Colloquium on Jan. 4, 2024

Search for Gravitational-Wave Background in Pulsar Timing Array

Speaker: Qingguo Huang (UCAS)

Venue: SWIFAR Building 2111

Time: 15:00 PM, Thursday, Jan. 4, 2024

Abstract:

Recently, the North American Nanohertz Observatory for Gravitational Waves, the European Pulsar Timing Array, the Parkes Pulsar Timing Array, and the Chinese Pulsar Timing Array all simultaneously released their latest independent observation results, showing strong evidence for a random signal consistent with a gravitational wave background. Based on astrophysical formation models, we interpret this signal as a gravitational wave background generated by supermassive black hole binaries, and find that the orbits of these supermassive black hole binaries may have a large initial eccentricity. In addition, the detection of different gravitational wave polarization modes can be used to test gravitational theories in a model-independent way. We recently found significant Bayesian evidence for scalar transverse polarization modes in the data from pulsar timing arrays, such as the NANOGrav 12.5-year data, and its 15-year data still cannot exclude this signal. Our results imply that the current data from pulsar timing arrays still cannot provide substantial evidence for the detection of gravitational waves.