Exploring B(z)CDM models beyond ΛCDM: Observational data and cosmographic analysis

With its model-independent approach, cosmography has emerged as an invaluable tool for faithfully representing a wealth of astrophysical observations, free from theoretical biases. This study employs cosmography to investigate two innovative cosmological models, B(z)CDM models 1 and 2, which introduce novel corrections to the standard ΛCDM model, B(z)=sin(z) and B(z)=log(1+z), respectively. By analyzing a variety of observational datasets, including 31 measurements from cosmic chronometers (CC), 1048 data points from the Pantheon dataset, 6 measurements from baryon acoustic oscillations (BAO), and data from cosmic microwave background (CMB) measurements, we derive constraints on model parameters and assess their compatibility with real-world observations. We find that the present values of the deceleration parameter for B(z)CDM models 1 and 2 are q₀=−0.54_−0.23^+0.24 and q₀=−0.56_−0.40^+0.45, respectively, for the combined datasets. The results reveal intriguing transitions in the expansion of the universe, confirming the presence of DE and quintessence-like behavior within the framework of B(z)CDM models.