Axion-like fields coupled to the Nieh-Yan term generate a chiral GW background during radiation domination, with parameter space explored for detectability in PTA and space-based observatories.
Chirality oscillation of primordial gravitational waves during inflation
2 Pith papers cite this work. Polarity classification is still indexing.
abstract
We show that if the gravitational Chern-Simons term couples to a massive scalar field ($m>H$), the primordial gravitational waves (GWs) will show itself the chirality oscillation, i.e., the amplitudes of the left- and right-handed GWs modes will convert into each other and oscillate in their propagations. This oscillation will eventually develop a permanent difference of the amplitudes of both modes, which leads to nearly opposite oscillating shapes in the power spectra of the left- and right-handed primordial GWs. We discuss its implication to the CMB B-mode polarization.
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A dipole pulsar timing array detects chiral nanohertz gravitational waves and extends PTA sensitivity into the microhertz regime.
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Chiral Gravitational Wave Background from Audible Axion via Nieh-Yan Term
Axion-like fields coupled to the Nieh-Yan term generate a chiral GW background during radiation domination, with parameter space explored for detectability in PTA and space-based observatories.
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Detecting Chiral Gravitational Wave Background with a Dipole Pulsar Timing Array
A dipole pulsar timing array detects chiral nanohertz gravitational waves and extends PTA sensitivity into the microhertz regime.