paper

Hints of FLRW Breakdown from Supernovae

arXiv:2106.02532 · doi:10.1103/PhysRevD.105.063514

Abstract

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 $I^$ CDM cosmology, we observe a correlation between higher $H_{0}$ and the CMB dipole direction, confirming our previous results for strongly-lensed quasars \cite{Krishnan:2021dyb}. Concretely, we record a $\sim 1$ km/s/Mpc variation in $H_{0}$ 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 $H_{0}$ .

5 pages, 5 figures, comments are most welcome; v2 appendix added on general trend; v3 presentation improved and streamlined; v4 references and appendix added, to appear in PRD