PoS - Proceedings of Science
Volume 454 - 1st General Meeting and 1st Training School of the COST Action COSMIC WSIPers (COSMICWISPers) - Wg1
Testing BSM Physics with Gravitational Waves
G. Villa
Full text: Not available
In this talk, we explore the effect of new Physics in the shape of the Cosmic Gravitational Wave Background (CGWB): a stochastic background of Gravitational Waves (GWs) sourced by the primordial plasma.
We argue that the shape of the CGWB is a direct probe for physics at energies much higher than those at the last scattering surface, which bounds electromagnetic astronomy.
Due to its characteristic frequency, around $80$ GHz, the CGWB is an example of an ultra high frequency source of GWs, which are attracting the attention of a growing community of both theorists and experimentalists~\cite{Aggarwal:2020olq}.
It is becoming increasingly clear that early Universe processes release backgrounds at these high frequencies, and that their potential detection provides a window for the direct study of high energy physics that is not achievable through electromagnetic astronomy or collider physics.
We conclude that, if the CGWB is detected at lower frequencies and amplitudes compared to the prediction of the Standard Model, it will hint at extra massive degrees of freedom or hidden sectors which are thermally active after reheating.
If it is instead measured at higher values, it will imply a period with $\omega >1/3$.
We argue that for certain scenarios with periods of kination in the early Universe, a significant fraction of the parameter space can be ruled out from dark radiation bounds at BBN.
This talk is based on~\cite{Muia:2023wru}.
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