SFB$/$TR 7: Gravitational Wave Astronomy

A. Gopakumar & D. Petroff, SFB/TR 7, gopu,petroff@tpi.uni-jena.de

The first meeting of researchers participating in a new German initiative on gravitational wave astronomy took place in Tübingen from October 9-10, 2003. The ambitious project entitled `Gravitational Wave Astronomy' and referred to as SFB/TR 7 (Sonderforschungsbereich/Transregio 7) is being funded by the DFG (Deutsche Forschungsgemeinschaft), for an initial period of four years (2003-2006) and with the possibility of extensions for up to twelve years. SFB/TR 7 brings together more than 50 scientists as well as numerous Diploma and Ph.D. students from five German academic institutions, to tackle various issues related to the realization of gravitational wave astronomy in the near future. Opening a new window to the universe by observing gravitational waves requires close interaction between experimentalists and theoreticians working on various aspects of gravitational radiation. It is highly desirable that experimentalists involved in the design and construction of gravitational wave detectors associate closely with theoreticians providing detailed information about the nature and abundancy of expected sources and their signals, as well as with those who analyse the raw detector data and develop new analysis strategies. It is to achieve the above objectives that the DFG is supporting experimental and theoretical physicists, astrophysicists and mathematicians from Universities in Hanover, Jena and Tübingen as well as Max-Planck Institutes for Astrophysics in Garching and Gravitational Physics in Golm.

Prof. G. Neugebauer (Jena) is the speaker of SFB/TR 7 and the executive board is also comprised of Profs. K. Danzmann (Hanover), W. Kley (Tübingen), E. Müller (Garching), G. Schäfer (Jena) and B. Schutz (Golm). The project is subdivided into three sections dealing with the analysis of the gravitational field equations, the structure and dynamics of compact objects and the detection of gravitational waves. Each of these sections consists of several working groups, which tackle specific issues relevant to the parent section as well as to gravitational wave astronomy in a broader sense.

During the meeting, each working group presented a brief status report of its work. Junior scientists were encouraged to assume the responsibility of preparing and delivering the talks, which helped to lend the conference a relaxed and open atmosphere. The three working groups analysing the structure of the field equations relevant to numerical simulations were the first to present their projects. This portion of the meeting was made up of the six talks listed below: $\bullet$ Vacuum Initial Data with Trapped Surfaces $\bullet$ A Program for the Numerical Treatment of Radiating Systems $\bullet$ Gravitational Radiation from Distorted Black Holes $\bullet$ Initial Data for the Conformal Einstein Equations $\bullet$ A Skeleton Solution of the Einstein Field Equations and $\bullet$ A Minimal No-Radiation Approximation to the Einstein Field Equations.

The second, and largest section in SFB/TR 7, is made up of six working groups, which presented ten talks related to their respective research interests. These can be broadly classified, according to the underlying astrophysical scenarios, into four categories. The first deals with the structure of solitary compact objects, the second with their dynamics and the third with the collapse of relativistic objects. The fourth category focuses on binary dynamics within the post-Newtonian and numerical relativity frameworks. The titles of these talks (in the order presented at the workshop) are $\bullet$ An Updated Version of a Computer Program for the Calculation of Rotating Neutron Stars and Specific Applications $\bullet$ Oscillation Modes of Rotating Neutron Stars $\bullet$ New Methods for Gravitational Collapse to Neutron Stars and Black Holes $\bullet$ Gravitational Collapse of Rotating Neutron Stars $\bullet$ Cylindrical Collapse $\bullet$ Binary Dynamics of Spinning Compact Objects $\bullet$ Gravitational Waves from Binary Systems with Oscillating Dust Discs as Components $\bullet$ Evolutions in 3D Numerical Relativity using Fixed Mesh Refinement $\bullet$ Binary Black Hole Evolutions from Innermost Quasi-Circular Orbits and $\bullet$ Merging Neutron Star Binaries - Results and Future Plans.

On the second day, the experimentalists and data analysts making up the third section of our SFB, briefed the participants on their research progress. The experimentalists gave talks on both currently implemented technologies, e.g. in GEO600, and on possible future methodologies with the titles $\bullet$ High Resolution Interferometer Concepts Based on Reflective Optical Components, $\bullet$ Low Loss Gratings for Gravitational Interferometry, Design Considerations and Fabrication and $\bullet$ Cryogenic Q-factor Measurement of Optical Substrates. The session on data analysis consisted of a detailed review and a discussion session on the iterative design of the sensitivity curve for future gravitational wave detectors.

Those interested in learning more about SFB/TR 7 are referred to the website http://www.tpi.uni-jena.de/~sfb/index.html.