The age problem in $\Lambda$CDM model

Understand

The age problem in the $\Lambda$CDM model is re-examined.

• We define the elapsed time $T$ of an object is its age plus the age of the Universe when it was born.
• Therefore in any cosmology, $T$ must be smaller than the age of the Universe.
• For the old quasar APM 08279+5255 at $z=3.91$, previous studies have determined the best-fit value of $T$, 1 $\sigma$ lower limit and the lowest limit to $T$ are 2.3, 2.0 and 1.7 Gyr, respectively.