Constraints on the speed of sound in the k-essence model of dark energy

Understand

We consider a particular k-essence scalar field model for the late-time cosmic acceleration in which the sound speed, parametrized as $c_s$ is constant.

• We compute the relevant background and perturbation quantities corresponding to the observables like cosmic microwave background, type Ia supernova, cosmic chronometers, baryon acoustic oscillations, and the $f\sigma_8$.
• We put constraints on the $c_s^2$ parameter from these observations along with other parameters.
• We find lower values of $c_s^2$ which are close to zero are tightly constrained.