Is the transition redshift a new cosmological number?

TL;DR

This paper discusses whether the transition redshift $z_t$ can serve as a new observational cosmological parameter to distinguish between different models of the Universe's acceleration, emphasizing future observational prospects.

Contribution

It analyzes the potential of the transition redshift $z_t$ as a new cosmic discriminator and discusses how upcoming observations could constrain its value.

Findings

Future observations may tightly constrain $z_t$.

$z_t$ could serve as a new cosmological parameter.

Degeneracy in models can be reduced with $z_t$ measurements.

Abstract

Observations from Supernovae Type Ia (SNe Ia) provided strong evidence for an expanding accelerating Universe at intermediate redshifts. This means that the Universe underwent a transition from deceleration to acceleration phases at a transition redshift $z_t$ of the order unity whose value in principle depends on the cosmology as well as on the assumed gravitational theory. Since cosmological accelerating models endowed with a transition redshift are extremely degenerated, in principle, it is interesting to know whether the value of $z_t$ itself can be observationally used as a new cosmic discriminator. After a brief discussion of the potential dynamic role played by the transition redshift, it is argued that future observations combining SNe Ia, the line-of-sight (or "radial") baryon acoustic oscillations, the differential age of galaxies, as well as the redshift drift of the spectral lines may tightly constrain $z_t$, thereby helping to narrow the parameter space for the most realistic models describing the accelerating Universe.