Gravitational waves are the new window to observe the universe. They are clean source of information, as they barely interact with matter. LIGO detected gravitational waves coming from the merger of binary black holes and binary neutron stars but these are not the only detectable sources of gravitational waves.
Gravitational waves may have also been generated from quantum fluctuations during inflation, cosmic strings and phase transitions in the early universe, when the energy scale was extremely high. Now, due to the large number of unresolved sources in our universe, these signals will appear as a Stochastic Gravitational Wave Background (see this review on the cosmological sources). I am interested in exploring cosmological sources of the gravitational wave background and the information that can be extracted about the history of our universe. In particular, I have explored the generation of induced1 gravitational waves in a general cosmological background in this article) for the first time in an analytical way. The induced gravitational waves are an essential contribution to the stochastic gravitational wave background as they carry information about the primordial fluctuations and may be linked to the primordial black hole scenario (check this review on primordial black holes). I have also proposed to use the induced gravitational waves as a probe of the thermal history of the universe here.
Interestingly, gravitational waves generated out of quantum fluctuations during inflation also leave an imprint in the Cosmic Microwave Background as B-mode2 polarization of the radiation we receive (check my works on inflation and CMB here). I also study technical aspects of the theoretical formulation of gravitational waves in cosmology.
