Hemispherical asymmetry of primordial power spectra
Abstract
Although the cosmic microwave background (CMB) is largely understood to be homogeneous and isotropic, the hemispherical power asymmetry anomaly seems to breakdown the isotropy, since the difference between the power spectrum in the two hemispheres of the CMB is of the order of $10^{-2}$ at large angular scales. We argue that the existence of an anisotropic power spectrum can simply be explained by considering the existence of two distinct power spectra in the two hemispheres of the CMB, without introducing any additional parameters. We propose a direct-sum vacuum structure for (single field) inflationary quantum fluctuations based on discrete spacetime transformations ($\mathcal{P}\mathcal{T}$). As a result, we are able to reproduce the amplitude of the observed dipolar asymmetry at different scales of $ 10^{-4} {\rm Mpc^{-1}}\lesssim k\lesssim 1 {\rm Mpc^{-1}}$. We also predict that a similar HPA should arise for the primordial gravitational waves (PGWs) as well and we compute the power asymmetry of PGW spectra at various wave numbers.
- Publication:
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arXiv e-prints
- Pub Date:
- September 2022
- DOI:
- 10.48550/arXiv.2209.03928
- arXiv:
- arXiv:2209.03928
- Bibcode:
- 2022arXiv220903928S
- Keywords:
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- General Relativity and Quantum Cosmology;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- High Energy Physics - Theory
- E-Print:
- 10 pages, 2 figures. With improved explanations and some minor notation changes