Imprints of primordial gravitational waves with non-Bunch-Davies initial states on CMB bispectra

It has been shown that both scalar and tensor modes with non-Bunch-Davies initial states can enhance the amplitudes of the primordial bispectra compared to those with the Bunch-Davies state, especially for wavenumber modes in a flattened triangle configuration. However, in the case of the non-Bunch-...

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Bibliographic Details
Published in:arXiv.org 2023-07
Main Authors: Akama, Shingo, Tahara, Hiroaki W H
Format: Article
Language:English
Subjects:
Cosmic microwave background
Gravitation theory
Gravitational effects
Gravitational waves
Mathematical analysis
Perturbation
Relativity
Tensors
Wavelengths
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Summary:It has been shown that both scalar and tensor modes with non-Bunch-Davies initial states can enhance the amplitudes of the primordial bispectra compared to those with the Bunch-Davies state, especially for wavenumber modes in a flattened triangle configuration. However, in the case of the non-Bunch-Davies scalar modes, it has also been found that those enhancements in Fourier space are somewhat reduced in bispectra of cosmic microwave background (CMB) fluctuations. In this paper, we show that the enhancement resulting from the tensor modes is partially reduced to a degree differing from that of the scalar modes, which makes the non-Bunch-Davies effects unobservable in gravitational theories with the same quadratic and cubic operators of the tensor perturbations as general relativity. Furthermore, we present examples of gravitational theories yielding enhancements that would potentially be detected through CMB experiments.
ISSN:2331-8422