Testing the scale-dependent hemispherical asymmetry with the 21-cm power spectrum from the epoch of reionization

Understand

Hemispherical power asymmetry has emerged as a new challenge to cosmology in early universe.

• While the cosmic microwave background (CMB) measurements indicated the asymmetry amplitude $A \simeq 0.07$ at the CMB scale $k_{\rm CMB}\simeq 0.0045\,{\rm Mpc}^{-1}$, the high-redshift quasar observations found no significant deviation from statistical isotropy.
• This conflict can be reconciled in some scale-dependent asymmetry models.
• We put forward a new parameterization of scale-dependent asymmetric power spectrum, inspired by a multi-speed inflation model.