Parity-violating primordial gravitational waves from null energy condition violation
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.
- Publication:
-
Journal of High Energy Physics
- Pub Date:
- September 2024
- DOI:
- 10.1007/JHEP09(2024)067
- arXiv:
- arXiv:2406.16549
- Bibcode:
- 2024JHEP...09..067J
- Keywords:
-
- Cosmological models;
- Classical Theories of Gravity;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- General Relativity and Quantum Cosmology;
- High Energy Physics - Theory
- E-Print:
- 32 pages, match published version, reference added