@misc{0a5330d6b1fc4991960125f6ca6f9033,
title = "Probing new physics with gravity: a safe approach across different scales",
abstract = "This thesis investigates gravity at different energy scales to understand the fundamental properties and constituents of the observable dark universe. The thesis contains two main approaches. In the first approach, we explore the interplay of gravity-matter and the predictive power of asymptotically safe quantum gravity. Through functional renormalization group techniques, we investigate under which conditions some new physics models of the dark universe (axion-like particles and kinetic gravity braiding) and beyond Standard Model physics (cosmic strings) belong to the landscape of asymptotically safe quantum gravity. This landscape contains theories that are made ultraviolet complete by asymptotic safety and, at the same time, are compatible with phenomenology at infrared energy scales. We find that it is not straightforward to accommodate these theories in the landscape. In the second approach, we explore pulsar timing data to search for signals of new physics in the stochastic gravitational wave background. Through Bayesian inference, we investigate how well cosmological sources (inflation and scalar-induced gravitational waves) fit the NANOGrav 15 years data. We find that it is possible to explain the observed signal with these sources. Then, we derive bounds on the duration of reheating for the inflationary model, and on the dark matter abundance in the form of primordial black holes for the scalar-induced model. Even though the scalar-induced models provide very good fits to the signal, we find that significant portions of the viable parameter space are in tension with the dark matter bound if we neglect the effect of non-Gaussianities. Finally, we combine constraints on stable cosmic strings from pulsar timing searches with spontaneous symmetry breaking realizations in asymptotic safety, illustrating a scenario where physics at the Planck scale connects with gravitational-wave phenomenology.",
keywords = "asymptotic safety, quantum gravity, gravitational waves, new physics, PTA searches, cosmology, dark matter",
author = "Santos, {Rafael Robson Lino}",
year = "2023",
month = dec,
day = "7",
doi = "10.21996/vvmm-qz66",
language = "English",
publisher = "Syddansk Universitet. Det Naturvidenskabelige Fakultet",
address = "Denmark",
school = "SDU",
}