Irregular universe in the Nieh-Yan modified teleparallel gravity
arXiv:2301.02847 · doi:10.1016/j.physletb.2023.137929
Abstract
The Nieh-Yan modified teleparallel gravity is a model which modifies the general relativity equivalent teleparallel gravity by a coupling between the Nieh-Yan density and an axion-like field. This model predicts parity violations in the gravitational waves if the axion-like field has a non-trivial background, and more importantly it is ghost free and avoids the pathologies presented in other parity-violating gravity models. The cosmological dynamics and perturbations of the Nieh-Yan modified teleparallel gravity have been investigated in detail, but all these previous investigations rely on the symmetry requirement that in the background universe both the metric and affine connection are homogeneous and isotropic. In this paper we relax the symmetry constraint on the connection and leave it arbitrary at the beginning, after all the cosmological principle only needs the metric of the background spacetime to meet the symmetry requirement. We find a new flat universe solution for the Nieh-Yan modified teleparallel gravity, for which the background dynamics itself is unchanged but the perturbations around it present a new feature that the scalar and tensor perturbations are coupled together at the linear level. The implications of this peculiar feature in primordial perturbations from inflation are also discussed.
20 pages, 1 figures, irregular universe, teleparallel gravity
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Cited by in corpus (10)
- Scalar induced gravitational waves in metric teleparallel gravity with the Nieh-Yan term
- Detectability of the chiral gravitational wave background from audible axions with the LISA-Taiji network
- Parity-violating primordial gravitational waves from null energy condition violation
- Chiral Gravitational Wave Background from Audible Axion via Nieh-Yan Term
- Field transformations and invariant quantities in scalar-teleparallel theories of gravity
- Spatially homogeneous teleparallel spacetimes with four-dimensional groups of motions
- Self-Excited Gravitational Instantons
- Post-Newtonian limit of generalized scalar-teleparallel theories of gravity
- Bridging inflation and reheating: chiral gravitational waves from aHz to GHz
- Testing the cosmological principle on gigaparsec scales