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

Abstract

This paper explores models of the FLRW universe that incorporate a time-varying cosmological term . Specifically, we assume a power-law form for the cosmological term as a function of the scale factor: , where represents the present value of the cosmological term. Then, we derive an exact solution to Einstein's field equations within the framework of CDM cosmology and determine the best-fit values of the model parameters using the combined + SNe Ia dataset and MCMC analysis. Moreover, the deceleration parameter demonstrates the accelerating behavior of the universe, highlighting the transition redshift , at which the expansion shifts from deceleration to acceleration, with confidence levels of and . In addition, we analyze the behavior of the Hubble parameter, jerk parameter, and diagnostic. Our analysis leads us to the conclusion that the CDM model is consistent with present-day observations.