A Robust Assessment of the Local Anisotropy of the Hubble Constant

Magnitude predictions of \(\Lambda\)CDM, as parametrized by the Planck collaboration, are not consistent with the supernova data of the whole Pantheon+ sample even when, in order to take into account the uncertainty about its value, the Hubble constant is adjusted. This is a likely consequence of the increase of the number of low-redshift supernovae in the Pantheon+ sample, with respect to previous such samples. Indeed, when supernovae at redshifts below 0.035 are ignored, \(\Lambda\)CDM predictions become consistent with Pantheon+ data. Interestingly, this is also the case if subsets of low-redshift supernovae roughly centered on the direction of the CMB dipole are considered, together with high-redshift ones. These results seem robust, since they are also obtained with a simple, single-parameter tired-light model.