| Name: Ramanpreet Singh |
| Affiliation: IISER Mohali |
| Conference ID: ASI2026_64 |
| Title: Constraints on Tachyonic Dark Energy from SNe and BAO Observations |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: RAMANPREET SINGH(IISER MOHALI, 140306, Punjab, India), ATHUL C. N.(IIT KANPUR, 208016, Uttar Pradesh, India), H.K. JASSAL(IISER MOHALI, 140306, Punjab, India) |
| Abstract: Despite being the simplest dark energy model, the cosmological constant explains many cosmological observations, but it faces significant challenges, including the Hubble tension. These shortcomings have motivated the search for alternatives to the cosmological constant. Results from Type Ia supernova cosmology indicate that the universe is not only expanding, but that this expansion is accelerating. In contrast, several recent analyses of Dark Energy Spectroscopic Instrument (DESI) BAO data suggest that the expansion may not be accelerating after all, raising the possibility of a future slow down or even collapse of the universe. Moreover, DESI data indicate a preference for dynamical dark energy models with equation of state (EoS) with a CPL parameterization, over the cosmological constant model.
Motivated by these findings, we investigate a tachyonic dark energy model with an exponential potential using the Pantheon\(+\), earlier BAO datasets, and the DESI BAO DR2 data. We take the present-day value of the EoS parameter, \( w_{\phi 0} = -1 \), as a reference model, and also examine the case where \( w_{\phi 0} \) is treated as a free parameter. We find that both classes of datasets predict a turnaround in the evolution of the EoS parameter, irrespective of whether \( w_{\phi 0} \) is fixed or allowed to vary. The deceleration parameter likewise exhibits a future turnaround for both datasets. However in the \( w_{\phi 0} = -1 \) case, it asymptotically approaches \(-1\). Model comparison using the AIC and BIC criteria reveals that the Pantheon\(+\) dataset prefers the model with a free \( w_{\phi 0} \), whereas BAO type datasets favor the \( w_{\phi 0} = -1 \) case. This indicates a disagreement between these two classes of datasets regarding the predicted future evolution of the Universe within the tachyonic dark energy model. |
