Dark Age Consistency in the 21 cm Global Signal

Area of Science:

• Cosmology
• Astrophysics
• Particle Physics

Background:

• The 21cm global signal during the cosmic dark ages offers a unique probe of the early universe.
• Current cosmological models, like the standard Lambda Cold Dark Matter (ΛCDM), predict specific signal shapes.
• Testing physics beyond the standard model requires sensitive observables.

Purpose of the Study:

• To propose a new observable, the "dark age consistency ratio," for the 21cm global signal.
• To establish this ratio as a critical test for models beyond ΛCDM.
• To enable early-stage testing of cosmological scenarios with limited data.

Main Methods:

• Analyzing the functional form of the 21cm signal against frequency in the ΛCDM model.
• Identifying a cosmological-parameter independent feature within the signal shape.
• Defining the "dark age consistency ratio" based on brightness temperature measurements at a few frequency bands.

Main Results:

• The 21cm signal's shape is nearly independent of cosmological parameters in the ΛCDM model.
• The "dark age consistency ratio" yields a definite value within the ΛCDM framework.
• This ratio can effectively falsify alternative cosmological models.

Conclusions:

• The "dark age consistency ratio" is a powerful tool for testing beyond-ΛCDM theories.
• Future lunar missions can utilize this observable for early cosmological model validation.
• This method is robust even with limited 21cm signal data.