The Hubble tension: Change in dark energy or a case for modified gravity?

Abstract

Recently, much controversy has been raised about the cosmological conundrum involving the discrepancy in the value of the Hubble constant as implied by Planck satellite observations of the CMBR in the early Universe and that deduced from other distance indicators (for instance using standard candles like supernovae, tip of the red giant branch, etc.) in the present epoch. The Planck estimate is about $67\; {\text{km}}^{ - 1} \;{\text{Mpc}}^{ - 1}$, while that deduced from distance indicators at the present epoch is around $73 - 74 \;{\text{km}}^{ - 1} \;{\text{Mpc}}^{ - 1}$. Also the independent determination of the local value of the Hubble constant based on a calibration of the tip of the red giant branch and applied to Type Ia supernovae found a value of $69.8\;{\text{km}}^{ - 1} \;{\text{Mpc}}^{ - 1}$. Here we propose a modification of the gravitational field on large scales as an alternate explanation for this discrepancy in the value of the Hubble constant as implied in the above-mentioned method, i.e., by Planck observations of the CMBR in the early Universe, and that deduced from other distance indicators in the present epoch.