Evidence of a decreasing trend for the Hubble constant

¹ School of Astronomy and Space Science, Nanjing University, Nanjing 210093, PR China
e-mail: fayinwang@nju.edu.cn
² Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China

Received: 9 March 2023
Accepted: 6 April 2023

Abstract

The current discrepancy between the Hubble constant, H₀, derived from the local distance ladder and from the cosmic microwave background is one of the most crucial issues in cosmology, as it may possibly indicate unknown systematics or new physics. Here, we present a novel non-parametric method to estimate the Hubble constant as a function of redshift. We establish independent estimates of the evolution of Hubble constant by diagonalizing the covariance matrix. From type Ia supernovae, baryon acoustic oscillation data and the observed Hubble parameter data, a decreasing trend in the Hubble constant with a significance of a 5.6σ confidence level is found. At low redshift, its value is dramatically consistent with that measured from the local distance ladder and it drops to the value measured from the cosmic microwave background at high redshift. Our results may relieve the Hubble tension, with a preference for recent solutions, especially with respect to novel physics.