Abstract
Recently, evidence of stochastic gravitational wave background (SGWB) signals observed by pulsar timing array (PTA) collaborations, has prompted investigations into their origins. We explore the compatibility of a proposed inflationary scenario, incorporating an intermediate null energy condition (NEC)-violating phase, with the PTA observations. The NEC violation potentially amplifies the primordial tensor power spectrum, offering a promising explanation for PTA observations. Numerical analyses, primarily focused on NANOGrav’s 15-year results, reveal the model’s compatibility with PTA data. Notably, the model predicts a nearly scale-invariant GW spectrum in the mHz frequency range, which sets our scenario apart from other interpretations predicting a red primordial GW spectrum on smaller scales.
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Acknowledgments
We are grateful to Yi-Fu Cai, Chunshan Lin, Yun-Song Piao, Fei Wang and Yi Wang for stimulating discussions. Y. C. is supported in part by the National Natural Science Foundation of China (Grant No. 11905224), the China Postdoctoral Science Foundation (Grant No. 2021M692942) and Zhengzhou University (Grant Nos. 32213984, 32340442). G.Y. is supported by NWO and the Dutch Ministry of Education, Culture and Science (OCW) (grant VI.Vidi.192.069). M.Z. is supported by grant No. UMO 2021/42/E/ST9/00260 from the National Science Centre, Poland. PTA data analysis is performed using the PTArcade software [132,133,134,135]. We acknowledge the use of the computing server Arena317 @ZZU.
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Ye, G., Zhu, M. & Cai, Y. Null energy condition violation during inflation and pulsar timing array observations. J. High Energ. Phys. 2024, 8 (2024). https://doi.org/10.1007/JHEP02(2024)008
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DOI: https://doi.org/10.1007/JHEP02(2024)008