Gravitation

The proposed thesis subject is focused on the global validation process of the instrument metrological performance. Preliminary concepts exist for the various optical metrology test benches that will be required measure the instrumental characteristics. Obviously, the full constellation cannot be tested in flight conditions on ground. The instrument validation will therefore rely on a ingenious combination of specific measurements performed on the different subsystems, as well as the results obtained with specifically designed lab experiments.

International Pulsar Timing Array is a consortium of four collaborations working on detecting gravitational waves (GWs) in the nano-Hz band. The analysis of the third combined dataset of radio observations from 9 worldwide telescopes will start at the end of 2023. We are searching for GWs from a population of supermassive black hole binaries (SMBHBs). The expected signal could be decomposed into two components: the stochastic signal that is the result of an incoherent superposition of thousands of weak signals and the resolvable signal(s) from particularly massive and nearby binaries.

Second generation gravitational wave (GW) detectors opened era of gravitational wave astronomy with the first GW detection in 2015 and are now approaching their design sensitivity. During the 3 past observations runs, they detected 90 GW signals produced by the merging of binary compact objects, providing a wealth of scientific results ranging from the general relativity, to astrophysics and cosmology.
 

Second generation gravitational wave (GW) detectors opened era of gravitational wave astronomy with the first GW detection in 2015 and are now approaching their design sensitivity. During the 3 past observations runs, they detected 90 GW signals produced by the merging of binary compact objects, providing a wealth of scientific results ranging from the general relativity, to astrophysics and cosmology.
 

Extreme Mass Ratio Inspirals (EMRI) are one of the most interesting signals which will be detected by Laser Interferometer Space Antenna (LISA). They will sample highly curved spacetime around Massive Black Holes (MBH) and allow for insight into the strong regime of gravity. EMRIs are signals which come from the compact objects falling onto MBH, they typically last for 10^5 number of cycles which translates into an order of one year length. They have relatively low signal-to-noise ratios (SNR) and typically it is required to observe them for a long time to be able to accumulate enough SNR.

Pulsar timing array (PTA) uses long-term monitoring of ultra-stable millisecond pulsars to search for gravitational wave (GW) signal in the nano-Hz band. The recently detected common red noise could potentially be a stochastic GW signal.  Such a signal could be generated by a population of supper-massive black hole binaries or by violent processes in the early Universe. We will assume that this signal was produced by a network of cosmic strings and infer their properties using observational data.