Cosmological constraints on time-varying cosmological terms: A study of FLRW universe models with (t) CDM cosmology

This paper explores models of the FLRW universe that incorporate a time-varying cosmological term (t). Specifically, we assume a power-law form for the cosmological term as a function of the scale factor: (t) =₀ a (t) ^-, where ₀ represents the present value of the cosmological term. Then, we derive an exact solution to Einstein's field equations within the framework of (t) CDM cosmology and determine the best-fit values of the model parameters using the combined H (z) + SNe Ia dataset and MCMC analysis. Moreover, the deceleration parameter demonstrates the accelerating behavior of the universe, highlighting the transition redshift zₓₑ, at which the expansion shifts from deceleration to acceleration, with confidence levels of 1- and 2-. In addition, we analyze the behavior of the Hubble parameter, jerk parameter, and Om (z) diagnostic. Our analysis leads us to the conclusion that the (t) CDM model is consistent with present-day observations.