Gravitational Wave Theory
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 was initially dominated by instrumental noise, with possible gravitational wave signals deeply buried in the noise. Today, ground-based detectors (such as LIGO and Virgo) have improved to the point that some gravitational wave signals are much more easily detected, while future space-based detectors, such as LISA, will detect signals with immense signal-to-noise ratios.
Professor Yunes' research group develops theoretical "templates" or gravitational wave models that describe the possible gravitational wave signals that could be present in ground-based and space-based detector data. These models underpin the optimal techniques for detection and characterization of the signals. Once a detection is made, the estimation of parameters, selection of theoretical models and testing of hypothesis requires the detailed modeling of the signal and is best carried out with Bayesian techniques. The latter start with our current (prior) knowledge, and then they use the data to update it. 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.