The sound of colliding black holes - and how to filter out the noise of the Universe from it

Meeting of experts at the AEI from 6 to 9 July, 2009

Background Information

In recent years, pioneering progress has been made in ​​numerical relativity and data analysis. On the one hand, the prediction of gravitational wave signals from various astrophysical sources has become more and more accurate; on the other hand, the analysis of the immense amounts of data produced by gravitational wave observatories has become faster and more reliable. Now is the time to link the information and methods of both research areas. The AEI scientists belong to some of the world's leading research groups in both areas.

Numerical relativity at AEI

The achievements of the Numerical Relativity Group led by Prof. Luciano Rezzolla, include:

• the calculation of so-called burst signals, which are signals from collapsing neutron stars, for the very first time. This represents the solution of a problem that had been discussed for more than 40 years and therefore constitutes a milestone in the direct detection of gravitational waves.
• the first completely relativistic simulation of a binary neutron star merger. This provides answers to questions such as: what exactly happens in this process, which ultimately gives rise to a black hole? How much energy is released? Is this the cause of the enigmatic gamma-ray bursts that take place?

Data analysis at AEI

At AEI there are two research groups that are involved in different aspects of data analysis:

• In the Gravitational Wave Analysis Group (led by Dr. Maria Alessandra Papa), the data provided by gravitational wave detectors is investigated and evaluated, using the powerful computer cluster Morgane. In particular, customised methods for analysing the data are developed. The area of research of ​​Dr. Badri Krishnan work is the better understanding of the sources of gravitational waves. In addition, the scientists are concerned with a key astrophysical question: What new findings will the observation of gravitational waves bring to light?
• The scientists in the Department of Observational Relativity and Cosmology at the AEI site in Hannover, Germany, operate the world's fastest and largest computer cluster that primarily analyses data from gravitational wave detectors: ATLAS. This is undertaken under the direction of Prof. Bruce Allen. All the data currently available in the US (LIGO) and Europe (GEO600 and Virgo) observatories is collected here. ATLAS is expected to confirm the first direct measurement of gravitational waves.

The task of analysing the extremely weak gravitational wave signals and separating them from the data flood is a task that scientists from all over the world are working on. They have joined together in the "LIGO-Virgo Scientific Cooperation" (LSC-V) and have agreed to a complete exchange of recorded data. In addition, all scientific results are published jointly. The LSC-V consortium is headed by Dr. Maria Alessandra Papa of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute).

The reliability and speed of the data analysis is tested in the context of so-called "mock data challenges" or even sample evaluations. Simulated gravitational wave signals are injected into the detector data. Up to now these artificial signals have been reliably identified.

The ATLAS Cluster is the world's largest resource for the analysis of gravitational waves. It unites about 1700 individual computers. It was created under the leadership of Prof. Bruce Allen, Director at the Max Planck Institute for Gravitational Physics.