# Projects

We are part of the Research Training Group (RTG) 'Models of Gravity'. In this RTG we are discussing various string theory motivated gravity models given by various generalized Einstein equations. First we derive and discuss solutions of these generalized Einstein equations, then explore the resulting space-times through the motion of test objects, and finally also apply the results to astrophysically and cosmologically given situations.mehr...

Within the QuantumFrontiers research program we explore light and matter at the quantum frontier. This means that we exploit quantum metrology and nanometrology to improve sensitivity and precision of measurements, i.e. the foundations of metrology. These advancements in the foundations of metrology enable new precision measurements and measurement technologies that allow us to understand nature better at the smallest and largest scales: from gravitational wave astronomy to light and matter on the quantum level. mehr...

The long term vision of TerraQ is to create a new geodesy based on quantum physics and general relativity, enabling unique prospects for satellite geodesy, gravimetric Earth observation and reference systems.mehr...

## DFG Project 'General relati-vistic theory of spin-fluid accretion disks around black holes'

Usually accretion disks are modeled either by an ideal fluid or by a fluid with viscosity. Also charged fluids and plasmas have been discussed. Since interstellar matter consists of atoms or elementary particles it is conceivable that also the spin or the magnetic moment of these atomic or sub-atomic constituents may play a role in the behavior of accretion disks. Accordingly, in this project we discuss spin fluids as matter models for accretion disks. Here additional couplings of the spin to the space-time curvature and to external electromagnetic fields may influence the physical properties of the disk. Spin also offers a preferred tool to search for a hypothetical space-time torsion.

## DFG Project 'Propagation of light signals near a black hole surrounded by a plasma'

It is the goal of this project to investigate how a plasma influences light rays emitted from a spinning or non-spinning source that orbits around a black hole. Among other things, the influence on the time of arrival at a distant observer is to be calculated. This is a joint project with colleagues from the Space Research Institute of the Russian Academy of Sciences.

## DFG Project 'Momentum dependent spacetime geometries: Traces of quantum gravity and fields in media'

The propagation of particles and fields in media and on quantum spacetimes can be described by energy-momentum dependent background and spacetime geometries. They emerge from the interaction between the particles and fields with the constituents of the medium or with quantum gravity. The goal of this project is to establish a rigorous mathematical description of curved momentum dependent spacetime geometries, in terms of Finsler and Hamilton geometry, or extension of these frameworks. Moreover, the aim is to rigorously derive observable predictions, like trajectories of point particles, time delays, and light deflections; to study the propagation of classical and quantum fields and to find dynamical equations which determine the energy-momentum dependent geometry of spacetime from its matter content, which extend the Einstein equations.

# Contact

Privatdozentin Dr. rer. nat. Eva Hackmann

+49 421 218-57862

Email: eva.hackmann

Privatdozent Dr. rer. nat. Volker Perlick

+49 421 218-57933

Email: volker.perlick