Searching for a Solution to the Age Problem of the Universe
  We present here a phenomenological cosmological model under perfect fluid distribution with a stiff equation of state $p=\rho$. The erstwhile cosmological constant is assumed to be a time dependent variable, i.e., $\Lambda = \Lambda(t)$ in our study. It has been shown that the estimates of different cosmological parameters from this model are in good agreement with the experimental results, especially 13.79 Gyr as the age of the universe is quite satisfactory. The behavior and relation of $\Lambda$-stiff fluid model with dust, viscous fluid and variable $G$ have also been investigated in detail. 
Saibal Ray & Utpal Mukhopadhyay