Circularly Polarized Gravitational Waves from the Ealy Universe as a Probe of New Physics

Gravitational waves (GWs) provide the only known direct signal of physics from the first second of the universe. Such relic GWs can be sourced by violent processes in the early universe (for a review see [1] and references therein), and after their generation they propagate almost freely throughout the expansion of the universe that causes the dilution of their strain amplitude and frequency. The presence of the possible violation (that might be a consequence of new physics beyond the standard model of cosmology) in the early-universe would be imprinted in the circular polarization of GWs. Detecting these relic polarized GWs is a challenging task due to their small amplitudes, the specific range of their characteristic frequencies, and the presence of astrophysical foregrounds. We explore the possibility to detect the GW polarization through the our proper motion (Lorentz boosting), for recent studies see [2-7] and references therein.

References:

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[6] A. Roper Pol, S. Mandal, A. Brandenburg and T. Kahniashvili, "Polarization of gravitational waves from helical MHD turbulent sources," JCAP 04, 019 (2022).

[7] G. Cusin and G. Tasinato, "Doppler boosting the stochastic gravitational wave background," JCAP 08, 036 (2022).