This group focus on five large areas of research:

• LISA PATHFINDER Scientific Operations: The LISA Pathfinder mission of the European Space Agency is demonstrating the technology to set up two test masses in space in a state of free-fall motion without precedents and compatible with the needs of a future space-based gravitational-wave observatory. The institute has been working in the design of experiments for LISA Pathfinder, the development of data analysis tools and pipelines, and in the scientific exploitation of the mission.

• Astrophysics and Cosmology of gravitational wave sources:  The study of physical mechanisms both at astrophysical and cosmological scales that can lead to the formation of sources of gravitational waves in any of the bands of interest (high, low and very low).  The idea is to understand the rate at which different types of sources form in the Universe and to understand the distribution of physical parameters (masses, spins, orbital parameters, distance, etc.).

• Simulations of sources of gravitational waves: One of the main topics in Gravitational Wave Astronomy is to produce a template bank of gravitational wave signals (waveforms) to be used in the data analysis. This is a crucial point and requires the use and development of techniques in Numerical Relativity (the solution of Einstein's field equations by means of supercomputers) and in Perturbative Relativity (the solution of Einstein's field equations using different types of approximation schemes).

• Fundamental physics with gravitational waves: One of the Holy Grails in Gravitational Wave Astronomy is to use gravitational wave detections of the coalescence of (supermassive) black holes and of extreme-mass-ratio inspirals to study different questions with impact in Fundamental Physics.  Those questions include: Tests of the Einstein Equivalence Principle; tests of the geometry of black holes, in particular of the no-hair conjecture that states that astrophysical black holes should be described by the Kerr solution of General Relativity (and hence described by two numbers: mass and spin); tests of the General Relativity theory and other alternative theories of gravity.

• Algorithms for gravitational waves data analysis: In contrast with other areas of Astronomy, the storage of the data of Gravitational Wave detectors does not present a challenge to the current available resources.  However, the processing of this data in order to detect and characterise gravitational-wave sources by means of data analysis techniques that use match filtering techniques constitutes a big challenge.  The computational cost for the most complex sources (in terms of the dimensionality of their parameter space) is so big that it makes necessary the development of smart algorithms for the search of sources and the estimation of their physical parameters.