Constraints on DBI dark energy with chameleon mechanism
In this work, we investigate the Dirac--Born--Infeld (DBI) scalar field model with and without the inclusion of the chameleon mechanism in light of the latest cosmological observations. We constrain the model using data from Pantheon Plus, DES Y5, DESI DR2, and the compressed Planck likelihood. We consider an AdS throat of the form $f(\phi) = \lambda / \phi^4$ and a potential $V(\phi) = m_0^2 \phi^2 + m_1^2 \phi^4$. Our analysis shows that, for both cases, the mean value $m_1 \simeq 0$ suggests that the DBI field may lack significant self-interaction, with only an upper bound on $m_1$. The warp parameter is constrained to $\eta \geq 0$, while the chameleon coupling satisfies $\beta \leq 0$. No crossing of the phantom divide is observed under the assumed form of the warp factor and potential. We perform a statistical model comparison using the $\Delta \mathrm{AIC}$ relative to the $\Lambda$CDM model. Although the DBI model provides a slightly better fit to the data in terms of $\Delta \chi^2$, the improvement is negligible. Consequently, the DBI model is mildly disfavored for both the cases compared to the $\Lambda$CDM model.