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arXiv · 2208.00188

Updated constraints on amplitude and tilt of the tensor primordial spectrum

Giacomo Galloni·Nicola Bartolo·Sabino Matarrese·Marina Migliaccio·Angelo Ricciardone·Nicola Vittorio
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Abstract

We have taken a comprehensive approach to update the limits on the tensor-to-scalar ratio ($r$) and the tensor spectral index ($n_t$), using 10 datasets from the BICEP/Keck Array 2015 and 2018, Planck releases 3 and 4, and LIGO-Virgo-KAGRA Collaboration. By fitting the complete $\Lambda$CDM+$r$+$n_t$ model with two different approaches for the tensor sector, we have not only established which method is the most reliable, but have also achieved the strongest constraint on the tensor-to-scalar ratio in current literature: $r<0.028$ and $-1.37 < n_t < 0.42$ at 95% confidence level. Furthermore, our examination of the common signal detected by the NANOGrav Collaboration further confirms that a simple power-law cannot reconcile the constraints from different datasets if the NANOGrav detection is due to a primordial inflationary gravitational wave background, as previously shown in the literature.

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Giacomo Galloni, Nicola Bartolo, Sabino Matarrese, Marina Migliaccio, Angelo Ricciardone, Nicola Vittorio. 2022-07-30. Updated constraints on amplitude and tilt of the tensor primordial spectrum. https://doi.org/10.1088/1475-7516%2F2023%2F04%2F062

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