# Gravitational Wave Science Analysis

Gravitational waves couple very weakly to matter. This means that they can propagate essentially unimpeded from large cosmological distance to Earth. But at the same time, this also means that they are very hard to detect. Given a photon that travels down a long 4 km tube, gravitational waves change the distance traveled by less than one part in a thousand of the radius of a proton. Such insanely small distances can only be measured with interferometry. But even then, the interferometric data is dominated by instrumental noise, with possible gravitational wave signals deeply buried in the noise.

The XGI develops and implements sophisticated data analysis and statistical techniques to extract information about the gravitational wave signals from noisy data streams. Theoretical templates describing the possible gravitational wave signals underpin the optimal techniques for detecting and characterizing the signals. Once a detection is made, the estimation of parameters, selection of theoretical models and testing of hypothesis is best carried out with Bayesian techniques. These start with our current (prior) knowledge then use the data to update our knowledge. Given a gravitational wave signal buried in the noise, the posterior knowledge obtained through such techniques yields probability distributions for the astrophysical parameters (such as the sky location, masses and spins of the systems etc) and the evidence that a particular model is preferred by the data.

The eXtreme Gravity Institute is a member of the LIGO Scientific Collaboration (ground-based detector), the LISA Science Team (space-based detector), and the NanoGrav collaboration (pulsar timing array).