research

The research of me and my group is about General Relativity and alternative theories of gravity. I am interested in the motion of particles and fluids as well as the timing of clocks in strong gravitational fields, as you find them close to black holes or neutron stars. Down to Earth, I am also working on relativistic geodesy, i.e the usage of clocks to measure the height.

topics

Realistic image of an accretion disk
Credit: arXiv:1502.03808

accretion disks

Astronomical objects are often surrounded by matter, which forms a disk like structure. Over time the matter falls onto the central object, a process which is known as accretion

Prague astronomical clock

clocks

According to Special Relativity, the rate of clocks depends on their state of motion. General Relativity predicts in addition that clocks in gravitational fields run slower.

relativistic geodesy

The idealized geometric shape of the Earth, the geoid, can be determined using clocks. Relativistic effects on satellites need to be taken into account for determing the gravitational field of the Earth.

Artists impression of a star near a supermassive black hole
Credit: ESA/Hubble, ESO, M. Kornmesser

probing the spacetime

With particle or fluid motion as well as clock effects the spacetime of strong gravitational fields can be tested. Observable effects include for instance the periastron shift.


publications

publications

my journal publications

on Google Scholar

on inspire-hep

on SAO/NASA ADS

my PhD thesis for download

Download
Geodesic equations in black hole spacetimes with cosmological constant
Diss_Hackmann.pdf
Adobe Acrobat Document 5.7 MB

my habilitation thesis for download

Download
Probing General Relativity in the strong gravity regime
Habil_Hackmann_complete.pdf
Adobe Acrobat Document 21.6 MB

collaborations

Research Training Group Models of Gravity

Models of Gravity is a collaboration of research groups at the Universities of Bremen, Oldenburg, Bielefeld, Hannover, Jacobs University and Copenhagen funded by the German Research Foundation (DFG). Our main theme is the study of models of gravity which, e.g., emerge as effective theories in the low energy limit of string theory or other approaches to quantum gravity. We characterizing the properties of these models, in particular, by studying the motion of classical point particles, particles with structure, or quantum fields. I am Principal Investigator of the research topic Environment of Compact Objects.

Collaborative Research center geo-Q

The collaborative research center Relativistic Geodesy and Gravimetry with Quantum Sensors (geo-Q)  is a multidisciplinary research programme funded by the German Research Foundation (DFG). The aim of geo-Q is to explore new frontiers and techniques for the determination of the Earth’s gravitational field and its temporal variations by monitoring the global and regional mass redistribution. Under-standing the processes relevant for these changes allows the scientific community to better quantify and conceive climate change. I am Principal Investigator of the project Relativistic orbit modeling of satellite constellations

The Cluster of Excellence QuantumFrontiers, funded by the German Research Foundation (DFG), develops new measurement concepts and sensor topologies based on photonic systems, dedicated semi-conductor systems, nanostructures, quantum-manipulated atomic and molecular ensembles, and even macroscopic objects. One of the many research fields it will advance is relativistic geodesy with sub-centimeter height resolution. I am member of the Research Unit "Relativistic Geodesy".