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arXiv · 2406.16549

Parity-violating primordial gravitational waves from null energy condition violation

Zi-Wei Jiang·Yong Cai·Fei Wang·Yun-Song Piao
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Abstract

We investigate the parity-violating effects in primordial gravitational waves (GWs) due to null energy condition (NEC) violation in two very early universe scenarios: bounce-inflation and intermediate NEC violation during inflation. In both scenarios, we numerically solve the power spectra of parity-violating primordial GWs generated by coupling the background field and the spectator field with the Nieh-Yan term, respectively. We find that the background field can significantly enhance parity-violating effects at scales corresponding to the maximum of the GW power spectra. In contrast, the parity-violating effects produced by the spectator show significantly weaker observability even if the coupling constant is large. Therefore, in NEC-violating scenarios, the significant observable parity-violating effects in primordial GWs primarily arise from the physics directly related to NEC violation. This result highlights the potential of primordial GWs as crucial tools for exploring NEC-violating and parity-violating physics.

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Zi-Wei Jiang, Yong Cai, Fei Wang, Yun-Song Piao. 2024-06-24. Parity-violating primordial gravitational waves from null energy condition violation. https://doi.org/10.1007/jhep09(2024)067

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