image: Bayesian posteriors for the scalar transverse amplitude obtained in the scalar transverse model under DE438 and BayesEphem ephemeris schemes, respectively. view more
Credit: ©Science China Press
In a paper published in Science China Physics, Mechanics & Astronomy, a team of scientists found strong Bayesian evidence for a spatially correlated process with scalar transverse correlations in the general metric theory of gravity beyond Einstein’s general relativity in the North American Nanohertz Observatory for Gravitational Waves 12.5-year data set.
This study was led by Prof. Qing-Guo Huang in the Institute of theoretical physics, Chinese Academy of Sciences. Even though Einstein’s general relativity is supposed to be the best theory for gravitation up to now, it is incompatible with quantum mechanics. Ones believe that Einstein’s general relativity should be modified in some extreme cases. The detection of gravitational waves provides an elegant arena for exploring the theory of gravity beyond Einstein’s general relativity.
Recently, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration reported strong evidence for a stochastic common-spectrum process, which is significantly preferred over an independent red-noise process in each pulsar. However, because of lacking definitive evidence for quadrupolar spatial correlations, it is inconclusive to claim a detection of gravitational waves consistent with general relativity. In fact, a most general metric theory of gravity can allow two vector modes and two scalar modes besides the two tensor modes in Einstein’s general theory of gravity, and these different modes have distinct correlation patterns, allowing the gravitational-wave detectors to explore them separately. By modeling the gravitational-wave background as a power-law spectrum, the team found strong Bayesian evidence for a spatially correlated process with scalar transverse correlations whose Bayes factor versus the spatially uncorrelated common-spectrum process is around 107.
This is a monumental claim! If the results in this paper are confirmed by the future Pulsar Timing Array data sets, they will have profound impacts on understanding the fundamental theory of gravity.
See the article:
Z.-C. Chen, C. Yuan, and Q.-G. Huang, Non-tensorial gravitational wave background in NANOGrav 12.5-year data set, Sci. China-Phys. Mech. Astron. 64, 120412 (2021), https://doi.org/10.1007/s11433-021-1797-y
Journal
Science China Physics Mechanics and Astronomy