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Updated: Aug 15, 2025

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Observing Nulling of Primordial Correlations via the 21-cm Signal
Shyam Balaji1, H V Ragavendra2, Shiv K Sethi3,4
1Laboratoire de Physique Théorique et Hautes Energies (LPTHE), UMR 7589 CNRS and Sorbonne Université, 4 Place Jussieu, F-75252, Paris, France.
Abstract:
The 21-cm line emitted by neutral hydrogen (HI) during the Dark Ages carries imprints of pristine primordial correlations. In models of inflation driven by a single, canonical scalar field, we show that a phase of ultra-slow-roll can lead to a null in all the primordial correlations at a specific wave number k_{dip}. We consider scenarios wherein the null in the correlations occurs over wave numbers 1≲k_{dip}≲10 Mpc^{-1}, and examine the prospects of detecting such a damping in the HI signal due to the nulls at the level of power and bispectra in future observational missions.
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