Viability of loop quantum cosmology at the level of bispectrum

TL;DR

This paper assesses whether the non-Gaussian bispectrum predicted by loop quantum cosmology (LQC) aligns with Planck observations, finding that its oscillatory features make it compatible with current CMB data despite its non-Gaussian nature.

Contribution

The study models the LQC-generated bispectrum and demonstrates its consistency with Planck CMB observations, highlighting the viability of LQC predictions.

Findings

LQC predicts a highly scale-dependent, oscillatory bispectrum at large scales.

The LQC bispectrum's oscillatory nature makes it similar to slow-roll inflation bispectrum.

LQC's non-Gaussian bispectrum is consistent with Planck CMB observations.

Abstract

Observations by Planck indicate that CMB anisotropies are consistent with predictions of nearly Gaussian primordial perturbations as the one generated in slow-roll inflation. On the other hand, loop quantum cosmology (LQC) generates a non-Gaussian bispectrum. In particular, calculations of primordial bispectrum generated in LQC shows that the non-Gaussianity function $f_{_{\rm NL}}(k_1,\, k_2,\, k_3)$ is highly scale-dependent and oscillatory at long wavelengths and is nearly scale-invariant as in slow-roll at small scales. We discuss the viability of such a non-Gaussian bispectrum in the light of observations by Planck. More specifically, we model the bispectrum generated in LQC and compute its imprints on the CMB bispectrum. We then show that the CMB bispectrum generated in LQC though non-Gaussian, due to its highly oscillatory nature, is similar to that generated in slow-roll inflation and hence consistent with the observations by Planck.