Exploring Circularly Polarized Stochastic Gravitational-Wave Background and the Impact of Doppler-Induced Dipole Anisotropies

Sevgi Karadag^1,2*, Chia-Hsuan Hsiung³, Guo-Chin Liu³, Kin-Wang Ng², Henry Tsz-King Wong²

¹Department of Physics Engineering, Istanbul Technical University, Istanbul, Turkey
²Institute of Physics, Academia Sinica, Nankang, Taiwan
³Department of Physics, Tamkang University, New Taipei, Taiwan

* Presenter:Sevgi Karadag, email:sevgik@gate.sinica.edu.tw

Some inflationary models indicate the existence of a circularly polarized stochastic gravitational wave background (SGWB); if such a signal is detected, it would have profound cosmological significance. This work focuses on investigating the detection and clarification of polarization properties in the SGWB, which comprises faint, unresolved gravitational wave sources. Also the presence of dipole anisotropies, particularly those arising from the Doppler boost effect due to our motion relative to the cosmic rest frame, underlines the necessity of enhancing search techniques for the SGWB. In this regard, we have developed a simulation and analysis pipeline to unveil the specific properties of a 100% circularly polarized SGWB, where kinematic dipole anisotropies are also considered. We concentrate our parameter estimation on the key components: polarization parameter Π, spectral index 𝛼, and amplitude parameter Ω_GW. By testing this pipeline on simulated data, we confirm its reliability and accuracy in characterizing SGWB signals under these assumptions. We then apply the validated pipeline to the LIGO O3 dataset, deriving constraints for each parameter to provide new insights into the possibility of detecting circular polarization in the SGWB and help broaden the scope of gravitational wave astronomy.



References

[1] Romano, J. D., & Cornish, N. J. (2017). Detection methods for stochastic gravitational-wave backgrounds: a unified treatment. Living reviews in relativity, 20, 1-223.
[2] Cusin, G., & Tasinato, G. (2022). Doppler boosting the stochastic gravitational wave background. Journal of Cosmology and Astroparticle Physics, 2022(08), 036.
[3] Chung, A. K. W., Jenkins, A. C., Romano, J. D., & Sakellariadou, M. (2022). Targeted search for the kinematic dipole of the gravitational-wave background. Physical Review D, 106(8), 082005.

Keywords: SGWB, Circular Polarization, Dipole Anisotropies