Cosmology with Causal and Non-Causal Dark Viscous Fluid Models

Multiple cosmological observations, including Type Ia supernovae, the Cosmic Microwave Background (CMB), and Baryon Acoustic Oscillations (BAO), confirm the accelerated expansion of the universe. This has prompted the need for theoretical models that go beyond the standard cosmological framework. Among various approaches, the incorporation of bulk viscous effects in the cosmic fluid content has attracted considerable attention. Bulk viscosity serves as an effective mechanism to account for irreversible processes in the cosmological fluid.