Research positions on the demographics of Active Galactic Nuclei and their variability properties are available from Sept. 2022 funded by the Hellenic Foundation of Research and Innovation> (HFRI). Successful candidates will work in the X-ray Astronomy Group of the Institute of Astronomy Astrophysics Space Applications and Remote Sensing of the National Observatory of Athens. The goal of the project is to analyse multi-epoch X-ray observations of distant AGN in deep extragalactic survey fields to measure their ensemble variability and, via appropriate modeling, infer the black-hole mass vs stellar relation of the AGN population. A proof of concept of the methodology is available in Georgakakis et al. (2021). The project involves the analysis of observational data and the development of (semi-)empirical models for the interpretation. For more information contact Dr. Antonis Georgakakis.