Gravitational Theory

Accretion disk around black hole

We study the motion of light, particles, and fluids close to black holes or neutron stars (image credit: James et al., CQG 32 (2015))

© Image by Oliver James, Eugénie von Tunzelmann, Paul Franklin and Kip S Thorne, Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar, Classical and Quantum Gravity, Volume 32, Number 6 (2015). DOI 10.1088/0264-9381/32/6/065001. Used under license CC-BY-3.0

Clocks on different heights in gravity field

Gravity influences the ticking of clocks. Therefore clocks can measure heights!

Content of the Universe

The Universe is mostly unknown! We are interested in modified/alternative theories of gravity and electrodynamics to find explanations. Image credit: Wolz, PhD thesis 2022

ABOUT OUR RESEARCH

Our research is focused on general relativity and its applications in astrophysics and geodesy as well as relations to quantum physics. This includes astrophysical extreme mass ratio systems and accretion disks around black holes as well as investigations of relativistic effects on the motion of satellites. The relativistic effects in rates of clocks on Earth and in space are crucial e.g. for height determination in geodesy. Moreover, we study fundamental problems in electrodynamics and in alternative theories of gravity.

Our fields of research

Dynamics of light, particles (stars), and fluids in relativistic spacetimes using mostly analytical techniques
Applications in relativistic astrophysics: extreme mass ratio systems, pulsar timing, accretion disks, gravitational lensing
Tests of gravity: investigation of relativistic effects on satellites orbiting the Earth as well as Earth- or space-based clocks
Relativistic geodesy: basic notions in General Relativity (GR), new concepts using the additional gravity degrees of freedom in GR; related topics are synchronisation and geodetic reference frames
Alternative/modified theories of gravity and electrodynamics

CONTACT

PD Dr. Eva Hackmann

+49 421 218 - 57862

eva.hackmann

Cluster of Excellence 'QuantumFrontiers'

The QuantumFrontiers program explores light and matter at the quantum frontier, advancing quantum and nanometrology to enhance measurement precision. These innovations enable groundbreaking technologies, from probing gravitational waves to understanding quantum-scale phenomena, deepening our knowledge of nature at both cosmic and microscopic scales.

Collaborative Research Center 'TerraQ - Relativistic and Quantum-based Geodesy'

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.

Research Unit 'Clock Metrology: A Novel Approach to TIME in Geodesy'

This research unit develops methods to enhance geodetic reference systems by linking all space geodetic techniques to a common time system. Accurate, stable global reference frames are essential for positioning, navigation, and understanding long-term geodynamic and climate processes, including plate tectonics and sea-level change.

Cost Action 23130 - Bridging high and low energies in search of quantum gravity (BridgeQG)

This COST Action Network brings together theorists and experimentalists to explore the regime where gravity meets quantum physics. From astrophysical observations to precision table-top experiments, the aim is to understand Planck-scale effects and study gravity's influence on quantum systems, bridging expertise in quantum-gravity, -optics, -mechanics, and high-energy astrophysics.

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

This project establishes a rigorous mathematical framework for effective quantum spacetime geometries using Finsler and Hamilton geometry. It seeks to derive observable predictions (e.g., particle trajectories, time delays, light deflections), study classical and quantum field propagation on quantum spacetime, and develops the dynamics that determine the quantum spacetime geometry.

DFG project: General relativistic theory of charged accretion disk structures around black holes: influence of the (self)-electromagnetic interaction

Accretion disks around black holes and neutron stars, shaped by electromagnetic fields, provide insights into strong-gravity regimes. This project explores charged fluid disks, focusing on their self-interactions through analytic models and GRMHD simulations, aiming to unravel complex phenomena in disk structure, physics, and evolution near compact objects.