Hints of FLRW breakdown from supernovae

A 10% difference in the scale for the Hubble parameter constitutes a clear problem for cosmology. Here, considering angular distribution of type Ia supernovae (SN) within the Pantheon compilation and working within flat Λ CDM cosmology, we observe a correlation between higher H₀ and the CMB dipole direction, confirming our previous results for strongly lensed quasars [Classical Quantum Gravity 38, 184001 (2021), 10.1088/1361-6382/ac1a81]. Concretely, we record a ∼1 km /s /Mpc variation in H₀ at antipodal points on the sky within the Pantheon sample, which is evident in the Low z subsample (z ≲0.075 ) and gets enhanced by higher redshift SN. Our work raises the possibility that we may be at the precision required to probe anisotropic Hubble expansions, while providing a concrete prediction for future inferences of H₀.