explained by one mechanism.
DOI: 10.1093/ptep/ptv168
Authors: Yuta Hamada, Hikaru Kawai, Kiyoharu Kawana
Institution: Kyoto University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $979
OpenAlex ID: W2206785672