Observing Nulling of Primordial Correlations via the 21-cm Signal

Area of Science:

• Cosmology
• Astrophysics
• Particle Physics

Background:

• The 21-cm line from neutral hydrogen (HI) during the Dark Ages contains information about primordial correlations.
• Inflationary cosmology models describe the early universe's rapid expansion.

Purpose of the Study:

• To investigate if a specific inflationary phase can cause a null in primordial correlations.
• To assess the detectability of this correlation null in future HI observations.

Main Methods:

• Analyzing theoretical models of single-field, canonical inflation with an ultra-slow-roll phase.
• Calculating the impact of this phase on primordial power and bispectra at specific wave numbers (1≲k_{dip}≲10 Mpc^{-1}).
• Simulating the detectability of these effects in future 21-cm signal observations.

Main Results:

• A null in all primordial correlations is predicted at a specific wave number (k_{dip}) under ultra-slow-roll conditions.
• This null can significantly damp the HI signal at observable scales.

Conclusions:

• The ultra-slow-roll phase in inflation offers a unique signature in the primordial correlation functions.
• Future 21-cm observational missions may be able to detect this damping effect, providing insights into early universe physics.