General Relativity and coherent time

• Applicant: Privatdozentin Dr. Eva Hackmann
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 490990195

The comparison of clock frequencies and their shown time depends on the state of motion of the clocks and their position in the gravitational field and must therefore be described in general relativistic terms. The present project P4 provides the relativistic theory for the research group dedicated to time in geodesy. This project is about the general relativistic theory of time and frequency comparisons as well as about reference systems and synchronization. First, general statements about synchronization and reference systems are given and then different methods of synchronization are precisely formulated and compared. In order to be able to analyze all procedures strictly, they are first analytically described in special space-times, using analytical solutions of the geodetic equation for light as well as for satellites. These procedures are then also treated in general gravitational fields which are given in terms of an expansion in mass- and spin-multipoles. The aim is, on the one hand, to theoretically derive in a top-down approach with high precision how practical synchronization on Earth can be carried out using satellites and VLBI, even for longer distances, and how control measurements can be made. The formalism will then be applied to real measurements in the second funding period. In this context, tests of the General Relativity will be described and performed. It will also be investigated whether new quantum technologies, e. g. entanglement-based synchronization, are advantageous for the intended purposes and whether new quantum mechanics tests can be proposed in this context.

• DFG Programme: Research Units
• Subproject of: FOR 5456: Clock Metrology: A Novel Approach to TIME in Geodesy
• Co-Investigator: Professor Dr. Claus Lämmerzahl