Stochastic gravitational wave background phenomenology in a pulsar timing array

12:30-13:30
Speaker :   Dr. Reginald Christian Bernardo (IoP, Academia Sinica) 
Abstract :
Pulsar timing arrays have observed strong evidence for a common spectrum process across millisecond pulsars. However, it is by the spatial correlation that one may unequivocally infer if the signal is due to the long sought stochastic gravitational wave background, and the present data and methodology have yet to reach maturity in this aspect. We present an algorithm based on a power spectrum formalism that predicts the spatial correlation from a stochastic gravitational wave background sourced by any cosmological degree of freedom. We showcase the methodology by calculating the low angle correlation, forecasting where pulsar timing array cosmology can find a departure from the traditional Hellings-Downs curve hosted by general relativity. Provided enough time, we also discuss the correlation signal for non-general relativity degrees of freedom that may perhaps have lingered in the unchartered nanohertz gravitational wave cosmic territory.