Director: Adjunctprofessor (Univ. of Wisconsin, Milwaukee, WI/USA) Dr. Bruce Allen
Research in the division of Observational Relativity and Cosmology is focused on the direct observational consequences of Einstein's General Theory of Relativity, particularly as it relates to astrophysics and cosmology.
The most exciting and active of these areas is the search for gravitational wave signals in the data from a new generation of ground-based broad-band detectors. In 1917 Einstein showed that gravitational waves are a fundamental prediction of his theory, but they have never been directly detected. Gravitational waves which are strong enough to detect can not be made in a laboratory. They could only be produced by massive and compact astrophysical objects, or by exotic processes in the early universe. In the past decade, advances in lasers and optics have led to new methods to detect gravitational waves, thus promising to open a new observational window on the universe.
The AEI is part of an international collaboration which shares data from this new generation of sensitive broad-band interferometric detectors. These detectors are based in the USA (LIGO), Italy (VIRGO) and Germany (GEO600, jointly operated by AEI Hannover and the Universities of Cardiff and Glasgow). The first generation of these detectors is now taking data at design sensitivity, and offers real hope of making a first direct detection. A second generation upgrade of these detectors in the coming decade will guarantee such observations. It will then be possible to infer information about the binary populations, and possibly probe the disruption of neutron stars, test alternative theories of gravity, bound the mass of the graviton, and do other types of gravitational wave astronomy.
The research specialties of this division include the development and implementation of data analysis algorithms to search for the four different expected types of sources (burst, stochastic, continuous wave, and inspiral). We also help to run the distributed computing project Einstein@Home, which searches for gravitational wave signals from pulsars, and are currently setting up dedicated large-scale cluster computing facilities (over 2000 CPU cores and 300 TB of data storage) for other compute-intensive searches.
We are also interested in other novel methods to detect gravitational waves, for example using pulsar timing residuals to set limits on (or detect!) a stochastic background of gravitational waves, or using polarization maps of the Cosmic Background Radiation as a very-low-frequency detector. The detection of a stochastic background of gravitational waves of cosmological origin would give us a snapshot of the very early universe when it was less than a picosecond old, hundreds of thousands of years before it even became transparent to light!