Primordial Gravitational Waves in Loop Quantum Cosmology: Regularization Ambiguities and Initial State Dependence
Abstract
We compute the primordial tensor power spectrum in standard loop quantum cosmology and in the modified models mLQC-I and mLQC-II, evolving the tensor perturbations across the bounce in the hybrid and dressed metric prescriptions with a Starobinsky potential. In mLQC-I, the emergent de Sitter contracting branch requires the use of dedicated initial states. We use de Sitter mode function in the dressed metric approach and a Hankel-function solution in the hybrid approach. For inflationary e-foldings Ne = 60 and $65$, the pivot-scale tensor-to-scalar ratio agrees with the value of standard inflation with this potential. The scale-dependent ratio r(k)=𝒫T/𝒫S cancels effects common to the two sectors and separates features that are independent of the initial state from those that depend on it. It varies slowly in the scale-invariant regime and oscillates around r⋆ at smaller k. The oscillations next to the scale-invariant regime do not depend on the adiabatic order, unlike the peaks and spikes at lower k. For a given initial state, the regularization dependence survives in the infrared, where long-wavelength modes retain a record of the bounce and of the pre-bounce branch. We propagate the normalized spectra to the CMB B-mode spectrum and discuss observational prospects.
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BibTeX
@misc{jamil2026primordial,
title = {{Primordial Gravitational Waves in Loop Quantum Cosmology: Regularization Ambiguities and Initial State Dependence}},
author = {Mah Noor Jamil and Parampreet Singh},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.37790},
eprint = {2610.37790},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.37790},
}
RIS
TY - UNPB
TI - Primordial Gravitational Waves in Loop Quantum Cosmology: Regularization Ambiguities and Initial State Dependence
AU - Mah Noor Jamil
AU - Parampreet Singh
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.37790
UR - https://arxiv.org/abs/2610.37790
AB - We compute the primordial tensor power spectrum in standard loop quantum cosmology and in the modified models mLQC-I and mLQC-II, evolving the tensor perturbations across the bounce in the hybrid and dressed metric prescriptions with a Starobinsky potential. In mLQC-I, the emergent de Sitter contracting branch requires the use of dedicated initial states. We use de Sitter mode function in the dressed metric approach and a Hankel-function solution in the hybrid approach. For inflationary e-foldings N_e = 60 and $65$, the pivot-scale tensor-to-scalar ratio agrees with the value of standard inflation with this potential. The scale-dependent ratio r(k)=𝒫_T/𝒫_S cancels effects common to the two sectors and separates features that are independent of the initial state from those that depend on it. It varies slowly in the scale-invariant regime and oscillates around r_⋆ at smaller k. The oscillations next to the scale-invariant regime do not depend on the adiabatic order, unlike the peaks and spikes at lower k. For a given initial state, the regularization dependence survives in the infrared, where long-wavelength modes retain a record of the bounce and of the pre-bounce branch. We propagate the normalized spectra to the CMB B-mode spectrum and discuss observational prospects.
ER -