[Yang, Rong-Jia] Hebei Univ, Coll Phys Sci & Technol, Baoding 071002, Peoples R China
; [Zhang, Shuang Nan] Chinese Acad Sci, Inst High Energy Phys, Key Lab Particle Astrophys, Beijing 100049, Peoples R China
; [Zhang, Shuang Nan] Univ Alabama, Dept Phys, Huntsville, AL 35899 USA
The age problem in the Lambda CDM model is re-examined. We define the elapsed time T of an object as 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 that the best-fitting value of T, 1 sigma lower limit and lowest limit to T are 2.3, 2.0 and 1.7 Gyr, respectively. Constrained from SNIa+R+A+d, SNIa+R+A+d+H(z) and WMAP5+2dF+SNLS+HST+BBN, the Lambda CDM model can only accommodate T(z = 3.91) = 1.7Gyr at 1 sigma deviation. Constrained from WMAP5 results only, the Lambda CDM model can only accommodate T(z = 3.91) = 1.7Gyr at 2 sigma deviation. In all these cases, we found that the Lambda CDM model accommodates the total age (14 Gyr for z = 0) of the Universe estimated from old globular clusters, but cannot accommodate statistically the 1s lower limit to the best-fitting age of APM 08279+ 5255 at z = 3.91. These results imply that the Lambda CDM model may suffer from an age problem.