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Gravitational waves from the early universe

by Rafael R. Lino dos Santos, Linda M. van Manen

Submission summary

Authors (as registered SciPost users): Rafael Robson Lino dos Santos · Linda van Manen
Submission information
Preprint Link:  (pdf)
Date submitted: 2023-10-30 21:49
Submitted by: Lino dos Santos, Rafael Robson
Submitted to: SciPost Physics Lecture Notes
Ontological classification
Academic field: Physics
  • Gravitation, Cosmology and Astroparticle Physics
Approaches: Theoretical, Phenomenological


Ongoing and future gravitational wave collaborations explore different frequency ranges of the gravitational wave spectrum, probing different stages of the early universe and Beyond Standard Model physics. Due to the very high energies involved, accelerators cannot probe these earlier stages. Therefore, until some years ago, knowledge about new physics was limited and relied on bounds from CMB observations and theoretical assumptions about higher energy scales. While models could be constrained by CMB data, they were left unconstrained at shorter wavelength scales. Nonetheless, each one of these models has a gravitational wave density spectrum at these shorter wavelength scales that can ultimately be compared to data from ground-based, space-born, and pulsar timing array searches. These lecture notes review the formalism of gravitational waves in General Relativity and introduce stochastic gravitational waves, with a focus on primordial sources and commenting on detection efforts. These lecture notes were inspired by the course "Gravitational Waves from the Early Universe" given at the 27th W.E. Heraeus "Saalburg" Summer School 2021 by Valerie Domcke.

Author comments upon resubmission

For v2, we did a major revision in the manuscript to address the previous referee's report and to include new results from PTA searches. Sections, figures, and references have been added to increase the clarity of the work and make the discussion more uniform.
Current status:
Awaiting resubmission

Reports on this Submission

Anonymous Report 1 on 2023-12-23 (Invited Report)


The authors have improved the lecture notes, and the addition of material on interferometers and pulsar timing is welcome. An explanation of the Hellings-Downs curve is very topical in view of the latest results strongly supporting the presence of a stochastic GW background.


See attached file.


The level of the discussion is still uneven, and there are still quite a few places, listed in the attachment, where these notes do not meet the criteria of being correct, systematic and intelligible. I regret that I cannot recommend the notes for publication in SciPost.


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