Probing the fundamental structure of quantum spacetime and the standard model

• Applicant: Professorin Dr. Astrid Eichhorn
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2016 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 288951741

What is the quantum structure of spacetime, that explains the origin of our universe and determines its evolution during its very early stages? How does quantum gravity interact with matter and what is the microscopic structure of matter? To solve these fascinating puzzles, we have to unify our understanding of matter - currently encoded in the standard model of particle physics - with our description of gravity in terms of spacetime curvature.In this project, I will zoom into spacetime and matter and unravel their microscopic dynamics by using the mathematical analogue of a microscope - the functional Renormalization Group. This tool provides a new, unifying vantage point from which main conceptual questions on quantum gravity are being addressed, tying together research on as yet unrelated models of quantum spacetime.Firstly, quantum fluctuations of spacetime lead to scale-dependent gravitational couplings - just as quantum fluctuations of matter yield running couplings in the standard model. In the asymptotic safety scenario, the fate of the couplings at high energies is governed by a Renormalization Group fixed point, generalizing the tremendous success-story of asymptotic freedom to quantum gravity.My first goal is to discover whether this fascinating idea can be realized when including the quantum effects of dynamical matter fields, such as those of the standard model. This will provide observational tests of asymptotically safe gravity by scrutinizing its compatibility with the standard model and possible extensions, such as massive neutrinos and dark matter candidates.The asymptotic safety scenario could simultaneously uncover the microscopic quantum structure of spacetime and provide a predictive ultraviolet completion for the standard model. I am intent on exploring this intriguing scenario by probing quantum gravity effects on the standard model. Quantum-gravity effects on matter at high energies could then open a new window onto the phenomenology of quantum spacetime in astrophysics and cosmology.Secondly, innovative Renormalization Group tools now play a major role in discrete models of quantum gravity, where a continuous spacetime emerges from the physics of discrete building blocks. I will explore the emergence of spacetime in four- dimensional tensor models by mapping out their phase structure. I will champion Renormalization Group techniques as a way to discover the continuum limit in these discrete models and bridge the gap to asymptotically safe gravity.

• DFG Programme: Independent Junior Research Groups