# Astrophysical and Cosmological Relativity

In general relativity spacetime is a dynamic and elastic entity both influencing and influenced by the distribution of mass and energy that it contains. As a consequence, the accelerated motion of mass and energy can generate ripples or gravitational waves in the fabric of spacetime propagating at the speed of light. Those ripples encode unique information about the source that has generated them.

Binary systems composed of black holes and/or neutron stars, spiraling in toward each other and loosing energy because of the emission of gravitational waves are the most promising and exciting sources for gravitational-wave detectors. However, to significantly increase the probability of identifying gravitational waves in the detector data, the search from these sources requires detailed knowledge of the expected signals.

The research carried out in the "Astrophysical and Cosmological Relativity" division aims at improving our ability to detect and extract unique astrophysical and cosmological information from the observed waveforms and test fundamental equations of general relativity.

Scientists in this division work on several aspects of gravitational waves emitted by binary systems, notably

(i) theoretical gravitational dynamics and radiation (post-Newtonian theory, gravitational self-force formalism, perturbation theory and effective-one-body approach),

(ii) numerical simulations of gravitational-wave sources,

(iii) source modeling and analysis of data from gravitational-wave detectors, and

(iv) astrophysics of black holes and neutron stars.

Most scientists of the division are members of the LIGO Scientific Collaboration (LSC), but the division also supports theoretical studies of gravitational-wave sources and the development of techniques for data analysis for the European Pulsar Timing Array collaboration and LISA, a planned space-based gravitational-wave detector.