2014/08/31 by Adam D. Helfer · 2 citations
Physics and Astronomy · #Anisotropy #Astrophysics #Black Holes and Theoretical Physics #Cosmic microwave background #Cosmology and Gravitation Theories #Fermion #General relativity #Geometry #Gravitation #Gravitational wave #Mathematical physics #Physics #Planck #Polarization (electrochemistry) #Pulsars and Gravitational Waves Research #Quantum electrodynamics #Quantum mechanics #Scalar (mathematics) #astro-ph.CO #gr-qc
paper · pdf · doi:10.1103/physrevd.94.124011
published in Physical review. D/Physical review. D. 94(12) (American Physical Society) · To appear in PRD. Considerably expanded from the earlier version; numerical results for effects on the CMB are given. The only substantive correction to the earlier version is to the overall sign of the effect. 21 pages, 4 figures
arxiv created 2016/11/28 · openalex publication_date 2016/12/08 · arxiv updated 2016/12/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In conventional general relativity without torsion, high-frequency gravitational waves couple to the chiral number density of spin one-half quanta: the polarization of the waves is rotated by 2\ensuremathπN5\ensuremathℓPl2, where N5 is the chiral column density and \ensuremathℓPl is the Planck length. This means that if a primordial distribution of gravitational waves with E-E or B-B correlations passed through a chiral density of fermions in the very early Universe, an E-B correlation will be generated. This in turn will give rise to E-B and T-B correlations in the cosmic microwave background (CMB). Less obviously but more primitively, the condition Albrecht called ``cosmic coherence'' would be violated, changing the restrictions on the class of admissible cosmological gravitational waves. This altered class of waves would, generally speaking, probe earlier physics than do the conventional waves; their effects on the CMB would be most pronounced for low (\ensuremath\lesssim100) multipoles. Rough estimates indicate that if the tensor-to-scalar ratio is less than about 10^\ensuremath-2, it will be hard to constrain a spatially homogeneous primordial N5 by present data.