Dr. Swagat Mishra

The nature of Dark Energy (DE) remains one of the deepest mysteries in modern physics. In the standard ¿CDM model, DE is attributed to the cosmological constant - a uniform energy density driving the accelerated expansion of the universe. However, recent high-precision observations from the DESI collaboration, when combined with CMB and supernova data, suggest that DE may not be truly constant but could evolve over time. Intriguingly, the data indicate that the DE equation of state may have transitioned from a phantom-like phase (w<-1) in the past to a quintessence-like one (w>-1) today, implying a recent crossing of the phantom divide at w=-1. We discuss a broad class of thawing scalar field models - including quadratic, quartic, exponential, symmetry-breaking, and axion potentials - evolving on a ghost-free (4+1)-dimensional phantom braneworld. These models naturally emerge in higher-dimensional theories such as string theory. We show that they can successfully reproduce the observed phantom-divide crossing, with the evolution of the Hubble parameter and the effective equation of state of DE matching DESI data remarkably well. Our MCMC analysis further demonstrates that these models achieve a statistical fit comparable to the widely used CPL parametrisation, reaffirming their excellent agreement with observational data.