Abstract
In recent years, several pulsar timing array collaborations have reported first hints for a stochastic gravitational wave background at nano-Hertz frequencies. Here we elaborate on the possibility that this signal comes from new physics that leads to the generation of a primordial stochastic gravitational wave background. We propose a set of simple but concrete models that can serve as benchmarks for gravitational waves sourced by cosmological phase transitions, domain wall networks, cosmic strings, axion dynamics, or large scalar fluctuations. These models are then confronted with pulsar timing data and with cosmological constraints. With only a limited number of free parameters per model, we are able to identify viable regions of parameter space and also make predictions for future astrophysical and laboratory tests that can help with model identification and discrimination.
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Acknowledgments
The authors would like to thank Toby Opferkuch and Kai Schmitz for very inspiring discussions. Work in Mainz is supported by the Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA+ EXC 2118/1) funded by the German Research Foundation (DFG) within the German Excellence Strategy (Project No. 39083149).
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Madge, E., Morgante, E., Puchades-Ibáñez, C. et al. Primordial gravitational waves in the nano-Hertz regime and PTA data — towards solving the GW inverse problem. J. High Energ. Phys. 2023, 171 (2023). https://doi.org/10.1007/JHEP10(2023)171
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DOI: https://doi.org/10.1007/JHEP10(2023)171