Seeking Evolution of Dark Energy

Understand

We study how observationally to distinguish between a cosmological constant (CC) and an evolving dark energy with equation of state $\omega(Z)$.

• We focus on the value of redshift Z* at which the cosmic late time acceleration begins and $\ddot{a}(Z^{*}) = 0$.
• Four $\omega(Z)$ are studied, including the well-known CPL model and a new model that has advantages when describing the entire expansion era.
• If dark energy is represented by a CC model with $\omega \equiv -1$, the present ranges for $\Omega_{\Lambda}(t_0)$ and $\Omega_m(t_0)$ imply that Z* = 0.743 with 4% error.