Age of High Redshift Objects - a Litmus Test for the Dark Energy Models
  The discovery of the quasar, the APM 08279+5255 at z = 3.91 whose age is 2-3 Gyr has once again led to ``age crisis''. The noticeable fact about this object is that it cannot be accommodated in a universe with $\Omega_m = 0.27$, currently accepted value of matter density parameter and $\omega = \mathrm{constant}$. In this work, we explore the concordance of various dark energy parameterizations ($w(z)$ models) with the age estimates of the old high redshift objects. It is alarming to note that the quasar cannot be accommodated in any dark energy model even for $\Omega_m = 0.23$, which corresponds to $1 \sigma$ deviation below the best fit value provided by WMAP. There is a need to look for alternative cosmologies or some other dark energy parameterizations which allow the existence of the high redshift objects. 
Deepak Jain, Abha Dev