Toward a concordance teleparallel Cosmology I: Background Dynamics

TL;DR

This paper investigates an infrared-corrected teleparallel gravity model as an alternative to ΛCDM, demonstrating its statistical viability and ability to reduce the H0 tension while fitting cosmological data well.

Contribution

It introduces a parameter-free infrared-corrected teleparallel gravity model and shows its phenomenological equivalence to ΛCDM with improved H0 tension resolution.

Findings

Model fits cosmological data comparably to ΛCDM

Reduces H0 tension without worsening S8 tension

Phenomenologically equivalent to ΛCDM at background level

Abstract

Assuming a spatially flat universe, we study the cosmological viability of an infrared corrected teleparallel gravity model, which accounts for late acceleration by weakening gravity at later times on cosmological distances. The theory does not introduce any additional free parameters into the cosmological model, as is commonly the case with modified gravity based cosmologies. This feature renders the cosmological model statistically comparable, on equal footing, with $\Lambda$CDM. In this context, using recent cosmological observations -- Pantheon supernova Type Ia, Hubble constant $H_0$, Baryon acoustic oscillation, redshift space distortions, Big Bang nucleosynthesis and the cosmic microwave background constraint on the decoupling acoustic scale -- we show that, although the exponential infrared-corrected gravity and $\Lambda$CDM are physically different, they are phenomenologically and statistically equivalent. However, the former is more adept at fitting accurately determined observational constraints while decreasing the $H_0$ tension without worsening the $S_8$ tension. This calls for full examination of the empirical viability of the theory at the linear perturbation level, which is the subject of paper II.